Unit 1 Topic 1 Molecules, Transport, and Health PDF

**UNIT 1: MOLECULES, DIET, TRANSPORT AND HEALTH By Mugo** **Topic 1 -- Molecules, Transport and Health** IONIC COMPOUNDS - Ionic compound is a chemical compound composed of **ions** held together by **ionic bonding**. It consists of positively charged ions called **cations** and negativ...

**UNIT 1: MOLECULES, DIET, TRANSPORT AND HEALTH By Mugo** **Topic 1 -- Molecules, Transport and Health** IONIC COMPOUNDS - Ionic compound is a chemical compound composed of **ions** held together by **ionic bonding**. It consists of positively charged ions called **cations** and negatively charged ions called **anions** - In other words, ionic substances such as sodium chloride are the ones that are formed when one atom gains one or more electrons and becomes an anion (a negative ion). The other atom, loses one or more electrons and becomes a cation (a positive ion). - Strong forces of attraction called ionic bonds hold the oppositely charged ions together. 1. In ionic compounds, electrons are transferred from one atom to another, forming ions 2. Ionic compounds have ionic bonds formed between their ions 3. Ionic substances are soluble in water. COVALENT MOLECULES - A covalent molecule is a chemical molecule consisting of atoms that **share** electrons and are held together by **covalent bonding.** - In other words, the atoms in the covalent molecules share electrons. They share electrons either equally or unequally. - If the atoms share the electrons equally then the molecules formed are neutral molecules e.g. Hydrogen molecule that is formed from hydrogen atoms - If they share electrons unequally then one part will be slightly negative and the other part will be slightly positive. The molecules formed are called polar molecules e.g. water, ethanol, ammonia, Sulphur dioxide **WATER** - The chemical formula of water is H~2~O - The atoms of water molecule are; i. 2 hydrogen atoms ii. 1 oxygen atom - The structure of a water molecule is as follows: - Delta (δ) indicates **small amounts, that is, small amount of** positive and negative charges. - The shape of water molecule is **triangular**. - The bonds that join atoms of water are called **covalent bonds**. A covalent bond is formed when electrons are shared by atoms. - Water molecules are joined by **hydrogen bonds.** One water molecule can be joined to 4 other water molecules by hydrogen bonds as follows:  **Stability of a water molecule** - Water molecule is **stable** but its atoms are unstable. - The outermost shell of hydrogen atom has 1 electron instead of 2, hence unstable. Oxygen atom has 6 electrons instead of 8 in its outermost shell, hence unstable. To form a stable water molecule, the 3 atoms must share electrons and in the process covalent bonds are formed.   **PROPERTIES OF WATER DUE TO HYDROGEN BONDS** **1. Liquid at room temperature** - Due to its dipolar nature, **hydrogen bonds** are formed between water molecules hence; water remains liquid at room temperature. **2. Cohesion** - This is attraction force between similar molecules. - **Hydrogen bonds** hold H~2~O molecules together giving it cohesion. - Cohesion is important to transport water and dissolved substances in the xylem, in a continuous unbroken column. **3. Adhesion** - Attraction force between non-identical molecules e.g. water and xylem wall. - **Hydrogen bonds** allow water to hold onto other substances e.g. to hold onto the walls of the xylem to allow water to be transported in a continuous unbroken column in the xylem. 4. **High surface tension** - Surface tension is the **tightness** of water molecules on the surface forming a skin like layer due to **hydrogen bonds**. - The water molecules beneath the ones on the surface pull the ones on the surface inwards by **hydrogen bonds**, creating a skin like layer. - The biological importance of high surface tension of water is to create a surface onto which aquatic insects such as pond skaters can *land, move, feed and breed*. **Dipole nature of water/Polarity of water** - When electrons are shared between atoms when forming water molecule, they are not shared equally between those atoms because some nuclei of these atoms attract more electrons than others. In a water molecule, the nucleus of the oxygen attracts more electrons than the two nuclei of the hydrogen atoms. So, oxygen is slightly negative while hydrogen atoms are slightly positive. - ***The condition where in a molecule one side is slightly positive and the other side is slightly negative is called dipole and the molecule is called dipolar/polar, so, a water molecule is dipolar/polar*** **Importance of dipolar nature of water** The importance of dipolar nature of water is that water is a Solvent for ionic substances. Water dissolves these ionic substances as follows: ***There is attraction** of the positive charge on the cation by the slight negative charge on oxygen of water and the attraction of the negative charge on anion by the slight positive charge on hydrogen of water. This causes d**issociation** of ions by breaking the ionic bonds in ionic molecules. The ions are hydrated by the water molecules allowing them to dissolve, forming ionic solutions.* The importance of dipolar nature of water is that water is a Solvent for polar substances. Water dissolves these polar substances as follows: ***Some polar (covalent) molecules dissolve in water when they form hydrogen bonds with water molecules, forming polar solutions.*** Due to this property, water is a, 1. Medium for chemical reactions. 2. Medium for transport of substances.  **Water is a good solvent. Explain why water is a good solvent. (2)** **Water is a polar / dipolar molecule** **Therefore the slight charge on oxygen and the positive charge on hydrogen in water molecules attract and surround (hydrates) ions that have dissociated from ionic molecules allowing them to dissolve, forming ionic solutions; and for some polar molecules, they form hydrogen bonds with water allowing them to dissolve forming polar solutions.** **Water as a medium for chemical reactions** - When in solid, substances are not reactive. - However, when ionic substances dissolve in water and separate into ions, these ions **freely move** and hence they are **chemically reactive.** So, as they freely move, they interact with other substances to carry out a reaction and form products. **Water as a medium for transport** - Water transports ionic, polar and **non-polar substances.** - Water **easily** transports ions, and polar substances in form of polar solutions - However, non-polar substances (no charges) such as lipids (fats and oils) are carried by **lipoproteins** so that they are now transported by water *Suggest how triglycerides are transported in the blood. **(2)*** *Triglycerides are insoluble in water; hence transported as **lipoproteins** (LDL/ HDL/* - The transport systems in organisms include: 1. Circulatory system -- blood 2. Lymphatic system -- lymph 3. Xylem vessels in plants -- water and minerals 4. Phloem in plants -- sucrose and amino acids. NB Water is **highly cohesive**---it is the highest of the non-metallic liquids. \... More precisely, the positive and negative charges of the hydrogen and oxygen atoms that make up water molecules makes them attracted to each other. **Explain why water is an effective molecule for transporting other molecules around living organisms.** - **Water is a dipolar molecule** - **Water is therefore a solvent** - **Polar and ionic molecules dissolve in water** - Water being a liquid, it transports these ions and polar substances in form of polar solutions in *mass flow* - Hydrogen bonds cause cohesion and adhesion that allow water to move in the blood vessels, phloem and xylem. The solubility of substances affects how they are transported in the blood. The diagram below shows the structure of a molecule of glucose. Suggest why glucose is soluble in water.**(1)** Glucose is a polar molecule, that is it forms hydrogen bonds with water **CARBOHYDRATES** - These are organic (carbon-containing) substances made up of 3 elements: i. Carbon ii. Hydrogen iii. Oxygen - The 3 groups of carbohydrates are: a. Monosaccharides b. Disaccharides c. Polysaccharides **To compare and contrast different types of carbohydrates** **Monosaccharides** **Disaccharides** --------------------------------------- --------------------------------------- **Sweet tasting** **Sweet tasting** **Soluble hence have osmotic effect** **Soluble hence have osmotic effect** **Small** **Large** **Single units** **Two units** **No glycosidic bonds** **Glycosidic bonds** **Cannot be hydrolysed** **Can be hydrolysed** **Monosaccharides** **Polysaccharides** --------------------------------------- -------------------------------------------- **Sweet tasting** **Not sweet tasting** **Soluble hence have osmotic effect** **Insoluble hence have no osmotic effect** **Small** **Large** **Monomers/Single units** **Polymers/More than10 units** **No glycosidic bonds** **Glycosidic bonds** **Cannot be hydrolysed** **Can be hydrolysed** **Disaccharides** **Polysaccharides** --------------------------------------- -------------------------------------------- **Glycosidic bonds** **Glycosidic bonds** **Can be hydrolysed** **Can be hydrolysed** **Sweet tasting** **Not sweet tasting** **Soluble hence have osmotic effect** **Insoluble hence have no osmotic effect** **Small** **Large** **Two units** **More than ten units** The **osmotic effect** causes a flow of water from the weak solution to the strong solution. Glucose is soluble in the water and can therefore have an osmotic effect as it can lower the water potential in cells. Starch is insoluble in water hence has no osmotic effect.\ \ **Oligosaccharides are carbohydrates with 3 to 10 sugar units joined by glyosidic bonds** **An example of oligosaccharide is raffinose (trisaccharide), found in sugar beet, beans, cabbage, broccoli; made up of glucose, fructose and galactose.** **Oligosaccharides are;** 1. **Sweet** 2. **Soluble** 3. **Physiologically active** **MONOSACCHARIDES** - These are the simplest sugars that cannot be hydrolyzed/single unit sugars - General formula for monosaccharides is C~n~H~2n~O~n~, where n is 3 to 10; from triose to decose. - All monosaccharides consist of 2 reactive groups called; a. Hydroxyl group (OH) b. Carbonyl group (**C=O**) - There are 2 forms of carbonyl groups called: a. Aldehyde group (H-C=O) - A carbonyl group becomes an aldehyde group when a hydrogen atom is attached to it. It is this aldehyde group that reduces metallic ions. A monosaccharide with an aldehyde group is called aldose sugar e.g. glucose and galactose.  b. Ketone group - A ketone group is formed when the carbonyl group is between carbon atoms. It reduces metallic ions but must be converted first to aldehyde group. Monosaccharides with keto-groups are called ketose sugars e. g fructose. Note: so, monosaccharides are either; a. Aldoses -- glucose and galactose b. Ketoses -- fructose **Linear and ring forms of monosaccharides** - Linear forms are less stable but they **reduce metallic ions** because of availability of carbonyl groups. - Ring forms have **molecular stability** but cannot reduce metallic ions due to hidden carbonyl groups. So, in Benedict's test, heating the monosaccharide is meant to open up the ring form into the linear form to expose the carbonyl groups that reduce metallic ions.  **Hexoses** - These are monosaccharides. - They are 6 carbon sugars. - They consist of both linear and ring forms. - Their chemical formula is C~6~H~12~O~6.~ - They are all respiratory substrates i.e. they are broken down to provide ATP during respiration that are then hydrolyzed to give energy. - The common hexoses are glucose, fructose and galactose α -**Glucose** **Note** - In α - glucose, OH on carbon atom One (C1) is below the ring/below carbon atom one (C1). *Below c1, c2 and c4 is OH* *Below c3 and c5 is H* - The importance of glucose include; a. It is a respiratory substrate that provides energy (ATP) when respired. b. It synthesizes disaccharides (maltose, sucrose and lactose) c. It synthesizes polysaccharides (starch, glycogen and cellulose). NB: Glucose is **pyranose** because it is a six sided ring. **Fructose** Fructose is a sugar which is present naturally in fruits, some vegetables and honey. The structure of fructose is as follows:  Fructose, when forming sucrose (together with glucose), it flips and groups of c2 and c5 change positions NB: Fructose is **furanose** because it is a five sided ring. - The importance of fructose include; a. It is a respiratory substrate that is respired to provide energy. b. It synthesizes disaccharide -- sucrose (Glucose + Fructose). c. It sweetens the fruits which attract animals, facilitating seed dispersal. **Galactose** - It occurs in our diet mainly as part of the disaccharide sugar called lactose (milk sugar) - The importance of galactose include; i. Food for infants as a respiratory substrate. ii. Synthesis of disaccharide called lactose (glucose + galactose) **NB. Galactose is structurally similar to beta glucose except at carbon 4** **DISACCHARIDES** - A sugar that contains two monosaccharide molecules - The formula for disaccharide is C~n~H~2n-2~O~n-1~, where n is 12 (or C~12~H~22~O~11~) - They are also called double sugars. - The common disaccharides are; i. Maltose (malt sugar) Glucose + Glucose ii. Sucrose (cane sugar) glucose + fructose iii. Lactose (milk sugar) Glucose + galactose - The chemical formula for all disaccharides is C~12~H~22~O~11~ **Condensation reaction in the formation of disaccharides** - Condensation reaction involves a **loss of water molecule** when 2 monosaccharides join through a bond. - In disaccharides, the bond that joins the monosaccharides together is called a **glycosidic bond.**  **Hydrolysis reactions in breaking down disaccharides.** - Hydrolysis reaction involves the **addition or gain of a water molecule** to break down the glycosidic bond in the disaccharide and polysaccharides in order to get individual monosaccharides. - There are 2 types of hydrolysis; **1. Acid hydrolysis** - The disaccharide is **boiled with dilute acid** to break down the glycosidic bond. For example, sucrose, a non reducing sugar, is boiled with HCL to break down the glycosidic bond in sucrose and then sodium hydrogen carbonate is added to neutralize the acid before the Benedict's test is carried. **2. Enzymatic hydrolysis** - The disaccharide is **incubated with the enzyme** to break the glycosidic bond as shown below; Maltose maltase glucose + glucose Sucrose sucrase glucose + fructose Lactose lactase glucose + galactose **Maltose** - It is a disaccharide - It is made up of 2 α-glucose molecules - Its chemical formula is C~12~H~22~O~11~ - *It is mainly found in seeds. **It is hydrolyzed into glucose** and this **glucose is respired** to provide energy for the germinating seeds.* - **Digestion** of starch in animals and **germination** in seeds release maltose because in both processes -- starch is hydrolyzed by **amylase** enzyme to get maltose. **Sucrose** - It is a disaccharide - Made up of glucose and fructose - Chemical formula is C~12~H~22~O~11~ - Mainly found in sugar cane and sugar beet - ***It is the form of carbohydrate transported in the phloem of plants.***  **Lactose** - It is a disaccharide - Made up of glucose and galactose - Its chemical formula is C~12~H~22~O~11~ - Mainly found in mammalian milk to provide energy for the infants when it is hydrolyzed. Glycosidic bonds in disaccharides 1. Maltose 1,4 2. Sucrose 1,2 3. Lactose 1,4 **Galactose, Glucose and Lactose** *The three most important disaccharides are **sucrose**, **lactose** and **maltose**. They are formed from the appropriate monosaccharides. Sucrose is a non-reducing sugar. Lactose and maltose are reducing sugars.* *Disaccharide* *Monosaccharides* ---------------- -------- --------------------------- *sucrose* *from* *α-glucose + β-fructose* *maltose* *from* *α-glucose + α-glucose* *α-lactose \** *from* *α-glucose + β-galactose* *\* Lactose also exists in a beta form, which is made from β-galactose and β-glucose* *Disaccharides are soluble in water, but they are too big to pass through the cell membrane by diffusion. They are broken down in the small intestine during digestion to give the smaller monosaccharides that pass into the blood and through cell membranes into cells.* *C~12~H~22~O~11~ + H~2~O  **  C~6~H~12~O~6~ + C~6~H~12~O~6~* *This is a **hydrolysis reaction** and is the reverse of a condensation reaction. It releases energy.*   **Polysaccharides** - These are macromolecules (large molecules) as well as polymers (a structure with repeated units/monomers). - They are made up of many glucose molecules which are joined by glycosidic bonds through condensation reactions. - The general formula is (C~6~H~10~O~5~)~n~, where n is between 40 and 3000 - The 3 common polysaccharides are; 1. Starch (made up of α glucose molecules). A molecule that stores energy in plant cells. 2. Glycogen (made up of α glucose molecules). A molecule that stores energy in animal cells (usually liver and muscle), bacteria and fungi. 3. Cellulose (made up of β glucose molecules). It is a structural carbohydrate that gives strength in the plant cell walls. **The structure of starch** - It is a **polysaccharide** made up of many **α-glucose molecules** - These **α-**glucose molecules are joined by **glycosidic bonds** formed in a condensation reaction. - Starch consist of both amylose and amylopectin. Amylose is helical/coiled and amylopectin is branched. The structure of amylose - It is a polysaccharide made up of many α-glucose molecules - These glucose molecules are joined by glycosidic bonds - It is helical/coiled. - It is unbranched hence has only 1,4 glycosidic bonds. N.B. When iodine solution is added, it turns blue black. This is because the iodine solution is trapped in the coils/spirals where it reacts with amylose to become blue black. - OH on carbon atom 2 attracts one another by H-bonds causing coiling/helical shape  Is amylose compact? It is because it is helical/coiled. Does amylose store a lot of energy compared amylopectin? It does not because it is not branched and so has very few terminal glucose molecules to be hydrolysed to give energy The structure of amylopectin - It is a polysaccharide made up of many α-glucose molecules - These α-glucose molecules are joined by glycosidic bonds - It is branched hence has both 1,4 and 1,6 glycosidic bonds. N.B When iodine solution is added, it turns reddish brown (colour of iodine solution). It does not turn blue black because iodine solution passes through the branched structure hence not held back or trapped.  NB 1-6 glycosidic bonds cause branching. Branching makes the molecule very effective in providing energy due to quick hydrolysis of terminal glucose molecules. Is amylopectin compact? It is compact because of branching. Explain how the structure of amylopectin affects its ability to provide energy. It is branched and therefore has many terminal glucose molecules hence amylopectin is quickly hydrolyzed to glucose Starch contains amylose and amylopectin. Compare and contrast the structures of amylose and amylopectin. 1. Both are polysaccharides 2. Both made from α glucose molecules 3. They are joined by glycosidic bonds 4. amylose has 1,4 glycosidic bonds, amylopectin has 1,4 and 1,6 glycosidic bonds 5. amylose is coiled / helical; amylopectin is branched State the differences between the structure of lactose and the structure of starch. 1\. Lactose is a disaccharide, starch is a polysaccharide 2\. Starch is composed of glucose only, lactose is composed of glucose and galactose 3\. Starch (amylopectin) has 1, 4 and 1,6 glycosidic bonds, lactose has 1,4 glycosidic bonds only **A secretary who sits for long with simple tasks is given starch with a lot of amylopectin. Explain the effects of this diet in her body.** **Energy input is greater than energy output. Extra energy is converted to fat and stored in the body causing overweight or obesity. Overweight and obesity increase the BP and type II diabetes and both are risk factors for CVD.** **The *functional* differences between amylose and amylopectin are;** **Amylose** **Amylopectin** ------------------------------------------------ ------------------------------------------ Turns blue black with iodine solution Turns reddish brown with iodine solution Less amount of energy due to lack of branching More energy due to branching **These are the structural similarities between amylose and amylopectin;** 1. Both are polysaccharides made of α- glucose molecules 2. Glyosidic bonds join the glucose molecules. **The functional similarity between amylose and amylopectin;** 1. Energy storage molecules **Question** Describe the structure of starch and explain why this structure makes it a suitable molecule to store energy. 1. Insoluble in water hence has no osmotic effect (cannot absorb water to increase cell mass) 2. Large molecule (polysaccharide) so that they do not diffuse out of the cell. 3. Amylose is helical hence making starch more compact so that they take up small space in the cell. Amylopectin is branched and so it is also compact. 4. Amylopectin is branched hence has many terminal glucose molecules that are quickly hydrolyzed to get a lot of glucose molecules that are respired to give a lot of energy when required. 5. They are inert hence cannot take part in chemical reactions. 6. Has many glucose molecules that are hydrolysed to give a lot of energy when required. **The structure of Glycogen** - It is a polysaccharide made up of many α- glucose molecules - Glucose molecules are joined together by glycosidic bonds - It is branched, hence, in addition to 1,4 glycosidic bonds it has 1,6 glycosidic bonds. Branches occur after every 8 to 12 glucose molecules hence it is more branched than amylopectin and therefore store more energy than amylopectin. **Role of glycogen** - It is an energy storage molecule in animal cells (especially liver and muscle cells), bacteria and fungi. **Note:** Amylopectin (starch) and glycogen are energy storage molecules, they are branched but glycogen is more branched, hence stores more energy. **Question** Describe the structure of glycogen. - It is a polysaccharide made up of many α glucose molecules - joined by glycosidic bonds - 1,4 and 1,6 (glycosidic bonds) hence branched structure Describe the structure of glycogen and explain why it is a suitable molecule for storing energy. - consists of (α) glucose - joined by 1,4 and 1,6 glyosidic bonds hence branched structure - Rapidly hydrolysed due terminal glucose molecules - Insolubility hence no osmotic effect - Large hence remains in the cell and stores a lot of energy. **Adaptations of starch (amylopectin) and glycogen as energy storage molecules;** 1. Large -- to store a lot of energy and to remain inside the cells. 2. Insoluble -- so that they have no osmotic effect (cannot absorb water) 3. Inert -- no chemical reaction 4. They are branched hence have terminal glucose molecules that are rapidly hydrolyzed to be respired to produce energy when required. **LIPIDS** - They are biological molecules made up of 3 elements; i. Carbon ii. Hydrogen iii. Oxygen - They have less amount of oxygen than carbohydrates. - They are insoluble in water but soluble in organic solvents such as ethanol. - The 2 major groups of lipids; 1. **Simple -- with glycerol only.** 2. **Complex -- with glycerol and fatty acids.** - The complex lipids are; 1. Triglycerides -- fats and oils 2. Phospholipids 3. Waxes **Triglycerides** - They are natural fats and oils. - At room temperature, fats are solids and oils are liquids. - Triglycerides are lipids made up of ; i. **Three** Fatty acids. ii. **One** glycerol molecule. - These 3 fatty acids and glycerol are joined by **ester bonds**  - Each ester bond is formed in a condensation reaction/esterification reaction in which a water molecule is lost. The reaction is catalyzed by an enzyme. **Glycerol** - The structure of glycerol is as follows;  - The chemical formula for a glycerol molecule is C~3~H~8~O~3.~ - There is only one type of glycerol molecule i.e. all glycerol molecules are the same. **Fatty acids** - A fatty acid is made up of 3 components; 1. Carboxyl group: (COOH): between carbon and oxygen there is a double bond: Carboxyl group is polar hence soluble. 2. Hydrocarbon Chain: (CH~2~)~n~ CH~3:~ It is non-polar hence insoluble. - Triglycerides consist of 3 fatty acids. - There are different types of fatty acids which vary in the followings ways; 1. *The length of the hydrocarbon chain, from 4-24 carbons.* 2. *The absence or presence of carbon --carbon double bonds in the hydrocarbon chain* 3. *The number of double carbon-carbon bonds in the hydrocarbon chain* - A fatty acid can be represented as follows **Formation of triglyceride** - Fatty acids join the glycerol molecule one at a time by an **ester bond, forming** monoglyceride, diglyceride and triglyceride - Formation of an ester bond is through condensation reaction where a water molecule is formed. - To form water, glycerol loses hydrogen and fatty acid loses OH. **Types of fatty acids** a. Saturated fatty acids b. Unsaturated fatty acids -------------------------------------------------------------------------------- Ratio of H:C is higher in saturated fatty acids than unsaturated fatty acids ; -------------------------------------------------------------------------------- **Saturated fatty acids** - Ratio of Hydrogen to carbon is higher - Have only single carbon --carbon bonds in their **hydrocarbon chain**. - Saturation refers to the amount of hydrogen in the molecule. - ***Triglycerides with saturated fatty acids are called saturated triglycerides.*** - Due to lack of double carbon -- carbon bonds in the hydrocarbon chain, there is no straining hence no kinking (bending) and therefore they have high melting point, above 40^0^C and therefore they remain solid at both room and body temperatures. - Saturated fatty acids have ***double bond between carbon and oxygen in the carboxyl group.*** - The following table summarizes examples of saturated fatty acids and the saturated triglycerides they are found in. +-----------------+-----------------+-----------------+-----------------+ | **Saturated | **No of double | **Abundant in | **M.P** | | Fatty acids** | C-C** | (saturated | | | | | triglycerides)* | | | | **bonds** | * | | +=================+=================+=================+=================+ | Palmitic | 0 | Palm oil | 63 | +-----------------+-----------------+-----------------+-----------------+ | Stearic | 0 | Cocoa and | 68 | | | | animal fat | | +-----------------+-----------------+-----------------+-----------------+ | Lauric | 0 | Coconut oil and | 44 | | | | palm oil | | +-----------------+-----------------+-----------------+-----------------+ **Stearic fatty acid has the following structure**  The chemical formula for stearic fatty acid is: C~17~H~35~ COOH **Unsaturated fatty acids** - Ratio of hydrogen to carbon is lower - Have at least one double carbon-carbon bond (C=C bond) in the hydrocarbon chain. In addition, there is a double bond between carbon and oxygen in the carboxyl group. - Due to double C-C bonds, there is straining, causing kinking that lowers the melting point and therefore they remain liquid at both room and body temperature. The more the double C-C bonds, the more the straining, kinking and the lower the melting point. - There are 2 types of unsaturated fatty acids; 1. Mono-unsaturated fatty acids. 2. Poly-unsaturated fatty acids. **Mono-unsaturated fatty acids.** - They have a single double C-C bond in the hydrocarbon chain. - Example is **oleic fatty acid** (C~17~H~33~COOH) whose M.P is 13.4^0^C and is mainly found in **olive oil**. - Another mono-unsaturated triglyceride in addition to olive oil is **peanut oil.** C:\\Users\\Administrator\\Desktop\\l.png **Poly-unsaturated fatty acids** - They have more than one double Carbo-carbon bonds in their hydrocarbon tail. - Example is **linoleic fatty acid** whose melting point is -4^0^C and is mainly found in **maize** and **sunflower**. - Other poly-unsaturated triglycerides include: fish oil, soya bean oil, cotton seed oil and sesame oil.  Structural differences between saturated and unsaturated fatty acids/fats: +-----------------------------------+-----------------------------------+ | **Saturated** | **Unsaturated** | +===================================+===================================+ | have a higher ratio of hydrogen | have a low**er** ratio | | to carbon | | | | of hydrogen to carbon | +-----------------------------------+-----------------------------------+ | have **no** carbon -- carbon | have carbon -- carbon double | | double bonds | bonds | +-----------------------------------+-----------------------------------+ | have straight chains | have bent chains (have kinks) | +-----------------------------------+-----------------------------------+ | Solid at room temperature | Liquids at room temperature | +-----------------------------------+-----------------------------------+ Explain why saturated fatty acids/fats have higher melting temperatures. - They do not have carbon-carbon double bonds that cause kinking. - So, fatty acids are closely packed together resulting in **[stronger intermolecular forces]** - So, more energy is needed to separate fatty acid molecules, hence they have higher melting temperatures. Explain why unsaturated fatty acids have lower melting temperatures. - They have carbon-carbon double bonds that cause kinking. - Due to kinks, fatty acids are spaced out resulting in **[weaker intermolecular forces]** - So, less energy is needed to separate fatty acid molecules, hence they have lower melting temperatures. **Functions of triglycerides** **1. Energy store** - Produce more than twice the energy produced by carbohydrates. Triglycerides are essential energy stores because of the following properties; a. Insoluble (no osmotic effect) b. Produces a lot of energy. This is due to l**ong hydrocarbon chains** that contain many **carbon-hydrogen bonds** with little oxygen (triglycerides are highly reduced).So when triglycerides are **oxidised** during cellular respiration this causes these bonds to break **releasing a lot of energy**  (ATP). **2. Buoyancy in aquatic animals** - Buoyancy is the ability to float - Triglycerides are ***less dense than water*** hence aquatic animals are able to float e.g. blubber in whales which contains oil. **3. Heat/thermal insulation** - Triglycerides are poor thermal conductors (poor conductors of heat) e.g. adipose tissue (tissue that stores a lot of fat beneath the skin) reduces heat loss from the body. **4. Protection of delicate organs** - Triglycerides are ***soft*** and therefore **cushion** the delicate organs such as heart, lungs and kidneys so that they are not damaged. **5. Sources of metabolic water when oxidized** - Metabolic water is important in desert mammals such as camels to supplement the little water they get. *[[Omega-3 fatty acids]](https://www.medicinenet.com/omega-3_fatty_acids_pictures_slideshow/article.htm) are a class of essential polyunsaturated fatty acids with the initial double bond in the third carbon. Foods high in [[omega-3]](https://www.medicinenet.com/omega-3_fatty_acids-oral/article.htm) fatty acids include salmon, halibut, sardines, albacore, trout, herring, walnut, [[flaxseed]](https://www.medicinenet.com/flaxseed_linum_usitatissimum-oral/article.htm) oil, and canola oil. Other foods that contain omega-3 fatty acids include shrimp, clams, light chunk tuna, catfish, **cod**, and **spinach**.* *Omega-6 fatty acids are a class of essential polyunsaturated fatty acids with the initial double bond in the sixth carbon position. Examples of foods rich in omega-6 fatty acids include **corn**, safflower, **sunflower**, **soybean**, and cottonseed oil.* *Trans fatty acids (trans fats) are made through hydrogenation to solidify liquid oils. Heating omega-6 oils, such as corn oil, to high temperatures creates trans fats. Trans fats increase the shelf life of oils and are found in vegetable shortenings and in some margarines, commercial pastries, fried foods, crackers, cookies, and snack foods. **The intake of trans fatty acids increases blood LDL-cholesterol** (\"bad\" cholesterol), decreases [[HDL cholesterol]](https://www.medicinenet.com/cholesterol_levels_pictures_slideshow/article.htm) (\"good cholesterol\"), and raises the risk of coronary [[heart disease]](https://www.medicinenet.com/heart_disease_quiz/quiz.htm)* ***Hydrogenation** converts liquid vegetable oils into solid or semi-solid **fats**, such as those present in margarine. During **hydrogenation**, the double bonds are converted to single bonds in the reaction. In this way unsaturated fats can be made into saturated fats -- they are hardened. The usual purpose is that they don\'t spoil as quickly as unsaturated fats. By hydrogenating, it is also easier to store the product.* **Phospholipids** - A phospholipid is a molecule made up of: One glycerol molecule bonded to two fatty acids by ester bonds and also bonded to phosphate group by Phosphate-ester bond  - The polar head consists of the phosphate and glycerol - Phospholipids are used to synthesize biological membranes. **Cholesterol** - This is a lipid. - Cholesterol is made in the **liver** and also obtained from **fatty foods**. - The structure of cholesterol is - In the cell membranes cholesterol has 2 major roles; 1. Controls fluidity so that the cell membrane is not too fluid or too rigid 2. Provides the mechanical strength to the cell membranes. So, the cell membranes with little or no cholesterol easily break down. ***Where do we get cholesterol?** Our bodies have the ability to make all of the cholesterol needed for proper functioning once we reach childhood, but most people also get cholesterol from foods. Different foods vary in the amount of cholesterol they contain. Only animal products have cholesterol; plant based products may contain fat, but they do not contain cholesterol.* **TRANSPORT SYSTEMS IN HUMANS** **Cardiovascular system/Circulatory system** - This is a mass transport system in humans. - It consists of the heart (cardio) and the blood vessels (vascular). - *Circulation is the passage of blood through the blood vessels.* Give two reasons why many animals have a circulatory system/cardiovascular system. - They have small surface area to volume ratio; so circulatory system overcomes limitations of diffusion. - Animals have high nutrient demand/requirement; so circulatory system provides a mass/bulk transport system. - Humans have small surface area to volume ratio and so cannot rely on diffusion for the exchange and transport of substances in their bodies. So, they need a specialized transport system to **overcome the limitation of diffusion in meeting the requirements of the organisms through mass transport of substances. Cardiovascular system overcomes the limitation of diffusion in meeting the requirements of the organisms through mass transport of substances.** - Small organisms such as amoeba have large surface area to volume ratio and therefore they rely on diffusion for exchange of substances and movement of these substances inside the organism. The following cubes illustrate the concept of surface area (SA) to volume ratio  **BLOOD VESSELS** - Mammals such as humans have closed circulatory system. This means that blood flows in vessels. These vessels are; 1. Arteries 2. Veins 3. Capillaries - Some organisms such as insects have open circulatory system. The heart of the insect is a long tube. It pumps blood into the body cavity/spaces so that blood surrounds the cells. The blood then passes back into the heart from the body cavity. The insect does not need blood vessels to transport blood around the body because; 1. Insects have large surface area to volume ratio and so **diffusion** of blood is enough to exchange materials. 2. The cells are always in contact with the blood. 3. The heart and blood are close together hence movement of blood back to the heart is fast 4. Low metabolism (chemical reactions in a cell) in insects and therefore only need diffusion of blood to get the requirements Closed circulatory system - Humans have closed circulatory system. This means that blood flows in tubes called blood vessels - The biological importance of closed circulatory system is that humans, having small surface area to volume ratio; this system increases pressure of blood so that it is transported to all parts of the body. **The blood vessels, structures and their functional significance** +-----------------------+-----------------------+-----------------------+ | **Vessel** | **Structure** | **Functional | | | | significance** | +=======================+=======================+=======================+ | 1. Artery | Tunica adventitia : | Collagen fibres | | | collagen fibres | provide strength so | | | | that arteries | | | : Some elastic | **withstand high | | | fibers. | pressure** of blood | | | | without bursting. In | | | | addition, they | | | | prevent | | | | overstretching of | | | | arteries. | | | | | | | | They **stretch** and | | | | **recoil** the | | | | arteries to | | | | **maintain pressure | | | | of blood** | +-----------------------+-----------------------+-----------------------+ | | Tunica media | They **contract** and | | | | **relax** to alter | | | a. Smooth muscles | the diameter of lumen | | | | to **regulate blood | | | b. Elastic fibres | flow.** | | | | | | | c. Some collagen | They **stretch** and | | | fibres | **recoil** the | | | | arteries to | | | | **maintain pressure | | | | of blood** or | | | | smoothen blood flow. | | | | | | | | For strength to | | | | withstand high | | | | pressure of blood. | +-----------------------+-----------------------+-----------------------+ | | Tunica intima | It reduces friction | | | (endothelium) | between the walls and | | | | the blood **to ease | | | Smooth, single layer | blood flow** | | | of cells (squamous | | | | epithelium). | | +-----------------------+-----------------------+-----------------------+ | | Narrow lumen | **To maintain high | | | | pressure of blood.** | +-----------------------+-----------------------+-----------------------+ | 2. Vein | Tunica adventitia -- | Blood is under low | | | thinner collagen | pressure due to wider | | | fibres | lumen hence veins | | | | cannot burst. | +-----------------------+-----------------------+-----------------------+ | | Tunica media | No pulse of blood so | | | | no alteration of the | | | a. Very little | diameter of the | | | smooth muscle | lumen. | | | | | | | b. Very little | No pulse of blood | | | elastic fibres | hence no stretching | | | | and recoiling of | | | | veins | +-----------------------+-----------------------+-----------------------+ | | Tunica intima -- | Reduces friction | | | (endothelium) -- | between the wall and | | | smooth, single layer | blood to **ease blood | | | of cells-squamous | flow** | | | epithelium. | | +-----------------------+-----------------------+-----------------------+ | | Wide lumen | To reduce resistance | | | | to blood flow | +-----------------------+-----------------------+-----------------------+ | | Series of valves | To stop the back flow | | | | of blood as it is | | | | under low pressure | +-----------------------+-----------------------+-----------------------+ | 3. Capillaries | Very thin wall (1 | Reduces/shortens | | | cell thick wall) | diffusion distance | | | | during exchange of | | | | materials. | +-----------------------+-----------------------+-----------------------+ | | Pores/gaps in the | Allows exchange of | | | wall | substances | +-----------------------+-----------------------+-----------------------+ | | Capillary network/bed | Increases surface | | | | area of exchange of | | | | substances | +-----------------------+-----------------------+-----------------------+ | | No valves | Narrow lumen | +-----------------------+-----------------------+-----------------------+ | | No collagen fibres | So that they can | | | | **easily fit between | | | No smooth muscles and | cells and speed up | | | | diffusion across | | | No elastic fibres | their thin walls** | +-----------------------+-----------------------+-----------------------+  **NB. In the artery, the thickest portion is for elastic fibres, then collagen fibres and then smooth muscle.** **Structural differences between veins and capillaries** +-----------------------------------+-----------------------------------+ | **Veins** | **Capillaries** | +===================================+===================================+ | 1. 3 layers | 1 layer | | | | | 2. Valves | No valves | | | | | 3. No pores | Pores | | | | | 4. Wider lumen | Narrower lumen | | | | | 5. Have collagen fibres, elastic | None | | fibres and smooth muscles | | +-----------------------------------+-----------------------------------+ **Structural differences between arteries and capillaries** +-----------------------------------+-----------------------------------+ | **Arteries** | **Capillaries** | +===================================+===================================+ | 1. 3 layers | 1 layer | | | | | 2. No pores | Pores | | | | | 3. Collagen fibres, elastic | None | | fibre and smooth muscles | | | | No valves | | 4. Some have valves | | +-----------------------------------+-----------------------------------+ Similarities; both have no series of valves and both have endothelium **Structural differences between arteries and veins** +-----------------------------------+-----------------------------------+ | **Arteries** | **Veins** | +===================================+===================================+ | 1. Thick walls | Thin walls | | | | | 2. Small lumen | Wide lumen | | | | | 3. No series of valves | Have series of valves | | | | | 4. Deeply seated | Shallowly seated | +-----------------------------------+-----------------------------------+ **Functional differences between arteries and veins** +-----------------------------------+-----------------------------------+ | **Arteries** | **Veins** | +===================================+===================================+ | 1. Carry blood away from the | Carry blood to the heart | | heart | | +-----------------------------------+-----------------------------------+ | 2. Except for pulmonary artery | Except for pulmonary vein and | | and umbilical cord artery, | umbilical cord vein, they carry | | they carry oxygenated blood | deoxygenated blood | +-----------------------------------+-----------------------------------+ | 3. They carry blood under high | They carry blood under low | | pressure | pressure | +-----------------------------------+-----------------------------------+ | 4. Blood flows in pulses | Blood flows smoothly. | +-----------------------------------+-----------------------------------+ **Describe how the blood moves in veins from the body back to the heart** 1. Series of semi-lunar valves that prevent back flow of blood. 2. Contraction of skeletal muscles so that they push on veins for blood to move forward. 3. Breathing in (inhalation/inspiration)- this reduces pressure in the thoracic cavity forcing the blood to move towards it. 4. Diastole (relaxation of the heart muscle)- this causes reduced pressure in the heart and the blood moves towards it. Explain why the structure of a vein differs from the structure of an artery +-----------------------------------------------------------------------+ | 1\. Walls have less collagen/walls are thinner; because blood | | pressure is lower | | | | 2\. Veins have less elastic fibers; as they do not need to stretch | | and recoil | | | | 3\. Veins have a series of valves; to prevent the back flow of blood | | | | 4\. Veins have a large lumen; to reduce resistance to blood flow | +-----------------------------------------------------------------------+ Explain how the structure of an artery is related to its function. +-----------------------------------+-----------------------------------+ | Collagen fibres provide strength | | | so that arteries **withstand high | | | pressure** of blood to prevent | | | overstretching and bursting of | | | arteries. | | | | | | Elastic fibres to allow stretch | | | and recoil to maintain blood | | | pressure | | | | | | Smooth muscle in the wall to | | | contract and relax to alter | | | diameter of lumen to regulate | | | blood flow. | | | | | | Smooth endothelium lining to | | | reduce friction between wall and | | | blood | | | | | | Narrow lumen to maintain high | | | pressure of blood. | | +-----------------------------------+-----------------------------------+ **The human heart** **Explain why many animals need a heart (2)** +-----------------------------------------------------------------------+ | 1\. To generate/produce pressure that ensures mass transport of | | substances throughout the body | | | | 2\. To overcome the limitations of diffusion because humans and | | other large mammals have small | +-----------------------------------------------------------------------+ **Describe the structure of the mammalian heart.** 1. There are four chambers in the heart: two upper atria and two lower ventricles. 2. It is made up of two pumps, left and right, separated by a septum. 3. The walls of the heart consist of cardiac muscles/heart muscles: the atria have thin cardiac muscles, right ventricle has thick cardiac muscles and left ventricle has thicker cardiac muscles. 4. Atrioventricular valves (AV valves) are located between the atria and the ventricles while semilunar valves are **located at the base** of the aorta and the pulmonary artery. 5. The aorta branches from the left ventricle to the body. Pulmonary vein joins the left atrium from the lungs. Pulmonary artery branches from the right ventricle to the lungs. Superior and inferior vena cava join the right atrium from the upper part of the body above the chest (chest is part of upper section) and lower part of the body, below the chest, respectively. Coronary arteries branch from the aorta and spread over the surface of the heart muscle. 6. Papillary muscles in the inner walls of the ventricles connect to the AV valves via tendons/heartstrings. 7. The sino-atrial node (SAN) is in the walls of the right atrium. Atrio- ventricular node (AVN) is located at the lower portion of the right atrium adjacent to the septum. A bundle of His comes from the AV node and moves along the septum and leads to Purkinje fibres/Purkyne fibres in the ventricular walls. **The external and internal structures of the human heart** 1. **The arc is aorta** 2. **The T shape is right and left pulmonary arteries** 3. **Structures below the upper part of T are pulmonary veins (sometimes on the right and left or sometimes are together on one side).** 4. **Vertical structure on the right side of heart is vena cava** 5. **Blood vessels on the surface of heart: coronary arteries and coronary veins** X left pulmonary artery (T like structure)\ W Aorta (Arc like structure) Y Pulmonary veins (Below the T like structure) A Superior vena cava (Vertical structure on the right) B Inferior vena cava (vertical structure on the right) Z Coronary arteries (Always on the surface) F Right atrium E Left atrium D Right ventricle C Left ventricle  A: superior vena cava B: aorta C: left pulmonary artery D: pulmonary veins E: left atrium F: bicuspid valve G: left ventricle H: septum I: left semilunar valve J: right semilunar valve K: right ventricle L: inferior vena cava M: tricuspid valve N: right atrium O: right pulmonary artery **Explain why a mammalian heart is divided into right side and left side.** - It keeps oxygenated and deoxygenated blood separate. This creates steep concentration gradient of gases in the lungs and tissues for efficient gas exchange. - Allows for different pressures, lower to the lungs to protect lung capillaries from bursting and higher to the body to pump blood to all parts of the body. **The heart as a double pump** - The human heart is a double pump. - These 2 pumps are joined together and work in perfect synchrony. - The right and the left pumps of the heart are separated by a septum. - The right side of the heart (right pump) receives deoxygenated blood from the body via the vena cava, and it pumps it to the lungs for oxygenation and removal of CO~2~ through the pulmonary artery. - The left side of the heart (left pump) receives oxygenated blood from the lungs through pulmonary vein and pumps it to the body via the aorta. - The blood in the left side of the heart does not mix with the blood in the right side of the heart. **The cardiac muscle** - The walls of the heart are made up of cardiac muscle - Cardiac muscle is also called heart muscle. - It has special properties 1. it contracts rhythmically without resting or fatigue. 2. It contracts on its own without being stimulated by nervous system and hormonal system. This is myogenic contraction. - Atrial walls have thinner cardiac muscles while ventricle walls have thicker cardiac muscles. However, the left ventricle wall has thicker muscles than the right ventricle wall. **Thickness of cardiac muscle** - The thickness of the cardiac muscle is proportional to the strength of contraction of the muscle and the amount of the pressure produced by the muscle. The thicker the muscle, the more the contraction and the greater the pressure produced and vice versa. a. **Thin cardiac muscles of the atria** - They pump blood to the shortest distance when they contract i.e. from the atria to the ventricles via atrio-ventricular valves (AV valves) i.e. tricuspid and bicuspid (mitral) valves. - As the blood enters the atria via vena cava and pulmonary vein, due to its weight, the A.V valves open and allow two-third of the ventricles to be filled passively with blood so that the contraction of the atria tops up the blood in the ventricles. Explain the importance of the thin cardiac muscle of the atria 1. When it contracts it produces lower pressure to push blood to a very short distance hence no need to have thick muscles. 2. Only a top up or a third of blood is moved from atria to the ventricles and so no need to have thick muscles b. **Thick muscles of the right ventricle** - When it contracts, it pumps blood to the lungs via pulmonary artery and back to the left atrium via pulmonary vein. This circulation of blood from the heart to the lungs and back to the heart is called **pulmonary circulation**. - As compared to the cardiac muscles of the left ventricle, the right ventricle has thinner muscles to contract less powerfully to produce lower pressure to the lungs for the following reasons; 1. *to prevent the bursting of lung capillaries* 2. *to ensure there is enough time for exchange of gases (the blood to absorb O~2~ and to remove CO~2~).* 3. *to prevent ultra-filtration in the lungs* c. **Thicker muscles of the left ventricle** - These muscles contract powerfully to produce more pressure that pumps blood from the left ventricle to the body via the aorta and back to the right atrium via the vena cava. This circulation of blood from the heart to the body and back to the heart is called **systemic/body circulation**. - These thicker cardiac muscles of the left ventricle have the following roles: 1. To pump blood to all parts of the body. 2. To overcome the effect of elastic recoil of arteries during cardiac diastole to prevent backflow of blood from arteries back to left ventricles. 3. To overcome the combined resistance of multiple capillary network. **Double circulation in humans** - Double circulation is when the blood flows through the heart twice in one circulation. - It involves pulmonary circulation (circulation of blood from the heart to the lungs and back to the heart) and systemic circulation (circulation of blood from the heart to the body and back to the heart).  **NB** Fish have single circulation where blood flows from the body to the heart, then from the heart to the gills and from the gills it does not flow to the heart but it flows to the body. So, it flows to the heart once in a single circulation. Fish has one atrium and one ventricle. **Advantages of double circulation in humans;** 1. **Allows differential pressure to the lungs and to the body so that the lungs have lower pressure of blood and the body has higher pressure:** - Low pressure to the lungs ensures that there is enough time for the blood to absorb O~2~ & remove CO~2,~ prevents the capillaries from bursting and to prevent ultra filtration. - High pressure to the body ensures that the blood reaches all parts of the body, it overcomes the effects of elastic recoil during cardiac diastole and the effects of the combined resistance of multiple capillary networks. 2. **No mixture of oxygenated and deoxygenated blood. Oxygenated blood is in the left side and deoxygenated in the right side. This creates steep concentration gradient of gases in the lungs and tissues for efficient gas exchange.** 3. Muscles of mammals are big and metabolically active and so need a lot of oxygen and double circulation serves this purpose. **Blood vessels associated with the heart** 1. Inferior vena cava -- it carries deoxygenated blood from the lower part of the body, below the chest, to the right atrium. 2. Superior vena cava -- it carries deoxygenated blood from the upper part of the body; head, neck, arms and chest to the right atrium. ***NB: vena cava is the largest vein*** 3. Pulmonary artery -- together with umbilical cord arteries, they are the only arteries that carry deoxygenated blood. It carries deoxygenated blood from the right ventricle to the lungs for the removal of CO~2~ and absorption of O~2~. **At the base of the pulmonary artery** there is a valve called pulmonary (right) semi-lunar valve whose role is to prevent the back flow of blood from the pulmonary artery back into the right ventricle. 4. Pulmonary vein -- together with umbilical cord vein, they are the only veins that carry oxygenated blood. It carries oxygenated blood from the lungs to the left atrium. 5. Aorta -- this is the largest artery. It carries oxygenated blood from the left ventricle to the body in order to deliver requirements such as oxygen to the tissues. **At the base of aorta**, there is a valve called aortic (left) semi-lunar valve that prevents the backflow of blood from the aorta back into the left ventricle. 6. Coronary arteries- These are right and left coronary arteries that supply the heart muscles with requirements. They are the first arteries to branch from the aorta. They are found on the left part of the heart. 7. Coronary veins/cardiac veins- they carry deoxygenated blood from heart muscle to **coronary sinus** (coronary veins join to form a large vessel called coronary sinus). The coronary sinus delivers deoxygenated blood into right atrium. **VALVES ASSOCIATED WITH THE HEART** - They are atrio-venticular valves found between the atria and the ventricles and the semi lunar valves found at the base of arteries. These are; 1. **Bicuspid valve (or mitral valve)** - It is found between the left atrium and the left ventricle. - its functions are: a. allows blood to flow from the left atrium into the left ventricle. b. Prevents the backflow of blood from the left ventricle to the left atrium during ventricular systole, so that the blood enters the aorta. 2. **Tricuspid valve** - It is found between the right atrium and the right ventricle. - Its functions are; a. It allows blood to flow from the right atrium into the right ventricle. b. It prevents the backflow of blood from the right ventricle in the right atrium so that the blood enters the pulmonary artery. 3. **Right semi-lunar valve (Pulmonary semi lunar valve)** i. It is located at the base of pulmonary artery ii. It prevents back flow of blood from the pulmonary artery back to the right ventricle during cardiac diastole 4. **Left semi-lunar valve (Aortic semi lunar valve)** i. It is located at the base of aorta ii. It prevents back flow of blood from the aorta back to the left ventricle during cardiac diastole Suggest why a faulty left AV valve can cause bursting of lung capillaries and also cause symptoms of breathlessness and lack of energy - During ventricular systole there is backflow of blood from left ventricle to left atrium. This lowers blood pressure and volume of blood to the body causing less O~2~ to reach the tissues. Breathlessness is due to the body trying to take in more oxygen. Tiredness is due to lack of energy that is due to reduced aerobic respiration. - Due to backflow, blood pressure in the lung capillaries increase that can lead to bursting of these lung capillaries. Some babies have a hole in the septum and if not repaired babies may not survive. Suggest why. - Oxygenated and deoxygenated blood will mix during ventricular systole and diastole. - During ventricular systole, some blood will move to right ventricle through the hole, leaving less blood with less oxygen moving to the body causing tiredness and breathlessness - Blood pumped to the lungs from right ventricle has a higher oxygen concentration, reducing concentration gradient of oxygen causing less efficient gas exchange so that blood moving to the body tissues has less oxygen causing tiredness and breathlessness. - During diastole, blood may move from the right ventricle to the left ventricle and this blood with more carbon dioxide can be pumped by the left ventricle into the aorta to the rest of the body reducing concentration gradient of carbon dioxide, hence reducing efficient gas exchange. - Systemic blood pressure will be low and so less oxygen will move to the body. **Control of the opening and closing of the atrio-venticular valves (AV valves)** - During ventricular systole, the papillary muscles contract producing a force that pulls on the heartstrings/tendons to close the valves so that these valves do not turn inside out/invert during ventricular systole. - During diastole, papillary muscles relax and this causes the heartstrings to loosen/slacken to open the valves. - So, heartstrings prevent the valves from inverting (turning inside out) during ventricular systole while papillary muscles adjust tension in the heartstrings, i.e. during ventricular systole they contract to pull on tendons and close the valves and during diastole they cause the valves to open. **How cardiac muscles are supplied with requirements;** - This is called coronary circulation. - The first arteries to branch from the aorta are right and left coronary arteries (major arteries) that further branch into arterioles and finally branch into capillaries that **that reach all the cardiac muscle cells.** - Through diffusion, the requirements such as glucose and oxygen enter the cardiac muscle cells through capillary walls. **How the heart muscles removes wastes** - This is called coronary circulation. - Through diffusion, wastes such as urea and CO~2~ from the cardiac muscle cells enter the capillaries. - These capillaries join to form venules (small veins) that further join to form cardiac veins/ coronary veins that join to form a large vessel called coronary sinus that carries deoxygenated blood to the right atrium. **CARDIAC CYCLE** - It is the sequence of events that take place in one heart beat and it lasts for 0.83 second. It is initiated at the sino-atrial node (SAN) also called pacemaker. These events are: Atrial systole (0.11s), ventricular systole (0.31s) and cardiac diastole (0.41s). **Events of the cardiac cycle** **1. Atrial systole** - This is the contraction of the atria when they are filled up with blood. - Its role is to pump blood into the ventricles from the atria via AV valves. - It lasts for about 0.11s. - During atrial systole, AV valves are open. - During atrial systole, semi-lunar valves are closed. - During atrial systole, atria are contracted and ventricles are relaxed. 2\. Ventricular systole - This is the contraction of the ventricles when they are filled up with blood. - Its role is to pump blood into the aorta and the pulmonary artery from the ventricles. - It lasts for 0.31s - At the start and during ventricular systole, the AV valves close to prevent the backflow of blood from the ventricles into the atria and to build up pressure in the ventricles. - During ventricular systole, semi-lunar valves are forced to open. - During ventricular systole, atria are relaxed and ventricles are contracted. 3\. Cardiac Diastole - This is the relaxation of the heart after ventricular systole. - During diastole the whole heart is relaxing, *reducing pressure in the heart* so that blood flows into the atria via the vena cava and pulmonary vein, hence *refilling the heart with blood*. - So, the role of the cardiac diastole is to refill the heart with blood. - It lasts for 0.41 second. - During diastole, the AV valves open. - During diastole the semi-lunar valves are closed. Describe and explain the role of heart valves during the cardiac cycle. - During atrial systole, AV valves open so that blood flows from atria to ventricles. Semi lunar valves are closed. - During ventricular systole, AV valves close to prevent backflow of blood into the atria and also build up pressure in the ventricles. Pressure from the ventricular systole causes semi-lunar valves to open so that blood leaves ventricles and enter arteries (pulmonary artery and aorta). - During cardiac diastole, semi- lunar valves close to prevent backflow of blood from aorta or pulmonary arteries back to the ventricles. During cardiac diastole, AV valves open to allow blood to enter ventricles from atria. Past paper Question June 2010 Q2 a. Read through the following passage about the heart and its major blood vessels, then write on the dotted lines the most appropriate word or words to complete the passage. **(5)** The mammalian heart consists of four chambers, two upper chambers called \...\...\...\...\...\...\...\...\...\...\...\...\...\...\..... and two lower chambers called ventricles. The \...\...\...\...\...\...\...\...\...\...\...\...\...\...\..... carries oxygenated blood away from the \...\...\...\...\...\...\...\...\...\...\...\...\...\...\....ventricle to the cells of the body and the pulmonary \...\...\...\...\...\...\...\...\...\...\...\...\...\...\..... carries deoxygenated blood to the lungs. The \...\...\...\...\...\...\...\...\...\...\...\...\...\...\..... returns deoxygenated blood back to the heart from the body. (b) The diagram below shows the structure of the heart. Suggest which stage of the cardiac cycle is shown in the diagram and give a reason for your answer. **2 marks** **Pressure changes in the left part of the heart during cardiac cycle.** - During atrial systole, the pressure in the left atrium is higher than the pressure in the left ventricular. Bicuspid valve is open during atrial systole so that blood enters the left ventricle. - When the pressure of the left ventricle exceeds the pressure of the left atrium, the bicuspid valve closes to prevent the backflow of blood from the left ventricle into the left atrium and to build up pressure in the left ventricle. The pressure of the left ventricle rises suddenly and forces open the left semi-lunar valve located at the base of aorta. - The pressure in the aorta begins to rise but it is less than the pressure in the left ventricle. When the pressure in the aorta exceeds the pressure in the left ventricle, the left semi-lunar valve closes to prevent the backflow of blood to the left ventricle from the aorta. This causes the pressure in the left ventricle to suddenly drop causing relaxation of the heart (cardiac diastole) and during this time, there is refilling of the left atrium that causes the opening of the bicuspid valve. - The pressure in the aorta continues to reduce as the blood flows to the tissues.  **CALCULATING THE HEART RATE FROM GRAPHS** - Heart rate is the number of beats per minute - Identify two repeating points and calculate the difference in time (in seconds) and this is the time for one heart beat. Then calculate the number of beats per minute (60 seconds) to get heart rate in bpm. During cardiac cycle, the pressure in the right ventricle rises to a maximum of about 3.3 kPa as opposed to 15 kPa in the left ventricle. Describe and explain this difference. *Left ventricle has thicker muscles than right ventricle and so contract more powerfully to generate more pressure unlike the right ventricle.* *The pressure in the left ventricle is to pump blood to all parts of the body, to overcome the effects of elastic recoil and to overcome the combined resistance of multiple capillary networks. The low pressure in the right ventricle is to ensure there is enough time for the blood to absorb O~2~ and to remove CO~2~, to prevent the bursting of lung capillaries and prevent ultra filtration.* Immediately after the ventricular systole, which ventricle has higher pressure? And why? *Right ventricle;* *This is because it has relatively thinner muscles than the left ventricle and therefore does not pump out all the blood leading to relatively more pressure.* **THE CONTROL OF THE CARDIAC CYCLE.** - The heart is myogenic (Contraction originates in the muscle tissue rather than from nerve impulses) - The Sino atrial node (SAN) contracts and produces impulse. - This impulse **spreads over the walls of atria**, causing atrial systole that lasts for about 0.11 second. - The impulse then pass to the atrio-ventricular node (AVN) where it delays for about 0.1 second. - This delay has two roles: i. Atrial systole is **completed** before ventricular systole **starts** so that blood flows from the atria into the ventricles. ii. Ventricles are filled with blood before they contract. - The impulse **passes into** the bundle of His that **carries the impulse along the septum to the apex of the heart and pass it to** the Purkyne tissue/Purkinje fibres that **carry the impulse to the** ventricular walls. - The impulse **spreads over the ventricle walls** causing contraction from the apex upwards. - Blood is squeezed into the arteries (pulmonary artery and aorta). This is ventricular systole.  Image result for location of SAN and AVN in human heart **Pressure changes in the blood vessels**  **1. Pressure in the arteries** - The pressure of blood in the arteries varies with the heart beat i.e. when the heart contracts, the blood pressure increases and when the heart relaxes and refills, the blood pressure in the arteries decreases. In the arteries, there is a high pressure because of the following reasons. a. Little peripheral resistance due to relatively wider lumen compared to arterioles and capillaries. b. Blood in arteries is under high pressure because these arteries are near the heart and so they experience the pulsing of the heart. (**Pulse**: The rhythmic dilation of an artery that results from beating of the **heart**. **Pulse** is often measured by feeling the arteries of the wrist or neck). -- -- **2. Pressure in the arterioles** - The pressure gradually decreases due to: a. Increased peripheral resistance due to narrower blood vessels. b. The artery divides into more arterioles, reducing the pressure. In other word, total cross-sectional area of arterioles are greater than the arteries. **3. Pressure in the capillaries** - Pressure decreases due to; a. Increased peripheral resistance due to very narrow blood vessels. b. They are far away from the heart and so do not experience the pulsing of heart. c. Loss of substances into the tissues from the blood due to ultra-filtration. d. Arterioles divide into many capillaries (capillary network) that reduce the pressure. In other words total cross-sectional area of capillaries are greater than the arterioles. **Questions** 1. Describe why the blood pressure in the capillaries does not increase even though they are very narrow? *This is because they form many capillaries which together have **greater total cross section area** than that of the main artery and so the **pressure is shared** by these many capillaries hence reducing the pressure.* 2. What is the importance of low blood pressure in the capillaries? - *It gives enough time for the exchange of materials with the tissues through diffusion.* - *To prevent bursting of capillaries* 3. What are the adaptations of capillaries to exchange of substances? - *The wall is one cell thick to reduce diffusion distance* - *The capillary wall has pores to allow for the exchange of substances* - *They form capillary network to increase the SA of exchange.* - *No collagen fibers , smooth muscles and elastic fibres* So that they can **easily fit between cells and speed up diffusion across their thin walls** 4. What controls the pressure of blood in the arteries? a. *Contraction and relaxation of the heart. Contraction increases pressure in the arteries and relaxation decreases pressure.* b. *Atherosclerosis. It can permanently change the arteries by narrowing them and cause permanent rise in pressure which can lead to cardiovascular diseases.* c. *Thrombosis (clot formation)* 5. What is the disadvantage of elastic recoil in the artery? And how does the heart overcomes this. *Elastic recoil is the shrinking of the artery when elastic fibres slacken/loosen due to the relaxation of the heart. This can lead to the backflow of blood. However, due to powerful contraction of the large muscular left ventricle, more pressure is produced which overcomes the effect of elastic recoil.* **BLOOD PRESSURE MEASUREMENTS** - Blood pressure is measured in millimeters of mercury (mmHg) - Blood pressure is measured using an apparatus called sphygmomanometer - Systolic reading of a 120mmHg and a diastolic reading of 80mmHg i.e. 120/80 is regarded as normal - A sustained value of over 140/90 is called hypertension/HBP. This damages arteries. - A sustained value of 90/60 or lower is called hypotension/LBP. A weakened heart will produce hypotension. NB - *The systolic pressure is the maximum pressure in the arteries when ventricles contract;120mmHg* - *The diastolic pressure is the minimum pressure in the arteries when the heart relaxes; 80mmHg* - *The two are measured using sphygmomanometer.* [TRANSPORT OF OXYGEN AND CARBON DIOXIDE] [Haemoglobin] - It is a protein made up of 4 polypeptides, 2 alpha and 2 beta - Each polypeptide contains one haem group. - Each haem group has an iron. Each iron combines with an oxygen molecule. Overall, each haemoglobin molecule can combine with 4 oxygen molecules (8 oxygen atoms). - Haemoglobin picks oxygen from the lungs where there is high partial pressure of oxygen and releases the same oxygen to the respiring cells where there is low partial pressure of oxygen. *NB: One RBC has about 270 million haemoglobin molecules* State what is meant by the term partial pressure. - *Pressure exerted by one type of gas in a mixture of gases* Suggest why the partial pressure of oxygen in the air in the alveoli is lower than in the atmosphere. Oxygen diffuses into lung capillaries to be used by cells for respiration Explain why the partial pressure of oxygen decreases as the blood flows through the arteries and into the veins. - arteries take blood to the cell while veins take blood away from cells - oxygen diffuses out of the capillaries into cells because there is a lower partial pressure of oxygen in the cells - Carbon dioxide diffuses into blood - So blood in veins has low partial pressure of oxygen Picking of oxygen in the lungs by the haemoglobin **The haemoglobin dissociation curve (oxygen dissociation curve)** - This is a curve that shows percentage saturation of haemoglobin with oxygen when the RBCs are in increasing partial pressure of oxygen.  - At low partial pressure of oxygen, the percentage saturation of haemoglobin is very low because haemoglobin is combined with very little oxygen. - At high partial pressure of oxygen, the percentage saturation of haemoglobin is very high because it is combined with large amounts of oxygen. - In the lungs, where the partial pressure of oxygen is high; this haemoglobin will be **95-97%** saturated with oxygen. - In an actively respiring muscle, where the partial pressure of oxygen is low, the haemoglobin will be about **20-25%** saturated with oxygen; This means that haemoglobin coming from the lungs carries a lot of oxygen; as it reaches a muscle, it releases around three-quarters of it. - The released oxygen diffuses out of the RBCs & into the muscle where it can be used in respiration. **The S-shaped curve of haemoglobin dissociation curve** - haemoglobin is composed of four polypeptides - binding of the first oxygen molecule is difficult - binding of the other oxygen molecules becomes easier due to a conformational change of haemoglobin. This is cooperative bonding. - as Hb becomes saturated, less oxygen can bind and so the curve flattens out Question As altitude (height above sea level) increases, the partial pressure of oxygen in the air decreases. Llamas are mammals that are adapted to living at high altitudes. The graph shows the oxygen dissociation curves for llama haemoglobin and human haemoglobin. Describe and explain the differences between the dissociation curves. Use the information in the graph to support your answer. **(4)** - Dissociation curve for the llama is to the left of that for the human; ***therefore llama haemoglobin has a higher affinity for oxygen; so, llama haemoglobin will be fully saturated with oxygen at lower partial pressures*** - This is necessary as there is less oxygen available in the atmosphere at high altitudes where llamas live **Describe and explain the oxygen dissociation curve of the fetus and the mother.**  - Dissociation curve for the foetus is to the left of the adult. - Therefore foetal haemoglobin has a higher affinity for oxygen - Foetal haemoglobin will be **fully saturated with oxygen at lower partial pressures** - The higher affinity of foetal haemoglobin for oxygen is necessary because, it has to absorb oxygen from the adult haemoglobin at the same partial pressure of oxygen Release of oxygen into the respiring cells by the haemoglobin - **Bohr effect/shift is** when high partial pressure of CO­~2~ in the respiring tissues causes haemoglobin to release oxygen. Bohr effect allows O~2~ to be released by haemoglobin needed for aerobic respiration. - Carbon dioxide diffuses from the respiring cells, into the tissue fluid and then diffuses across the capillary wall into the blood plasma. 5% of carbon dioxide remains in the blood plasma and 95% diffuses into the cytoplasm of RBCs. - In the cytoplasm of RBCs the following takes place for the 95% carbon dioxide: a. 10% of CO~2­~ combines directly with oxyhaemoglobin molecules to form carbaminohaemoglobin, which changes its conformation and releases oxygen that diffuses into blood plasma, tissue fluid and into respiring cells to provide ATP. b. 85% of CO~2~ combines with water catalyzed by carbonic anhydrase to form carbonic acid (H~2~CO~3~) that dissociates into hydrogencarbonate ions (HCO~3~^-^) and hydrogen ions (H^+^). Oxyhaemoglobin (HbO~8~) in the cytoplasm of RBC readily combines with the hydrogen ions, forming haemoglobinic acid, HHb. In doing so, it changes its conformation and releases the oxygen which it is carrying. The formation of HHb has two effects: i. Increases the pH of cytoplasm of RBC so that it is close to neutral. Oxyhaemoglobin mops up the hydrogen ions to form HHb. So oxyhaemoglobin acts as a buffer. ii. Releases O~2.~ Oxyhaemoglobin combines with hydrogen ions to become HHb so that it releases O~2.~ This is called Bohr effect. [SUMMARY OF HOW OXYHAEMOGLOBIN RELEASES O2 IN THE RESPIRING CELLS.] 1. Oxyhaemoglobin combines with carbon dioxide to form carbaminohaemoglobin (CO~2~ + Hb) that causes conformational change to release oxygen. 2. Oxyhaemoglobin combines with hydrogen ion (H^+^), to form haemoglobinic acid (HHb) that causes conformational change to release oxygen **[TRANSPORT OF CARBON DIOXIDE FROM RESPIRING TISSUES TO THE LUNGS]** [SUMMARY OF HOW CARBON DIOXIDE IS TRANSPORTED TO THE LUNGS] 1. 5% of carbon dioxide dissolves in solution in the blood plasma and is transported to lungs 2. 10% of carbon dioxide is transported by haemoglobin as carbaminohaemoglobin in the RBC 3. 85% of carbon dioxide is transported as hydrogen carbonate ions(HCO~3~^-^) in blood plasma [DETAILS OF HOW CARBON DIOXIDE IS TRANSPORTED TO THE LUNGS] - Carbon dioxide diffuses from the respiring cells, into the tissue fluid and then diffuses across the capillary wall into the blood plasma. 1. 5% of CO~2~ remain as CO~2~ molecules & dissolve in the blood plasma and it is transported in this way to the lungs. 2. The remaining 95% of carbon dioxide diffuse into the cytoplasm of RBCs where: a. 10% of CO~2­~ combines directly with haemoglobin molecules to form carbaminohaemoglobin and carbon dioxide is transported in this way to the lungs. In the lungs, due to diffusion gradient of carbon dioxide between the blood in lung capillaries and alveoli,carbon dioxide detaches from the haemoglobin and diffuses from the lung capillaries into the alveoli. b. 85% of CO~2~ combines with water catalyzed by carbonic anhydrase to form carbonic acid (H~2~CO~3~) that dissociates into hydrogencarbonate ions (HCO~3~^-^) and hydrogen ions (H^+^). Hydrogencarbonate ions diffuse into the blood plasma and is transported to lungs. **NB:** When HCO~3~^-\ ­­^diffuses into the blood plasma, chloride ions diffuse from the blood plasma into the cytoplasm of RBCs to compensate for the loss of negative ions. This is called chloride shift. How Hydrogen carbonate ions are formed in the cytoplasm of red blood cells  RELEASE OF CO~2~ BY HYDROGEN CARBONATE IONS IN THE LUNGS (UNLOADING OF CO~2~) In the lung capillaries, HCO~3~^-\ ­­^diffuses back into the cytoplasm of RBCs & combines with H^+^ to form carbonic acid (H~2~CO~3~), which then breaks into CO~2~ and H~2~O catalyzed by carbonic anhydrase. CO~2~ diffuses out into the alveoli. **NB:** When HCO~3~^-\ ­­^diffuses back into the cytoplasm of RBCs, chloride ions diffuse from the cytoplasm to blood plasma to compensate for the loss of negative ions. This is called chloride shift. [High altitude & the increase in RBC's count] - At high altitude, the partial pressure of O~2~ in the air is low. So haemoglobin will be less saturated in the lungs causing less O~2~ in the body. The person may begin to feel breathless & ill. - To get adapted to high altitude, the number of RBC's must increase. The more the RBCs, the more the haemoglobin one has to increase the efficiency of O~2~ transport from lungs to tissues. The haematocrit This is the proportion of the blood that is composed of red blood cells. Explain why the haematocrit increases at higher altitude. - Partial pressure of oxygen is lower at high altitude than at sea level - At high altitude, haemoglobin is less saturated with oxygen - To compensate this, more red blood cells / more haemoglobin are made at high altitude - This now increases saturation of haemoglobin with oxygen in the lungs so that tissues receive sufficient oxygen Questions Carbon dioxide is transported in the blood in various forms. Describe how carbon dioxide molecules reach RBCs from respiring cells. - Diffusion - Down concentration gradient until equilibrium is reached. An enzyme in RBC's catalyses the reaction between carbon dioxide & water as blood flows through respiring tissues. Name the enzyme that catalyses this reaction. - Carbonic anhydrase. Explain the significance of this reaction in the transport of carbon dioxide. - The reaction is faster. - Hydrogen carbonate ions diffuse into blood plasma. - Carbon dioxide is transported to the lungs as hydrogen carbonate ions/ bicarbonate ions in blood plasma - 80-90% CO~2~ transported this way. Name the effect of increasing carbon dioxide concentration on the oxygen dissociation curve. Explain the importance of the effect of carbon dioxide on haemoglobin. i. Carbon dioxide influences percentage saturation of haemoglobin with oxygen. ii. At the same partial pressure of oxygen, carbon dioxide causes haemoglobin to release more oxygen than it would in absence of carbon dioxide. iii. This oxygen is used to increase the rate of aerobic respiration in cells. Describe 2 events that take place when oxyhaemoglobin combines with hydrogen ions. - It forms haemoglobinic acid, HHb & in the process, releases O~2~. - It maintains the pH of blood close to neutral hence act as a buffer. The percentage saturation of haemoglobin with oxygen decreases as the partial pressure of carbon dioxide increases. Explain how this happens. - Hydrogen ions/protons react or combine with oxyhaemoglobin to form haemoglobinic acid/HHb; so stimulate haemoglobin to release more oxygen. - Carbon dioxide combines with (oxy)haemoglobin to form carbamino-haemoglobin (so) stimulate haemoglobin to release more oxygen. - Haemoglobin has a higher affinity for carbon dioxide than oxygen in the tissues One function of blood is transport of the requirements needed by body cells such as oxygen. Majority of the oxygen (around 98.5) in the body is transported when bound to haemoglobin. At a high altitude, the partial pressure of oxygen in the atmosphere is lower than at sea level. If a person travels from low altitude to high altitude and remains there for a few weeks, the red blood cell count increases. Explain why the body needs to respond to high altitude by increasing the number of red blood cells. (4) Due to lower partial pressure of oxygen in the atmosphere, less oxygen is inhaled causing less oxygen to diffuse from alveoli into the lung capillaries Haemoglobin has lower affinity for oxygen at low partial pressure. So, haemoglobin carries less oxygen becoming less saturated with oxygen. This causes less oxygen to reach the body cells. To compensate this, more RBCs are made to have more haemoglobin so that more oxygen reaches body cells. **CARDIOVASCULAR DISEASES (CVDS)** - These are the diseases of the **heart** (cardio) and **blood vessels** (vascular) as a result of damage to blood vessels. The damage is caused by: 1. Atherosclerosis (narrowing and hardening of blood vessels) due to plaque/atheroma formation in the blood vessels. 2. Thrombosis, that is, clot formation in the blood vessels - Both Atherosclerosis and thrombosis cause **blockage** and **narrowing** of the blood vessels that lead to CVDs. - Atherosclerosis is a condition of the blood vessels where **atheroma** (fatty deposits mainly cholesterol or simply LDLs) are deposited in the walls of blood vessels. Atheroma then hardens due to accumulation of calcium salts and fibrous tissue to form a **plaque**. - Thrombosis is a condition in which a blood clot (thrombus or embolus) forms inside a blood vessel. If the clot is stationary it is called **thrombus** but if it moves along with blood it is called **embolus**. **FORMS OF CARDIOVASCULAR DISEAES (CVDS)** A **transient ischemic attack** (**TIA**) happens when blood flow to part of the brain is blocked or reduced, often by a blood clot. After a short time, blood flows again and the symptoms go away. With a stroke, the blood flow stays blocked, and the brain has permanent damage. **Process of blood clotting in the blood vessel** - Damage to tunica intima of the blood vessel (endothelium), due to high blood pressure or toxins in the tobacco smoke, causes **collagen fibres** to be exposed in the lumen of the blood vessel. - Platelets **rapidly stick** to the **exposed collagen fibres** and these platelets release a clotting factor called thromboplastin (enzyme) that starts the cascade reactions (product of each reaction is the catalyst of the next reaction) - In the presence of **calcium ions** and **vitamin K**, thromboplastin **catalyses** the conversion of prothombin (inactive plasma protein) to an **enzyme** called thrombin (an active plasma protein). - Thrombin (enzyme) catalyses the conversion of **fibrinogen** (soluble plasma protein) into fibrin (insoluble plasma protein). - Fibrin forms a mesh that traps blood cells and platelets to form a blood clot. - *Fibrinogen is globular (spherical) and fibrin is fibrous (long).* - *Fibrinogen is soluble and fibrin is insoluble* - *They are of different sizes* **How atherosclerosis develops (formation of atheroma/plaque)** 1. **Damage to the endothelial lining** due to **high blood pressure** and **toxins** in tobacco smoke. 2. **Inflammatory response** -- this is increased flow of blood to the damaged area to bring in a lot of **white blood cells.** 3. **Plaque formation:** The white blood cells **cause** **fatty deposits/LDLs** to build up in the damaged area to form atheroma (fatty deposit, mainly cholesterol). Calcium salts and fibrous tissue accumulate hardening the atheroma to form a **plaque** on the inner wall of the artery. 4. **Raised blood pressure** -- this is due to formation of plaque. Formation of plaque causes; a. formation of clot on the plaque b. loss of elasticity of artery c. narrowing of the lumen of the artery **Immediate consequences of atherosclerosis (Plaque formation).** 1. Clot formation on the plaque 2. Narrowing of the lumen of the artery 3. Loss of elasticity in the artery The above three immediate consequences of atherosclerosis cause [High blood pressure]. **Coronary heart disease (CHD)** - There are 4 forms of CHD 1. Heart attack 2. Angina 3. Heart failure 4. Arrhythmias - *CHD is disease that affects a pair of coronary arteries which supply the heart muscle with the glucose and oxygen needed for respiration.* - When one of these arteries becomes **blocked**, the area of the heart muscle that it supplies is cut off from oxygen and glucose and it dies giving rise to **heart attack or myocardial infarction**. - When one of these arteries is **partially blocked**, it leads to **angina pectoris**, Arrhythmias and Heart failure. - The two main reasons why blockages/partial blockages occur in the coronary arteries are: a. *Atherosclerosis -- formation of atheroma/plaque* b. *Thrombosis -- formation of clot that is usually formed on the rough surface of plaque* - So, there are two main forms of CHD (coronary heart disease); a. *Heart attack -- due to blockage of a coronary artery.* b. *Angina pectoris -- due to partial blockage of a coronary artery.* **Other forms of CHD** i. Heart failure -- condition in which the heart cannot pump enough blood to meet the body's requirements because it is weak. ii. Arrhythmias- irregular heartbeat. **Stroke (cerebral infarction)** - Supply of oxygenated blood to part of the brain is cut off causing its death. **Peripheral vascular disease (PVD)** - This is due to blockage/narrowing of arteries leading to periphery especially in the legs. This leads to tissue death (infarction) and then tissue decay (gangrene). **Thrombosis (clot formation)** There are two ways of forming a clot; 1. Through atherosclerosis i.e. a clot is formed on a rough surface of a plaque to block the artery. 2. Direct formation of a clot -- platelets come into contact with damaged endothelium and trigg