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42 Cards in this Set

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1.Why does the body store energy in the form of fat rather than carbohydrate (glycogen)?
Triglycerides are stuck inside the fat cell and the fatty acids range from 16-21 carbons long. The must go to the muscle cell to be used for energy. Any energy consumed not used immediately forms a triglyceride. Fat is also lighter because it is nearly anhydrated and it’s more calorically dense than fat.
Why isn’t protein a preferable energy source?
Protein is stored in mostly muscle tissue. It is used for tissue synthesis and membrane construction. You don’t want to use protein as an energy source because then muscles would be torn down. Protein also does not give up energy as readily as carbohydrates and fat do.
Under what conditions is protein used for energy?
Protein supplies up to 15% of energy needed during long endurance activities lasting over 2 hours when carbohydrate stores are low (during rest, it only supplies 2% of the necessary energy). All 20 of the amino acids except leucine and lysine can be degraded into Krebs cycle intermediates. When glycogen stores are depleted in muscle during exercise and the liver during fasting, catabolism of muscle proteins to amino acids contributes to the maintenance of blood glucose levels.
Explain the purpose of the lactate shuttle.
Lactate is produced inside the muscle cell and it is diffused out of the cell. Transporters put the lactate in the blood which is then either sent to the liver (where it is converted back into glucose), or to other muscles where it is used as a fuel for type I muscle fibers. These slow twitch fibers convert lactate to pyruvate which then can be transformed into Acetyl-CoA to go through the Krebs cycle. Lactate is not a waste product. Active recovery keeps blood flow active throughout the muscle to diffuse better and to redistribute to other muscle tissues faster.
Explain lactate threshold and the benefit of training to improve lactate threshold. What type of training would be use to improve lactate shuttle?
With increased intensity, glycolysis increases. Glycolysis is limited by the fact that it cannot shuttle the NADH through the mitochondrial membrane fast enough, so pyruvate becomes lactate (anaerobically). During this high intensity exercise, the rate of lactate production exceeds the rate of lactate clearing. It’s easier to improve lactate threshold than VO2 max. It’s important for everybody because it is great for functional capacity (it’s possible to do more without fatiguing). The intensity at the lactate threshold is the maximal intensity at which steady-state exercise can be maintained. High intensity aerobic exercise is needed to improve lactate threshold because the rate of lactate production exceeds the rate of lactate clearance. In short, you want to work at a higher intensity before you start to accumulate lactate. This will give large visible improvements in functional capacity because the number of mitochondria will increase as well as the number of capillaries around each fiber type.
The intensity at which lactate threshold is reached is considered the
See notes
Explain the purpose of the Krebs Cycle for carbohydrate, fat, and protein metabolism.
The Krebs cycle converts or oxidizes carbohydrates, fats and protein to Acetyl-CoA, It transfers energy in the form of hydrogen to NAD and FAD. It does not provide ATP. For every 1 glucose, you get 2 pyruvates, which give you 2 acetyl-coA’s so you go through the cycle twice. 1 cycle forms 3NADH, 1FADH, 1ATP.
What are key Krebs Cycle enzymes?
- Isocitrate Dehydrogenase (IDH): rate limiting enzyme of the Krebs cycle. Converts isocitrate into alpha-ketoglutarate, produces NADH from NAD. Produces carbon dioxide. (RATE LIMITING KREBS)

- Succinate Dehydrogenase (SDH): used in the Krebs cycle, enzyme which converts succinate into fumarate, and FAD to FADH.

- Pyruvate Dehydrogenase (PDH): enzyme which converts pyruvate into acetyl-CoA. Biproducts would be CO2.
Explain the purpose of the electron transport chain (ETC) (system).
produce a proton gradient through the transfer of electrons and protons which leads to the formation of H2O, and a gradient which then triggers ATPsynthase. During this passage, enough energy is released to rephosphorylate ADP to form ATP. The bulk of the NADH and FADH come from the krebs cycle, but 2 can come from glycolysis. As electrons are pumped along the gradient, energy is released to pump the hydrogens (from the NADH and FADH) from the inside of the mitochondria across the inner mitochondrial membrane. The accumulation of H+ is a source of potential energy that can be captured and used to recombine inorganic phosphate with ADP to form ATP.
Explain the function of e- in the ETC
Electrons are transported along the ETC, providing energy to pump H+ into intermembrane space
Explain the function of H+ in the ETC
Hydrogen protons translocated into the intermembrane space (only moved through by electrons) [electrons carry the hydrogens]to form a gradient
Explain the function of oxygen in the ETC
Oxygen is the final electron acceptor, combining with 2 electrons and 2H+ ions to form water
Explain why oxygen is a limiting factor in the ETC oxygen combines with electrons and hydrogen forming water in cytochrome oxidase.
It’s the rate limiting step in ETC. 2 oxygens, hydrogen and electron form two water molecules. This is the only thing that oxygen does.
Explain why 2.5 ATP’s are derived from NADH+H+ and only 1.5 from FADH2.
NADH enters the ETC at the very beginning, whereas FADH enters later on, thus the FADH yields less energy.
What is the primary limiting factor of the ETC oxygen (in cytochrome oxidase)?
oxygen combines with electrons and hydrogen forming water. 2 oxygens, hydrogen and electron form two water molecules. This is the only thing that oxygen does, thus making it the rate limiting step in the ETC.
What are three enzymes in the ETC.
- NADH dehydrogenase: NADH becomes NAD+, and 4 hydrogens are pumped from the innermembrane matrix to the intermembrane space. The electrons are then taken to cytochrome b-C1 through ubiquinone.

- Cytochrome b-C1: more hydrogens get pumped through from the matrix to the innermembrane space. Electrons are picked off from the ubiquinone and are accepted 1 at a time by cytochrome c.

- Cytochrome oxidase: oxygen combines with electrons and hydrogens forming water. This is the rate limiting step and is dependent on the oxygen. 2 oxygens, hydrogen and electrons form 2 water molecules.

- ATPsynthase: 3 hydrogens pass through to get 1ATP (energy from the change in gradient)
What are four factors that determine fat utilization for energy production?
- Concentration of fat in blood: the greater the concentration, the greater the use. It takes time to release those fatty acids.

- Intensity: less than 70% VO2 max (average person); trained person can go up to 80%; highly trained can go up to 85% (otherwise the subject will fatigue quickly, so it’s all based on endurance fitness).

- Duration: minimum 20 minutes before you burn any fat (fuel as fat…NOT weight loss) significant fat burning is at lleast 45-90 minutes (90=best).

- Fitness level: increased fat burning with increased aerobic fitness
What is the sequence for fat burning? Explain how free fatty acids are mobilized from the fat cell.
- Mobilization: from fat cell and into blood (hormonally controlled)

- Circulation: transport of free fatty acids to muscle (Cardiovascular dynamics)

- Uptake into muscle, concentration dependent (increased arterial free fatty acid concentration, increased uptake)

- Activation: with coenzymeA – costs 2 ATP

- Tranlocation: into mitochondria (Acetyl-carnitine)

- Beta-oxidation: breakdown of free fatty acids to Acetyl-CoA and 1NADH, 1FADH per Acetyl-CoA.

- Oxidation: in krebs cycle and ETC.
What is the function of Beta oxidation? How may times would a 20 carbon fat pass through beta oxidation? How many NADH’s and FADH’s are produced via beta oxidation for a 20 carbon fat? How many NADH’s and FADH’s are produced via Krebs Cycle for a 20 carbon fat?
Beta oxidation breaks down carbon chains into 2 carbon molecules (Acetyl-CoA) from fatty acids to enter the Krebs cycle. Each time a molecule passes through, 1 NADH and 1 FADH is produced. Then the Acetyl-CoA goes to the Krebs cycle where 3NADH, 1 FADY and 1 ATP are produced. A 20 carbon fat would pass through beta oxidation 9 times because it would produce 10 Acetyl-CoAs. 9 NADH, and 9 FADH are produced. In the krebs cycle, then 27 NADHs are produced, 9 FADH are produced and 9 ATP are produced.
What are the protein requirements for:
- A person doing endurance training

- A person doing resistance training who is trying to increase muscle mass
- A person doing endurance training needs a small amount extra (if more than 90 minutes of exercise) which is used as fuel during endurance exercises derived from muscle protein. This will replace amino acids used for energy and some repair post exercise. 1.2-1.4g/kg of body mass/day.

- A person doing resistance training and who is trying to increase muscle mass Resistance athletes need extra protein to repair muscle fibers and to remodel muscle tissues in response to the weight lifting. 1.4-1.8g/kg of body mass/day.

- Athletes need more protein than sedentary people due to post-exercise muscle repair.

- Athletes do not need to automatically add protein to their diet, but if they are hoping to gain muscle mass then extra protein is needed.

- Protein increases amino acid pools in their blood prior to exercise which immediately begins repair post exercise.

- Most athletes already consume excess protein, so they do not need to add more protein in their diet.
For a person who does endurance training, what is the problem with high protein diets or low carbohydrate diets?
A 40% carb diet (low carb)does not replenish muscle glycogen. A high carb (70%), low protein diet has muscle glycogen drop during the workout, but then it is replenished. The protein isn’t excessive so the demand to replenish carbohydrates is easier with the excess carbohydrates. High protein diets which are low in carbs are counterproductive. Endurance athletes need to fuel up on carbohydrates days prior to the endurance activity. The days prior are more important than what you consume on the day of. High protein diets are too low in carbohydrates for adequate glycogen replacement following high intensity, moderate to long duration training. Want your glycogen to last as long as you can, so you’ll store it longer
Explain VO2max. Why is it considered a measure of cardiovascular fitness?
VO2max is the greatest rate of oxygen uptake by the body measured during severe dynamic exercise. Its regarded as a measure of Cardiorespiratory endurance. Its one of the limiting factors of aerobic exercise when it lasts longer than 3 minutes. VO2 max is the rate at which you can consume oxygen (it binds to hemoglobin on the red blood cells). VO2 max depends on cardiac output, mitochondrial function (a-VO2 difference), gender (increased in males due to larger heart, and therefore larger Q), age (decreases with age around 30 or 40), and genetics. High VO2 max means you’re able to tolerate high intensity exercise for a long time. Exercising (improving VO2 max) could reduce sensitivity of diabetes and obesity
Explain oxygen deficit. How does appropriate training affect oxygen deficit and why?
- Oxygen deficit is the lack of oxygen during the first few minutes of exercise because the aerobic system cannot meet the demand. The oxygen deficit is considered the difference between the oxygen uptake in the first few minutes of exercise and an equal time period after steady state has been obtained.

- It’s important to pace yourself at the beginning, start off slowly as a ‘warm-up’ for a smoother workout. The energy for the exercise is met by the smooth blending and overlap of the body’s 3 energy systems over time.

- Aerobic training will decrease the time to steady state
1. Increased cardiac output
i. Which may increase VO2 max
2. Increased mitochondria/enzyme function
3. Increased capillaries/muscle fiber
What is the significance of an extended EPOC?
EPOC is important for weight loss due to a higher percentage of calories burned in the 8hours burned post exercise. It’s the recovery period after exercise where the VO2 max is elevated (the amount of oxygen consumed during recovery is in excess of that which would have ordinarily been consumed at rest). EPOC increases with intensity and duration. EPOC increases caloric cost of exercise, weight loss or control.
EPOC is important for weight loss due to a higher percentage of calories burned in the 8hours burned post exercise. It’s the recovery period after exercise where the VO2 max is elevated (the amount of oxygen consumed during recovery is in excess of that which would have ordinarily been consumed at rest). EPOC increases with intensity and duration. EPOC increases caloric cost of exercise, weight loss or control.
- Fatty acid utilization as a fuel (not weight loss, but you will lose weight):
o Untrained: 55-65% VO2 max; 25-45 minutes
o Trained: 70-75% VO2 max; 90-120 minutes
o Highly trained: 80% VO2 max; 90-120 minutes
- Lactate threshold (need aerobic exercises):
o Continuous: 30-45 minutes (greatly enhances quality of life and functional capacity)
 70-80% of VO2 max (75-85% of maxHR)
• 15-20min warmup; 30-45 min steady state; 10-20 min cool down. A
o Interval training: rest interval < work interval
 80-85% of VO2 max (85-90% maxHR)
• 15-20min warmup; total work time > 30 minutes; 10-20 minute cool down
o 10-15 x 800m with 200m easy between 800s. this helps prepare for longer runs at a fast pace
o Can work at a higher aerobic intensity before becoming anaerobic.
- MaxVO2: most intense form of aerobic training (borderline anaerobic)
o Interval training: most effective: 85-95% of VO2 max, or 90-95% HRmax
 15x15 workout=47x15sec fast with 15 sec active rest
o Repetition training = rest interval > work interval
 4x4 workout=4 minute fast, 4 minute active recovery
o Fartlek training: speed play (threshold training)
o All get VO2 in range for 3-4 minutes at a time
- In short….fat utilization is moderate; lactate is moderate/high; aerobic is high.
- You must stimulate ffa, VO2 max, etc, must be specific.
- All improve mitochondrial function
List the specific physiological adaptations for each type of training.
- Fatty Acid Utilization:
o Increased sensitivity of hormone sensitive lipase to epinephrine and glucagon.
 Increased mobility of free fatty acids in the blood (uptake of free fatty acids into the muscles)
o Enzyme activity in beta-oxidation will increase
o Increased capacity of mitochondria to produce ATP
 Increased mitochondria density
 Increased aerobic (mitochondrial enzymes)
 Possible increase in activity of aerobic enzymes – Krebs cycle, beta oxidation and ETC.
- Lactate Threshold:
o Increase capacity of mitochondria to produce ATP
o Increase aerobic metabolism of glycogen
o Increase mitochondrial density
o Increase aerobic [mitochondrial] enzymes
o Increase a-VO2 difference (arterial-venous difference)
 you want a lower number because then its improved utilization of oxygen
o increase capillary density (more O2 to diffuse into tissue)
o Increased LDHheart lactate  pyruvate (in slow twitch fibers, it’s used for fuel, so not everything goes to type II causing fatigue).
- MaxVO2:
o Increase stroke volume means increased cardiac output
 Increased capillary density within active muscle tissues
 Increased capillary density (increased oxygen availability to muscle)
o Increase capacity of mitochondria to produce ATP
 Increased mitochondrial density
 Increased aerobic (mitochondrial enzymes)
 Possible increase in activity of aerobic enzymes (Krebs cycle, ETC)….does not use beta oxidation!
Explain why MaxVO2 is considered a measure of cardiovascular fitness. What does oxygen utilization in the electron transport chain have to do with the cardiovascular system?
High VO2 max means you’re able to tolerate high intensity exercise for a long time. Exercising (improving VO2 max) could reduce sensitivity of diabetes and obesity. Oxygen is used by cytochrome oxidase in the electron transport chain. The oxygen combines with electrons and hydrogen ions forming water, which is the rate limiting step (dependent on the oxygen). The oxygen consumption is directly dependent on cardiac output. VO2 max is a cardiac output estimation (high cardiac output means a high VO2 max (partially genetic).
Because the percentage fat utilization is highest during low to moderate exercise intensity, exercise for weight loss should be low to moderate intensity exercise. T F Explain.
False. Exercise at 50% VO2 max is fueled by 50% fat for the first hour. After 2 hours, 70% of the fuel is fat. 3+ hours is 80%+ fat. If you bike at 75% VO2 max, fat provides 33% of the required calories. Take home message, if exercise duration is the same, then you will expend more calories at a higher intensity. Also the EPOC will be higher, so even more weight loss will occur.
What is the function of the following enzymes and hormones?
a. Hexokinase: enzyme which turns glucose into glucose-6-phosphate. Costs 1ATP. Glucose stimulates.
b. Phosphorylase: enzyme turns glycogen into glucose. Stimulator is an increased concentration of calcium from the sarcoplasmic reticulum, and epinephrine which is released faster at higher intensities. The increased epinephrine concentration forms cAMP which directly activates phosphorylase.
c. FAD: coenzyme, a hydrogen acceptor in the cell mitochondria
d. Phosphofructokinase: a very adaptive enzyme and is the rate controlling portion of the pathway. ADP and AMP are activators because they increase the rate and the demand during exercise. ATP and a decreased pH and increased free fatty acids are inhibitors. PFK turns F-6-P into F1,6 Biphosphate. (RATE LIMITING GLYCOLSYSIS)
e. Lactate dehydrogenase muscle: enzyme which turns pyruvate into lactate. Thus, turning NADH into NAD so that the NAD can be recycled.
f. NAD+: Transports hydrogen’s to be later used for ATP generation. 2 hydrogens are added to G3P which creates NADH+H thus forming 1,3-Bisphosphate. The NADH+H is then recycled to NAD when pyruvate is either turned into lactate or sent to the mitochondria.
g. Succinate Dehydrogenase (SDH): used in the Krebs cycle, enzyme which converts succinate into fumarate, and FAD to FADH.
h. insulin: hormone, allows glucose to be stored as glycogen to later be used in glycolysis. During rest, insulin binds to binding site in cell membrane which activates glut-4.
i. Epinepherine: hormone, concentration increases as exercise intensity increases. Stimulates glut4.
j. Isocitrate Dehydrogenase (IDH): rate limiting enzyme of the Krebs cycle. Converts isocitrate into alpha-ketoglutarate, produces NADH from NAD. Produces carbon dioxide. (RATE LIMITING KREBS)
k. Pyruvate Dehydrogenase (PDH): enzyme which converts pyruvate into acetyl-CoA. Biproducts would be CO2.
l. Lactate dehydrogenase heart: lactate  pyruvate (in slow twitch fibers, it’s used for fuel, so not everything goes to type II causing fatigue).
m. ATP synthase: enzyme which provides energy through producing ATP from ADP and Pi.
n. Cytochrome oxidase: oxygen combines with electrons and hydrogen forming water. It’s the rate limiting step in ETC. 2 oxygens, hydrogen and electron form two water molecules. This is the only thing that oxygen does.
o. Glucagon: stimulates the mobilization of glucose from liver stores (glucogenolysis) and free fatty acids from adipose tissue (to spare blood glucose as a fuel).
p. Hormone Sensitive Lipase: Increased mobility of free fatty acids in the blood (uptake of free fatty acids into the muscles)
What factors determine oxygen consumption (VO2)?
- Cardiac output (semi trainable)
- Mitochondrial function (aVO2 difference) (extremely trainable)
- Gender (males have higher VO2 because of their larger heart, and therefore larger Q)
- Age (decreases with age starting at age 30 or 40)
- Genetics
What is the role of oxygen in energy production?
In cytochrome oxidase, two oxygens combine with hydrogen and electrons forming 2 water molecules. This is the rate limiting step as its dependent on oxygen consumption.
How is energy production via aerobic pathways limited by the VO2.
The rate of Vo2 determines rate of aerobic ATP production. ATP can only be made as fast as oxygen can be consumed. As cardiac output increases, more oxygen can be transported faster into the cell mitochondrion which increases VO2 max.
What is the function of Glycolysis during aerobic metabolism?
Glycolysis is the breakdown of glucose (or glycogen) into pyruvate, which then turns into acetyl-CoA. Oxygen is not directly involved in glycolysis, but when oxygen enters the mitochondria, pyruvate can participate in the aerobic production of ATP since NADH and FADH are sent to the ETC. Slow Glycolysis is aerobic, which produces 30-32 ATP fairly slowly, but efficiently. Glycolysis is the first step in the aerobic degradation of carbohydrates.
What is the function of Krebs Cycle?
Take the acetyl-coA and oxaloacetate (formed from pyruvate) which then enter the Krebs cycle to form NADH, FADH and ATP. For every 1 glucose, you get 2 pyruvates, which give you 2 acetyl-coA’s so you go through the cycle twice. 1 cycle forms 3NADH, 1FADH, 1ATP.
What is the function of the Electron Transport Chain (ETC)?
produce a proton gradient through the transfer of electrons and protons which leads to the formation of H2O, and a gradient which then triggers ATPsynthase. During this passage, enough energy is released to rephosphorylate ADP to form ATP. The bulk of the NADH and FADH come from the krebs cycle, but 2 can come from glycolysis. As electrons are pumped along the gradient, energy is released to pump the hydrogens (from the NADH and FADH) from the inside of the mitochondria across the inner mitochondrial membrane. The accumulation of H+ is a source of potential energy that can be captured and used to recombine inorganic phosphate with ADP to form ATP.
What is the function of Beta Oxidation?
Beta oxidation breaks down carbon chains into 2 carbon molecules (Acetyl-CoA) from fatty acids to enter the Krebs cycle. Each time a molecule passes through, 1 NADH and 1 FADH is produced. Then the Acetyl-CoA goes to the Krebs cycle where 3NADH, 1 FADY and 1 ATP are produced.
What are the two primary determinants of VO2max? Explain how training enhances the function of each.
- Cardiac output: heart rate x stroke volume (amount of blood ejected/heart beat).
- Mitochondrial function (a~vO2 difference): measure of how much oxygen is removed from arterial blood and used by the tissues
- Training can increase both of these because the heart will be able to pump more blood with each beat, therefore becoming more efficient. Also, the tissues will become more efficient at removing oxygen from the hemoglobin which flows from the blood to the cells and capillary density is increased as well.
How is VO2max linked to cardiovascular health?
High VO2 max means you’re able to tolerate high intensity exercise for a long time. Exercising (improving VO2 max) could reduce sensitivity of diabetes and obesity
Under what conditions is protein metabolism (breakdown) increased?
After endurance (because minimal protein is used for energy) and resistance training (post exercise repair, increased muscle mass)
Discuss protein need for the endurance and power resistance trained athletes and non-athlete. Justify the greater protein needs of the athlete.
- Endurance athlete needs a small amount extra (if more than 90 minutes of exercise) which is used as fuel during endurance exercises derived from muscle protein.
- Resistance athletes need extra protein to repair muscle fibers and to remodel muscle tissues in response to the weight lifting.
- Athletes need more protein than sedentary people due to post-exercise muscle repair.
- Athletes do not need to automatically add protein to their diet, but if they are hoping to gain muscle mass then extra protein is needed.
- Protein increases amino acid pools in their blood prior to exercise which immediately begins repair post exercise.
- Most athletes already consume excess protein, so they do not need to add more protein in their diet.
What is/are the cause(s) of fatigue during endurance activities? Explain the circumstance for each.
- Activities lasting 30 minutes: decreased pH inhibits O2 binding to hemoglobins at the lungs.
- activities lasting 90min-4hrs:
1. muscle glycogen depletion: need for CHO to burn fat and CHO to make oxaloacetate from pyruvate…energy production slows down, so you fill up on carbs several days ahead of time, and then also watch your pace. The faster you go (higher intensity), the more CHO dependent you become. In short, pace yourself early on.
2. liver glycogen depletion: liver glycogen is glucose supply for CNS, no glucose means FATIGUE fast, refuel glucose stores the morning of.
-Dehydration: blood becomes viscous (hard to transport). Its important to hydrate during and prior to the activity. You want pale yellow urine.
9. How would improved lactate threshold be beneficial to the mid-distance, distance athlete AND how would it be beneficial to the non-athlete and to someone with heart disease?
see notes