MYE Revision Year 11 Biology PDF

MYE Revision Year 11 Biology  What are cells? 1. Cells are thebuilding _______________ blocks of life, i.e. all living organisms are made up of cells. 2. Cells exist in various shapes and sizes. 3. There are smaller componentscell ca...

MYE Revision Year 11 Biology  What are cells? 1. Cells are thebuilding _______________ blocks of life, i.e. all living organisms are made up of cells. 2. Cells exist in various shapes and sizes. 3. There are smaller componentscell called __________ structures within a cell, each perform a special function within the cell and for the cell.  Plant cells vs Animal cells The basics: Similarities: Both plant and animal cells havenucleus ①__________ , ②__________ cell , and ③__________ cytoplasm. membrane Differences: 1. Plant cells have ①__________ cell wall , ②__________ vacuole , and if they are green they contain ③__________. Plant cells have chloroplast regular __________ shapes. vacuole 2. Animal cells do not havecell wall ①__________ , ②__________ , and ③__________ chloroplast which are common to plant cells. Animal cells are of irregular __________ shapes.  Cell membrane 1. It is a thin membrane around the cytoplasm of a cell. 2. It is partially permeable. 3. It is made up of two lipid layers calledFigure 1. Plasma membrane structure. lipid bilayer. Cell 1 Function: 4. Separates a cell from its external A environment. 5. Holds the cell contents together. B 6. Controls the exchange of molecules Cell 2 A between the cell and its external environment through active transport, passive transport and simple diffusion. Figure 2. An electron micrograph showing (A) plasma membrane and (B)  Cell wall Cell wall is the rigid cellulose layer surrounding the plasma membrane of Plasma membrane plant cells Note: peptidoglyca Bacterial cell wall made of n __________________. chitin Fungal cell wall made of _____________. Function: 1. Provides support and protection for the cell. 2. Prevents the cell from bursting in dilute Figure 1. An electron micrograph solution. showing cell wall and plasma membrane  Cytoplasm 1. Refers to everything between the cell membrane and the nucleus. 2. Is a continuous aqueous solution, containing organelles, salts, dissolved gases, nutrients, enzymes, and other organic molecules. Note: An aqueous solution is a solution in which the solvent is water. Function: 3. Gives shape to the cell 4. Supports and protects the cell organelles 5. Provides medium for all cellular metabolic reactions to occur 6. Provides medium to produce energy (in the mitochondrion), to manufacture materials (in the Figure 1. An electron micrograph of endoplasmic reticulum) and to store materials. an animal cell.  Nucleus Is an organelle bounded by the nuclear membrane containing chromosomes and nucleoplasm. Function: 1. Contains the genetic materials. Figure 1. An electron micrograph of a nucleus. 2. Controls all the cell activities.  Nuclear membrane 1. Is a double-layer membrane with a space in between that surrounds the nucleus. 2. Outside layer called outer nuclear membrane, inside layer called inner nuclear membrane. 3. Has pores. Function: 4. It is selectively permeable to control movement of materials in or out. Figure 1. An electron micrograph of a nucleus. 5. Separates the genetic material from the cytoplasm.  Chromosomes 1. Are thread-like structures containing the genetic material, DNA. 2. Appear as chromatin (made up of DNA attached to proteins) spread throughout the nucleus in the form of tiny granules. Figure 1. Micrograph showing nucleus at 3. During cell division, different stages of cell division. chromatin condenses into chromosomes. Function: 4. Carry genetic information of the cell in its DNA. Figure 2. An electron micrograph of a human chromos  Rough endoplasmic reticulum (RER) 1. Is a flat sealed sac of membrane that is continuous with the outer nuclear membrane. 2. With ribosomes embedded on its surface. Function: 3. Synthesizes and transports proteins made by the ribosomes 4. Present in large amounts in cells that make proteins, such as the gut cells that manufactures digestive Figure 1. An electron micrograph showing enzymes. the nucleus, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum Smooth endoplasmic reticulum (SER) 1. Is tubular sac of membrane. 2. May extend from the RER or separately from the outer membrane of the nucleus. 3. Does not have ribosomes. Function: 4. Synthesizes and transports lipids. 5. Present in large amounts in cells that make lipids, such as the Figure 1. An electron micrograph showing cells of the liver and testes. the nucleus, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum  Ribosomes 1. Are small dot-like organelles found in large numbers in all cells. 2. Are either attached to the ER or occur freely in the cytoplasm. Function: Synthesize all types of Figure 1. An electron micrograph showing free proteins. ribosomes and bound ribosomes.  Golgi apparatus 1. Also called the Golgi body. 2. Consist of a stack of membrane- bound sacs with small vesicles budding off the edges. Function: 3. Receives, modifies, stores, and transports proteins and lipids. 4. Forms lysosomes and secretory vesicles. e.g. produces digestive enzymes and secretes them into the digestive tract, secretes waste products from the cell, secretes carbohydrates to Figure 1. An electron micrograph showing form the cell walls of plant cells, the Golgi apparatus and its vesicles. secretes hormones.  Mitochondrion Note: Mitochondrion – singular; Mitochondria – plural. 1. Is rod-shaped. 2. Has two membrane: an inner membrane and an outer membrane. 3. The outer membrane limits the organelle. 4. The inner membrane is folded inwards to form cristae. Function: 5. It is the cell’s powerhouse. adenosine Produces ____________________ triphosphate Figure 1. An electron micrograph of a (ATP), which is an energy mitochondrion.  Chloroplasts 1. Are lens-shaped organelles Chloroplasts 2. Have inner and outer membrane 3. Contain chlorophyll to trap sunlight energy Function: Carry out photosynthesis Figure 1. An electron micrograph showing a plant cell with chloroplasts.  Vacuole 1. Is a cavity in the cytoplasm of a cell, bound by a single membrane. 2. Containing water, food or metabolic waste. Function: 3. For storage, digestion, and waste removal. 4. Central vacuole in plant cells Vacuol for storage and cell e expansion. 5. Food vacuoles in Amoeba for phagocytosis. 6. Contractile vacuole in Paramecium to expel water. Figure 1. An electron micrograph showing a plant cell central vacuole. Structure of Bacteria vs Virus  Passive transport 1.Diffusion 2.Osmosis  Diffusion Definition: Movement of ions or molecules from a region higher of __________ concentration to a regionlower of __________ concentration, down a concentration gradient*, through a ___________________________ membrane until _______________** is partially permeable equilibrium achieved. *Concentration gradient: the difference in the concentration of a particular substance in one region compared to another region. **Equilibrium: the concentration of a particular substance is the same in all regions. Diffusion happens as a result kinetic energy of random movement of particles. Diffusion  Osmosis Definition: higher The movement of water molecules from a region of __________ water lower potential to a region of __________ water potential, through a ___________________________ partially permeable membrane until _______________ equilibrium is achieved. Terms to know: 1. High water potential =higher _____ water concentrationlower = _____ solute concentration 2. Low water potential = _____ water concentrationhigher lower = _____ solute concentration Osmosis Equilibrium Terms to understand 1. The concentration of a solution refers to the quantity of solute dissolved in a unit volume of solvent (example: grams per liter, grams per milliliter, molarity or percentage concentration). higher 2. A concentrated solution has a ________ amount of solute dissolved in the solvent. 3. A dilute solution haslower a ________ amount of solute dissolved in the solvent. Tonicity of Solutions - refers to the ____________ of the solution. 1. Isotonic solution “Iso” means thesame _____ as. e.g. Two solutions are isotonic if they have same the ______ solute concentration. 2. Hypotonic solution “Hypo” means less _____ than. less e.g. Solution A is hypotonic to solution B – solution A has a ______ solute concentration than solution B. 3. Hypertonic solution more “Hyper” means _____ than. more e.g. Solution A is hypertonic to solution B – solution A has a ______ solute concentration than solution B.  The effect of isotonic solution on plant cells 1. The solute concentration of external solution is equal to the solute concentration of the cell sap. 2. This means that the concentration of water molecules in the external solution and the cell sap is equal. WATER 3. Therefore, water diffuses into and out of the cell at equal rates. 4. No net movement of water across the cell membrane. 5. There is no change in the original size of the cell.  The effect of hypotonic solution on plant cells 1. The solute concentration of external solution is less than the solute concentration of the cell sap. 2. This means that the concentration of water molecules in the external solution is greater than the concentration of water molecules in the cell sap. 3. Therefore, water diffuses into the cell by WATER osmosis. 4. There is net movement of water into the cell across the cell membrane, turgor pressure increased. 5. The cell contents are pushed outwards, against the cell wall and becomes turgid. 6. The strong and rigid cell wall pushes back  The effect of hypertonic solution on plant cells 1. The solute concentration of external solution is greater than the solute concentration of the cell sap. 2. This means that the concentration of water molecules in the external solution is less than the concentration of water molecules in cell sap. 3. Therefore, water diffuses out of the cell by osmosis. 4. There is a net movement of water out of the cell across the cell membrane. 5. The cytoplasm shrinks away from the cell wall, the cell is plasmolysed. 6. Plasmolysis is the separation of cytoplasm and cell membrane from the cell wall in a plant cell as a result of water WATER loss. 7. Turgor pressure decrease, no longer a push against cell wall. 8. The plant cell becomes flaccid (soft and weak). 9. The plant cells no longer provide support causing plant to wilt. 10. If a plasmolysed cell is placed in a hypotonic solution, it absorbs water causing the cytoplasm to expand and comes into contact with the call wall again. This is called deplasmolysis.  The effect of isotonic solution on animal cells 1. The solute concentration of external solution is equal to the solute concentration in the cell. 2. This means that the concentration of water molecules WATER in the external solution and in the cell is equal. 3. Therefore, water diffuses into and out of the cell at equal rates. 4. No net movement of water across the cell membrane. 5. There is no change in the original size of the cell.  The effect of hypotonic solution on animal cells 1. The solute concentration of external solution is less than the solute concentration in the cell. 2. This means that the concentration of water molecules in the external solution is greater than the concentration of water molecules in the WATER cell. 3. Therefore, water diffuses into the cell by osmosis. 4. There is net movement of water into the cell across the cell membrane. 5. The cell inflates and finally ruptures. The rupturing of the cell is called cell lysis.  The effect of hypertonic solution on animal cells 1. The solute concentration of external solution is greater than the solute concentration in the cell. 2. This means that the concentration of water molecules in the external solution is less than the concentration of water molecules in the cell. 3. Therefore, water diffuses out the cell WATER by osmosis. 4. There is net movement of water out of the cell across the cell membrane. 5. The cell shrinks. This is called crenation.  Active transport Active transport uses ______________________ energy to move molecules or ions across the cell membrane against __________ the concentration gradient. 1. A particular molecule attaches itself to the binding site of a protein carrier. 2. Using energy from respiration. 3. Then, the protein carrier changes shape and delivers the molecule across the cell membrane against the concentration gradient of the molecule. Examples of active transport in biology: 4. Ion uptake by root hairs. 5. Uptake of glucose by epithelial cells of villi and kidney tubules Active transport 80 °C  Benedict’s test: allow the estimation of the concentration of reducing sugar Iodine solution test for starch A chemical test for starch is to add iodine solution and see if the brown turns blue-black in colour.  Biuret test for proteins The biuret test is a chemical test used for detecting the presence of peptide bonds using the Biuret reagent (blue alkaline solution of CuSO4). If peptides are present, it bind to the Cu2+ ions in the Biuret reagent to form violet-coloured complexes. If protein is absent the solution remain blue after test.  Test for lipids Emulsion test 1. Add ethanol to the sample solution and shake to mix well. 2. Fat will dissolved in the ethanol. 3. Reaction with water will form a milky emulsion. Emulsion test: left, negative; right positive Testing for Vitamin C  Enzymes as biological catalysts 1. A metabolic pathway is a number of reactions catalyzed by a sequence of enzymes. Without enzymes, most of the biochemical reactions in living cells at body temperature would occur very slowly or not at all. 2. Enzymes are biological catalysts produced by living cells. 3. Enzymes speed up the rate of biochemical reactions in the cell but remain unchanged at the end of the reactions.  What are of enzymes? All enzymes are proteins (but not all proteins are enzymes) 1. Enzymes are synthesized by living organisms. 2. Intracellular enzyme – produced and retained in the cell for the use of the cell itself; found in cytoplasm, nucleus, mitochondria, lysosome, chloroplast. 3. Extracellular enzyme – produced in the cell but secreted from the cell to function externally; example – digestive enzymes produced by cells in the pancreas are secreted into the small intestine for food digestion.  Enzyme action The lock-and-key hypothesis In the lock-and-key hypothesis, the shape of the substrate (the key) fits into the active site of the enzyme (the lock) forming an enzyme-substrate complex, reaction takes place and products are formed and released. The same enzyme is now free to react with another substrate. substrate (key) product is entering active formed and site of enzyme released active site formation of an enzyme is free to enzyme (lock) react with another enzyme-substrate  Effects of temperature 1. At low temperature, enzyme reaction occurs very slowly. The molecules in the solution moves slowly and take a longer time to bind to active sites. 2. Increasing temperature increases the kinetic energy of the substrate and enzyme molecules, and increases the number of collisions of the molecules to form enzyme- substrate complex.  Effects of temperature 1. At suboptimal temperatures, the rate of enzyme reaction doubles for each 10 °C rise in temperature. 2. At optimum temperature, the rate of reaction is at a maximum. 3. At above optimum temperatures, the increased kinetic energy causes the atoms in the enzyme molecules to vibrate violently. Hydrogen and ionic bonds which holed the specific three-dimensional shape of the enzyme molecule is broken. The enzyme molecule unfolds and become denatured. The effect is irreversible. Substrate can no longer fit into the active site. The rate of reaction falls rapidly. Effects of temperature Example:  Effects of pH 1. Most enzymes are effective only within a narrow pH range. 2. The optimum pH is the pH at which the maximum rate of reaction occurs. Different enzymes have different optimum pH. 3. Deviation from this narrow optimum pH range alters the acidic and basic groups of amino acids in the enzyme. The three- dimensional shape of the enzyme is altered and the enzyme is denatured. 4. The ionic charge on the active site and the surface of substrate may also be altered. 5. The substrate cannot fit into the active site to form enzyme- substrate complex. The rate of reaction decreases. Effects of pH Salivary amylase  Transport in plants Xylem vessels: Transportwater minerals Phloem Vessels:sucrose __________ and dissolved __________ from the root up to all the Transport amino acid food nutrients other parts of the plant. Feature of xylem related to the function such as __________ from of water transport: the leave and 1. thick / strong, (cell) wall - withstanding, tension / collapse / hydrostatic pressure _______________ to other 2. lignin (in walls) / walls are impermeable - prevents collapse / waterproofing parts of the plant. 3. wide diameter - transport large volumes of water 4. no (cell) contents / empty / dead cells / like pipes / like tubes - no / little resistance to flow of water / allows water to flow easily / lots of water / continuous columns of water / no obstruction 5. no, cross walls / end walls - no / little, resistance to flow of water / allows water to flow easily / lots of water / continuous columns of water / no obstruction 6. bordered pits - lateral transport STRUCTURE OF XYLEM XYLEM VESSELS ADAPTATIONS OF XYLEM VESSELS  Water uptake Root hairs are where most absorption happens. They are long and thin so they can penetrate between soil particles, and they have a large surface area to increase the rate of the absorption. 1. Water passes from the soil water to the root hair cell’s osmosis cytoplasm higher by __________. This happens because the soil water has a __________ water potential than the root hair cell cytoplasm. Osmosis causes water to pass into the root hair cells, through the root cortex cells, into the xylem vessels active and transport finally mesophyll cells. 2. The absorption of mineral ions by ____________________. Transpiration Transpiration is the loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by the diffusion of water vapour through the stomata. 1. The main force that draws water from the soil and through the plant is caused by this. 2. Water evaporates from the leaves and causes a kind of ‘suction’, which pulls water up the stem. 3. The water travels up the xylem vessels in the vascular bundles and this flow of water is called the transpiration stream. 4. Transpiration stream: Root → Stem → Leaf Describe how water vapour loss is related to cell surfaces, air spaces and stomata: 1. Transpiration is the loss of water vapour from the leaf; 2. Water in the mesophyll cells form a thin layer on their surfaces; 3. The water evaporates into the air spaces in the spongy mesophyll; 4. This creates a high concentration of water molecules in the air spaces. 5. Water vapour diffuses out of the leaf into the surrounding air, through the stomata. Mechanism of water movement through a plant: 1. Transpiration continuously removes water from the leaf. 2. Thus water is constantly being taken from the top of the xylem vessels, to supply the cells in the leaves. 3. This reduces the effective pressure at the top of the xylem vessels. 4. This creates a transpiration stream or ‘pull’, pulling water up. 5. Water molecules have a strong tendency to stick together. This is called cohesion. 6. When the water is ‘pulled’ up the xylem vessels, the whole column of water stays together. 7. Roots also produce a root pressure, forcing water up the xylem vessels.  Factors affecting the rate of transpiration: Factor Effect Explanation Temperatur Increased Evaporation and diffusion are faster e at higher temperatures Humidity Decrease Diffusion of water vapour out of the d leaf slows down if the leaf is already surrounded by moist air Wind speed Increased Moving air removes water vapour, increasing the rate of diffusion of water vapour from the leaf Light Increased The stomata open wider to allow intensity more carbon dioxide into the leaf for photosynthesis  Wilting 1. Wilting occurs when the transpiration rate is faster than the rate of water absorption. 2. The amount of water in the plant keeps on decreasing. 3. The water content of cells decreases and cells turn from turgid to flaccid. 4. The leaves shrink, the plant wilts and will eventually die. Structure of phloem Sieve tubes Companion cells Translocation Translocation is the movement of sucrose and amino acids in the phloem, from regions of production source (the __________ ) to regions where they are used in respiration or growth or to regions sink of storage (the __________ ). 1. This is the movement of sucrose and amino acids in the phloem tubes of the plant. 2. Glucose is very important as it makes many other important nutrients. For example, glucose is used to make sucrose. 3. Sucrose then enters the phloem. 4. The phloem then transports the sucrose all across the plant where it can be made used of. Source and Sink Some parts of a plant can act as a source and a sink at different times during the life of a plant. Example: 1. While a bud containing new leaves is forming it would require nutrients and therefore act as a sink. 2. However, once the bud has burst and the leaves are photosynthesizing, the region would act as a source, sending newly synthesized sugars and amino acids to other parts of the plant.  Main Nutrients Nutrien Elements Use in Good t presen body food Carbohydrat t Source of sources e Carbon, energy Rice, potato, hydrogen, bread Fats and oxygen Source of Butter, milk, oils Carbon, energy cheese, hydrogen, Insulation egg yolk Protei oxygen Growth and Meat, fish, eggs, n Carbon, tissue repair soya, milk hydrogen, oxygen, What happens to the food we eat? Ingestion – Intake of food into the mouth Digestion – Breaking down large, insoluble food molecules into smaller soluble ones using enzymes  Absorption – Digested food molecules pass across the wall of the small intestine into the blood or the lymph Assimilation – Uptake of food molecules by cells  Egestion – Passing out of undigested food, in the form of faeces, from the anus Deamination – Removal of nitrogen containing part of an amino acid as urea.  Salivary mouth glands oesophagus tongue trachea liver stomach Gall bladder pancreas Small Duodenum intestine colon Large ileum rectum intestin e appendix anus Human Jaw  teet h There are different types of teeth, each specially shaped to perform a particular job. – Incisor A broad flat sharp tooth found at the front of the mouth. Designed for biting and cutting food. – Canine A sharp pointed tooth for piercing flesh and tearing. – Pre-molar & molar A broad flat tooth with many cusps. Its rough surface is used for crushing, grinding and chewing food Structure of a tooth enamel crown dentine gum Pulp cavity root ceme nt Absorption in the ileum The small intestine is well designed for absorption, it has – Thin lining – A good blood supply – A very large surface area (about 9m2) Villi Increase the surface area for absorption Each villus contains – Blood capillaries that absorb glucose and amino acids – Lacteals which absorb fatty acids and glycerol Absorption is by – Diffusion – thin lining only 1 cell thick – Active transport – cells contain mitochondria to provide energy Absorption in the Villi  Pathogen and transmissible disease 1. Pathogen is a disease-causing organism. 2. They feed or reproduce in or on body cells causing damage to tissues and organs. They can also produce harmful substances called toxins. 3. A person is said to be infected when pathogens are inside the body. 4. Transmissible disease is a disease in which the pathogen can be passed from one host to another. 5. Pathogens responsible for transmissible diseases can be spread either through: - direct contact: through blood or other body fluids - indirectly: from contaminated surfaces, contaminated food or water, from animals, or from the air  How do pathogens spread? Air Droplets containing microbes fly into the air when people sneeze or cough. The microbes they contain get into other people if breathed in. Example: Chicken pox, colds, flu, measles and tuberculosis are spread like this. Animals Animals may carry harmful microbes. The microbes can get into a person who is scratched or bitten by such an animal. Example: Malaria is a tropical disease spread by mosquitos. Food Food can have harmful microbes in and on it. The microbes get into the body when the food is eaten, causing food poisoning. Thorough cooking kills most microbes, but they can survive under-cooking. Careless handling of food increases the risk from harmful microbes. Example: Salmonella enterica  How do pathogens spread? Touch Microbes can be passed from one person to another when people touch each other, or when they touch something an infected person has handled. Athlete's foot is spread like this. Bacteria on the skin can be killed by antiseptics, and bacteria on surfaces can be killed by disinfectants. Washing your hands reduces the chance of spreading microbes. Water Water can have harmful microbes in it. The microbes get into the body when the water is swallowed. Cholera is a disease caused by a bacterium that spreads like this. Thorough boiling or adding chlorine to the water can reduce the chance of spreading microbes in this way.  How do pathogens spread? Body fluid Certain body fluids can contain blood borne pathogens that infect humans and spread from person to person. Any body fluid with blood is potentially infectious. Semen, vaginal secretions and saliva in dental procedures are considered potentially infected body fluids. Most blood borne pathogens are transmitted when blood or body fluid from an infected person enters the body of another person. This can happen through abrasions, needle sticks, human bites, through mucous membranes or sexual intercourse.  Controlling the spread of disease To control the spread of disease, it is important to maintain: 1. a clean water supply 2. hygienic food preparation 3. good personal hygiene 4. waste disposal 5. sewage treatment  Defences against disease Mechanical barriers – skin and hair in the nose. Chemical barriers – stomach acid, mucus produced by the lining of the trachea and bronchi, and tears which contain an enzyme called lysozyme. Cells – phagocytosis and antibody production by white blood cells. Vaccination – can enhance the body’s defense.  Mechanical barrier The skin The skin covers the whole body. It protects the body from physical damage, dehydration and microbe infection. The skin is slightly acidic (lactic acid) and has good bacteria. Its dry, dead outer cells are tough and difficult for microbes to penetrate. Sebaceous glands produce oils which help kill microbes. Mechanical barrier Blood clotting Pathogens can get into the body through a cut in the skin. Therefore, most important thing to do is to close a wound quickly so that pathogens cannot enter. A scab does just that. The blood contains tiny structures called platelets, and a protein called fibrin. A scab is basically platelets stuck in a fibrin mesh. Blood clotting mechanism  Mechanical and Chemical barriers Mucous membranes The respiratory system is protected in several ways. Nasal hairs keep out dust and larger microorganisms. Sticky mucus traps dust and microbes, which are then carried away by cilia - tiny hairs on the cells that line the respiratory system.  Chemical barrier Stomach acid Hydrochloric acid in the stomach kills harmful microorganisms that might be in the food or drink that we swallow.  Antibodies and immunity 1. Once pathogens enter the body, the immune system destroys them. 2. White blood cells called lymphocytes and phagocytes are important components of the immune system. 3. On the surface of all cells there are chemical substances called antigens. 4. Lymphocytes produce proteins called antibodies which attack the antigens of pathogens that invade the body. 5. The antibodies may attach to the antigens on the surface of pathogens to mark Each pathogen has its own set antigens, them, making it easier for the which have specific shapes, so specific phagocytes to find and ingest them. antibodies which fit the specific shapes 6. At the end of the infection, the infected of the antigens are needed. individual gains immunity as lymphocytes form long-lived memory cells that remember the same pathogen for faster antibody production in future Watch: https://www.youtube.com/watch?v=PSRJfaAYk infections. https://www.youtube.com/watch?v=0oCqNUZl  Stages of Phagocytosis 1. Pathogens are recognised by antigens on their surface. 2. Phagocyte moves towards the pathogen and surrounds it with its pseudopodia during chemotaxis in response to chemical signals produced by the pathogen. 3. Phagocyte engulfs the pathogen endocytosis creating a phagosome. 4. Lysosomes fuse with the phagosome releasing digestive enzymes. 5. Digestion products are released from the cell via exocytysis and absorbed into the cytoplasm.  Immunity - active Active immunity: The long-term defense against a pathogen by rapid antibody production in the body. This is gained after an infection by a pathogen or by vaccination. Vaccination: https://www.youtube.com/watch?v=rb7TVW77ZCs People can be immunised against a pathogen through vaccination. Vaccination involves putting a small amount of an inactive or dead pathogen, into the body. When injected into the body, vaccine stimulates white blood cells to produce antibodies against the pathogen. Because the vaccine contains only a weakened or harmless version of a pathogen, the vaccinated person is not in danger of developing disease, although some people may suffer a mild reaction. If the person does get infected by the pathogen later, the required lymphocytes are able to reproduce rapidly and destroy it. Systemic immunization can protect whole populations. Vaccines are available for: Diphtheria, whooping cough, polio, tetanus, meningitis, measles, mumps, tuberculosis and rubella. Systemic immunization by vaccination can protect whole populations as it controls the spread of dangerous diseases.  Immunity - passive Passive immunity: Is a short-term and temporary defense against a pathogen as no memory cells are formed. Passive immunity through: 1. Antibodies acquired from another individual. 2. A baby’s immune responses are not yet fully developed, so when a mother breastfeeds her baby, the milk which contains the mother’s white blood cells produces antibodies and provide the baby with protection against infection.  Cholera 1.Bacteria attach to the wall of the small intestine. 2.They produce a toxin. 3.The toxin stimulates the cells lining the intestine to release chloride ions from inside the cells into the lumen of the intestine. 4.The chloride ions accumulate in the lumen of the small intestine and lower the water potential there. 5.Once the water potential is lower than that of the cells lining the intestine, water starts to move out of the cells into the intestine (by osmosis). The heart pumps blood through the circulatory system to all the major organs of the body. The appearance of the heart from the outside is showns the left side cut open, a diagram of a vertical section to show its internal structure. Since the heart is seen as if in a dissection of a person facing you, the left side is drawn on the right. Diagram of the heart, vertical section If you study the figure you will see that there are four chambers. The upper, thin-walled chambers are the atria (singular = atrium) and each of these opens into a thick-walled chamber, the ventricle, below. Blood enters the atria from large veins. The pulmonary vein brings oxygenated blood from the lungs into the left atrium. The vena cava brings deoxygenated blood from the body tissues into the right atrium. The blood passes from each atrium to its corresponding ventricle, and the ventricle pumps it out into the arteries. The left chambers are Diagram of separated from the right chambers by the heart, a wall of muscle called a septum. vertical The artery carrying oxygenated blood to the body from the left ventricle is the aorta. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. In pumping the blood, the muscle in the walls of the atria and ventricles contracts and relaxes. The walls of the atria contract first and force blood into the two ventricles. Then the ventricles contract and send blood into the arteries. Valves prevent blood Diagram of heartbeat (only flowing backwards during or the left side is shown) after heart contractions. The heart muscle is supplied with food and oxygen by the coronary arteries. There are a number of ways by which the activity of the heart can be monitored. These include measuring pulse rate, listening to heart sounds and the use of electrocardiograms External view of the heart Diagram of the heart cut open (left side Coronary heart disease In the lining of the large and medium arteries, deposits of a fatty substance, called atheroma, are laid down in patches. This happens to everyone and the patches get more numerous and extensive with age, but until one of them actually blocks an important artery the effects are not noticed. It is not known how or why the deposits form. Some doctors think that fatty substances in the blood pass into the lining. Others believe that small blood clots form on damaged areas of the lining and are covered over by the atheroma patches. The patches may join up to form a continuous layer, which reduces the internal diameter of the vessel. The surface of a patch of atheroma sometimes becomes rough and causes fibrinogen in the plasma to deposit fibrin on it, causing a blood clot (a thrombus) to form. Atheroma and thrombus formation If the blood clot blocks the coronary artery, which supplies the muscles of the ventricles with blood, it starves the muscles of oxygenated blood and the heart may stop beating. This is a severe heart attack from coronary thrombosis. A thrombus might form anywhere in the arterial system, but its effects in the coronary artery and in parts of the brain (strokes) are the most drastic. External view of the heart In the early stages of coronary heart disease, the atheroma may partially block the coronary artery and reduce the blood supply to the heart. This can lead to angina, i.e. a pain in the chest that occurs during exercise or exertion. This is a warning to the person that he or she is at risk and should take precautions to avoid a heart attack. Atheroma partially blocking the coronary artery Possible causes of coronary heart disease Atheroma and thrombus formation are the immediate causes of a heart attack but the long-term causes that give rise to these conditions are not well understood. There is an inherited tendency towards the disease but incidences of the disease have increased very significantly in affluent countries in recent years. This makes us think that some features of ‘Western’ diets or lifestyles might be causing it. The main risk factors are thought to be an unbalanced diet with too much fat, stress, smoking, genetic disposition, age, gender and lack of exercise. Diet The atheroma deposits contain cholesterol, which is present, combined with lipids and proteins, in the blood. Cholesterol plays an essential part in our physiology, but it is known that people with high levels of blood cholesterol are more likely to suffer from heart attacks than people with low cholesterol levels. Blood cholesterol can be influenced, to some extent, by the amount and type of fat in the diet. Many doctors and dieticians believe that animal fats (milk, cream, butter, cheese, egg-yolk, fatty meat) are more likely to raise the blood cholesterol than are the vegetable oils, which contain a high proportion of unsaturated fatty acids. An unbalanced diet with too many calories can lead to obesity. Being overweight puts extra strain on the heart and makes it more difficult for the person to exercise. Stress Emotional stress often leads to raised blood pressure. High blood pressure may increase the rate at which atheroma are formed in the arteries. Smoking Statistical studies suggest that smokers are two to three times more likely to die from a heart attack than are non-smokers of a similar age. The carbon monoxide and other chemicals in cigarette smoke may damage the lining of the arteries, allowing atheroma to form, but there is very Smoking littledisease. and heart direct Obviously, as evidence for you you get older this. are more likely to die from a heart attack, but notice that, in any age group, the more you smoke the higher your chances of dying from heart disease. Genetic predisposition Coronary heart disease appears to be passed from one generation to the next in some families. This is not something we have any control over, but we can be aware of this risk and reduce some of the other risk factors to compensate. Age and gender As we get older our risk of suffering from coronary heart disease increases. Males are more at risk of a heart attack than females: it may be that males tend to have less healthy lifestyles than females. Lack of exercise Heart muscle loses its tone and becomes less efficient at pumping blood when exercise is not untaken. A sluggish blood flow, resulting from lack of exercise, may allow atheroma to form in the arterial lining but, once again, the direct evidence for this is slim. Gas exchange is the interchange of O2 and CO2 between an organism and its environment -It is also called respiration 1. Good ventilation with air 2. Thin surface 3. Large surface area (alveoli) 4. Good blood supply  Features of gas Copyright © 2014 Henry Exham exchange surfaces in humans They have a large surface area for diffusion. Fluid to help dissolve gases and increase diffusion rate. A rich blood supply to maintain a steep diffusion gradient between the alveoli and the blood. Due to both the alveoli and the capillary only having walls one cell thick (Thin surface) there is a short diffusion distance between the air and the blood which increases diffusion rate. good ventilation with air (constant Copyright © 2014 Henry Exham The Gaseous Exchange System larynx Nose Mouth Lung Trachea s Pleural membranes Bronchi Ribs Bronchiole Intercostal muscles Alveoli Diaphrag m State and Explain the differences in composition between inspired and expired air Inspired air Expired air Reason for difference Oxygen (O2) 21% 16% Oxygen is absorbed across the gas exchange surface, then used by cells in respiration Carbon 0.04% 4% Carbon dioxide dioxide (CO2) is made inside respiring cells, and diffuses out across the gas exchange surface. Argon and 1% 1% other noble gases 14.1 Nervous control in humans Coordination is the way the nervous system is to control the body where all the organs and systems of the body are made to work efficiently together. For coordination to happen, the cells, tissues, organs and systems of the body must communicate with one another via nerve cells called neurons. Electrical signal called nerve impulse passes information along the neurons. The human nervous system consists of: 1. Central nervous system (CNS) – the brain and spinal cord 2. Peripheral nervous system (PNS) – cranial nerves and spinal nerves that carry information to or from the CNS The nerve cell: Neuron Neurons are adapted to carry electrical impulses from one place to another: 1. The axon is an extended thread along which nerve impulse travel. 2. Axons are coated by a layer of fat called myelin sheath, this is an electrical insulating layer which is essential for nerve impulse to travel very quickly. 3. The dendrite receives nerve impulses from other neurons. 4. The axon terminal passes the electrical impulses from the neuron to the next neuron or effectors. Types of neurons 1. Sensory Neuron: carry nerve impulses from the receptors to the CNS. 2. Interneuron/Relay Neuron: Relay neurons are located in the CNS. Their function is to pass electrical impulses from the sensory neuron to the motor neuron. 3. Motor Neuron: Transmits electrical impulses from the CNS to the effectors.  Synapse 1. Where two neurons meet, there is a tiny gap called the synaptic A synapse is a junction between two cleft. neurons. 2. Information crosses this gap using chemical messengers called neurotransmitters, instead of electrical impulses. 3. When an electrical impulse reaches the axon terminal of a sending neuron, it releases neurotransmitters into the synaptic cleft which diffuse across and binds with neurotransmitter receptors on the dendrites of a receiving neuron. 4. This triggers an electrical impulse in the receiving neuron. Many drugs produce their effects by interacting with receptor molecules at Negative Feedback Mechanism - Thermoregulation  Body temperature regulation: Summary The human body is designed to function most efficiently at 37°C. If you become too hot or too cold, there are ways in which your body temperature can be controlled: 1. Insulation: provided by fatty tissue retains heat. Hairs become erect to trap warm air by contracting erector muscles and vice versa. 2. Vasodilatation: when it is hot, arterioles, which supply blood to the skin surface capillaries, dilate (become wider) to allow more blood near to skin surface to increase heat loss (face redder) 3. Vasoconstriction: when it is cold, arterioles, which supply blood to the skin-surface capillaries, constrict (become smaller) to allow less blood near to skin surface to decrease heat loss 4. Sweating: the water evaporates giving a cooling effect 5. Skin receptors: sense heat and sensory neurons send impulses to the hypothalamus 6. Shivering: muscular activity generates heat 7. Thermoregulatory center: in the hypothalamus, it controls the use of corrective mechanisms (e.g. sweating and shivering).  Respiration Definition: The chemical reactions in cells that break down nutrients and release energy for metabolism. Respiration is a chemical process that takes place in cells and involves enzymes the action of _______________. Can sometimes be called cellular respiration, internal respiration or tissue respiration. Most of the processes taking place in cells need energy to make them happen. Examples of energy-consuming processes in living organisms are: 1. The contraction of muscle cells, to create movement of the organism, or peristalsis to move food along the alimentary canal, or contraction of the uterus wall during childbirth. 2. Building up proteins from amino acids. 3. The process of cell division to create more cells, more replace damaged or worn out cells, or to make reproductive cells. 4. The process of active transport, involving the movement of molecules across a cell membrane against a concentration gradient. 5. Growth of an organism through the formation of new cells or a permanent increase in cell size. 6. The conduction of electrical impulses by nerve cells. 7. Maintaining a constant body temperature in homoeothermic (warm- blooded) animals to ensure that vital chemical reactions continue at a predictable rate and do not slow down or speed up as the surrounding temperature varies.  Aerobic respiration 1. In aerobic respiration oxygen is used in the breakdown of glucose. 2. The process is called oxidation and the glucose is said to be oxidized. 3. In aerobic respiration, energy is released in mitochondria. glucose + oxygen → carbon dioxide + water + large amount energy C6H12O6 + 6O2 → 6CO2 + 6H2O + large amount energy *Cells also respire fats and proteins to provide energy.  Anaerobic respiration 1. The word anaerobic means ‘in the absence of oxygen’. 2. It is possible for chemical reactions in cells to break down nutrient molecules to release energy without using oxygen. 3. Anaerobic respiration is the release of relatively small amounts of energy from glucose in the absence of oxygen. Two types of anaerobic respiration: 4. in muscles 5. in plant cells and some microorganisms  Anaerobic respiration in muscles 1. During vigorous exercise, not enough oxygen may reach the body muscles for aerobic respiration to supply all the energy the muscles need. Muscle tissue respires anaerobically to release energy. 2. The stages of respiration that occur in mitochondria do not happen without oxygen. As a result the glucose is not broken down to carbon dioxide and water, but to lactic acid instead: glucose → lactic acid + energy [small amount] C6H12O6 → 2C3H6O3 + energy [small amount] *Cardiac muscle in the heart, do not normally respire anaerobically as this would not release enough energy to keep the heart beating properly. *Some bacteria also respire anaerobically to make lactic acid in the same way, for example those used to make yogurt.  Anaerobic respiration in muscles 1. There is a buildup of lactic acid in the muscles during vigorous exercise. 2. The lactic acid needs to be oxidized to carbon dioxide and water. 3. This causes an oxygen debt, that needs to be ‘repaid’ after the exercise stops. 4. Lactic acid needs to be removed from the bloodstream into the liver. 5. The blood needs to move more quickly during and after exercise to maintain this lactic acid removal process, so the heart rate is rapid. 6. In the liver, lactic acid is oxidized to carbon dioxide and water, using up oxygen in the process. 7. That is why, even exercise has stopped, a high level of oxygen consumption persist until the excess of lactic acid has been oxidized. 8. This is characterized by faster and deeper breathing. Anaerobic respiration in yeast and plant cells 1. Other microorganisms, such as yeast, respire anaerobically when oxygen is absent or in short supply in their surroundings, to make alcohol and carbon dioxide. glucose → ethanol + carbon dioxide + energy [small amount] C6H12O6 → 2C2H5OH + 2CO2 + energy [small amount] 2. Plant roots respire anaerobically when land is flooded and soils become saturated with water so little or no oxygen is available.  30 Fermentatio n ONE FORM OF ANAEROBIC RESPIRATION IN BACTERIA AND YEASTS IS CALLED FERMENTATION. DURING FERMENTATION, SUGAR IS BROKEN DOWN TO ALCOHOL AND CARBON DIOXIDE THE REACTION DESCRIBED IN SLIDE 25 IS AN EXAMPLE OF FERMENTATION FERMENTATION IS INVOLVED IN BREWING AND WINE-MAKING  Aerobic versus Anaerobic 1. respiration Anaerobic respiration is much less efficient than aerobic respiration because it releases much less energy per glucose molecule broken down. 2. This is because glucose is not completely broken down and a lot of energy remains stored in the lactic acid and alcohol in the form of chemical bond energy. Aerobic respiration: glucose + oxygen → carbon dioxide + water + large amount energy C6H12O6 + 6O2 → 6CO2 + 6H2O + large amount energy Anaerobic respiration: In muscles : glucose → lactic acid + small amount energy C6H12O6 → 2C3H6O3 + small amount energy In yeast : glucose → ethanol + carbon dioxide + small amount energy (plant cell) C6H12O6 → 2C2H5OH + 2CO2 + small amount energy  Deamination The liver removes these amine groups via the process of deamination and converts them into harmless products. The amine group is first converted into ammonia which is toxic and then converted into urea. Urea is non-toxic and excreted from the body by the kidneys in the urine. The remaining carbon skeleton is recycled to produce compounds that can be oxidized for energy. Alternatively: The amine group can be transferred via Transamination to make new amino acids These amino acids are non-essential - as they can be synthesized by the Human excretory (urinary) system Urine contains water, urea and salts. Urea is produced in the liver when excess amino acids are broken down. It is the main waste product removed in the urine. Blood is brought to the kidney in the renal artery. The kidneys filter the blood and then reabsorb useful materials. After it has been purified, the blood returns to the circulation through the renal vein. Urine produced is taken from the kidneys through the ureters to the bladder. The bladder stores the urine until it is convenient to be expelled from the body through the Structures and explanation  The Kidney 1. A renal artery carries 1. The cortex is the outer 1. A nephron is a single blood to the kidney and a region. glomerulus with its renal vein carries it away. 2. The medulla is the inner renal capsule, renal 2. The ureter carries urine zone. tubule and blood from the kidney to the 3. Where the ureter joins the capillaries. Sexual Reproduction in Plants Menstrual cycle and hormones  HIV Unprotected sexual intercourse can lead to the transfer of pathogens via exchange of body fluids Infections passed on in this way are known as sexually transmitted infections (STIs) An example of an STI is HIV (Human Immunodeficiency Virus), the virus that usually leads to the development of acquired immunodeficiency disease (AIDS) HIV can also be spread via sharing needles with an infected Immediately after infection, people often suffer mild person, blood transfusions with infected blood and from mother flu-like symptom to fetus through the placenta and mother to baby via breastfeeding These symptoms pass and for a period of time infected people might not know they are infected The virus infects a certain type of lymphocyte of the body's immune system Normally lymphocytes seek out and destroy pathogens that enter the body, producing antibodies that attach to pathogens, enhancing phagocytic activity However HIV avoids being recognised and destroyed by lymphocytes by repeatedly changing its protein coat It then infects a certain type of lymphocyte and uses