Chapter 24 Metabolism and Nutrition PDF

CHAPTER 24 Metabolism and Nutrition 24.1 – Overview of Metabolic Reactions Catabolic – breaking down molecules (food) to release energy Anabolic – producing larger molecules by using the energy from catabolism If net energy change is positive, we store energy (glycogen, fat) If net energy is negativ...

CHAPTER 24 Metabolism and Nutrition 24.1 – Overview of Metabolic Reactions Catabolic – breaking down molecules (food) to release energy Anabolic – producing larger molecules by using the energy from catabolism If net energy change is positive, we store energy (glycogen, fat) If net energy is negative, we use stored energy 24.1 – Catabolic Reactions Energy is released from the chemical bonds 40% of energy goes toward ATP, the energy currency of the body 60% of energy is given off as heat ATP – Adenine, ribose, and a phosphate group. Result is ADP and P Carbohydrates break down to glucose which is the most common fuel for ATP Glucose is used for fuel, stored as glycogen, or converted into fat Fat is stored and triglycerides are used for energy in beta oxidation Protein breaks down into AA which can build other proteins or be used for energy 24.1 – Anabolic Reactions Monosaccharides form polysaccharides Fatty acids form triglycerides Amino acids form proteins Nucleotides form nucleic acids 24.1 – Hormone Regulation Cortisol, glucagon, and epinephrine are catabolic Growth hormone, IGF, insulin, testosterone, and estrogen are anabolic 24.1 – Oxidation-Reduction reaction Redox reaction – electron passes between molecules, the donor is oxidized and the recipient is reduced Often a series of reactions to combine ADP and P These reactions are catalyzed by enzymes that remove the hydrogen atom 24.2 – Carbohydrate Metabolism Glycolysis – cells take up glucose in response to insulin Glycolysis uses 2 ATP to form 4 ATP, 2 NADH molecules, and 2 pyruvate molecules Pyruvate continues on to the Krebs cycle if O2 is present NADH will produce more ATP later in the mitochondria Anaerobic – pyruvate is converted to lactic acid which generates 1 ATP and lets glycolysis continue Aerobic – pyruvate enters the Krebs cycle, electrons are passed to the electron transport chain, and more ATP is produced 24.2 – Krebs Cycle/Citric Acid Cycle/ Tricarboxylic Cycle Pyruvate moves into matrix of the mitochondria and is metabolized by enzymes Pyruvate becomes acetyl CoA (a double carbon + Coenzyme A) Acetyl CoA combines with oxaloacetate to form citric acid Citric acid breaks down through the cycle until it becomes oxaloacetate again 3 high energy molecules are created – ATP, NADH, and FADH2 NADH and FADH2 pass electrons to the electron transport chain for more ATP, they are known as electron donors Each citric acid molecule produces 1 ATP, 1 FADH2, and 3 NADH 24.2 – Electron Transport Chain (ETC) NADH and FADH2 are transferred through protein complexes NADH → NAD+ and H+ and 2e As molecules are oxidized and reduced energy is released to pump H+ out of the matrix H+ now forms a gradient and finds ATP synthase to move back into the matrix causing the complex to rotate and push ADP together with inorganic P 2e- and 2H+ and ½ O2 → H2O Electrons are transferred to O2 which is why we need O2 to live End result is 38 ATP produced from glycolysis, Krebs cycle, and ETC 24.2 - Gluconeogenesis Making glucose in the liver from pyruvate, lactate, glycerol, alanine, or glutamine Happens due to low glucose (fasting, starving, dieting) 24.3 – Lipid Metabolism Oxidation of fatty acids for energy Cholecystokinin (CCK) stimulates the release of pancreatic lipase and bile salts, it also travels to the brain to suppress hunger Triglycerides are broken down and rebuilt after they are absorbed, they travel with cholesterol Lipolysis – hydrolysis separates the triglyceride into a fatty acids and glycerol Fatty acids are oxidized into acetyl CoA Glycerol enters the glycolysis pathway 24.3 - Ketogenesis Excessive acetyl CoA due to the Krebs cycle is overloaded with fatty acids Acetyl CoA is used to create ketone bodies Ketone bodies - fuel if glucose is low (starvation, diabetes) Too many ketone bodies – break down into CO2 and acetone Acetone is exhaled and causes breath to be sweet like alcohol CO2 decreases blood pH and can lead to diabetic ketoacidosis 24.3 - Lipogenesis Lipids are formed from excess acetyl CoA if glucose is plentiful 24.4 – Protein Metabolism Much of the body is made of proteins, it can be a source of energy if needed Excess protein isn’t stored for later so it must be converted to glucose or triglyceride Excess amino acids may also be decomposed and form nitrogenous waste Nitrogen can be toxic and is processed through the urea cycle Urea cycle – amino acid is converted to an ammonium ion Ammonium ion enters the cycle to combine with CO2 to form urea and water 24.5 – Metabolic States of the Body Absorptive state – digesting and absorbing food, catabolism < anabolism Absorption lasts up to 4 hours Insulin causes glucose to be stored and stimulates protein synthesis Postabsorptive state – fasting state, food has been stored, glycogen is broken down Starvation – “survival mode”, first provide glucose for CNS, use fatty acids for all other energy needs possible Ketone bodies become primary energy source after several days Survival is dependent on fat and protein stores 24.6 – Energy and Heat Balance Thermoregulation is a negative feedback loop (sweating vs. shivering) During ATP production 60% of energy used creates heat A naked human is comfortable at 84 degrees (thermoneutral) Conduction – transfer of heat by contact (3% of heat is lost this way) Convection – transfer of heat to the air or water (15% lost this way) Radiation – transfer of heat via infrared waves (60%) Evaporation – transferring heat by evaporating water (20%) 24.6 – Metabolic Rate Energy consumed minus energy expended, will be higher with more activity or LBM Basal Metabolic Rate (BMR) – energy expended at rest, neutral environment, and Postabsorptive state Basic organ function in the body (70%) Physical activity (20%) Thermoregulation (10%) 24.7 – Nutrition and Diet Energy in minus energy out equals weight gain or loss 3500 calories is 1 pound of fat Proteins use more energy to break down and carb uses the least energy Vitamins – organic compounds needed for biochemical reactions Fat soluble – A, D, E, and K Water soluble – B and C Minerals – inorganic compounds that ensure proper bodily functions (electrolytes, iron, copper, iodine, etc.)