UGEB2380 The Chemistry of Life Lecture Notes PDF

UGEB2380 The Chemistry of Life Academic Year 2024-25 Dr. Sam CK HAU (Department of Chemistry) Energy of Foods Foods and Drinks helps to define our culture and forms an integral part of our families and social lives Trans fats, saturated fats, omega-3s … … ? Food is the chemical fuel...

UGEB2380 The Chemistry of Life Academic Year 2024-25 Dr. Sam CK HAU (Department of Chemistry) Energy of Foods Foods and Drinks helps to define our culture and forms an integral part of our families and social lives Trans fats, saturated fats, omega-3s … … ? Food is the chemical fuel that provides the energy for the human engine; just like gasoline for the engines of motor vehicles 3 Energy, Heat and Work In our body, nutrients in food supply the chemical energy to do work and sustain life by a complex process “Metabolism” Energy - a capacity to do work and is typically measured in terms of its equivalent in heat A common unit used in quantifying heat or energy is the calorie (Latin: calor - heat) 1000 cal = 1 kcal = 1 Cal The technique of measuring the amount of heat is called calorimetry - calorie: the amount of heat (or energy) needed to raise the temperature of 1 gram of H2O by 1℃ Calorie: 1000 calories, or 1 kilocalorie 4  Watts, Joules and Calories 1O watt = 1 Joule per 1 second Y related not 1 Joule = 0.24 calories to heat 1 calorie = 4.2 joules Example: How many minutes could a 100-watt light bulb remain lit at full brightness if it consumed the energy content of a 275-Calorie candy bar? I S 5 The Human Body Metabolism - all the chemical reactions that take place in a living organism to support life Convert food into energy and physical substance of the body the * oxygen is key => C12H22O11 + 12O2 sucrose Je O 12CO2 + 11H2O + Energy Metabolism occurs more slowly than combustion and under much milder conditions lot won't fluctuate a body temperature 6  Nutrients Macronutrients The major components of our foods that provide us with energy and the materials that form our bodies Can be classified as three categories ⑪ ✓ Fats & Oils ⑳ ✓ Carbohydrates ⑬ ✓ Proteins Micronutrients Nutrients we need in very small quantities, such as vitamins and minerals essential to body , but does not give us 7 energy Energy In and Out Energy In amount of give you large energy Fat and Oil -& 9 Cal/g; E will Carbohydrates - 4 Cal/g; Proteins - 4 Cal/g Alcohol (ethanol) - 7 Cal/g Energy Out Uses energy through exercises and several forms of metabolism Two forms: 1) Thermic effect of food; 2) Basal metabolism Energy Stored Converting an excess of macronutrients to energy storage & no matter you do exercise or not they will still help you lose energy Long term storage: body fat; Short term storage: glycogen & much easier to 8 break down than starch ( growth rate ofPlant sa store energy Energy In and Out Thermic Effect of Food (TEF) -due to Energy used in digesting and metabolising food Sense TEF - grow a bit warmer and find your heartbeat a bit faster after a meal (body may feel warm during eating process) Drowsiness after a large meal - diversion of blood from the brain to the digestive system; digestion takes momentary precedence over mental alertness 9 Energy In and Out Basal Metabolism Energy used to keep our & minimum hearts beating, our lungs expanding and contracting, and all other organs G working to maintain life To measure, a person lies at rest after 12 hours fasting (i.e. Lying at rest - in the absence of exercises; 12-h fasting - precludes the energy used through TEF) A healthy adult - roughly 1 Calorie per hour per kg of body weight; increases with 3 can enced be any body stress like illness or pregnancy by emotions - use up more t heart bumps faster energy 10  Fats and Oils Work both for and against functions life and good health ⑭ Served as energy storage ⑫ Helps insulate our bodies heat loss ⑬ Form a protective cushioning around major organs Have no flavours but substances doSadd flavours( are highly soluble in fat oil soluble & non-polar 11 Fatty acids Contains a long hydrocarbon (building up by Carbons and Hydrogens only) side chain and a carboxylic acid head - Such chains can vary in: ✦ The number of carbons contained, therefore the determine saturated / + unsaturated fatty length of the chain acid O ✦ The number and nature of carbon-carbon double bonds in the chain E Photo credit: https://www.savemyexams.co.uk/ 12 Saturated & Unsaturated Saturated fatty acid - a fatty acid with no carbon-carbon double bonds linear& straight shape much more in I - Chocolate’s rich, creamy, melt-on-tongue texture derives largely from the nature of its fat. Stearic acid ( , H3C(CH2)16COOH) ↳ makes up about one-third of the fatty acid in chocolate have high meeting point Unsaturated fatty acid - a fatty acid with one or more carbon-carbon double bonds usually in C C bond will cause = the liquid state X The fat/oil in avocados, chain to bend into a rather almonds, and olive oil are ↑ irregular shape rich in the mono- O unsaturated fatty acid, oleic acid ( ) O HO H 3C 13 Fats and Oils All fats and oils are triglycerides - molecules composed of a glycerol backbone connected to three fatty acids The fatty acid structures be same or O- can will affect the physical different properties like the melting point C * through condensation 14 Photo credit: https://www.savemyexams.co.uk/  Fats A triglyceride with a high melting temperature and a tendency to exist as a fat (solid at room temperature) → long side chain and high degree of saturation Saturated side chains adopt a linear orientation * Regularity allows for stronger associations between triglyceride molecules → more heat energy to disrupt these strong intermolecular forces → high melting point I have large surface area to overlap Triglycerides with saturated side-chains witheacher Strong temporary association between molecules Saturated side chains follow more linear patterns, allowing for stronger intermolecular interactions, which result a higher melting temperature 15  (everything in the opposite way Oils A triglyceride with a low melting temperature and a tendency to exist as a oil (liquid at room temperature) → short side chain and low degree of saturation Unsaturated side chains adopt a bent orientation (due to bond) C= < * Irregularity allows for weaker associations between triglyceride molecules → less heat energy to disrupt these weak intermolecular forces → low melting point Triglycerides with unsaturated side-chains irregular shape Unsaturated side chains have kinks, which prevent close, orderly association between molecules, and gives Weaker temporary association rise to a lower melting between molecules temperature 16 Fats and Oils Nature is not that neat and simple Fats and oils of our diets are complex mixtures of triglycerides containing a variety of side chains: long, short, fully saturated, monounsaturated, polyunsaturated no clear cut for saturated or unsaturated (= usually mixture, depends on the percentage Photo Credit: European Food Information Council 17 Fats and Oils Extent of unsaturation can be determined by a measure called “iodine number” - the number of grams of iodine C C bond(s) on the side chain that can add to 100 g of of triglycerides (colorless) triglycerides H H I I + C C Coloured Mixture Higher iodine number - more unsaturated; lower Iodine (I2) iodine number - less Dark Purple until the point there is no where unsaturated & more fully Addition Reaction colour change saturated & H H I C C I Colourless Mixture 18 Fat, Cholesterol and Heart Disease The body requires cholesterol like estrogen ( ) and testosterone ( ) to aid in digestion, produce Vitamin D and hormones. High levels of cholesterol are closely associated with atherosclerosis ( e ) - build-up of fat deposits on the inner lining of arteries → reduce blood flow and leads to high blood pressure and heart disease H 3C H 3C CH3 H 3C H 3C HO Cholesterol is a hydrophobic molecule (very little tendency to dissolve in water), and is classified as a steroid because of its core & molecule structure of four rings oil soluble 19 Fat, Cholesterol and Heart Disease Transport of cholesterol through the blood Wrap packets of cholesterol in a sheath proteins and triglycerides (more hydrophilic in the surface) - lipoprotein HDL: high density lipoprotein; LDL: low density lipoprotein HDLs are beneficial by removing & cholesterol deposits from the wall of arteries and transport to the liver for disposal!; LDLs deposit cholesterols on arterial walls" # 20 Photo credit: Healthline  Fats and Oils in Our Diet Triglycerides rich in mono-unsaturated and polyunsaturated fatty acids - more healthier, lowering the risk of heart disease Those rich in saturated fatty acids or trans-fatty acids - potentially harmful > - convert saturated to unsaturated oil Trans-fatty acids - unintended byproduct of the catalytic hydrogenation of vegetable oil or high temperature cooking ↳ may change from cis to trans Catalytic Hydrogenation still bending 5 H H H H Cis C C bond + Hydrogen atoms on H H C C same side of the C C Vegetable Oil H 3C CH3 double bond H C C CH3 Trans C C bond Hydrogen atoms on opposite side of the Catalyst if H 3C H double bond H H Process used in food industry to harden a linear The C C bonds found in vegetable oils H C C H vegetable oils in order to more stable orientation are typically in the cis configuration convert them into semi- solids for margarines form => looks like saturated acid fatty 21 LDL =p Fats and Oils in Our Diet Essential fatty acids (EFAs) Necessary for good health Must come from the diet and cannot produce by our bodies e.g Omega-3 fatty acid - an unsaturated fatty acid with a C C occurring between the third and fourth carbons from the end of the chain O C HO H H H H H C C C H C C a sa Some C C H H C H C H C 2 C C CH2 3 H C C H 1 CH3 H H Lower the risk of heart disease, and rich in salmons, other fatty fishes, walnuts and flaxseed ( ) inculation water , cold temp , good ↓ : living in deep 22 on fish => fat on belly, develop Carbohydrates A class of macronutrients including sugars and starches that is an important energy source for organisms Composed exclusively of three elements: carbon, hydrogen and oxygen Ratio of hydrogen to oxygen atoms in all carbohydrates is almost exactly 2:1, as it is in water (H2O) In early days, such chemicals were suggested to be the hydrates of carbon 23 Types of Carbohydrates Classified according to the number of connected sugar molecules, called saccharides The smallest, simplest carbohydrates are the monosaccharides CH2OH C O o H HC OH H CH Gluocose un OH C C OH H OH CH2OH OH O C CH Fructose C OH H CH2OH OH CH2OH OH C O H HC OH CH Galactose H C C OH H OH 24  Types of Carbohydrates Remove a –OH group from one of the monosaccharides and a –H group from the other, two monosaccharides will join into one by a covalent bond (glycosidic linkage) and become a disaccharide This process is named as dehydration; on the other hand, when one disaccharide split into two monosaccharides is hydrolysis * reversible reaction Gluocose Fructose umb CH2OH C O CH2OH OH # H O HC OH CH C H CH H OH C C OH H O C C H H CH2OH OH OH (+H2O) Hydrolysis CH2OH C O 8 CH2OH Dehydration (-H2O) # OH H O HC OH CH C H CH H OH C H C O C C H CH2OH # OH OH Glycosidic Linkage 25 Carbohydrates and Diet (High G2) => high sugde content High glycemic-index food (rich in carbohydrates) - associated with high risk of diabetes and obesity (i.e. refined sugars in soft drinks and the flours in white bread) Low glycemic-index food (low in carbohydrates) - digest and absorb slowly and results in more controlled changes in blood sugar levels (i.e. whole grains, whole fruits, beans and most vegetables) - Enzyme sucrase (as a catalyst) helps to separate the large sugar into smaller ones, which can penetrate the intestinal wall to enter the bloodstream 26 Carbohydrates and Diet Starch in foods serves as macronutrients; Cellulose in the more fibrous structure of plants like celery stalks provides us the dietary fibre of molecule But we can digest starch but not cellulose, why? * structure CH2OH CH2OH CH2OH CH2OH H H H H H H H H OH OH OH OH O O O 𝛽-side OH OH OH OH CH2OH 𝛼-glycosidic linkage H H CH2OH OH OH OH CH2OH H OH CH2OH H OH CH2OH H OH O H 𝛼-side O H OH OH O H OH the H OH H OH Thydroxyl gy not at bottom but at the side OH 𝛽-glycosidic linkage M Enzymes in our bodies can only recognise the shape of the 𝛼-linkage of starch 27 Carbohydrates and Diet Glycogen Serves as a source of quick energy in animals Make up of 𝛼-glucose rings but highly branched and less units Deposit largely in liver and muscles, where can cleaved quickly to yield individual glucose molecules Cannot be stored up and used up as we sleep and be replenished the next day I will be used up don't keep , glucose/carbohydrates over night) 28  know difference mono & disaccharides > - Carbohydrates and Diet Lactose Dependance on the enzyme (lactase) to hydrolyse sugars The digestive systems of infants and children with plenty of lactase (40% of their calories from the lactose of their mothers’ milk) Gradually, adults lose the ability to produce lactase in large quantities (lactase-deficient) Unabsorbed lactose → fermentation to become lactic acid, CO2 and H2O → gastric distress 29 Proteins Proteins are polymers of amino acids A gene carries the blueprint for a specific protein and each protein serves a particular purpose Proteins are required in daily diet to provide amino acids for making muscles, hair, enzymes and many other cellular components 30  to know how Amino acids need to differentiate ; ↑ categories An organic compound that contains both an amino (-NH2) group and a carboxyl no need to remb structure of a ↳ usually (no overall charge (-COOH) group 2 and Standard amino acid is the of 20 amino acids normally found in proteins Amino acids are grouped into four categories according to side-chain CR-group) polarity usually haa ↳Our te Carboxylic Group Amino Group ↓ may underso H H O neutralisation N C C process H R OH can be more water Side Chain Group soluble General Structure of Amino acids 31 Amino acids Non-polar amino acid contains one amino group, one carboxyl group and a hydrophobic side chain Polar neutral amino acid contains one amino group , one carboxyl group and a hydrophilic side chain but neutral 32 Amino acids A in exam: show structure of an & Polar acidic amino acid. · differentiate which category contains one amino group, to it belongs two carboxyl groups and one of which being part of the side chain -Va = Polar basic amino acid Lave contains two amino group, one carboxyl group and the second amino group being ↓ part of the side chain the I-ve : 33 Structures of Proteins Four protein structural levels, listed in order of increasing when have complexity, are primary certain length = structure, secondary structure, tertiary structure cil and quaternary structure 34 Structures of Proteins Primary structure Two amino acids join together with loss of a water molecule to form a peptide link The length of amino acid chain can vary from a few amino acids to many; two amino acids - dipeptide; three amino acids - tripeptide; a polypeptide is a long unbranched chain of amino acids undergo H 2O H 2O H 2O hydrolysis can H O H O H O H O be separated H H H H H N H C C O H N H C C O H N H C C O H N H C C O back to original R1 R2 R3 R4 a G ,. H O R2 H O R4 H N H C C N H C C O H C N C C N C H H R1 H O R3 H O 35 Structures of Proteins Secondary structure Regions of the chain form organised structures like coils Tertiary structure In some types of proteins, the coils bend and twist to form complex, globular shapes Quaternary structure Two of more tertiary structures can bind together to form larger complexes 36 Fibrous and Globular Proteins Our hair, nails and muscles are tough and strong because of their fibrous protein structures The strength comes from the organisation of these protein molecules, lying in parallel strands, entwining much like strands of fibre twisted into strong rope * can elongate 37 Fibrous and Globular Proteins The peptides of globular proteins bend and twist back to themselves, forming small spheres Move around easily in the blood and other fluids, and are available to do their works when needed Enzymes are globular ↑ proteins, as are the proteins of egg white exists like globular protein 38 Protein Denaturation Cooking an egg disrupt the attractive force that hold the protein molecules in their native globular shapes Such protein is considered as denature, and form bonds to other protein molecules, which gives the characteristic white colour and texture It is not a reversible transformation E form other may linkage become an > totally new change original 3D scructure. protein shape