IB SL Option C: HUMAN BIOCHEMISTRY Compiled by Minna Pöntinen 20/11/02 ----------------------------------------------------------------------------- REQUIREMENTS FOR A HEALTHY DIET - Water - Carbohydrated, proteins, fats, vitamins, minerals - Food from different food groups: - Milk gr -> calcium, protein, vit. A & D - Meat gr -> iron, energy, vit. B - Vegetable/fruit gr -> vit. C - Bread gr -> energy, vit, minerals, protein ----------------------------------------------------------------------------- PURPOSES OF THE DIFFERENTS PARTS OF THE DIET Part Purposes Carbohydrates (60%) - Providing energy - Storing energy - Acting as a precursor to biological molecules Proteins (20-30%) - Biological catalysts (enzymes) - Structure (e.g hair) - Some hormones are proteins Fats (10-20%) - Providing energy - Thermal insulation & protection - Part of cell membranes Vitamin A - Night vision -"- B - Formation of skin -"- C - Healing of wounds (collagen synthesis), preventing bacterial infections, involved in biosynthesises -"- D - Formation of bone structure -"- E - Sex stuff? (Deficiency leads to sterility) -"- K - Blood clotting ----------------------------------------------------------------------------- GM FOOD - Genes are transferred from one species to another - Benefits: - Improve flavour, texture, nutritional value and shelf life of food - Foods with "health effects" could be produced - Plants could be made more resistant - Concerns: - Outcome of alterations uncertain - May cause diseases and allergic reactions - May alter the balance of ecosystems ----------------------------------------------------------------------------- CARBOHYDRATES - Simple chs, such as glucose are converted into e.g starch and cellulose - Monosaccharides: - some monosaccharides: glucose, fructose, ribose - contain only one sugar unit - the empirical formula CH2O - between three and six C atoms - C5H10O5 = pentoses, C6H12O6 = hexoses - lots of structural and optical isomerism - also open chain and ring structures - D-glucose = glucose found in nature: - alpha-D-glucose: OH group in the first chain downwards - beta-D-glucose: OH group in the first chain upwards - Five-membered ring = furanoses (e.g ribose) - Six-membered ring = pyranoses (e.g glucose and fructose) - Classified into aldoses and ketoses - Polysaccharides: - Some polysaccharides: - starch, glycogen (storage polysaccharides) - cellulose, glycoproteins (structural polysaccharides) - Monosacch. -> (condensation reactions) -> disacch. -> polysaccharides - Example: alpha-D-glucose -> sucrose - Link between two sugars = glycosidic link = glycosidic bond = ether bond - Starch & cellulose: - Glucose units form a long chain containing amylose & amylopectin parts - Difference in number of branches - Amylose: starch that is water soluble - Amylopectin: starch that is insoluble in water Functional Group Reactions Ketones (-C=O) Reducing (-OH) Aldehydes (-CHO) Reducing (-OH), Oxidation (-COOH) Hydroxyl gr. (-OH) Oxidizing/condensation (-COOH) ----------------------------------------------------------------------------- FATS - Triesters (triglycerides) formed with condensation reactions between glycerol and long chain carboxylic acids - Fats (s) contain saturated carboxylic acid groups (no double bonds) whereas oils (l) are unsaturated, meaning they contain at least one double bond - Polyunsaturated = many C=C bonds; better for the health - Effect of C=C bond - The more unsaturated the fatty acid the lower the melting point (C=C bond angle produceds a kink in the chain) - Unsaturated fats can go through addition reactions - Addition of iodine -> colour disappears -> addition reactions - Iodine number = grams of iodine that add to 100 g of the fat - Soap - Saponification: Alkali + fats -> soap - Long non-polar hydrophobic tail, polar hydrophilic head ----------------------------------------------------------------------------- PROTEINS - Large molecules made up of chains of 2-amino acids - About 20 amino acids occur naturally - Amino acids -> condensation reactions -> polypeptides; amino acids join together by amide link (= peptide bond) - Structures: - Primary: Fixed number of amino acid residuces connected to each other - Secondary: The chain of amino acids folds itself due to intermolecular H bonding - alpha-helix: a spiral - beta-pleated: sheet-like structure - Tertiary: overall folding of the chains by interactions between distant amino acids to give the protein the 3-dimensional shape - Quaternary: separate polypeptide chains interact together (example: haemoglobin) - Analysis of proteins: - Paper chromatography - Spot of sample on paper -> paper to solvent -> solvent rises up the paper due to capillary action -> paper is dried and sprayed with ninhydrin - Electrophoresis = PAGE - Sample is placed on polyacrylamide gel -> depending on pH it will move towards positive and negative electrodes; at isoelectric point the samples will stop ----------------------------------------------------------------------------- VITAMINS - General properties: - Water soluble vitamins: B, C -> polar molecules - Fat soluble vitamins: A, D, E, K -> long non-polar hc chains - The body is not able to synthesize vitamins (exception: vitamin D) - Prolonged cooking destroys vitamins - Vitamin A (retinol) - found in cod liver, green vegetables, fruit - in the body retinol is oxidized to retinal - retinal + opsin -> rhodopsin (converting light into electic signals) - Vitamin C (ascorbic acid) - found in fresh fruit and vegetables - Vitamin D (calciferol) - found in fish liver oils and egg yolk - formed on skin by ultraviolet light and 7-dehydrocholesterol ----------------------------------------------------------------------------- HORMONES - Chemical messengers produced in glands, transported to places by blood - Glands are controlled by the pituitary gland, which is controlled by the hypothalamus - Adrenaline (epinephrine) - Produced in adrenal glands - A stimulant; fight or flight -hormone - Dilates the pupils, increases heartbeat, increases the rate of release of sugar onto the bloodstream - Thyroxine - Produced in the thyroid gland - Regulates the body's metabolism - Low level of thyroxine: lethargy, sensitivity to cold, dry skin - High -"-: anxiety, weight loss, intolerance to heat, protruding eyes - Insulin - Formed in the pancreas - Regulates blood sugar levels - Too little insulin: thirst, weight loss, lethargy, coma, problems with circulation - Too much insulin: blood sugar level falls -> dizziness, fainting - Anabolic steroids - Build up muscle - Sex hormones - Steroids; four-ring structure; cholesterol is the basic building block - Cholesterol is formed in the liver and omnipresent in the body - Male sex hormones (testosterone & andosterone) - Produced in the testes - Anabolic = encouracing tissue, muscle and bone growth - Androgenic = conferring the male sexual characteristics - Female sex hormones (oestradiol & progesterone) - Produced in the ovaries - Very similar to male sex hormones; just small changes in the functional groups - Responsible for sexual development and the menstrual and reproductive cycle - Oral contraceptives - Pituitary releases follicle stimulating hormone -> FSH goes to ovaries -> oestradiol is released -> prepared for the release of the egg -> after 2 weeks supply of FSH stops, the supply of lutenizing hormone starts -> releases progesterone in the ovaries -> causes the egg to be transported to the uterus -> if egg is fertilized it sticks to the uterine wall and hormone levels rise dramatically; if not, hormone levels drop and menstruation begins - Most common pills contain a mixture of oestradiol and progesterone -> mimics pregnancy / keeps hormone levels high so that eggs are not released -----------------------------------------------------------------------------