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Transcript
Human Biochemistry Energy [484-486] Energy in food is determined using calorimetry • Exercise 1 page 486 Functions of proteins [486] 1) 2) 3) 4) 5) 6) 7) Structural Biological catalysts Hormones Protection Transport Storage lubrication Structure of Proteins [487] • Proteins are polymers of amino acids • General structure of amino acids • 20 naturally occurring • Called 2-amino acids (or amino acid) Structure of Proteins [488] • Amino acids are both acidic and basic Structure of Proteins [488] • Amino acids in the body exist as zwitter ions • Have high melting points, water soluble, act as buffers Structure of Proteins [489] • At the isoelectric point: – amino acids have no net charge – will not move in an electric field and are least soluble • Isoelectric point depends on R group Structure of Proteins [489] Reactions of amino acids [490] • Amino acids undergo condensation reactions Structure of Proteins [490-495] • Proteins are actually polypeptides • Proteins have primary, secondary, tertiary, and quaternary structure Structure of Proteins [490-495] • Primary structure is amino acid sequence • Secondary structure refers to folding of protein chain – H-bonds form between amino acids – -helix and pleated sheets Structure of Proteins [490-495] • Tertiary structure refers to twisting, folding, and coiling of protein chain due to interactions between R groups – Compact structure known as conformation – Most stable – H-bonds – Hydrophobic interactions – Ionic bond between R groups – Disulfide bridge Structure of Proteins [490-495] • Quaternary structure is association between protein chains Analysis of Proteins [495-497] How are proteins analyzed? • First protein is broken down into amino acids – Hydrolysis reaction using enzyme or heat/acid – Amino acid sequence will not be known – Amino acids separated and analyzed by 1)electrophoresis or 2)chromatography Electrophoresis of Proteins [497] – Separation based on movement of amino acids in an electric field (charged) – Amino acids stop moving at isoelectric point – Detected by stain or UV light Electrophoresis of Proteins [497] – electrophoresis of amino acids 49 Chromatography of Proteins [496] • Chromatography – Separation based on solubility differences between mobile phase and stationary phase – Amino acid spots become visible with ninhydrin Exercises 2,3,4 page 497 Carbohydrates [498] • Functions of carbohydrates in humans 1) Energy source (glucose, fructose) 2) Energy reserve (glycogen) 3) Precursor of other biologically important molecules (fats, amino acids, nucleic acids) In plants carbs have a structural function (cellulose) Structure of Carbohydrates [498-501] • types of carbohydrates 1) Monosaccharides (simple sugars) 2) Disaccharides 3) Polysaccharides Monosaccharide Structure [498-499] • Classified by number of carbons – eg: pentose sugar has 5 C • Essential features are 2 or more OH groups and a C=O, empirical formula = CH2O • Monosaccharides can be in chain or ring form Straight chain monosaccharides [498] Ring monosaccharides [498 -499] Disaccharides [499] • two monosaccharides reaction via a condensation reaction – Glycosidic link • Examples are – Lactose (milk) -glucose + -galactose – Maltose (starch digestion) -glucose + -glucose – Sucrose (cane sugar) -glucose + -fructose Disaccharide Structure [499] Polysaccharides [499-501] • Polysaccharides are polymers of monosaccharides • Examples – Starch (plant carb storage) – Glycogen (animal carb storage) – Cellulose (plant structure) Starch [500] • Starch – Polymer of -glucose – Mixture of two polysaccharides • Amylose – straight chain 1,4 link of -glucose • Amylopectin – branched chain 1,4 and 1,6 links of -glucose Glycogen [500] • Glycogen (animal carb storage) similar to amylopectin with more 1,6 links Cellulose [500] • Cellulose (plant structure) 1,4 link of -glucose Digestion of polysaccharides [501] – Insoluble in water so must be broken down into monosaccharides for transportation in blood – Humans have enzymes to break down starch and glycogen, not cellulose – No enzyme for linkage, although some bacteria in gut have, cellulose mostly passed through undigested – Cellulose is main bulk in waste Digestion of polysaccharides [501] • Dietary fiber is the undigested substances • Benefits – Aids movement of undigested food – Prevents constipation, hemorrhoids, irritable bowel syndrome, colorectal cancer Lipids [502-509] 3 main types of lipids 1) Triglycerides 2) Phospholipids 3) steroids Function of lipids [502-503] 1) Energy source • More energy than carbs, lipids less oxidized 2) Protection of organs and insulation • Adipose tissue 3) Component of hormones and bile 4) Cell membranes Function of lipids [502-503] Negative effects of lipids 1) obesity 2) increased risk of heart disease Main culprit in heart disease is cholesterol Cholesterol [503] • Cholesterol is not soluble in blood, transported in body bound to lipoproteins – Low density lipoprotein (LDL) • “Bad cholesterol” • Increased artery build up • Saturated and trans fat – High density lipoprotein (HDL) • “good cholesterol” • Protection against heart attack • Thought to carry cholesterol away from arteries Types of Lipids 1) Triglycerides 2) Phospholipids 3) steroids Triglycerides [504-508] • Major component of fats and oil • Formed by condensation reaction between glycerol and 3 fatty acids Triglycerides [504-508] Fatty Acids [504-508] • Most fatty acids have even number of carbons • Number is between 14 and 22 • Fatty acids can be saturated, monounsaturated, or polyunsaturated • Saturated are solids at RT, known as fats, increase LDL • Unsaturated fats are liquids at RT, known as oils Fatty Acids [504-508] Fatty Acids [504-508] • Essential fatty acids – Our body cannot synthesize all the fatty acids we need, we must get these from our food – Linoleic acid (omega-6-fatty acid) – Linolenic acid (omega-3-fatty acid) – Lower LDL – Prostaglandins synthesized from essential fatty acids, prostaglandins lower blood pressure Fatty Acids and Iodine Number [504-508] • Degree of unsaturation of a fatty acid can be determined using iodine • Iodine number is the number of grams of iodine that react with 100 g of fat • Exercise 6 page 509 Fatty Acids [504-508] • Food industry uses hydrogenation to produce saturated fats in foods – High melting point – More convenient to store and transport – More stable • Process produces trans fats Fatty Acids [504-508] lipids - Triglycerides Digestion of triglycerides [508] • Fats must be broken down into glycerol and fatty acids to be transported in blood • Fats undergo hydrolysis using enzymes – Lipases • Slow process Phospholipids [508] • Glycerol + 2 fatty acids + a phosphate group and one of several nitrogen-containing molecules. • Polar head and hydrophobic tail • Phospholipid bilayer makes up cell membrane Phospholipids [508] Phospholipids [508] Steroids [509] • have a structure of 17 carbon atoms arranged in four rings • Cholesterol used in synthesis of other steroids such as testosterone, estrogen Steroids [509] Micronutrients and Macronutrients [509-513] • Nutrients – molecules required in diet for absorption and use by the body • Micronutrients are needed in extremely small amounts, mainly function as co-factors of enzymes (less than 0.005% of body mass) – mg or mg – Examples are vitamin B, and the minerals Fe, Cu, F, Zn, I, Se, Mn Mo, Cr, Co Micronutrients and Macronutrients [509-513] • Macronutrients are needed in relatively large quantities, used to provide energy and to build and maintain structure – Carbohydrates, proteins, lipids – Na, Mg, K, Ca, P, S, Cl Micronutrients and Macronutrients [509-513] • Vitamins are organic compounds needed for growth and metabolism that must be taken in the diet (not made in body) • Either water or fat soluble (not both) • Water soluble transported directly in blood and excess passed through kidneys – Vitamins B and C Micronutrients and Macronutrients [509-513] • Fat soluble slowly absorbed and excess build up in fat tissues – Can cause serious side effects – Vitamins A, D, E, and K Micronutrients and Macronutrients [509-513] • Solubility depends on structure • Compare structures of retinol (vitamin A), ascorbic acid (vitamin C), and calciferol (vitamin D) Micronutrients and Macronutrients [509-513] • Malnutrition is the lack of nutrients in the diet – Poor, underdeveloped countries – Consumption of processed, energy dense, but nutrient poor foods – Lack of distribution of global resources – Depletion of soil nutrients – Lack of education – Use of chemicals in food production Micronutrients and Macronutrients [509-513] • The World Health Organization has identified iodine, vitamin A, and iron as the most important microdefiencies globally Macronutrient and disease • Protein – marasmus and kwashiorkor Micronutrients and Macronutrients [509-513] Micronutrient and disease • Iron – anemia • Iodine – goiter • Retinol – xerophthalmia, night blindness • Niacin – pellagra • Thiamin – beriberi • Ascorbic acid – scurvy • Calciferol - rickets Micronutrients and Macronutrients • Solutions to malnutrition – Fresh and nutrient rich food rations – Adding nutrients to common foods – Genetic modification of food – Nutritional supplements – Increased nutritional information on foods – education Hormones [513-516] • Hormones are chemical messengers • Secreted directed into the blood by endocrine glands and act on target cell – Target cells have specific receptors for hormone • Important hormone/endocrine gland/target cell are shown on page 514 • Compare and contrast structures of cholesterol and sex hormones oral contraceptives [515] • Mode of action of oral contraceptives – Prevent ovulation – Pills contain progesterone and estrogen that suppress secretion of follicle stimulating hormone and luteinizing hormone which trigger ovulation – Simulates hormonal conditions during pregnancy – Pill taken for 3 weeks with 1 week off – Prescription only – Morning after pill Steroids [516] • Use and abuse of steroids • Female hormones – Oral contraceptive use steroids – Hormone replacement therapy use steroids Steroids [516] • Male steroids are called androgens – Testosterone is used in treatment of testes and breast disorders – aka anabolic steroids which promote tissue growth, especially muscle – Used to gain weight after debilitating disease – Abused by athletes • Side effects include infertility, liver damage, sexual characteristics