Chapter note 4.pdf

9/17/20 Lecture 4 Metabolism – Cellular Respiration Fates of Macronutrients • Carbohydrates are broken down to glucose • Proteins and Fats are broken down and their subunits feed into carbohydrate breakdown pathway Fats Carbohydrates Fatty acids Glycerol Glucose Glycolysis NH3 Proteins Pyruvic...

9/17/20 Lecture 4 Metabolism – Cellular Respiration Fates of Macronutrients • Carbohydrates are broken down to glucose • Proteins and Fats are broken down and their subunits feed into carbohydrate breakdown pathway Fats Carbohydrates Fatty acids Glycerol Glucose Glycolysis NH3 Proteins Pyruvic acid 2-carbon fragment ATP Amino acids Cytosol Mitochondrion Figure 4.23 1 9/17/20 Enzymes and Metabolism • Enzymes: Proteins that catalyze (speed up) chemical reactions • Metabolism: All chemical reactions that occur in the body • Activation energy: The energy required to start the metabolic reaction – a barrier to catalysis Enzymes work by lowering the activation energy needed for a reaction (a) No enzyme present (b) Enzyme present Activation energy barrier Activation energy barrier Enzyme Reactants Reactants Products Products Figure 3.6 2 9/17/20 Enzymes and Metabolism • calorie: A unit of energy - The amount of energy to raise 1 g of water by 1oC - Calorie (=1 kilocalorie = 1000 calories): used on nutritional labels • Metabolic Rate: The rate at which the body uses energy - Basal metabolic rate: The resting energy use - 70 Cal/h, 1680 Cal/day - Males > Females Figure 3.8 To calculate the number of Calories you are burning per hour, multiply your weight by these numbers. Walking Hiking Activity Bicycling Tennis Mowing lawn Swimming Basketball Jogging Running How many Calories would a 160-pound person burn in 30 min of swimming? 2.16 2.52 2.70 3.00 3.06 3.48 * 160 * 0.5 = 278.4 Cal 3.48 3.78 4.15 5.28 Calories/hour/ pound of body weight 3 9/17/20 Body Fat and Health • Extra calories can be stored as fat - Balance energy intake vs. output - Eating the correct amount of food • Body Mass Index (BMI): a value that correlates amount of body fat with risk of illness and death - Healthy: 20-25 - Obesity: >30 4 9/17/20 Health Problem Related to Obesity • Diabetes: carbohydrate metabolism disorder - Insulin: hormone to trigger cells to take up glucose Pancreas Insulin 2 Liver When blood sugar is high, a healthy pancreas secretes insulin 4 into the bloodstream. 3 Capillary 1 Blood sugar is higher following a meal. Excess glucose is stored in the liver as glycogen. Insulin triggers all the body’s cells to take up glucose. Figure 3.16 • Type 1 Diabetes (Insulin-dependent): can not produce insulin at all - Usually arise in childhood, not due to obesity - Treat with daily insulin injections • Type 2 Diabetes (non-insulin-dependent, adultonset): not enough insulin, or resistant to insulin - Most common form, may be due to obesity - May be controlled by diet and exercise • Gestational Diabetes: develop just during the pregnancy - Resolve itself after the birth of the child 5 9/17/20 Body Fat and Health • Hypertension: high blood pressure – The force exerted on blood vessels by the blood - Systolic: blood pressure as the heart contracts - Diastolic: blood pressure as the heart relaxes - Examples: 120 (systolic)/80 (diastolic) – normal >140/90 – hypertension How to measure blood pressure? Tools: Stethoscope and Sphygmomanometer 6 9/17/20 Cellular Respiration • Main function: convert energy from food into energy that cells can use – Which cells? • Product: adenosine triphosphate (ATP) - Contain 3 phosphate group - High-energy phosphate bond Initial Step – Glycolysis • Convert 6-carbon sugar (glucose) to 3-carbon intermediate product (pyruvate) - In the cytosol – the portion of the cytoplasm not contained in any organelles - Not require oxygen - Produce ATP 7 9/17/20 • The subsequent digestion of pyruvate depends upon oxygen availability - In presence of O2: Aerobic respiration - In the mitochondrion - In absence of O2: Anaerobic respiration - In the cytosol Aerobic Respiration – Mitochondrion • Envelop: double layer membrane • Cristae: Inner folding of the inner membrane • Matrix: The medium that contains enzymes and nucleic acids 8 9/17/20 Aerobic Respiration • Citric acid cycle: convert pyruvate to CO2 and H2O, highly enzyme-dependent - Must transport pyruvate: cytosol à mitochondrion - Produce ATP Aerobic Respiration mitochondrion • Oxidative Phosphorylation: transfer electrons, use oxygen, produce most ATP 32 9 9/17/20 Anaerobic Respiration • Fermentation: pyruvate is converted to lactic acid or alcohol (ethanol), without O2 - No energy formation - Less efficient * How many ATP molecules are produced per glucose? - Not being used for long Aerobic vs. Anaerobic Respiration (Primary) 10 9/17/20 Aerobic vs. Anaerobic Exercise • Aerobic Exercise: Physical exercise of moderate intensity and long duration • Anaerobic Exercise: High intensity exercise in which your muscles do not receive enough oxygen to generate energy • You need both! Are These Aerobic or Anaerobic Exercises? 11