Biochemistry 12 Bioenergetics and Regulation of Metabolism

Biochemistry 12: Bioenergetics and Regulation of Metabolism Thermodynamics and Bioenergetics Hormonal Regulation of Metabolism Open System: Matter & energy can be exchanged with the environment Closed System: Only energy can be exchanged with the environment. No work is performed because pressure and volume remain constant. ∆enthalpy='∆internal'energy= heat'exchange Entropy: A measure of energy dispersion in a system Change in Free Standard Free Energy, DG°: The energy change that occurs Energy: at 1 M concentration, 1 atm, and 25°C. Modified Standard State, DG°’: Indicates physiological conditions. [H= ] = 10@A𝑀, so pH is 7. The Role of ATP ATP structure ATP is a mid-level energy molecule. It contains high-energy phosphate bonds that are stabilized upon hydrolysis by resonance, ionization, and loss of charge repulsion. Energy Source: ATP provides energy through hydrolysis and coupling to () energetically unfavorable reactions. ATP= 30' Insulin: Secreted by pancreatic b -cells, regulated by glucose ¯blood glucose by increasing cellular uptake "rate of anabolic metabolism Glucagon: Secreted by pancreatic a -cells, stimulated by low glucose and high amino acid levels "blood glucose by promoting gluconeogenesis and glycogenolysis in the liver Glucocorticoids: "blood glucose in response to stress by mobilizing fat stores and inhibiting glucose uptake. They increase the impact of glucagon and catecholamines. Ex: cortisol Catecholamines: Promote glycogenolysis and "basal metabolic rate through sympathetic nervous system activity. “Adrenaline rush”. Ex: epinephrine and norepinephrine Thyroid "basal metabolic rate, as evidenced by "O2 consumption Hormones: and heat production when they are secreted. T3 is more potent than T4, but has a shorter half-life and is available in lower concentrations in the blood. T4 is converted to T3 at the tissues. Thyroid hormones are tyrosine-based. *+ Phosphoryl ATP can donate a phosphate group to other molecules. Group Transfers: For example, in Glycolysis, it donates a Phosphate group to glucose to form glucose 6-phosphate Biological Oxidation and Reduction Biological oxidation and reduction reactions can be broken down into component half-reactions. Half-reactions provide useful information about stoichiometry and thermodynamics High Energy May be soluble or membrane-bound. Includes NADH, Electron Carriers: NADPH, FADH2, ubiquinone, cytochromes, and glutathione. Flavoproteins: A subclass of electron carriers that are derived from riboflavin (vitamin B2). Examples: FAD and FMN Metabolic States Equilibrium: Equilibrium is an undesirable state for most biochemical reactions because organisms need to harness free energy to survive. Postprandial State: Well-fed, absorptive. "Insulin. Anabolism prevails. Postabsorptive State: Fasting. ¯Insulin. "glucagon and catecholamine. Transition to catabolism. Prolonged Fasting: Starvation. ""glucagon and catecholamine. Most tissues rely on fatty acids. 2/3 of brain activity can be derived from ketone bodies. Integrative Metabolism Respiratory RQ. Estimates the composition of fuel that is actively Quotient: consumed by the body. RQ='EFG'HI+JKLMJ F 'L+NOK*MJ G Regulatory Ghrelin: "appetite. (sight, sound, taste, smell of food) Hormones: Orexin: "appetite. Leptin: ¯appetite by suppressing orexin production *SOO TMUVTWG Liver: The most metabolically diverse tissue. Hepatocytes are responsible for the maintenance of blood glucose levels by glycogenolysis and gluconeogenesis in response to pancreatic hormone stimulation. The liver also processes lipids and cholesterol, bile, urea, and toxins. Adipose Tissue: Stores lipids under the influence of insulin and releases them under the influence of epinephrine. Skeletal Muscle: Skeletal muscle metabolism will differ depending on current activity level and fiber type. Resting muscle: Conserves carbohydrates in glycogen stores and uses free fatty acids from the bloodstream. Calorimetry: Measures metabolic rates Body Mass Index: BMI=' Tissue-Specific Metabolism Active muscle: May use anaerobic metabolism, oxidative phosphorylation of glucose, direct phosphorylation from creatine phosphate, or fatty acid oxidation, depending on fiber type and exercise duration. Cardiac Muscle: Uses fatty acid oxidation in both the well-fed and fasting states. Brain and Consume only glucose in all metabolic states, except for Nervous Tissue: prolonged fasts, where up to 2/3 of the brain’s fuel may come from ketone bodies.