Chapter 9 Nutrition Notes PDF

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Metabolism: Chemical reactions in the body 1. Metabolism refers to the entire network of chemical processes involved in maintaining life 2. Chemical reactions 3. Enable biochemical reactions enable us to release energy from carbohydrate, fat, protein, and alcohol 4. Allows us to synthesize a new substances from another and prepare waste products for excretion

Metabolic pathway 1. Series of chemical reactions occurring in a cell, such as glycolysis, beta-oxidation, citric acid, and electron transport chain 2. Compounds formed in any of the many steps in a metabolic are intermediates

Anabolic 1. Pathways that use small, simple compounds to build larger, more complex compounds (Body uses compounds like glucose, fatty acids, cholesterol, and amino acids as building blocks for compounds) (Use energy) Ex: Formation of glycogen

Catabolic

1. Pathways that break down large compounds into smaller compounds (Energy usually needed) (Produced energy) Ex: Glycogen molecule can be broken down into many glucose molecules when energy is needed (Later complete catabolism of glucose release CO2, H2O, and ATP)

Converting Food into energy 1. Energy used by all cells typically comes from the sun Ex: Photosynthesis

Stages 1. Digestion: Breakdown of complex molecules to their component building blocks 2. Conversion of building blocks to acetyl-CoA (or other simple intermediates) 3. Metabolism of acetyl-CoA to CO2 and formation of ATP

ATP 1. Organic compound adenosine bound to 3 phosphate groups 2. Bonds between the phosphate groups contain energy and are called high-energy phosphate bonds 3. Hydrolysis of the high-energy bonds releases this energy 4. To release ATP, cells break a high-energy phosphate bond which makes ADP plus Pi, a free inorganic phosphate group 5. Hydrolysis of ADP results in the compound AMP 6. Only the energy in ATP and related compounds can be used directly by the cell to synthesize new compound (anabolic pathways) contract muscles, conduct nerve impulses, and pump ions across the membrane

Recycling ATP 1. ATP is regenerated by adding phosphate back to AMP and ADP 2. Release during catabolism permits Pi to reform a high-energy bond with AMP and ADP regenerating ATP 3. Cells break down ATP for energy and the rebuild to maintain constant supply of fuel for the body (survival strategy) 4. Body contains 100 g of ATP; Adult breaks down 88 pounds of ATP each day 5. Requirement increases with exercise

Oxidation-Reduction Reactions: Key Processes in Energy Metabolism 1. The synthesis of ATP from ADP and Pi involves the exchange of electrons, mostly in the hydrogen ions (H+); from energy-yielding compounds eventually to oxygen 2. Niacin and Riboflavin in energy metabolism assist dehydrogenase enzymes and in turn, play role in transferring the other hydrogens from energy-yielding compounds to oxygen in the metabolic pathways of the cells 3. Niacin functions as the coenzyme NAD 4. NAD is found in cells in both its oxidized form (NAD) 5. During intense anaerobic exercise, the enzyme lactate dehydrogenase helps reduce pyruvate (made from glucose) to form lactate 6. Lactate is oxidized back to pyruvate by losing 2 hydrogens 7. Riboflavin in its oxidized form coenzyme is FAD (When reduced gains 2 hydrogens

known as FADH2) 8. Reduction of oxygen (O) to form water is the driving force for life since cells synthesize ATP

ATP Production from Carbhydrates 1. 2. 3. 4.

ATP is generated through cellular respiration Cellular respiration oxidizes (removes electrons) food molecules to gain ATP Oxygen is the final electron acceptor When oxygen is available, cellular respiration may be aerobic; if not available then it is anaerobic pathways are used 5. Aerobic respiration is more efficient at producing ATP Ex: A single molecule of glucose will result in a net gain of glucose can only gain +2

Stages of Aerobic cellular respiration of glucose 1. Glycolysis 2. Transition reaction 3. Citric acid cycle 4. Electron transport chain

Glycolysis: Glycolysis breaks down carbohydrates to generate energy and provide building blocks for synthesizing other needed compounds ● ●

Glucose is converted to 2 units of a 3-carbon compound called pyruvate Requires 2 ATP, but generates 4 ATP yielding a net of 2

Transition Reaction Synthesis of Acetyl-CoA 1. When oxygen is present pyruvate dehydrogenase enzyme complex converts pyruvate into a 2-carbon bond called acetyl-CoA 2. Takes place in the mitochondria known as the transition reaction (Reduces NAD+ 2 NADH + 2 H+ which enters electron transport chain) 3. Irreversible so acetyl-CoA can not go back to glucose (Significance is individuals who have a deficiency of pyruvate dehydrogenase (lactic acidosis) 4. Acetyl-CoA requires coenzymes from thiamin, riboflavin, niacin, and panthothenic acid 5. CoA is made from panthothenic acid

Citric Acid Cycle 1. Acetly-CoA molecules produced by the transition reaction enter the citric acid cycle 2. Chemical reactions that cells use to convert the carbons of an acetyl group to carbon dioxide while harvesting energy to produce ATP 3. 2 turns of the citric acid cycle to process 1 glucose molecule because glycolysis and transition reaction yield 2 acetyl-CoA (Each complete turn produces 2 molecules of CO2 and 1 ATP in form of 1 GTP with 3 molecules of NADH+ + H+ and 1 molecules of FADH2 4. Oxygen does not participate, but electron transport chain does

Electron transport chain 1. Located in the mitochondria 2. Functions in most cells in the body 3. Cells that need a lot of ATP; muscle cells have thousands of ATP while others use less adipose cells 4. Almost 90% of ATP produced from the catabolism of glucose is produced by the electron transport chain 5. Involves passage of electrons along a series of electron carriers (As they pass, small amounts of energy are released) 6. NADH + H+ and FADH2, produced by glycolysis, the transition, and the citric acid cycle supply both hydrogen ions and electron transport chain

Oxidative phosphorylation 1. The way in which energy derrived from NADH + H+ and FADH2 is transferred to ADP + Pi to form (Requires copper and iron) 2. Copper is a component of an enzyme and iron is a component of cytochromes (electrontransfer compound that participates in the electron transport chain) 3. In addition to ATP production, hydrogen ions, electrons, and oxygen combine to form water

Importance of Oxygen 1. Oxygen is essential for energy metabolism 2. NADH + H+ and FADH2 produced during the citric acid cycle can be regenerated into NAD+ and FAD only by the eventual transfer of their electrons and hydrogen ions to oxygen occurs in the electron transport chain 3. Citric acid cycle can not oxidize NADH + H+ and FADH2 back to NAD+ and FAD

Anaerobic Metabolism

1. Cells with mitochondria are capable of turning anerobic metabolism when oxygen is lacking 2. When oxygen is absent, pryuvate that is produced through glycolysis is converted into lactate 3. Only about 5% of the energy in a molecule of glucose to energy stored in the highenergy phosphate bonds of ATP 4. Anaerobic glycolysis pathway encompasses glycolysis and the conversion of pyruvate to lactate 5. The 1-step reaction, catalyzed by the enzyme lactate dehydrogenase, involves a simple transfer of a hydrogen from NADH + H+ to pyruvate to form lactate and NAD+ 6. Synthesis of lactate dehydrogenase, transfer of hydrogen from NADH + H+ to pyruvate to lactate and NAD+ 7. Synthesis of lactate regenerates the NAD+ required from the continued function of glycolysis 8. For cells that mitochondria and cannot use electron transport and oxidative phosphorylation pathways, anaerobic glycolysis is the only way to make ATP 9. When red blood cells convert glucose to pyruvate, NADH+ concentration falls too low to permit glycolysis to continue 10. Anaerobic glycolysis pathway produces lactate to regenerate NAD+ 11. Lactate red blood cells is the released into the blood stream, picked up by the liver, and used to synthesize pyruvate glucose, or some other intermediate in aerobic respiration

Cori Cycle 1. Muscle cells during high intensity excercise they rely heavily on anerobic glycolysis to quickly produce ATP 2. Anaerobic glycolysis causes lactate accumulations and NAD+ regeneration, both allow anerobic glycolysis to continue in the muscle 3. Lactate generated is transported from the muscles to the liver, where it is converted to glucose which can then be returned to the muscles

ATP production from fats 1. Lipolysis: Breaking down triglycerides into free fatty acids and glycerol 2. The further breakdown of fatty acids for energy production is called fatty acid oxidation because the donation of electrons from fatty acids to oxygen (Takes place in the mitochondria) 3. Fatty acids used to generate energy can come from triglycerides in the diet or from stored triglycerides in adipose tissue 4. Following high-fat meals, the body stores adipose tissue; during low calorie intake/fasting, triglycerides from fat cells are broken down into fatty acids by an enzyme called horomone-sensitive 5. The activity of this enzyme is increased by horomones such as glucagon, growth by the hormone insuln 6. Fatty acids are taken up from the bloodstream by cells throughout the body and are shuttled from the cell cytosol into the mitochondria using a carrier called carnitine

ATP Production from Fatty Acids Almost all fatty acids in nature are composed of an even number of carbons, ranging from 2 to 26 1. Transferring the energy in such cleave the carbons, 2 at a time , and convert the 2-carbons, 2 at a time, and convert the 2-carbon fragements to acetly-CoA molecules begins with the betacarbon, the second carbon on a fatty acid During beta-oxidiation, NADH+ + H+ and FADh2 are produced 2. Thus, as with glucose, a fatty acid is eventually degraded 2 carbons at a time into acetyl-CoA whole some of the chemical energy contained in the fatty acids is transferred to NADH + H+ and FADH2 3. Acetyl-CoA enters the citric acid cycle, and 2 Co2 are released, just as with the acetyl-CoA produced from the glucose 4. Glucose and fatty acids is that most fatty acids have far more carbons and thus, can go around the citric acid cycle (6 carbon glucose forms 2 acetyl-CoA and thus can go around the citric acid cycle only twice) 5. Fatty acid carbon results in about 7 ATP, wheras glucose oxidation results in only about 5 ATP per carbon)

Carbohydrate Aids Fat Metabolism 1. Citric acid cycle provides compounds that leave the cycle and are used for other pathways (Slowing of the cycle, as eventually not enough oxaloacetate is formed to combine with the acetyl-CoA entering the cycle)(Cells compensate for this by synthesizing additional oxaloacetate (source is pyruvate)) 2. Acetyl-CoA created by fatty acids are needed to keep concentration of pyruvate high enough to resupply oxaloaxetate to the citric acid cycle

Ketones: By-products of Fat Catabolism 1. The formation of ketone bodies occurs mainly with horomonal imbalances (mainly insulim) 2. Imbalances lead to a significant production of ketone bodies and a condition called ketosis 3. Lipolysis continues, which means acetyl-CoA production from fatty acids buildup of acetyl-CoA because oxalocetate is not available to allow acetyl-CoA because oxaloaetate is not avaliable to allow acetyl-CoA to enter the citric acid cycle 4. Acetyl CoA cannot enter the citric acid cycle, these molecules join together and form ketone bodies

Protein Metabolism 1. Takes place in the primarily in the liver (Only branched-chain amino-acids - leucine, isolecine, and valiner are metabolized mostly at other sites like muscles 2. Begins after proteins are degraded into amino acids 3. To use amino acid for fuel cells must first dominate them (remove the amino group) 4. Pathways often require vitamin B-6 to function 5. Removal of amino groups produces carbon skeletons, most enter citric acid cycle (Some carbon skeletons also yield-acetly-CoA or pyruvate) 6. Some carbon skeletons enter the citric acid cycle as acetyl-CoA, or glyolysis 7. Any part of the carbon skeleton that can form pyruvate or bypass acetyl-CoA and enter the citric acid cycle directly are called glucogenic amino acids (These carbons can become the carbons of glucose) 8. Any parts of carbon skeletons that become acetyl-CoA are called ketogenic amino acids (These carbons become acetyl-CoA and if insulin is low, they become ketones) 9. Factor that determines wheter an amino acid is glucogenic or ketogenic is whether part or all of the carbon skeleton of the amino acid can yield a "new" oxaloacetate molecule during metabolism (2 needed to form glucose)

Glucogenesis 1. Pathway to produce glucose from certain amino acids (present only in the liver and certain kidney cells) 2. Liver is the primary gluconeogenic organ 3. Typical starting material is oxaloacetate which comes from the carbon skeletons of some amino acids, usually alanine 4. Pyruvate also can be converted to oxaloacetate and other gluconeognic precursors such as lactate and glycerol 5. Begins in the mitochondria with the production of oxaloacetate (4-carbon oxaloacete eventually returns to the cytosol, where it loses 1 CO2, forming 3-carbon compound phosphoenolpyruvate, 2 ot these 3-carbon compounds to produce 6 carbon glucose) 6. Process requires ATP and coenzyme forms of the B-vitamin biotin, riboflavin, niacin, and B-6

Glutamine to Glucose 1. Glutamine first loses its amino group to form its carbon skeleton which enters the citric acid cycle and is converted by stages to oxaloacetate 2. Oxaloacetate loses 1 carbon as carbon dioxide, and the 3-carbon phosphoenlopryuvate produced then moves throough the gluconegenic pathway to form glucose 3. Eventually, 2 glutamine molecules are needed to form 1 glucose molecule

Gluconegenesis from Typically Fatty Acid NOT Possible 1. Typical fatty acids cannot be turned into glucose because those with an even number of

carbons- the typical form in the body- break down into acetyl-CoA molecules 2. Acetyl-CoA can never re-form into pyruvate; step between is irreversible 3. Acetyl-CoA can form ketones or combine with oxaloacetate in the citric acid cycle (2 carbons of acetyl-CoA are added to oxaloacetate at the beginning of the citric acid cycle and 2 carbons are lost as CO2 when citrate converts back to oxaloacetate 4. No acetyl-CoA are left to go to glucose 5. Glycerol portion of a triglyceride is part that can become glucose 6. Glycerol enters the glycolysis pathway and can follow the gluconeogenesis pathway from glyceraldehyde 3-phosphate to glucose (Yield is insignificant) Disposal of Excess Amino Groups from Amino Acid Metabolism 1. Catabolism of amino acids, primarily from the liver, yields amino groups (-NH2), which then are converted to ammonia (NH3) (Must be excreted because buildup is toxic to the brain) 2. Liver prepares the amino groups for excretion in the urine with urea cycle (Some stages occur in the cytosol and some mitochondria)(2 nitrogen groups- 1 aminmonia a series of steps with CO2 molecules to form urea and water) 3. Liver disease, ammonia can build up to toxic concentrations in the blood: kidney disease the toxic agent is excess amounts of urea 4. Form of nitrogen in the blood- ammonia or urea- diagnostic tool for detecting liver or kidney disease

Alcohol Metabolism 1. ADH pathway is the main way alcohol is metabolized 2. First, alcohol is converted in the cytosol to acetaldehyde by the action o alcohol dehydrogenase enzyme and NAD+ coenzyme dehydrogenase enzyme and NAD+ coenzyme 3. NAD+ picks up 2 hydrogen ions and 2 electrons from the alcohol to form NADH+ + H+ and produces the intermediate acetaldehyde 4. Metabolism of alcohol occurs in the liver, 10-30% metabolized in the stomach 5. Different forms of alcohol dehydrogenase and aldehyde dehydrogenase are found in the stomach and liver 6. Acetyl-CoA formed through the ADH pathway has several metabolic fates (Small amounts can enter the citric acid cycle to produce energy) 7. Breakdown of alcohol in the ADH pathway utilizes NAD+ and converts it to NADH (If NAD+ is limited NADH builds-up the citric acid cycle slows and blocks entry of acetylCoA 8. Due to alcohol toxicity metabolism of alcohol takes priority over citric acid cycle 9. Most acetyl-CoA is directed toward fatty acid and triglyceride synthesis resulting is fat in the liver (steatosis) 10. MEOS uses oxygen and different niacin-containing coenzyme (NADP) and produces water and acetaldehyde 11. MEOS uses potential energy (in the form of NADPH + H+ another niacin coenzyme)

Regulation of Energy Metabolism

1. Carbohydrates can be used for fat synthesis- the acetyl-CoA from the breakdown of carbohydrates is the building block for fatty acid synthesis 2. Glycolysis and citric acid cycle, cells can convert carbohydrates into carbon skeletons for the synthesis of certain amino acid and can use the energy in carbohydrates to form ATP 3. These pathways also can turn the carbon skeletons of some amino acids into the carbon skeletons of others (They can convert carbon skeletons from some amino acids to glucose or have them drive ATP synthesis by serving as substrates for intermediates in the citric acid cycle) 4. Fatty acids can provide energy for ATP synthesis or produce ketone bodies, but can't become glucose 5. Glycerol part of the triglyceride can be converted into glucose an used for fuel or can contribute to ATP synthesis via participation in glycolysis, citric acid cycle, and electron transport chain metabolism 6. Liver plays a major role-- responds to hormones and makes use of vitamins 7. Additional means of regulating metabolism involve ATP concentrations, enzymes, hormones, vitamins, and minerals

Liver 1. 2. 3. 4.

Location of many nutrient interconversions Most nutrients must pass first through the liver after absorption into the body What leaves the liver is different that what enters Key metabolic functions of the liver are conversions between various forms of simple sugars, fat synthesis, production of ketone bodies, amino acid metabolism, urea production, and alcohol metabolism 5. Nutrient storage

ATP concentration 1. Regulate metabolism 2. Decrease energy-yielding reactions such as glycolysis, and promote anabolic reactions (protein synthesis) 3. ADP concentrations stimulate energy-yielding pathways

Enzymes, Hormones, Vitamins, and Minerals 1. Enzymes are key regulators of metabolic pathways 2. Enzymes synthesis and rates of activity are controlled by cells and by products of the reactions where enzymes participates 3. Hormones like insulin, regulate metabolic processes (Low levels promote gluconeogenesis protein of glycogen, fat, and protein) 4. B-vitamins as well as the minerals iron and copper are needed for metabolic pathways to operate 5. Metabolic pathways depend on nutrient input

Fasting 1. Both fasting and feasting affect metabolism (The type of macronutrient and the rate at which it is used vary when the calorie supplies are insufficient or exceed needs) 2. Body fuels itself with stored liver glycogen and fatty acids from adipose tissue 3. Body fat continues to be broken down and liver glycogen becomes exhausted 4. Most cells can use fatty acids for energy, the nervous system and red blood cells can only use glucose for energy 5. Glucose is made by breaking down lean body tissue and converts glucogenic amino acids via glucogenesis to glucose 6. During the first few days, body protein is broken down rapidly-- 90% of needed glucose with the remaining 10% glycerol (Death within 2-3 weeks of not eating) 7. Sodium and potassium depletion also can result from fasting because these elements are drawn into the urine along with ketone bodies 8. Blood urea levels increase because of the breakdown of protein 9. Adaptions is slowing of metabolic rate and a reduction in energy requirements and the nervous system to use less glucose and more ketone bodies

Feasting 1. Accumulation of body fat 2. Increases insulin ...