test Flashcards
What is the basics of metabolism and what occurs?
ATP hydrolysis
- ATP converts to ADP + Pi via myosin ATPase
What type of molecule is ATP? Where does it come from?
ATP: large, hydrophilic molecule
ATP is formed through the foods we consume (CHO, protein, and fats) that become stored energy → ATP
What is the storage form of carbohydrates? Where are the two areas they can be found?
Glycogen - storage form of carbohydrates
Found: Liver and skeletal muscle
What is the transport form of carbohydrates? Where can it be found?
Glucose - transport form of carbohydrates
Found: In bodily fluids (blood!)
Where are the two areas that fat can be found?
- Subcutaneous (under skin) and visceral (around organs)
- Intramuscular
Between carbohydrates and fats, which is more storage efficient in energy source?
Fats
What are the three sources of potential energy in our body?
- Glucose
- Glycogen
- Triglycerides
What type of form of CHO is glucose and what is it composed of?
Glucose - transport form of carbohydrates
Composed of 6 carbon base compund
What type of form of CHO is glycogen and what is it composed of?
Glycogen - storage form of carbohydrates
Simply composed of glucose molecules linked together (1-4 link + 1-6 link)
What type of exercise intensity can carbohydrates support?
Can support high intensity exercise >50% VO2max
What is a triglyceride and what is it composed of/its structure? How much potential energy does it have compared to glucose?
- Triglyceride is a form of fat with a glycerol backbone and 3 fatty acids (FA)
- Composed of a 16 carbon compound molecule
- Has a much higher source of potential energy compared to CHO
What type of exercise intensity can fats support up to?
Slow intensity exercise up to 50% VO2max
Even though fats have a lot more potential energy than carbohydrates why does it support a smaller VO2max than carbohydrates?
Since fats have a greater number of carbon, fats have to undergo more steps to be oxidized compared to carbohydrates.
What is the most common triglyceride in mammalian tissue?
Palmitate
What type of metabolic pathway does the body use in a 2-3 sec. exercise? Why does it use this substrate and what type of exercise intensity could this individual be doing?
ATP
- ATP should be readily available in the sarcoplasm
- Only 1 simple explosive moment (standing up from a chair, pushing something over your head)
What type of metabolic pathway does the body use in a 15-20 sec. exercise? What type of exercise intensity could this individual be doing?
ATP/CrP
- High intensity exercise
- 100m sprint
What type of metabolic pathway does the body use in a 2-3 minute exercise and why? What type of exercise intensity could this individual be doing?
(Fast) glycolysis
- ATP production is a bit lower as it consists a bit more steps of metabolizing carbohydrates = CANNOT support as high intensity of an exercise
- 800m
What type of metabolic pathway does the body use if one was to exercise for hours? What type of exercise intensity could this individual be doing and distinguish which substrates is responsible for a long period of low intensity exercise and explain why.
Oxidative system (slow/aerobic glycolysis)
- Consists of FULLY metabolizing carbohydrates and fats
- Supports exercise for long hours, however at a low intensity, especially fats
~ Fats have higher number of carbon, thus having to undergo more steps of being able to extract the full potential energy that can support that exercise
- Marathon
What is hormone sensitive lipase (HSL)?
Hormone sensitive lipase: an enzyme that is found on the glycerol backbone of a triglyceride
- Breaks the fatty acids off the glycerol backbone = converting triglyceride to glycerol and 3 FFA
What is that preparation process for fatty acids in the mitochondria?
B-oxidation
Where does glycolysis occur?
In the sarcoplasm of the muscle fiber
What is the first intermediate of glycolysis and its compund? What is the last intermediate of glycolysis and its compund?
First intermediate - G6P ; glucose-6-phophate (6 carbon compound)
Last intermediate - Pyruvate (3 carbon compound)
Trace the pathway of (fast) glycolysis. How is glycogen flux maintained as exercise prolongs and where does it come from? What enzyme does it use?
Glycogen (prolonged exercise = stored glycogen depletes)
↓
G6P (first intermediate of glycolysis) ← Glucose (from bloodstream to muscle via Hexokinase)
↓
Pyruvate
↓
HLa (lactic acid)
(a) What enzyme is used to convert glycogen into glucose-1-phosphate?
(b) What is this process also called?
(c) What is this enzyme also activated by and where do they come from?
(a) Glycogen phosphorylase
(b) glycogenolysis
(c) Ca2+ from the skeletal m. is the primary activator, and the catecholamines from the liver
What is hexokinase?
An enzyme that allows (blood) glucose to pass through the cell membrane of the muscle fiber
What is the most simplest metabolic pathway in the skeletal muscle and why?
Creatine kinase / PCr metabolic pathway
Why? - It includes only one enzyme
Trace the phosphocreatine (PCr) metabolic pathway? What activates the enzyme involved? What are the byproducts? What can the byproducts of this metabolic pathway also form?
Creatine kinase (enzyme; activated by hydrolysis products of ATP)
↓
breakdown phosphocreatine
↓
By-products: Creatine + Pi + Free energy
Pi (from PCr) + ADP (in the muscle fiber) = ATP!
What happens/is the relationship between the ATP/PCr metabolic pathway during rest to high intensity exercise? What happens after 8 seconds into high intensity exercise?
- At resting value, ATP and PCr is at 100% within the muscle fiber
- When high intensity exercise starts, the percentage of ATP is maintained, but PCr depletes
- Why? - PCr is active during this time and is being used while also maintaining ATP
- After 8 seconds in, all of PCr has been used, and ATP will start to deplete
- Exhaustion/fatigue sets in after 14 seconds
Detail how PCr is resynthesized in the skeletal m. post-exercise from the aerobic production of ATP with the given time of 1 min, 3 mins, and 5 mins.
- Post-exercsie = individual breathes heavily
- Aerobic production of ATP becomes PCr in sarcoplasm
- 1 min post-exercise = 50% resynthesizes
- 3 mins post-exercise = 80% resynthesizes
- 5 mins post-execise = 100%
List the number of electron carriers that are produced during “fast” glycolysis starting from glucose to pyruvate.
- 2 NADH
How much ATP is produced in the “fast” glycolysis of glucose vs glycogen? Why?
2 ATP produced for glucose
3 ATP produced for glycogen
- Glycogen is already stored in the muscle cell, thus does not have to invest ATP to bring glucose in the cell.
What is phosphofructokinase (PFK)? When does this enzyme appear? What activates and inhibits this enzyme? Which investment of ATP is this for glucose and glycogen?
Phosphofructokinase (PFK): a rate limiting enzyme that must be activated in order for the glycolytic pathway to occur/continue
- Appear when G6P converts to pyruvate
- (+) Activated by: contractile activity products (ADP, Pi)
- (-) Inhibited by: ATP and citrate
- 2nd investment for glucose, 1st investment for glycogen
Which enzyme causes the true splitting of sugar in glycolysis? What does this result in?
Aldose
- Splits the 6-carbon compound of glucose into 2 3-carbon compound
How many pyruvate do we get at the end of (fast) glycolysis?
2 pyruvate
Where does the oxidative / “slow” glycolysis metabolic pathway occur?
In the mitochondria
Trace the pathway of (slow) glycolysis / oxidative metabolism starting from pyruvate. Distinguish what’s the first intermediate of this pathway.
Pyruvate
↓ Enters mitochondria
AcCoA (first intermediate of oxidative pathway)
↓
Kreb Cycle
↓
Electron Transport Chain (ETC)
↓
ATP!
How many Acetyl-Coenzyme A do we have coming from the oxidation of CHO vs fats? Why?
CHO - 2 AcCoA
Fats - 8 AcCoA
- Fats have a higher number of carbon ions (16) compared to the carbohydrates 6 base carbon compound
(a) What determines the number of turns of the Kreb Cycle?
(b) How many NADH do we get per turn of the Kreb Cycle?
(c) How many FADH2 do we get per turn of the Kreb Cycle?
(d) How many ATP is produced per turn of Kreb Cycle?
(e) What’s the product/first intermediate of the Kreb Cycle?
(f) What products of the Kreb Cycle goes to the electron transport chain (ETC) to produce ATP aerobically?
(a) The # of ACCoA in the mitochondria
(b) 3 NADH
(c) 1 FADH2
(d) 1 ATP
(e) Citrate
(f) ALL electron carriers produced enters the ETC (NADH + FADH2)
What is isocitrate dehrydogenase and where is it found? What will activate and inhibit this enzyme?
Isocitrate dehydrogenase is the rate-limiting enzyme in the Kreb Cycle
- Must be activated in order for fat + carbohydrate oxidation to continue
- (+) Activated by: contractile activity products (ADP, Pi)
- (-) Inhibited by: ATP
What is the relation of O2 and CO2 with the Kreb Cycle? What is used or not used? What is being produced?
In the Kreb Cycle:
- NO O2 is used
- Produces CO2
What is the last step/molecule required in the ETC in order for ATP to be produced aerobically in the oxidative system? What is it also called?
Oxygen
- “The last terminal electron acceptor”
What enzyme is used for the electron transport chain?
Cytochrome oxidase
Oxidative phosphorylation is also known as…?
The aerobic production of ATP
(a) What enters the ETC?
(b) For every NADH that enter the ETC, how many ATP will be produced aerobically?
(c) For every FADH2 that enter the ETC, how many ATP will be produced aerobically?
(d) Which electron carrier produces a smaller amount of ATP and why?
(a) Electron carriers (NADH + FADH2)
(b) 3 ATP is produced aerobically for every NADH that enters the ETC
(c) 2 ATP is produced aerobically for every FADH2 that enters the ETC
(d) FADH2; It enters the ETC at a lower energy state than NADH
What is the total energy yield of ATP for glucose? How about for glycogen? Why?
Glucose total energy yield = 38 ATP
Glycogen total energy yield = 39 ATP
Glycogen DOES NOT have to invest in ATP for glucose to enter in the muscle cell
Give a simple pathway/overview of fat metabolism?
Fats(FFA) → B-oxidation → (8) Acetyl CoA → Krebs cycle → ETC → ATP!
After being hydrolyzed by HSL, what proteins do fatty acids bind to able to travel in blood?
Albumin
How many Acetyl CoA is produced when going through the fat metabolism pathway and explain why? Thus how many turns does the Kreb Cycle go through?
8 ACCoA; due to 16 carbon compound from triglycerides, more ACCoa is produced from fats compared to carbohydrates
- Kreb Cycle will turn 8 times
(a) What is the total energy yield of ATP produced from a single FA?
(b) What is the total energy yield of ATP produced from all 3 FA?
(c) How much ATP does glycerol produce?
(d) What is the total energy yield of ATP produced from the complete oxidation of fats?
(e) Why can’t fat support high intensity exercise? But what can it maintain?
(a) 129 ATP
(b) 387 ATP
(c) 19 ATP
(d) 406 ATP
(e) Even though fats yield this much energy, it CANNOT support anything higher than 50% VO2max due to many steps it takes to fully oxidize fat. But it CAN maintain/produce prolonged exercise
What is calorie referred to and what is it actually?
“Calorie (C)” is what we refer to in food
- It’s actually a kilocalorie (c)
- 1 kilocalorie (c) = 1 calorie (C)
What is a kilocalorie? What is heat synonymous with?
The amount of heat required to raise the temperature of 1 kilogram of water one degree Celsius
- heat = energy
What is a direct calorimetry and what does it determine? What is it only useful for? Name an example of a direct calorimeter?
Direct calorimetry is able to measure the energy expended by allowing the subject to be inside this structure. The heat that is being produced and released by the subject will be measured, which can then determine what their kcal burn is.
- ONLY USEFUL for resting BMR
- Bomb calorimeter
List out the pros (2) and cons (4) for direct calorimetry.
Pros:
- Accurate over time
- Good for RESTING metabolic measurements
Cons:
- Expensive, slow
- Exercise equipment adds extra heat
- Sweat creates errors in measurements
- Not practical or accurate for exercise = errors caused ; not practical for energy expenditure of exercise
What is used to measure energy expenditure during exercise and how?
Indirect calorimetry
- Estimates total body expenditure based on O2 used and CO2 produced
What is VO2?
VO2: volume of O2 consumed per minute
What is VCO2?
VCO2: volume of CO2 produced per minute
What can the measurements of VO2 and VCO2 be also used for? What calculation is used?
- These measurements are used to assess the fuel selection our body is making during exercise
- Respiratory exchange ratio / R-value
What is the calculation for respiratory exchange ratio (RER or R-value)?
RER = VCO2/VO2
What does R-value range from? What is the intensity at those range and what fuel source will you be predominantly using?
0.71 - 1.00
0.71 - Low intensity, predominantly using fats
1.00 - High intensity, predominantly using carbohydrates, but still oxidizing fats
What are two things that R-value can inform us of an individual?
- Can help calculate what fuel source one is using in a given activity(fat, CHO, or both).
- Give an indication of the training status of the individual (trained or untrained); from calculation of energy expenditure for a given activity
If two individuals were given different exercise intensity (one is running and the other walking), is caloric expenditure the same in a fixed distance or a timed distance? Why?
Caloric expenditure is still the the SAME in a FIXED DISTANCE even if two individuals were given different exercise intensity. Since the distance being covered is the same, both individuals will expend the same amt. of calories wether you walk or run
However, with a timed distance, the individual that is running is not only able to cover more distance than the individual walking, but also expend MORE calories per minute
What is more effective for weight loss, high intensity short duration exercise or prolonged low intensity endurance exercise? Why?
High intensity short duration is more effective for weight loss since the caloric expenditure per min is higher, thus being more efficient for weight loss compared to prolonged low intensity exercise. Furthermore, high intensity turns on the oxidation for both fats and carbohydrates
What will be the R-value for an individual that is aerobically trained? Why?
They will have a slightly lower R-value as they do not have to use as much oxygen to combust carbohydrates and fats.
If an individual goes from rest and start increasing exercise intensity, what is the first fuel they will be predominantly using? How long will they continue to rely on it?
Fats
- Up to 50% VO2max (maximal rate of fat oxidation)
If one is doing low intensity exercise, up to 50% VO2max, what is 100% of your fuel coming from?
Fats
As intensity of exercise increases, what happens to the rate of fat oxidation? What other fuel source will be implemented to sustain that exercise intensity?
The individual will continue to oxidize fat at that SAME RATE and SAME AMOUNT.
- But when working at a higher intensity, the individual will have to start adding/using carbohydrates, turning glycolysis on at a HIGHER rate.
* WE DO NOT CHANGE THE AMT. OF FAT, WE ARE JUST ADDING CHO!
(a) What is VO2max?
(b) What is it the the best single measurement of?
(c) What is it not the best predictor of? Give an example
(d) What is VO2max expressed in? What is it suitable for?
(e) What is VO2 max scaled/normalized for?
(a) Maximal O2 uptake
(b) Aerobic fitness (how much O2 one actually consumes)
(c) Not the best predictor of endurance performance
- Marathon runners have nearly identical VO2max , thus can’t dictate who will win
(d) Expressed in L/min. Suitable for non-weight bearing activities
(e) Normalized for body weight
What is lactate threshold?
Lactate threshold: Point at which blood pyruvate accumulation increased markedly
- Pyruvate production rate > pyruvate clearance rate
How is lactate threshold measured? How is LT typically depicted in a graph?
- Measured by having the subject on a bicycle or treadmill and attaining a blood sample throughout while also increasing the workload
- Shown as a nonlinear increase
How does lactate threshold occur?
As exercise intensity increase, glycolysis is turned on at a high rate to be able to produce as many ATP.
- At some point, more pyruvate is produced than can be taken into the mitochondria, thus can cause an accumulation of lactate
- This is where we see the nonlinear increase of blood lactate concentration.
What is lactate threshold a good indicator of? Why? Give an example?
LT is a good indicator of potential for endurance exercise
- Why? An individual with a lactate threshold that occurs at a higher % VO2max may run faster for a longer period of time as they have LESS PYRUVATE accumulating
- Marathon runners who have a higher LT may run for a longer period of time than those who have a lower LT
What is lactate threshold usually expressed as?
Expressed as a percentage of VO2max
What is the lactate threshold for an untrained individual vs. trained individual?
UT: 50-60% VO2max
TR: 70-80% VO2max
What would be the lactate threshold for world-class elite marathon runners?
Can be as high as 88-92% VO2max
How does one self-select their running pace?
One selects a running pace that is at or below their lactate threshold
What is EPOC? What happens to O2 during and after exercise?
EPOC: Excess Post-Exercise Oxygen Consumption; the rate of O2 consumption that is relatively high and an excess from the given state of your activity (post-exercise)
- During exercise, consumption of O2 is at a steady-state
- At the end of exercise, O2 consumption remains relatively high as that is the amt. we would typically use if exercise was to continue
What are the 5 components of EPOC? Elaborate.
- Replenishing of the ATP/CrP stores
- Continued substrate cycling (glucose and FAs) = can still be used to produced ATP aerobically as the substrates don’t just go away instantaneously
- Elevated rates of fatty acid oxidation
- Increased body (muscle) temperature = enzymes will work more efficiently with glycolysis + Kreb Cycle + ETC
- Increase levels of catecholamines in the blood ; takes a while for these hormones to be cleared from the blood
- EVERYTHING GRADUALLY REVERSES ITSELF
What are the 2 definitions of fatigue? How can it be reversed?
- Decrements in muscular performance with continued effort, accompanied by sensations of tiredness
- Inability to maintain required power output to continue muscular work at a given intensity
- Reversible by rest
What are two scenarios that fatigue can occur?
- Short duration, high intensity
- Prolonged endurance exercise
Describe the 2 factors that causes fatigue during short duration, high intensity exercise.
- CrP depletion
- Fatigue sets in at 14 sec. due to muscle running out of CrP - Metabolic by-products (glycolysis is turned on at a high rate = fatigue sets in at 3-5 mins.)
- High amt. of pyruvate → Increased lactate concentration = Increase of [H+]
a. Decrease in pH = make muscle acidic (~6.4 pH)
b. Decreased rate of glycolysis (enzyme doesn’t work in acidic environment)
c. Interferes with Ca2+ binding to troponin; H+ binds to troponin (competitive inhibition) = no contraction (fatigue)
Describe the factors that causes fatigue during prolonged endurance exercise (in terms of not adding anymore fuel and only with the fuel you start with)
- LOW LIVER + MUSCLE GLYCOGEN
- LOW BLOOD GLUCOSE
= RUN OUT OF FUEL
Occurs within 70% VO2max with 2-3 hours of exercise (marathon)
a. Glycogen depletion
1. Muscle glycogen levels
- As exercise continues, muscle glycogen levels gets lower, so it will have to start relying on the glycogen in the liver and the blood glucose in order to maintain that glycolytic flux
2. Liver glycogen levels
- Liver glycogen converts to glucose via glycogenolysis to maintain the blood glucose
- However, due to limited supply of glycogen in the liver, the blood glucose level will also go down later in the exercise.
- Therefore, the rate of liver glycogenolysis is LESS/SLOWER than the rate of blood glucose uptake by the muscle, resulting in blood glucose to also go down
- Fatigue sets in due to the inability to provide an adequate supply of fuel to the muscle
(a) What will happen to a marathon runner during the race after they have become fuel depleted?
(b) What fuel source did the runner run out of to complete the race at a high intensity?
(c) So what fuel source does the runner have to rely on now to finish the race?
(d) What are things that marathon runners can consume to maintain glycolytic flux during a race?
(a) They will finish the race but at a much lower rate and very low intensity.
(b) The runner ran out of carbohydrates (glycogen depleted)
(c) Runner now has to rely on fats which can now only support up to 50% VO2max
(d) Ingest carbohydrates
What does the endocrine system consists of?
- The organ (gland) ; secretes the hormones
- The substance released (i.e., hormones)
- Not much hormone is needed to get affect - The target tissue (has to have a specific receptor for the hormone in order for an effect to an occur)
How do we get adequate fuel delivery/fuel mobilization to our skeletal muscle during exercise?
Via hormonal control
What are the 2 family types of hormones?
Steroid and nonsteroid hormone
What are steroid hormones?
- Derived from cholesterol (from fat w/n body stored)
- Lipid soluble, diffuse through membranes
- Anabolic hormones = growth differentiate (transcription + translation of protein synthesis)
Describe the process of how a steroid hormone gets activated as it enters the cell.
- Steroid hormone diffuses through the cell membrane easily and will bind to its receptors in the cytoplasm or the nucleus
- The hormone-receptor complex will get activated w/n the nucleus, resulting in transcription and translation of the cell’s DNA
What are nonsteroid hormones? What are the two groups of nonsteroid hormones?
- Not lipid soluble, cannot cross membranes
- Has to bind to a receptor located on the cell membrane to enter, and another for it to be activated
- Divided into two groups:
1. Protein/peptide hormones
2. Amino-acid derived hormones
Describe the process of how a nonsteroid hormone gets activated as it enters the cell. Consider the hormone that is needed to activate this system.
*Catecholamines will need to activate this system
1. Nonsteroid hormone binds to its receptor on the cell membrane, which will result in the activation of adenylate cyclase (converts ATP to cAMP)
2. From activation of cAMP, this leads to amplification of signals resulting in cellular changes and hormonal effects
What are two factors that regulate and control the release of hormone?
- Intensity of exercise (↑ intensity = greater release of hormone for fuel mobilization; vice-versa)
- Prolonged endurance exercise - fatigue mechanisms: hormones will ensure adequate fuel delivery to active muscle
What is gluconeogenesis?
“Creation of new glucose”
Where does gluconeogenisis occur?
Gluconeogenisis can occur w/n two places: liver (predominantly) + kidneys
What are the three carbon compounds that gluconeogenisis takes?
- (MAINLY) Amino acids
- Pyruvate
- Lactate
Which part of the nervous system can only run on glucose?
CNS - Central nervous system
Determine the gland + location and its effect on fuel mobilization on the following hormone. Mention its fun fact:
Growth hormone
Gland and location: Pituitary gland, anterior lobe (base of brain)
Effect on Fuel Mobilization:
↑ lipolysis- GH activates the enzyme HSL
↑ liver gluconeogenesis
Post-exercise promotes muscle growth (can be an anabolic hormone post-exercise)
Hormone Fun Fact:
As intensity or duration of exercise ↑, the [hormone] released into the blood
What hormone is known as the “permissive hormone” and why?
Thyroxine (T4) and Triiodothyronine (T3)
- Permits other hormones to do their jobs and is NEEDED for other hormone to function properly
Determine the gland + location and its effect on fuel mobilization on the following hormone:
Thyroxine (T4) and Triiodothyronine (T3)
Gland and location: Thyroid Gland (midline of neck below larynx)
Effect on Fuel Mobilization: (T3 & T4 share similar functions)
↑BMR
- hypothyroidism (BMR is low = weight gain) vs hyperthyroidism (BMR is high = hard time gaining weight)
↑glucose uptake
↑glycolysis & gluconeogenesis
↑lipid mobilization
*Needed for other hormones to function properly