Bioenergetics and Metabolic Rate PDF

BIOENERGETICS AND METABOLIC RATE Thobeka Madide [email protected] YBOD 200 MBCHB II 03 June 2024  LEARNING OBJECTIVES -Describe how ATP functions as an energy currency in metabolism under the following headings: oIts formation from carbs, fatty aci...

BIOENERGETICS AND METABOLIC RATE Thobeka Madide [email protected] YBOD 200 MBCHB II 03 June 2024  LEARNING OBJECTIVES -Describe how ATP functions as an energy currency in metabolism under the following headings: oIts formation from carbs, fatty acids and protein by respectively combustion (glycolysis), oxidation and hydrolysis oHow it energizes synthesis of cellular components, muscle contraction, active membrane transport, glandular secretions and nerve conduction. -Explain the biological significance of phosphocreatine -Compare aerobic versus anaerobic energy -Describe what is meant by the metabolic rate and how it is measured. -Describe energy metabolism - energy output, overall energy requirements for daily activities, and the basal metabolic rate -Describe factors affecting the metabolic rate and the energy used for physical activities, the thermogenic effect of food, thermogenesis and brown fat ATP Production  ATP utilisation Peptide linkages during protein synthesis Synthesizing glucose from lactic acid Addition of CoA to fatty acid Urea excretion Muscle Contraction Membrane Transport and Glandular secretions Sodium/Potassium pump Potassium/proton pump Nerve conduction Potential energy due to high concentration of stored ions in or outside neurons ATP energizes retrograde transport of ions back to membrane Phosphocreatine Most abundant store of high energy phosphate bonds Excess ATP can be converted to phosphocreatine (reversible) Serves to recycle ATP for muscular activity  Anaerobic respiration -One of the prime examples of anaerobic energy utilization occurs in acute hypoxia + strenuous exercise -Oxygen debt must be paid – hard breathing 1. Reconvert the lactic acid into glucose 2. ADP to ATP 3. Creatine and phosphate to phosphocreatine 4. Re-establish normal [O2] bound with Hb and myoglobin 5. Raise [O2] in the lungs to its normal level Control of energy release in cells Rate control of enzyme catalyzed reactions Enzyme concentration Substrate concentration Rate limiting step (slowest step) ADP concentration  Metabolic Rate The metabolism of the body simply means all the chemical reactions in all the cells of the body, and the metabolic rate is normally expressed in terms of the rate of heat liberation during chemical reactions. -Heat is the end product of almost all the energy released in the body -Not all the energy in foods is transferred to ATP- a large portion of this energy becomes heat -The calorie – “c” = gram calorie-unit for expressing the quantity of energy released from different foods or expended by different functional processes of the body -”quantity of heat required to raise the temperature of 1 gram of water 1°C” -“C” = kCal = 1000 c Calorimetry Measurement of whole body metabolic rate Direct – heat liberated from body Indirect – “Energy equivalent” of oxygen Average diet, the quantity of energy liberated per liter of oxygen used in the body averages about 4.825 Calories , which is called the energy equivalent of oxygen Factors affecting energy output Performing Digestion, essential Maintaining Physical absorption, metabolic body activities processing of functions of temperature food the body  Basal Metabolic Rate -Minimum level of energy required to exist is called the basal metabolic rate (BMR) -The person must not have eaten food for at least 12 hours. -The BMR is determined after a night of restful sleep -No strenuous activity is performed for at least 1 hour before the test -All psychic and physical factors that cause excitement must be eliminated -The temperature of the air must be comfortable (RT) -No physical activity is permitted during the test Normal BMR rates Factors influencing BMR ↑ Metabolic rate ↓ Metabolic rate Thyroid hormone Sleep Testosterone Malnutrition Growth hormone Fever  Thermogenic effect of food After a meal is ingested, the metabolic rate increases as a result of the different chemical reactions -Digestion, absorption and storage -This increase is called the thermogenic effect of food because these processes require energy and generate heat -Carb and fat foods ↑ by 4% but protein ↑ 30% ie. specific dynamic action of protein  Non-shivering thermogenesis Produce heat in response to cold stress Sympathetic nervous system  norepinephrine and epinepherine  ↑ metabolic rate  heat In Brown fat tissue- sympathetic nervous stimulation causes liberation of large amounts of heat Brown fat  high in mitochondria and several small fat globules OXPHOS “uncoupled” = heat generation but not ATP REFERENCES Guyton and Hall Medical Physiology, Chapter 73- Energetics and metabolic rate