Midterm: ch 6, 7, 21, 15-17 Flashcards
(48 cards)
Discuss two contributions of high-energy phosphates for energizing biologic work
- Conserve energy from food in ATP bonds, 2. extract and transfer chemical energy in ATP to power work
List 2 important functions of carbohydrate in energy metabolism
- Provide the only macro substrate for anaerobic glycolysis, 2. Creates intermediates needed for fat catabolism
Discuss dynamics of lactate formation and accumulation during increasing exercise intensity
- At <50% of aerobic capacity, blood lactate production = blood lactate clearance. Rapid and large accumulation occurs during max PA of 60-180 sec.
- Some lactate produced at low PA/rest, thru metabolism of RBCs and limitations by enzyme activity in muscle fibers.
- When it forms, it diffuses into interstitial space and blood for removal, or provides gluconeogenic substrate for glycolysis.
Discuss the role of the citric acid cycle (aerobic) in energy metabolism
- Releases last 95% of energy in glucose, happens when pyruvate converts to acetyl CoA. The CAC degrades acetyl CoA to Co2 and hydrogen atoms. ATP formed when hydrogen oxidizes during electron transport oxidative phosphorylation.
- 34 ATP is total yield
Contrast ATP yield from catabolism of a molecule of carbohydrate, fat, and protein.
- Fat: 460 ATP, plentiful source of energy. Becomes primary energy fuel for exercise and recovery when intense, long duration exercise depletes both blood glucose and muscle glycogen. Aerobic.
- Protein: After deamination, the remaining carbon skeleton produces ATP aerobically.
- Carb: only anaerobic! Supplies about ⅓ of bodys energy requirement during light and moderate physical activity. 32 ATP.
Explain the meaning of: “fats burn in a carbohydrate flame”
FAs require intermediates generated in carb breakdown for continual catabolism to produce energy in the metabolic mill → fats burn in carb flame. Acetyl Coa enters CAC by combining with oxaloacetate to form citrat (key step). Oxaloacetate then reforms from pyruvate from carb breakdown. Conversion is under enzymatic control of pyruvate carboxylase which adds a carboxyl group to the pyruvate molecule. Only continues if theres sufficient oxaloacetate to combine w the acetyl CoA formed during beta oxi.
Outline the interconversions among carbohydrate, fat, and proteins
Carbs → fats or nonessential AAs
Fats → nonessential AAs
Proteins → carbs or fats
Describe lactate threshold.
occurs when muscle cells can neither meet energy demands aerobically nor oxidize lactate at its rate of formation.
Describe lactate threshold differences between sedentary and endurance-trained individuals.
- Untrained: lactate accumulation starts at 50-55% of max aerobic capacity.
- Trained persons perform SR aerobic exercise at 80-90% of max aerobic capacity due to: genetics, local training adaptations, more rapid lactate removal at any intensity.
Describe the pattern of oxygen uptake during progressive increments of exercise intensities to maximum.
O2 uptake initially rises exponentially before plateau, then remains in SR.
Differentiate between type 1 and type 2 muscle fibers.
- Fast twitch: rapid contraction speed and high capacity for anaerobic ATP production in glycolysis, highly active in change of pace and stop and go activities. Type IIA - high aerobic capacity.
- Slow twitch: generates energy thru aerobic pathways, slower contraction speed than fast twitch fibers, active in continuous activities requiring steady rate aerobic energy transfer.
Discuss differences in recovery oxygen uptake from light, moderate, and intense exercise.
Recovery VO2 follows a logarithmic curve, decreasing by 50% over each subsequent 30 sec period until reaching pre exercise levels. Light activity with rapid steady state VO2 attainment produced a small O2 deficit with rapid recovery VO2. moderate to intense aerobic activity requires a longer time to achieve steady rate VO2. this creates a larger O2 deficit with a longer recovery time for the VO2 to restore resting levels.
List three factors that account for excess post-exercise oxygen consumption.
Body temperature, blood returning to lungs from active muscles, restoring oxygen dissolved in bodily fluids and bound to myoglobin within muscle.
Discuss the rationale for intermittent exercise applied to interval training
•Produces rapid recovery and enables subsequent intense exercise to begin following a brief recovery.
•Manipulating the duration of exercise and rest intervals can effectively overload an energy system of choice.
- Relative balance between energy requirements during PA and aerobic energy transfer within muscles.
- Rapid recovery in O2 uptake, because high energy phosphates supply most energy, minimal reliance on glycolysis.
Discuss and provide examples of the exercise training principles of overload, specificity, individual differences, and reversibility.
- Overload: manipulating frequency, intensity and/or duration
- Specificity: Specificity of local changes - definition, greater BF in active tissue - results from incr microcirculation, more effective redistribution of CO, combined effect of both. Only happens in muscle being trained
specificity of vo2max: aerobic overload requirements: engage appropriate muscles required by activity, provide exercise a level sufficient to stress the cardiovascular system. Little improvement is noted when measuring aerobic capacity with dissimilar exercise. - Individual differences
- Reversibility: detraining rapidly occurs when terminating a training program. Only 1-2 wks of detraining reduces metabolic and exercise capacity. Beneficial effects of prior training remain transient and reversible.
Outline the metabolic adaptations to anaerobic exercise.
1) Incr. levels of anaerobic substrates.
2) Incr quantity and activity of key enzymes that control the anaerobic phase of glucose catabolism.
3) Incr capacity to generate high levels of blood lactate during all-out exercise:-Increased levels of glycogen and glycolytic enzymes-Improved motivation and tolerance to “pain”
Metabolic adaptations to aerobic exercise training
•Aerobic training improves capacity for respiratory control in skeletal muscle.
•Endurance-trained skeletal muscle fibers contain larger and more numerous mitochondria than less active fibers.
•Mitochondrial enzyme activity increases by 50%.
• Increased intramuscular fatty acid oxidation via:
1)Greater blood flow within trained muscle.
2)More fat-mobilizing and fat-metabolizing enzymes.
3)Enhanced muscle mitochondrial respiratory capacity.
4)Decreased catecholamine release for the same absolute power output.
Cardiovascular adaptations to aerobic exercise training
Cardiac hypertrophy, incr plasma volume, decr RHR, incr SV → incr max CO, incr O2 extraction, greater BF distribution, incr in capillaries, decr BP
Pulmonary adaptations to aerobic exercise training
Incr VE, incr tidal volume, lower % Total exercise O2 cost → incr exercise endurance, decr breathing frequency
ATP - limited energy source
ATP, a limited currency: cells have to constantly resynthesize ATP (at its rate of usage) because they only contain a small amount. ATP levels in muscle only decrease in extreme conditions.
Major energy transforming activities: extract potential energy from food and conserve it within the ATP bonds, extract and transfer the chemical energy in ATP to power biological work.
ADP forms when ATP joins with water, catalyzed by the enzyme adenosine triphosphate (ATPase).
Body stores 80-100g of ATP at any time under normal rest, enough to power ⅔ sec of max exercise.
PCr - energy reservoir
Fat and glycogen are the main energy source for ATP resynthesis. Some energy also comes from anaerobically splitting a phosphate from phosphocreatine (PCr) → also an intracellular high energy phosphate compound. ATP and PCr provide anaerobic sources of phosphate-bond energy. The energy freed from hydrolysis of PCr rebonds the ADP and Pi to form ATP. training increases the muscles’ quantity of high energy phosphates. P + Cr = PCr. ADP + P = ATP. PCr hydrolysis catalyzed by creatine kinase derives ADP phosphorylation to ATP. cells store 4-6x more PCr than ATP. PCr is a reservoir of high energy phosphate bonds. ADP phosphorylation > energy transfer for stored muscle glycogen ← because of high activity rate of creatine kinase.
Cells store 4-6x more PCr than ATP, PCr reaches max energy yield in 10 sec. The adenylate kinase reaction represents another single enzyme mediated reaction for ATP regeneration.
Cellular oxidation
Most energy for phosphorylation comes from oxidation of dietary carbs, lipid and protein macros. Molecule accepts electrons from a donor → becomes reduced, the donor becomes oxidized. Provides hydrogen atoms from the catabolism of stored macros. Mitochondria carrier molecules remove electron from hydrogen (oxidation) and pass them to oxygen (reduction). Oxidation reactions (those that donate electrons) and reduction reactions (those that accept electrons) are coupled and constitute the biochemical mechanism that underlies energy metabolism. This process continually provides hydrogen atoms from the catabolism of stored macronutrients. The mitochondria contain carrier molecules that remove electrons from hydrogen (oxidation) and eventually pass them to oxygen atoms (reduction), ATP synthesis occurs during redox reactions. During cellular oxidation, hydrogen atoms are not merely turned loose in intracellular fluids. Substrate specific dehydrogenase enzymes catalyze hydrogens release from the nutrient substrate. The coenzyme component of the dehydrogenase accepts pairs of electrons from hydrogen. Nicotinamide adenine dinucleotide (NAD+)gains hydrogen and two electrons and reduces to NADH;the other hydrogen appears as H+ in the cell fluid. Flavin adenine dinucleotide (FAD) serves as another electron acceptor and becomes FADH2 by accepting two hydrogens.
Electron transport
During cellular oxidation, NAD+ (in dehydrogenase enzyme) accepts pairs of electrons from hydrogen, when the enzyme catalysez hydrogen’s release from nutrient substrate.
→ NAD+ gains hydrogen + 2 electrons and reduces to NADH (the other hydrogen is H+ in the cell fluid)
→ FAD is another electron acceptor (to oxidize food fragments) - it catalyzes dehydrogenation and accepts electron pairs. FAD becomes FADH2 by accepting both hydrogens.
The cytochromes, a series of iron protein electron carriers dispersed on the inner membranes of the mitochondrion, then pass in bucket brigade fashion pairs of electrons carried by NADH and FADH2.
Electron transport represents the final common pathway where electrons extracted from hydrogen pass to oxygen. Mitochondrial oxygen levels drive the respiratory chain by serving as the final electron acceptor to combine with hydrogen to form water. For each pair of hydrogen atoms, two electrons flow down the chain and reduce one atom of oxygen to form one water molecule. During the passage of electrons down the chain, enough energy is released to phosphorylate ADP to ATP.
Macronutrient fuel sources
Energy release in macro catabolism aims to phosphorylate ADP to reform the energy rich compound ATP. 3 stages: 1. Digestion, absorption and assimilation of large food macromolecules into smaller subunits for use in cellular metabolism. 2. Degrades amino acid, glucose, fatty acid and glycerol units within the cytosol into acetyl-coenzyme A, with limited ATP and NADH production. 3. Within the mitochondrion, acetyl-coenzyme A degrades to CO2 and H2O with considerable ATP production.
6 fuel courses that supply substrate for ATP production:
- Triacylglycerol and glycogen molecules stored within muscle cells
- Blood glucose (derived from liver glycogen)
- Free fatty acids *derived from triacylglycerols in liver and adipocytes)
- Intramuscular and liver derived carbon skeletons of amino acids
- Anaerobic reactions in the cytosol in the initial phase of glucose or glycogen breakdown (small amount of ATP)
- Phosphorylation of ADP by PCr under enzymatic control by creatine kinase and adenylate kinase
