NUTR Exam 1 Study Guide PDF
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This document is a study guide for a NUTR exam, covering the topics of macronutrients and energy balance. It details metabolism, enzymatic reactions, and the impact of food intake and energy expenditure on the body's processes.
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Chapter 1: Macronutrients and energy balance - Metabolism: set of chemical reactions in the body that sustain life - Consist of enzymatic reactions - Affected by food intake and energy expenditure - Differs from per...
Chapter 1: Macronutrients and energy balance - Metabolism: set of chemical reactions in the body that sustain life - Consist of enzymatic reactions - Affected by food intake and energy expenditure - Differs from person to person - Macronutrients → ATP - ATP: primary energy carrier in living cells. 3 phosphate groups, a ribose sugar, & adenine nucleotide - The trip-phosphate structure allows for multiple energy releasing reactions - Structure also allows ATP to move to all cell compartments without help from carrier - Metabolic regulation: maintaining anabolic and catabolic processes for homeostasis - Anabolism: synthesis of complex molecules from simpler ones requiring energy (ATP) - Catabolism: breakdown of molecules releasing energy - Stress and responses affect metabolism - We must provide ATP to cells for proper function. We must restore balance when imbalance - excess/ inadequate nutrient intake - Responses to environment changes - Eating is a “stressful” event - environment change - There are short term and long term methods of regulation - Different responses at different times, hours vs. weeks - Metabolic regulation beings on the cellular level - Transcription, translation, post-transcriptional, post translational; each step is subject to metabolic regulation - Central dogma of DNA: DNA → mRNA → protein - NA transcription: RNA polymerase turns DNA into mRNA. D - DNA → RNA → mRNA → amino acid chain → protein - Promoter, exon (coding), intro (noncoding) - mRNA processing - mRNA splicing - Translation - ranscription and translation must happen quickly and all processes simultaneously in order to T elicit a fast response (e.g., a hormone) - Allosteric regulation of an enzyme: - Substrate binds at different spot than the active site and then inhibits activity (usually feedback) - Allosteric regulation can be inhibitory or excitatory - Energy balance: tightly regulated because our bodies use a lot of energy - First law of thermodynamics: law of conservation of energy - total energy of a system is constant; energy can be transformed; not created nor destroyed. - The state in which energy intake, food or alcohol, matches the energy expended through basal metabolism, the thermal effect of food (digestions), and physical activity. - Basal metabolism (70%): metabolism if you did nothing - Thermal effect of food (10%): the energy it takes to digest food - Physical activity (20%): voluntary or involuntary - Non-exercise thermogenesis - Calories in = calories out → energy balance - If one outweighs the other then you will gain or lose weight - Macronutrients: bulk of calorie intake - Carbohydrates, proteins, lipids - Micronutrients: facilitators in metabolism - Cofactors in enzymes - Coenzymes - Total number of calories is about 90% of available energy; 10% is lost in feces, urine, respiration. - Thermal effects of food: - Alcohol: 15% for thermic effect , 7 cal./g, 85/100 cal stored - Exogenous ketones: 3% thermic effect, 4 cal./g, 97/100 cal stored - Protein: 25-30% thermic effect, 4 cal./g, 70-75/100 cal stored - Carbs: 7-10% thermic effect, 4 cal./g, 90/100 cal stored - Glycogen spillover: 15-20% thermic effect, 4 cal./g, 80/100 cal stored - Fat: 3% thermic effect, 9 cal./g, 97/100 cal stored - Glycogen spillover: when you eat too many carbs, the body stores as glycogen - Respiratory energy expenditure (REE) - resting metabolic rate (RMR) - Energy required for metabolism at rest - 70% in some sedentary individuals - Measured during sleep, 5% higher while awake - Affected by age, body size/ composition, physical activity, hormones, genetics, diet, sleep, stress, illness, and drugs/medications - Thermogenesis: heat production in response to environmental changes in temperature - Shivering in cold, sweating when hot - 10-15% more energy needed for every 1 degree celsius needed - How to measure energy balance? - Daily food intake: self reporting, recall surveys, determining energy expenditure, nuclear magnetic resonance, indirect calorimetry, dual x-ray absorptiometry, anthropogenic measurements - Determining energy expenditure: - Indirect calorimetry - measuring gases produced - Resting energy expenditure - Exercise energy expenditure (tredmill) - DEXA: measures leann vs fat mass Chapter 2: Energy - Adenosine Triphosphate - 2 phosphoanhydride bonds (between the phosphate groups) - Hydrolysis yield = 7.3 kcal each - Energy before hydrolysis > energy after hydrolysis - Bond energy is also affected by resonance stability and solvation of prod. Vs reac. - ADP + a phosphate is more stable than ATP - Adenosine Diphosphate - Most body processes use energy that goes between ATP and ADP - Adenosine Monophosphate - How do muscles store ATP? - They “store” it in phosphocreatine (energy reserve) - 1. Mitochondrial creatine kinase phosphorylates creatine forming phosphocreatine that migrates to the cytosol - cytosolic creatine kinase phosphorylates ADP using phosphocreatine as its substrate - ATP is used by skeletal muscles during contraction - his is substrate level phosphorylation (does not require O2 & only 1 enzyme is T responsible) - Generates ATP by direct phosphorylation instead of through oxidative phosphorylation - Oxidation/ Reduction reactions: - Electron donor loses an electron (oxidized) and electron acceptor gains an electron (reduced) - Nicotinamide Adenine Dinucleotide - NAD → NADH: NAD is reduced to NADH & NADH is oxidized to NAD - Flavin Ninucleotide - FAD → FADH2: FAD is reduced to FADH2 & FADH2 is oxidized to FAD - Mitochondrial structure: - Outer membrane: - permeable to most small ions and molecules - Contains porins - Inner mitochondrial membrane: - Impermeable to most ions and polar molecules - Transmembrane proteins needed - Matrix side - negative charge - cytosolic side - positive charge - Large difference in charge is responsible for energy gradient - Cell energy status: ratios of ATP: ADP & NADH: NAD+ - High ATP:ADP and NADH:NAD+ means the cell has a lot of energy - Low ATP:ADP and NADH:NAD+ means the cell is lacking energy and needs more - If you have high ratios, then the body stores excess calories in the form of adipose tissue; lipogenesis - If you have low ratios, then the body seeks to get calories and draws of fat stores (lipolysis) and provides glucose for itself through degradation of skeletal muscle - products travel to liver to synthesize glucose (gluconeogenesis) - Macronutrient oxidation - Glycolysis - Occurs in the cytoplasm - TCA cycle: - Occurs in mitochondria - Glycolysis: the metabolic pathway that breaks down glucose to generate ATP. - Glycolysis pathway: 10 steps Glucose → pyruvate 1. Phosphorylation of glucose a. Glucose → glucose-6-phosphate b. Enzyme = hexokinase c. 1 ATP used 2. Isomerization of glucose-6-phosphate a. Glucose-6-phosphate → fructose-6-phosphate b. Enzyme = phosphoglucose isomerase c. No ATP used 3. Phosphorylation of fructose-6-phosphate a. Fructose-6-phosphate → Fructose-1,6-bisphosphate b. Enzyme = phosphofructokinase-1 c. 1 ATP used 4. Cleavage of fructose-1,6-bisphosphate a. Fructose-1,6-bisphosphate → glyceraldehyde-3-phosphate + dihydroxyacetone phosphate b. Enzyme = aldolase c. No ATP used and we now have 2 molecules 5. Isomerization of dihydroxyacetone phosphate a. Dihydroxyacetone phosphate → glyceraldehyde-3-phosphate b. Enzyme = triose phosphate isomerase c. No ATP used; DHAP is converted into G3P to ensure only 1 product enters the next phase. PHASE 2 6. Oxidation and phosphorylation of glyceraldehyde-3-phosphate a. G3P + NAD+ + phosphate → 1,3-bisphosphoglycerate + NADH b. Enzyme = glyceraldehyde-3-phosphate dehydrogenase c. No ATP; NAD+ → NADH + H+ 7. ATP generation via substrate-level phosphorylation a. 1,3-Bisphosphoglycerate + ADP → 3-Phosphoglycerate + ATP b. Enzyme = phosphoglycerate kinase c. 2 ATP produced (one per G3P) 8. Mutase reaction: a. 3-phosphoglycerate → 2-phosphoglycerate b. Enzyme - phosphoglycerate c. No ATP used 9. Dehydration of 2-Phosphoglycerate a. 2-phosphoglycerate → phosphoenolpyruvate + H2O b. Enzyme = enolase c. No ATP; water is removed forming PEP which has a high energy Pi bond 10.ATP formation and pyruvate production a. Phosphoenolpyruvate + ADP → pyruvate + ATP b. Enzyme = pyruvate kinase c. 2 ATP produced (one per PEP) - Net balance of glycolysis: - ATP: 2 used, 4 produced = net 2 - NADH: 0 used, 2 produced = net 2 - Pyruvate: 0 used, 2 produced = net 2 - Pyruvate oxidation must happen for pyruvate to become a 2 Carbon molecule (acetyl-CoA) must take place before it can enter the TCA cycle - CA cycle: metabolic pathway that oxidizes acetyl-CoA to CO2, generating NADH, FADH2 (high energy T carriers), and ATP. Uses oxidative phosphorylation. 1. Formation of Citrate a. Acetyl-COA + Oxaloacetate → citrate b. Enzyme = citrate synthase****** might have more steps 2. Isomerization of citrate to isocitrate (aconitase) a. Citrate → isocitrate b. Enzyme = aconitase 3. Isocitrate dehydrogenase a. Isocitrate → 𝜶-ketoglutarate + CO2 b. Enzyme = isocitrate dehydrogenase c. NAD+ → NADH, H+ 4. 𝜶-ketoglutarate dehydrogenase a. 𝜶-ketoglutarate → Succinyl-CoA + CO2 b. Enzyme = 𝜶-ketoglutarate dehydrogenase c. NAD+ → NADH, H+ 5. Succinyl-CoA Synthetase a. succinyl-CoA → Succinate + GTP (or ATP) b. Enzyme = succinyl-CoA synthetase c. Produces ATP or GTP 6. Succinate dehydrogenase a. Succinate → Fumarate b. Enzyme = succinate dehydrogenase c. FAD is reduced to FADH2 d. Succinate is oxidized to fumarate (^ note redox rxn.) 7. Fumarase a. Fumarate + H2O → Malate b. Enzyme = fumarase 8. Malate dehydrogenase a. Malate → oxaloacetate b. Enzyme = malate dehydrogenase c. Malate is oxidized producing NADH d. ^ this restarts the cycle - Net balance per Acetyl-CoA: - 3 NADH, 1 FADH2, 1 ATP (or GTP), 2 CO2, ~10 ATP (double for 2 cycles) - Regulatory reactions of the TCA cycle: - Citrate synthase - Substrates = oxaloacetate and acetyl CoA - Procut = citrate - Inhibited by - NADH (allosteric), citrate, succinyl CoA - High NADH = sufficient ATP - Citrate is a competitive inhibitor or oxaloacetate - Succinyl CoA is a competitive inhibitor for acetyl CoA - Isocytrade dehydrogenase - Substrate = isocitrate - Product = a-ketoglutrate - Calcium is an allosteric stimulator - A-ketoglutarate dehydrogenase - NADH inhibits - Calcium is an allosteric stimulator - Succinyl CoA is a competitive inhibitor for a-ketoglutarate - Macronutrient oxidation: - Beta oxidation: fatty acid oxidation: primary fatty acid catabolism pathway converting long-chain fatty acids into ATP - Occurs in the mitochondria - Each cycle produces acetyl CoA to enter the TCA cycle - Each cycle produced 1 NADH and 1 FADH2 to enter the ETC - Carbon portions of ketogenic amino acids are also converted to acetyl CoA and enter the TCA cycle - Before beta oxidation can occur, fatty acids must be activated into fatty acyl-CoA (in cytosol) 1. Oxidation (dehydrogenation) a. Fatty Acyl-CoA → trans-Δ^2-enoyl-CoA + FADH2 b. Enzyme = acyl-COA dehydrogenase 2. Hydration a. trans-Δ^2-enoyl-CoA + H2O → L-β-hydroxyacyl-CoA b. Enzyme = enoyl-CoA hydratase 3. Oxidation a. L-β-hydroxyacyl-CoA → β-Ketoacyl-CoA + NADH b. Enzyme = β-hydroxyacyl-CoA dehydrogenase 4. Thiolysis (cleavage) a. β-Ketoacyl-CoA + CoA → Acetyl-CoA + shortened fatty acyl-C0A (by 2C) b. Enzyme = β-ketothiolase - B oxidation occurs until only 2 Carbons remain - lectron transport: electrons carried by reduced coenzymes are passed through a chain of proteins and E coenzymes to drive the generation of a proton gradient across the inner mitochondrial membrane - Oxidative phosphorylation: the proton gradient runs downhill to drive the synthesis of ATP - Chemiosmotic theory: ADP + Pi is highly thermodynamically unfavorable - Possible because: - Phosphorylation of ADP is not a result of a direct reaction between ADP and a high energy phosphate carrier - nergy needed to phosphorylate ADP is provided by the flow of protons down the E electrochemical gradient - The energy released by electron transport is used to transport protons against the electrochemical gradient - Chemiosmotic energy coupling requires membranes: - The proton gradient needed for ATP synthesis can be stably established across a membrane that is impermeable to ions - Plasma membrane in bacteria - Inner membrane in mitochondria - Thylakoid membrane in chloroplasts - The membrane must contain proteins that couple the “downhill” flow of electrons in the electron-transfer chain with the “uphill” flow of protons across the membrane - The membrane must contain a protein that couples the “downhill” flow of protons to the phosphorylation of ADP - Electron transport chain: - Four protein complexes in the inner mitochondrial membrane - A lipid soluble coenzyme (Ubiquinone, aka Coenzyme Q) and a water soluble protein (cytochrome C) shuttle between protein complexes - Each complex contains multiple redox centers consisting of: - Flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD) - Cytochrome a, b, or c - Iron sulfur cluster (e-jumping) - Three types of electron transfer occur 1. Direct transfer of electrons (reduction of Fe3+ to Fe2+) 2. Transfer as a hydrogen atom H+ + e-) 3. Transfer as hydride ion: H- which bears 2 electrons - Flavoproteins - Contain tightly bound flavin nucleotide (FMN or FAD) - Oxidized flavin nucleotide can either accept one electron or two (FADH2 or FMNH2) - Electron transfer occurs because the flavoprotein has a higher reduction potential than the compound that is oxidized (accepts easier) - Reduction potential is the quantitative measure of the tendency of a given species to accept electrons - Reduction potential depends on interactions with the protein with which it is associated - 2 molecules cannot have the same reduction potential - Cytochromes - One-electron carriers - Iron coordinating porphyrin ring derivatives - A, b, or c differ by ring additions - iron -sulfur Clusters - One electron carriers - Coordinated by cystines in the protein - Contain equal number of iron and sulfur atoms - Coenzyme Q or ubiquinone - Ubiquinone is a lipid-soluble conjugated dicarbonyl compound that readily accepts electrons - Upon accepting two electrons, it picks up two protons to give an alcohol, ubiquinol - biquinol can freely diffuse in the membrane, carrying electrons with protons from one side of U the membrane to another side - Coenzyme Q is a mobile electron carrier transporting electrons from Complexes I and II to complex III - Complex I: NADH to Ubiquinone: - Electron transfer from N-2 iron-sulfur cluster to ubiquinone on the membrane forms QH2; this diffuses into the lipid bilayer - This e- transfer drives 4 protons out of the matrix per electron pair. - Complex I is a proton pump driven by the energy of electron transfer - NADH binding site in the matrix side - Flavin mononucleotide accepts two e- from NADH - Several iron-sulfur center pass one electron at a time toward the ubiquinone binding site - Complex II: succinate dehydrogenase - FAD accepts two e- from succinate - E- are passed via iron-sulfur centers to ubiquinone, which becomes reduced QH2 - Does NOT pump protons - Heme b protects against reactive oxygen species - Succinate dehydrogenase is a single enzyme but has two roles 1. Convert succinate to fumarate in TCA cycle 2. Capture and donate e- in the ETC - Complex III: ubiquinone: Cytochrome c oxidoreductase: - Uses 2 e- from QH2 to reduce 2 molecules of cytochrome c - Contains iron-sulfur clusters, cytochrome b, and cytochrome c - Clearance of e- from reduced quinones via Q-cycle pumps 4 more e- into intermembrane space - The Q-cycle: - 4 protons are transported across the membrane per 2 e- that reach cytochrome c - Two molecules of QH2 become oxidized and release protons into intermembrane space - One molecules of QH2 is re-reduced, so there is a net transfer of 4 protons per reduced coenzyme Q - Complex IV: cytochrome C oxidase: - Has 13 subunits, 2 heme groups, and copper ions - Has a binuclear center that transfers four e- to oxygen - 4 e- used to reduce one oxygen into two water - 4 protons are picked up from the matrix - 4 additional protons are passed from the matrix to the intermembrane space - Inhibitors of the ETC disrupt oxidative phosphorylation: - Rotenone is an insecticide that is toxic to wildlife and humans - Antimycin - Cyanide is a reversible inhibitor of cytochrome oxidase. Chapter 3: macronutrient metabolism: turning carbohydrates into usable energy: - Carbohydrates: - Simple carbohydrates: - Monosaccharides - glucose, fructose, galactose - Disaccharides - lactose, sucrose, maltose - 1-4 C linkage - Complex carbohydrates - Oligosaccharides - small chain between 3-10 sugars - Polysaccharides - many sugars - Starch (plant storage) - Glycogen (animal storage) - Dietary fiber - 1-4 C linkage - Simple carbs = fast foods - These break down quickly in the body - Complex carbs = whole foods - Take longer to break down in the body - Important thinking about time vs. blood sugar, simple carbs are going to “spike” - Glucose Homeostasis: - Liver is the main organ - We must have a stable supply of glucose for bodily functions - Normal fasting BG = 90-126 mg/dL - Hypoglycemia = 126 mg/dL - Liver glucose output = 150 mg/min - Matches utilization, so this depends on how much a person uses - With exercise, utilization increases - sedentary , utilization decreases - Glucogenesis: glucose production by liver - Stages of fatty liver disease - Normal liver - Steatosis (reversible) - steatohepatitis/ fibrosis (reversible) - Cirrhosis (irreversible) - Hepatocellular carcinoma (irreversible) - Fatty liver disease (non alcohol related) - Glycogen vs. Strach: - Amylose is the form of glucose storage in plants - Glycogen is looser than amylose, so enzymes have easier access for faster breakdown - Glycogen is more soluble than amylose; it packs into tight helical structures - Glucose can be stored for later use as glycogen - Glycogen storage occurs in liver and muscle (also brain) - Glycogen is degraded to glucose units for use in energy production - Glycogen can be made from excess BG or recycling of glucogenic metabolites - Glucogenic metabolites = lactate or certain amino acids - How the body uses glycogen for energy: - Glycogenolysis: process by which glycogen is broken down to glucose 1-phosphate - In the liver and skeletal muscle, out branced of glycogen enter the catalytic pathway through: - Glycogen phosphorylase - Glycogen debranching enzyme - Phosphoglucomutase - Glycogen phosphorylase: enzyme that removed glucose residues from glycogen - Breakdown occurs at one end and not in the middle - Degradation starts at the non-reducing end - Glycosidic linkage between reducing end of one sugar (C1, aldehyde) and another position (C4, alcohol) - The reducing end is in the center of the branched glycogen molecule - Pyridoxal phosphate: active form of B6 that is an essential cofactor in the glycogen phosphorylase reaction - Three isoforms of glycogen phosphorylase: 1. Muscle glycogen phosphorylase 2. Liver glycogen phosphorylase 3. Brain glycogen phosphorylase - All 3 have the same action: - Catalyze conversion of glycogen to glucose 1-phosphate + a glycogen molecule that is 1 glucose shorter - A phosphorylation reaction: Pi attacks the alpha 1-4 glycosidic linkage that joins that last two glucose molecules on the non-reducing end - The difference is in how they are allosterically regulated by AMP - Glucose-1-phosphate must be isomerized to glucose-6-phosphate for metabolism: - Phosphoglucomutase: enzyme that moves in glucose-1-phosphate from position 1 to position 6 to make glucose-6-phosphate (mutates the phosphate group) - glucose -6-phosphate can enter glycolysis or the pentose pathway - This reaction is reversible and will need to happen in reverse for glycogen synthesis - How glycogen is utilized in various tissues: - In muscle, glucose-6-phosphate products from glycogenolysis can enter glycolysis for energy products to support muscle activity - In live, glucose-6-phosphate from glycogenolysis is converted to glucose and released from the hepatocytes into the bloodstream - In brain, glucose-6-phosphate is used for learning and memory and motivation to exercise - Glucose-6-phosphate must me dephosphorylated in the liver in order to leave the liver - In the liver, G6P is transported from cytosol to ER by T1 - G6P is hydrolyzed at the ER by glucose 6 phosphatase - Glucose and Pi are transported back to the cytosol by T2 and T3 - Glucose leaves the cell based on a GLUT2 gradient - How liver glycogen contributes to BG: - Muscle and adipose tissue (and brain) lack the enzyme glucose 6 phosphatase and cannot convert G6P to glucose - Glycogen that is broken down in the muscle and adipose tissue and brain does not contribute to BG (only liver) - Glycogenolysis: glycogen → glucose-1-phosphate → glucose-6-phosphate → glucose - Sugars can enter glycolysis at any point and the products go into the TCA cycle - The rate limiting step of glycolysis: - Rationale - Traps glucose inside the cell - Lowers intracellular (unphosphorylated) glucose concentration to allow further uptake - 1st committed step of glycolysis: - Fructose 1,6 bisphosphate is committed to become pyruvate and yield energy - Triose phosphate isomerase deficiency (step 5) - Only glycolytic enzyme deficiency that is lethal in humans; mutation on chromosome 12 - Characterized by hemolytic anemia, progressive neurological symptoms during childhood - Fates of pyruvate: - acetyl-CoA - Lactate - vertebrates - Lactic acid when our muscles use up all of the oxygen provided - Ethanol - microorganisms - NADH is shuttled into mitochondria via the glycerol phosphate shuttle or malate aspartate shuttle
