Anatomy and Physiology 1: Introduction to Chemistry of the Human Body (Part 2) PDF

Anatomy and Physiology 1 Topic 1 :Introduction Chemistry of the Human Body (PART 2) Prepared by Madam Leong Yee Leng 1 LEARNING OUTCOME At the end of this session, students will be able to : define the following terms: atoms, molecules and compoun...

Anatomy and Physiology 1 Topic 1 :Introduction Chemistry of the Human Body (PART 2) Prepared by Madam Leong Yee Leng 1 LEARNING OUTCOME At the end of this session, students will be able to : define the following terms: atoms, molecules and compounds; describe the structure of atom; discuss the types of bonds that hold molecules together; state the concept of molar concentration; explain the importance of buffers in the regulation of pH. 2 ATOMS, MOLECULES AND COMPOUNDS Atoms is the smallest unit of an element that can exist as a stable entity. An element is a chemical substance whose atoms are all of the same type. e.g. Iron contains only iron atoms. Compounds contain more than one type of atom. E.g. water contains hydrogen and oxygen atoms. Matter is anything that occupies space and has mass. Mass is the amount of matter in an object. Weight results from the force exerted by earth’s gravity on matter. 3 ATOMIC STRUCTURE Atoms are mainly empty space, with tiny central nucleus containing protons and neutrons surrounded by clouds of tiny orbiting electrons. Atom consist of protons, neutrons, and electrons. Protons are positively charged, electrons are negatively charges and neutrons have no charge. Protons and neutrons are in the nucleus; This Photo by Unknown Author is licensed under CC BY-SA electrons are located around the nucleus and can be represented by an electron cloud. 4 ATOMIC STRUCTURE Electrons are so small that their mass is negligible, but the bigger the neutrons and protons carry one atomic mass unit each. The atomic number is the unique number of proton in an atom. The mass number is the sum of protons and neutrons. Isotopes are atoms that have the same atomic number but different mass numbers. 5 ATOM The atomic mass of an element is the average mass of its naturally occurring isotopes weighted according to their abundance. A mole of a substance contains Avogadro’s number (6.022x 1023) of atoms, ions, or molecules. The molar mass if a substance is the mass of 1 mole of substance expressed in grams. 6 MASS NUMBER AND ATOMIC NUMBER If an atom has 17 protons and 18 neutrons, ▪ What is the mass number? 17+18= 35 ▪ What is the atomic number? 17 7 8 MOLECULES & COMPOUND A molecules is two or more atoms chemically combined to form a structure that behaves as an independent unit. A compound is two or more different types of atoms chemically combined. The kinds and numbers of atoms (or ions) in a molecule or compound can be represented by a formula consisting of the symbols of the atoms (or ions) plus subscripts denoting the number of each type of atom (or ion). The molecular mass of a molecules or compound can be determined by adding up the atomic masses of its atoms (or ion). 9 MOLECULAR MASS CALCULATION EXAMPLE: Atomic mass of sodium is 22.99 and chloride is 35.45 The molecular mass if NaCl is therefore: 22.99+35.45 =58.44 10 11 ELEMENT All matter, living, and non living, is composed of elements. An element is the simplest form of matter; it cannot be broken down into simpler form by ordinary chemical means. Four of the element- carbon (C) , oxygen (O), Hydrogen (H) and Nitrogen (N) make up a little over 95% of the human body weight 12 TYPES OF BOND 1. Ionic bond 2. Covalent bond 3. Hydrogen bond (intermolecular bond) 13 1. IONIC BOND The chemical behaviour of atoms is determined mainly by their outermost electrons. A chemical bond occurs when atoms share or transfer electron. E.g. Na+Cl- Sodium Chloride Ions are atoms that have gained or lost electrons. ✓An atom that loses 1 or more electrons becomes positively charges and is call cation. ✓An anion is an atom that becomes negatively charged after accepting 1 or more electrons. ✓An ionic bond results from the attraction of the oppositely charged cation and anion to each other. 14 2. COVALENT BOND A non-polar covalent bond forms when electron pairs are shared between atoms. E.g. Hydrogen A polar covalent bond results when the sharing of electrons is unequal and can produce a polar molecule that is electrically asymmetric. E.g. water 15 3. HYDROGEN BOND A hydrogen bond is weak attraction between a positively charged hydrogen and negatively charged oxygen or other polar molecule. E.g. water molecules Hydrogen bonds are important in determining properties of water and the three-dimensional structure of large molecules. 16 MOLECULES & COMPOUND Solubility is the ability of one substance to dissolve in another. Ionic compound that dissolve in water by dissociation are called electrolyte because it can conduct electricity. Electrolytes are important body constituents because: ✓Some conduct electricity, essential for muscle and nerve function ✓Some exert osmotic pressure, keeping body fluids in their own compartments. ✓Some function in acid-base balance, as buffers to resist pH changes in the body fluids. Molecules that do not dissociate are nonelectrolytes. 17 MOLECULES & COMPOUND A larger compounds present in the body are not ionic, and therefore have no electrical properties when dissolved in water, e.g. carbohydrates. Important electrolytes other than sodium chloride include potassium (K+), calcium (Ca2+), bicarbonate (HCO3-) and Phosphate (PO42-) 18 19 ACIDS & BASES the number of hydrogen ions H+ in a solution is a measure of the acidity of the solution. Control of the normal hydrogen ion concentration within the body is an important factor in maintaining a stable internal environment. An acid substance is one that releases hydrogen ion when in solution. A base (alkaline) substance accepts hydrogen ions, often with the release of hydroxyl (OH-) ions. A salt releases other anions and cations when dissolved; sodium chloride is therefore a salt because in solution it releases sodium and chloride ion. 20 pH A standard scale for the measurement of the hydrogen ion concentration in solution has been developed: the pH scale. The scale measure from 0-14 , with 7, the mid point, as neutral. Strong acids and bases are damaging to living tissues, and body fluids contain buffers, weak acids and bases, to keep their pH within narrow range. 21 NEUTRALIZATION REACTIONS Neutralization is the reaction between an acid and a base. The hydrogen ion (H+) from the acid reacts with the hydroxide ion (OH-) from the base to form water. The acid removes or neutralises the effect of the base and vice versa. E.g. HCL + NAOH → NACL + H2O acid base salt water Neutralization reaction help to maintain the proper pH of the blood (7.35-7.45 ) 22 BUFFERS SYSTEM The buffering mechanism are important homeostatic mechanisms and temporarily neutralise fluctuations in pH. The organs most active in buffering mechanism are the lungs and the kidneys. Lung are important regulators of blood pH because they excrete carbon dioxide (CO2). CO2 increases H+ in the body fluids because it combines with water to form carbonic acid, which then dissociates into a bicarbonate ion and hydrogen ion. CO2 + H 2O H2CO3 H+ + HCO3- Carbon water Carbonic Hydrogen Bicarbonate dioxide acid ion ion 23 BUFFERS SYSTEM The lungs help to control blood pH by regulating levels of excreted CO2. The brain detects rising in H+ in the blood- stimulates breathing, causing increased CO2 loss and fall in H+ If blood pH becomes too basic, the brain can reduce the respiration rate to increase CO2 levels and increase H+ , decreasing pH to normal. 24 BUFFERS SYSTEM Kidneys regulate blood pH by adjusting the excretion of hydrogen and bicarbonate ions. If pH falls, H+ excretion is increased and bicarbonate conserved; the reverse happens if pH rises. Kidney generate bicarbonate ions as a by-product of amino acid breakdown in the renal tubules. This process also generates ammonium ions, which are rapidly excreted. Other buffer system: ✓body proteins, ✓haemoglobin in red blood cells, which absorb excess H+, ✓phosphate, which is particularly important in controlling intracellular pH. 25 IMPORTANCE OF BUFFERS When pH falls below 7.35 and all the reserves of alkaline buffers are used up, the condition of acidosis exist. When pH rises above 7.45 , the increased alkali uses up all the acid reserve and the state of alkalosis exists. Acidosis and alkalosis are both dangerous – central nervous system & Cardiovascular system. Acidosis – lungs are not able to excrete CO2 Alkalosis- loss of acidic substances through vomiting, diarrhea, endocrine disorders or diuretic therapy 26  COMMON SUBSTANCES IN LIVING SYSTEM Nutrients and Metabolites Nutrients are essential chemical compounds obtained from the diet Metabolites are molecules synthesized or broken down inside the body These can be classified as organic or inorganic compounds/ substances Organic compounds have carbon and hydrogen as their primary structural component Inorganic compounds are not primarily carbon and hydrogen  INORGANIC SUBSTANCES Inorganic substances in cells include Water Oxygen Carbon dioxide and inorganic salts  INORGANIC SUBSTANCES Water is the most abundant compound in living material and accounts for about two-third of the weight of an adult human. Most metabolic reactions occur in water. Water plays an important role in transporting chemicals within the body. Water absorbs and transport heat. Oxygen molecules enter internal environment through respiratory organs and transported throughout the body by the blood. Within the cells organelles use oxygen to release energy from nutrient molecules.  INORGANIC SUBSTANCES Carbon dioxide is a simple, carbon-containing inorganic compound. It is produced as a waste product when energy is released during certain metabolic reactions. Most of the carbon dioxide reacts with water to form a weak acid (carbonic acid) Inorganic salts are abundant in body fluids. ▪ Examples are sodium, chloride, potassium , calcium , magnesium , phosphate, carbonate, bicarbonate and sulphate. ▪ These ions help in metabolism and helping to maintain proper water concentrations in the body fluids, pH, blood clotting, bone development, energy transfer within cells, and muscle and nerve functions.  ORGANIC SUBSTANCES Five major classes of organic compounds are Carbohydrates Lipids Proteins Nucleic acids Adenosine triphosphate (ATP) High energy compounds are also organic compounds Important Biological Molecules 32 LEARNING OUTCOMES After this session, students will be able to : describe in simple terms the chemical nature of sugars, proteins, lipids, nucleotides and enzymes; discuss the biological importance of each of these important groups of molecules 33  CARBOHYDRATES Carbohydrates (sugars and starches) contain carbon, oxygen, and hydrogen, usually in the ratio 1:1:2 Two sugar molecules combine to form bigger sugar molecule, a water molecules is expelled and the bond formed is call a glycosidic linkage. 34  CARBOHYDRATES Glucose, is the cell preferred fuel molecule. Is a monosaccharide (mono= one; saccharide- sugar) Two sugar units (disaccharides) Long chains containing many thousands of monosaccharides such as starch are called polysaccharides. Glucose can be broken down in either aerobically (with O2) or anaerobically (without O2). During this process- energy, water and carbon dioxide are released. 35  CARBOHYDRATES Functions of sugars include: Providing a ready source of energy to fuel cell metabolism Providing a form of energy storage, e.g. glycogen Forming an integral part of the structure of DNA and RNA Acting as receptors on the cell surface, allowing the cell to recognise other molecules and cells. 36 AMINO ACIDS Amino acids always contain carbon, hydrogen, oxygen, and nitrogen and many carry sulphur, magnesium, phosphate, iron, or other trace metals in addition. 20 amino acids are used as the principal building blocks of protein in human. Amino acids used in human protein synthesis have a common structure, including amino group (NH2), a carboxyl group (COOH) and a hydrogen atom. Amino acids different from next is a variable side chain. 37 AMINO ACIDS & PROTEINS Proteins are made from amino acids joined together, and are the main family of molecules from which the human body is built. Protein chains can vary in size from a few amino acids long to many thousands. Characteristic: single strands of proteins; twisted & folded three – dimensional structures The function of protein will depend on the 3-dimentional shape into which it has been twisted. changes in pH are so damaging to living tissues is that hydrogen ions disrupt these internal stabilising forces and change the shape of the protein. 38 AMINO ACIDS & PROTEINS Examples of protein biological active substances: ✓Carrier molecules (haemoglobin) ✓Enzyme ✓Hormones (insulin) ✓Antibodies Protein can also be used as an alternative energy resource, usually in starvation. Muscle wasting during starvation 39 LIPIDS Are a diverse group of substances. Inability to mix with water- hydrophobic Made up of mainly carbon, hydrogen, and oxygen atom Most important group of lipid include: Fat (triglycerides), stored in adipose tissue and an energy source. Insulates the body and protect the internal organs. A molecules of fat - 3fatty acids + 1 molecule of glycerol 40  LIPIDS 1. Fats are most common type of lipid and are classified as saturated or unsaturated , depending on the chemical nature of the fatty acids present. Saturated (solid) Unsaturated (oils) 41  LIPIDS 2. Phospholipids, integral to cell membrane structure. Form double layer, providing a water-repellent barrier membrane structure 3. Certain vitamins. Fat- soluble vitamins are A, D, E, K. 42 LIPIDS 4. Prostaglandins, important chemicals derived from fatty acids. They are involved in inflammation and other processes. 5. Steroids, including important hormones produced by gonads. Cholesterol is a steroid that stabilises cell membranes and is the precursor of steroid hormones mentioned above, as well as being used to make bile salts for digestion. 43 NUCLEOTIDES A nucleotide is made up of a sugar, a base and a phosphate group. Nucleic acids are the largest molecules in the body and are built from nucleotides. Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) 44 NUCLEOTIDES Adenosine Triphosphate Adenosine triphosphate (ATP) is a nucleotide built from ribose ( the sugar unit), adenine (base) and three phosphate groups attached to the ribose. Also called energy currency of the body. The body has to earn (synthesis) it before it can ‘spend’ it. 45 NUCLEOTIDES Adenosine Triphosphate (cont.) Cell synthesis ATP in the specialised organelles called mitochondria. The breakdown of sugars in the presence of oxygen releases energy. Enzyme in the mitochondria capture the energy released by these reactions, using it to make ATP from adenosine diphosphate (ADP). Cell uses chemical energy (ATP) to fuel metabolic activities. ATP is broken down into ADP again releasing water and a phosphate group and energy from the splitting of high energy phosphate bond. 46 NUCLEOTIDES Adenosine Triphosphate (cont.) Energy generated from ATP breakdown fuels muscle contraction, motility of spermatozoa, anabolic reactions and the transport of materials across membranes. 47  CHEMICAL REACTION A chemical reaction is the process which atoms or molecules interact to form new chemical combinations The atoms and molecules present before the chemical reaction occurs are called the reactants The new atoms and molecules created as a result of reaction are called the products  CHEMICAL REACTIONS A chemical reaction occurs when reactants combine to generate one or more products All chemical reactions in the body constitutes metabolism Metabolism provides for the capture, storage and release of energy  CHEMICAL REACTION When the bonds in a complex reactant break to form new simpler product the reaction is called DECOMPOSITION This are the catabolic reactions of metabolism. When water is used to break the bonds the reaction is called HYDROLYSIS. The digestion of food involves hydrolysis reactions.  METABOLISM Metabolism is the sum of all reactions Through catabolism cells gain energy (break down of complex molecules) Anabolism uses energy (synthesis of new molecules)  ENZYMES, ENERGY AND CHEMICAL REACTIONS A catalyst is a substance that changes the rate of a reaction without itself being chemically altered in the process. Activation energy is the amount of energy needed to begin a reaction Enzymes are protein molecules that are very specific for the reactions they control. Enzymes are catalysts Reduce energy of activation without being permanently changed or used up Promote chemical reactions ENZYME The molecules entering the reaction is called substrate and it binds to a specific site on the enzyme, called active site. Substrate bound to active site the reaction proceeds and once it is complete the product of the reaction breaks away from the enzyme and the active site is ready for use again. 53 ACTIVATION ENERGY AND ENZYME Activation energy is required to initiate chemical reactions. Without an enzyme, a chemical reaction can proceed, but it needs more energy input. Enzymes lower the activation energy, making it easier for the reaction to proceed. 54 ENZYMES Factors that influence Enzyme action are: Increase or decrease temperature that reduce activity Changes of pH Presence of cofactor, an ion or small molecule that allows the enzyme to bind its substrate (e.g. vitamin) Enzyme can catalyse both synthetic and breakdown reactions, and their names end in ‘ase’ Anabolic reaction -When enzyme catalyses the combination of two or more substrates into a larger product Catabolic reaction-breakdown of substrate into smaller products (during digestion of food) 55 CONCLUSION Element are composed of atoms. Electron are negatively charged, protons positively charges and neutrons uncharged. Isotopes are atoms with same atomic number but different atomic weights. Hydrogen bonds occur between polar molecules. Three kind of chemical reactions are synthesis, in which larger molecules form from smaller particles; decomposition, in which smaller particles form from breakdown of larger molecules; and exchange reactions, in which parts of two different molecules trade positons. 56 Exercise Homeostasis can best be described as: ____. A. A constant state maintained by living and nonliving organisms B. A state of relative constancy C. Adaptation to external environment 57 Exercise Homeostasis can best be described as: ____. A. A constant state maintained by living and nonliving organisms B. A state of relative constancy C. Adaptation to external environment 58  Exercise Which of the following is not one of the basic components in a feedback control loop? A. Effector mechanism B. Transmitter C. Sensor 59  Exercise Which of the following is not one of the basic components in a feedback control loop? A. Effector mechanism B. Transmitter C. Sensor 60 Exercise The contraction of the uterus during the birth of a baby is an example of: ____. A. Negative feedback B. Positive feedback C. Inhibitory feedback 61 Exercise The contraction of the uterus during the birth of a baby is an example of: ____. A. Negative feedback B. Positive feedback C. Inhibitory feedback 62 Exercise Negative feedback mechanisms: ____. A. Minimise changes in blood glucose levels B. Maintain homeostasis C. Are responsible for an increased rate of sweating when air temperature is higher than body temperature 63 Exercise Negative feedback mechanisms: ____. A. Minimise changes in blood glucose levels B. Maintain homeostasis C. Are responsible for an increased rate of sweating when air temperature is higher than body temperature 64