Nutrition Test 3 Study Guide Metabolism 11/7/12 4:58 PM What is metabolism ? metabolism is the sum total of all the chemical reactions that go on in living cells • Energy metabolism includes all the reactions by which the body obtains and expends the energy from food What is anabolism? anabolism are reactions in which small molecules are put together to build larger ones. Anabolic reactions REQUIRE ENERGY Metabolic work of the liver : 1. Carbohydrates : • converts fructose and galactose into glucose • makes and stores glycogen • breaks down glycogen and releases glucose • breaks down glucose for energy when needed • makes glucose from amino acids and glycerol • converts excess glucose to fatty acids 2. Lipids: • builds and breaks down triglycerides, phospholipids, and cholesterol • breaks down fatty acids for energy • packages extra lipids in lipoproteins for transport to other body organs • manufactures bile to send to the gallbladder for use in fat digestion • makes ketone bodies when necessary 3. Proteins: • manufactures nonessential amino acids when in short supply • removes excess amino acids or deaminates them and converts them to glucose or fatty acids • removes ammonia from the blood and converts it to urea to be sent to the kidneys for excretion • makes other nitrogen containing compounds the body needs, ex: bases used in DNA and RNA • makes plasma proteins such as clotting factors 4. Other: • detoxifies alcohol and other drugs/ poisons. • Prepares waste products for excretion • Helps dismantle old red blood cells and captures the iron for recycling• Stores most vitamins and minerals What is Catabolism? reactions in which larger molecules are broken down to smaller ones, RELEASE ENERGY Glucose has 6 carbons Glycerol has 3 carbons Fatty acids commonly has 16 or 18 carbons Amino acids has 2 or 3 with a nitrogen attached Acetic acid + CoA = acetyl CoA CoA= a coenzyme derived from the B vitamin pantothenic acid and central to energy metabolism TCA Cycle ( tricarboxylic acid cycle) – a series of metabolic reactions that break down molecules of acetyl CoA to carbon dioxide and hydrogen atoms, also known as the Krebs Cycle Electron transport chain the final pathway in energy metabolism that transports electrons from hydrogen to oxygen and captures the energy releases in the bonds of ATP Glycolysis the metabolic breakdown of glucose to pyruvates. Glycolysis does not require energy ( Anaerobic) Anaerobic = does not require energy , and or oxygen Aerobic = requires energy Pyruvate may be converted to : lactic acid anaerobically (without oxygen) acetyl CoA aerobically (with oxygen) Lactate a 3 carbon produced from pyruvates during anaerobic metabolism Cori Cycle muscle glycogen glucose pyruvates lactate liver Fatty Acid Oxidation the metabolic breakdown of fatty acids to acetyl CoA; also called beta oxidation • Oxidation of fatty acids occurs in the mitochondria of cells Fatty acids cannot be used to synthesize glucose Deamination results in two products: • Keto acid • Ammonia Keto Acid an organic acid that contains a carbonyl group ( C=O) Ammonia produced during the Deamination of amino acidsTransamination the transfer of an amino group from one amino acid to a Keto acid, producing a new Keto acid and a new nonessential amino acid Glucogenic amino acids that can make glucose via either pyruvates or TCA cycle Ketogenic amino acids that are degraded to acteyl CoA Urea the principal nitrogen excretion product of protein metabolism Oxaloacetate a carbohydrate intermediate of the TCA cycle Adenosine triphosphate (ATP) • High energy compound • Can be used directly by cell • Made of adenine, ribose, and three phosphate groups ATP to adenosine diphosphate (ADP) • When body needs energy • Hydrolyzes one of the phosphate group ADP to ATP • Added back phosphate group to ADP to reform ATP during catabolism - Protein meets glucose (90%) needs - The shift to Ketosis Ketones are produces when glucose is not available Energy Balance •Balance energy (kcal) in = energy (kcal) out •Feasting energy in > energy out ( energy in is greater) •Fasting energy in < energy out ( energy our is greater) - Brain and red blood cells need glucose - Protein providing energy in absence of glucose - First few days of fast: glucose needed is provided 90% by body protein, 10% by glycerol Ketosis (prolonged fasting) • Fat converted to ketone bodies • Slows down use of body protein for energy • Increased ketone bodies = decreased pH of blood Consequences of fatty liver from alcohol abuse • Difficulty activating vitamin D, producing bile• Difficulty with gluconeogenesis • Ketosis and lactate disrupt acid-base balance • Decreased protein synthesis (weaker immune system) Microsomal ethanol-oxidizing system (MEOS) • Enzymes that metabolize ETOH and other drugs • 1/5 total ETOH consumed • Stimulated by excess ETOH à tolerance of its effects Narcotic: dulls senses, induces sleep, becomes addictive with prolonged use -Repeated alcohol exposure kills brain cells -Decreases production of antidiuretic hormone (ADH) -Causes water and mineral losses -Increases thirst (dehydration) Review Questions : 1. Hydrolysis is an example of – catabolic reaction 2. during metabolism , released energy is captured and transferred by – ATP 3. Glycolysis – converts glucose to phyruvate 4. The pathway from pyruvates to acetyl CoA – is metabolically irreversible 5 . for complete oxidation, acetyl CoA enters- the TCA cycle 6. Deamination of an amino acid produces – ammonia and keto acid 7. before entering the TCA cycle, each of the energy yielding nutrients is broken down it – acetyl coA 8. the body stores energy for future use in – triglycerides 9. during a fast, when glycogen stores have been depleted, the body begins to synthesize glucose from – amino acids 10. during a fast, the body produces ketone bodies by- condensing acetyl coAEnergy Balance and Body Composition 11/7/12 4:58 PM •Equilibrium (Zero Balance) –Energy in = Energy out •Positive Energy Balance: –Energy In > Energy Out –Weight gain –Energy stored as fat •Negative Energy Balance: –Energy In < Energy Out –Weight Loss •3500 Kcal= 1lb fat Deficit of 500 kcals/day during a week would
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