Human A&P Metabolism Practice Questions

Anabolism a) refers to all chemical reactions of the body. b) is endergonic, requiring more energy than is produced. c) breaks down complex organic molecules into less complex molecules. d) All of these choices are correct. e) None of these choices is correct. Metabolic Reactions Metabolism r...

Anabolism a) refers to all chemical reactions of the body. b) is endergonic, requiring more energy than is produced. c) breaks down complex organic molecules into less complex molecules. d) All of these choices are correct. e) None of these choices is correct. Metabolic Reactions Metabolism refers to all of the chemical reactions taking place in the body Reactions that break down complex molecules into simpler ones are catabolic (decomposition) Reactions that combine simple molecules to make complex molecules are anabolic (synthesis) Metabolism results from the balance of anabolic and catabolic reactions ATP (adenosine triphosphate) is the energy molecule that couples the catabolic reactions to anabolic reactions → energy transfer  Catabolic reactions generate ATP  Anabolic reactions require ATP, directly or indirectly Interactions Animation: Introduction to Metabolism  Energy Transfer & redox reactions Oxidation-Reduction reactions are one category of reactions important in energy transfer Oxidation involves the loss of electrons from an atom or molecule  An example is the conversion of lactic acid to pyruvic acid: Reduction involves the gain of electrons to a molecule  An example is the conversion of pyruvic acid to lactic acid: Oxidation and reduction are always coupled so the two reactions together are called oxidation-reduction or redox reactions  The oxidation of lactic acid to pyruvic acid and the associated reduction of NAD + may be written as: Energy Transfer & redox reactions When a substance is oxidized, the liberated hydrogen atoms are transferred by 2 coenzymes to another compound These are nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD) ATP Shuttle e-, transfer energy Energy transfer via phosphorylation reactions Some of the energy released during oxidation reactions is captured when ATP is formed  A phosphate group is added to ADP (phosphorylation) along with energy to form ATP ATP Negative delta Gibbs Humans can generate ATP through 1. substrate-level phosphorylation. 2. oxidative phosphorylation. 3. photophosphorylation. a) 1 only b) 2 only c) 3 only d) 1 and 2 are correct e) 1, 2, and 3 are correct  Interactions Animation: Carbohydrate Metabolism Carbohydrate Metabolism Carbohydrate metabolism is mostly glucose metabolism The body’s use of glucose depends on the needs of cells These needs include:  ATP production  Amino acid synthesis  Glycogen synthesis  Triglyceride synthesis Glucose must pass through the plasma membrane to be used by the cell Facilitated diffusion makes this happen  In most body cells, GluT molecules perform this Insulin increases the insertion of GluT4 transporters into the plasma membrane increasing the rate of facilitated diffusion The oxidation of glucose to produce ATP is cellular respiration Four sets of reactions are involved: 1. Glycolysis 2. Formation of acetyl coenzyme A 3. Krebs cycle reactions 4. Electron transport chain reactions Metabolism - summary Glycolysis: a) is the conversion of one molecule of glucose into two molecules of pyruvic acid. b) is the conversion of two molecules of glucose into one molecule of pyruvic acid. c) concludes with formation of acetyl coenzyme A. d) generates a usable total of 4 ATP molecules. e) requires oxygen for efficient conversion of glucose into pyruvic acid. Carbohydrate Metabolism - Glycolysis Glycolysis is the process whereby a 6-carbon glucose molecule is split into two 3-carbon molecules of pyruvic acid Glycolysis involves 10 chemical reactions Takes place in the cytoplasm  Carbohydrate Metabolism – Acetyl CoA What happens to the pyruvic acid depends on the availability of oxygen If oxygen is scarce (anaerobic conditions), pyruvic acid is reduced by the addition of 2 hydrogen atoms to form lactic acid If oxygen is plentiful (aerobic conditions), most cells convert pyruvic acid to acetyl coenzyme A The liver clears lactic acid by converting it back to pyruvate for use in krebs cycle and oxidative phosphorylation Carbohydrate Metabolism – Krebs The Krebs cycle is also known as the citric acid cycle cycle This cycle occurs in the matrix of mitochondria and consists of eight reactions  Carbohydrate Metabolism- oxidative phosphorylation The electron transport chain is a series of electron carriers in the mitochondria  Each carrier in the chain is reduced as it picks up electrons and oxidized as it gives up electrons  Exergonic reactions release energy used to form ATP  This mechanism links chemical reactions with the pumping of hydrogen ions and is known as chemiosmosis Electron carriers include:  Flavin mononucleotide (FMN)  Cytochromes  Iron-sulfur centers  Copper atoms  Coenzyme Q Carbohydrate Metabolism- oxidative phosphorylation Inside the inner mitochondrial membrane, the carriers are clustered into three complexes, each acting as a proton pump that expels H+  Carbohydrate Metabolism – net reaction Cellular respiration will generate either 30 or 32 ATP molecules for each molecule of glucose catabolized The reaction is:  Carbohydrate Metabolism Glucose not needed immediately is stored as glycogen by a process called glycogenesis When glucose is low and ATP is needed for body activities glucose is produced:  Stored glycogen is broken down by a process called glycogenolysis, and /or  Glucose may be formed from some amino acids (protein breakdown), from glycerol (triglyceride breakdown), lactic acid and pyruvate (lipolysis). This is gluconeogenesis.  T3, Glucagon and Cortisol stimulate these pathways  Lipid Metabolism Most lipids are nonpolar (hydrophobic), i.e. do not dissolve in water Blood plasma is over 90% water, Lipids are shuttled in plasma in combination with proteins produced by the liver and intestines called lipoproteins There are four classes of lipoproteins: 1. Chylomicrons - transport dietary lipids to adipose tissue 2. Very-low-density lipoproteins (VLDLs) - transport triglycerides from hepatocytes to adipocytes 3. Low-density lipoproteins (LDLs) - carry about 75% of the total cholesterol in blood and deliver it to cells 4. High-density lipoproteins (HDLs) - remove excess cholesterol from body cells and the blood and transport it to the liver for elimination Cholesterol can be ingested (eggs, dairy, organ meats). Over 80% is synthesized by hepatocytes Increases in total cholesterol levels are associated with a greater risk of coronary artery disease These are the Exercise, diet, and certain drugs are used to reduce “good” vs high cholesterol Interactions levels Lipid Metabolism Animation: “bad” cholesterol Lipid Metabolism Lipids may be oxidized (lose electrons) to produce ATP  When not needed for energy, lipids get stored in adipose tissue  Some are used as structural molecules or to synthesize other essential substances Adipose tissue is used to remove triglycerides from chylomicrons and VLDLs  VLDLs triglycerides constitute 98% of all body energy reserves Lipid catabolism (lipolysis) is the process of splitting triglycerides into fatty acids and glycerol Lipid anabolism (lipogenesis) is the process of synthesizing lipids from glucose or amino acids; It occurs when individuals consume more calories than needed  Beta oxidation and glycerol C metabolism -acyl CoA + FAD + NAD + H O + CoA → C -2-acyl CoA + FADH n + 2 n 2 + NADH + H+ + acetyl CoA Happens inside the mitochondria Fatty acid chains are chopped down 2C at a time Each cycle is a beta oxidation cycle Each cycle generates one Acetyl CoA Each Acetyl CoA can enter the Krebs Cycle Or, enter ketone body production Source ATP Total 1 FADH2 x 1.5 ATP = 1.5 ATP (Theoretically 2 ATP) 1 NADH x 2.5 ATP = 2.5 ATP (Theoretically 3 ATP) 1 acetyl CoA x 10 ATP = 10 ATP (Theoretically 12 ATP) TOTAL = 14 ATP  Protein Metabolism Proteins are the most versatile of all biomolecules (structural, signaling, receptors, enzymatic or catalytic functions, and others) Digested proteins are broken down into amino acids (20 amino acids total) Amino acids are not stored. They are either oxidized to produce ATP or used to synthesize new proteins Protein catabolism (breaking down) yields amino acids  Amino acids can be converted to other amino acids, fatty acids, ketone bodies, or glucose  Or oxidized to generate ATP via the Krebs cycle Protein anabolism (synthesis) creates new proteins by bonding together amino acids Interactions Animation: Protein Metabolism  Key Molecules at Metabolic Crossroads Of the thousands of different chemicals in cells, these are critical molecules in cellular energetics (metabolism): Glucose 6-phosphate is involved in:  Synthesis of glycogen  Release of glucose into the bloodstream  Synthesis of nucleic acids  Glycolysis Pyruvic acid is involved in:  Production of lactic acid  Production of alanine  Gluconeogenesis Acetyl coenzyme A is involved in:  Helping 2-carbon acetyl groups enter the Krebs cycle  Synthesis of lipids