MOVESCI 340 Exam 1

Complete the equation
ATP —> Energy + _____ + _____

ATP —> Energy + ADP + Pi (inorganic!)

what are the two largest components of daily energy expenditure that we have the ability to modify?

non exercise activity thermogenesis AND exercise

what is the major/predominant fuel source utilized by cells DURING REST

lipids

how does CHO contribution to fuel change as exercise intensity increases

contribution of CHO as fuel increases as exercise increases

balance the following equation and determine what the RER is, use RER to determine the substrate type
C18H32O2 + ___O2 —> ___CO2 + ___H2O
RER for oxidation: _____

Substrate type: _____

The rate of carbohydrate energy transfer is about ____ compared to the rate of energy transfer from lipid

two-times faster

via what processes do we generate ATP in cells? (3 types)

glycolysis, oxidative phosphorylation, and phosphagen system

which enzyme is sensitive to epinephrine and results in triglyceride breakdown?

hormone sensitive lipase

glycolysis

breakdown of glucose to pyruvate

glycogenolysis

breakdown of glycogen to glucose

glycogenesis

production of glycogen (glucose to glycogen)

gluconeogenesis

production of glucose from non-carbohydrate substrates (ex. protein —> glucose)

what is a hormone released during higher intensity exercise that has a direct impact on fuel/substrate utilization?

epinephrine/norepinephrine

During an acute bout of exercise, what are the major variables that can impact substrate utilization during exercise?

intensity and duration

During high intensity exercise lasting longer than 10 seconds, what is the primary energy system used?

glycolysis

Following consumption of a high glycemic index food, blood glucose __________ then ___________

increases rapidly, decreases rapidly

What is the impact of exercise on circulating insulin levels?

decreases insulin levels

T or F: Considering the situation described in question two, the timing of pre-exercise meals has an impact on blood glucose levels during exercise.

transient hypoglycemia, TRUE

Which of the following is false?

 

The different energy systems cannot all be active at the same time

 

ATP-PCr system is predominantly utilized during a quick sprint (less then 10 seconds)

 

There are aerobic and anaerobic pathways to produce ATP

 

Aerobic metabolism is relied upon for long durations of exercise

 

The different energy systems cannot all be active at the same time

What happens to ATP levels in muscle cells during contraction/exercise?

no change

What is the enzyme that produces ATP at the end of oxidative phosphorylation?

ATP synthase

What would a high ADP/ATP ratio indicate?

 

Low energy state in the cell

what is basal metabolic rate

• minimal amount of energy required to sustain the body’s vital functions

• measurements made under strict conditions

  • greater than or equal to a 12-hour fast

  • not active during the hours before the test

  • sit quietly for roughly 30 minutes before measuring

• roughly 70% of daily expenditure

what is resting metabolic rate

• less strict conditions than BMR

• Both BMR and RMR measure oxygen consumption

what is the conversion between O2/kg/min and metabolic equivalent of task (MET)

3.5 ml O2/kg/min = 1 metabolic equivalent of task (MET)

what factors affect energy expenditure (6)

• physical activity —> exercise activity thermogenesis (EAT)

• eating —> thermic effect of food (TEF)

• non-exercise activity thermogenesis (NEAT)

• climate

• pregnancy/lactation

• emotions (high or low stress)

physical activity VS. exercise (and their influence on energy expenditure

• physical activity includes the activities of daily living such as vacuuming, moving around at work, or commuting to class

• exercise is planned physical activity with the purpose of training such as weight lifting, a marathon, or sports

• physical activity and exercise are the great change/variation in energy expenditure, normally accounts for 15-30% of daily energy expenditure

physical activity guidelines for americans

• 150-300 mins/week of moderate intensity aerobic activity

OR

• 75-150 mins/week of vigorous intensity aerobic activity

OR

• a combination of both in addition to 2x/week muscle strengthening at moderate or greater intensity

• these are MINIMUMS to reduce the risk of lifestyle related diseases

• in terms of METs, 500-1000 MET min/week

sedentary vs. maximal intensities for METs, %VO2max, %HRmax, rate of perceived exertion (RPE)

METs: <1.5 to >9

%VO2max: <37 to >91

%HRmax: <40 to >93

RPE: 1-2 RPE/6 Borg to 9-10 RPE/18-20 Borg

IMPORTANT CONVERSIONS: L to kcal AND kg to lbs

1 L of oxygen consumed = 5 kcals (5kcals/L O2)

1 kg = 2.2 lbs

draw the relationship between exercise volume/fitness level and risk of disease

draw the relationship between exercise volume & risk of atrial fibrillation

what are METs good for? (why do we calculate MET minutes)

• 150 min/week of aerobic activity = 500-1,000 MET min/week for significant health benefits

• METs are a good way to calculate/compare intensity across multiple types of aerobic exercise

MET-minutes to kcals calculation:

• 920 MET-min

• 100 kg individual

920 METs minutes * 3.5 ml O2/kg/min * 100kg/200 = 1610 kcals

TEF obligatory thermogenesis

energy requiring processes of digesting, absorbing, and assimilating food

TEF facultative thermogenesis

related to an increased activation of sympathetic nervous system which can lead to an increase in energy metabolism

ex. cold environments

TEF in energy expenditure

• generally reaches maximum 1 hr after meal

• can account for 10-35% of calories ingested (WE WILL USE 10%)

• wide variability among individuals

• obese people often found to have lower TEF

NEAT in energy expenditure

• best activities are stair climbing and walking (even though most of us sit all day)

• has overall decreased in the general population due to more sedentary jobs

• london transport workers study - seated drivers vs. standing conductors —> drivers are 2x more likely to have heart disease

how does climate effect energy expenditure

lowest to highest GENERALLY when comparing energy expenditure: moderate climates, warm environments, cold environments

where is the main location of breakdown of substrates for energy?

mitochondria

BUT some glucose breakdown occurs in the cytoplasm (glycolysis)

air inspired percent breakdown by O2, CO2, and N2

O2: 20.93%

CO2: 0.03%

N2: 79.04%

what are the macronutrients used as fuel (3 + non macronutrient)

1. carbohydrates (CHO): C_n(H2O)_n where n = 3-7

GLUCOSE: C6H12O6

2. lipids: major fuel source at rest

3. protein: very small contribution, often near starvation it creates fuel

4. ketones: NOT a macronutrient, but can be used as fuel

standard energy content of macronutrients

• carbohydrate = 4 kcal/g

• fat = 9 kcal/g

• protein = 4 kcal/g

• alcohol = 7 kcal/g

carbohydrate distribution in the body

what is glycogen, where is it stored, and what is breakdown called

• storage form of CHO (long linkage of glucose)

• stored in liver and muscle

  • liver glycogen: maintenance of blood glucose

  • muscle glycogen: local store of fuel for muscle contraction

• glycogen breakdown

  • glycogenolysis is the breakdown into glucose for fuel

• main source of fuel during moderate to high intensity exercise

how is fat stored in the body?

triglyceride breakdown

• triglycerides must be broken down to release fatty acids for energy

• LIPOLYSIS: triglyceride breakdown

• LIPASE: enzyme that breaks down triglycerides

• HORMONE-SENSITIVE LIPASE (HSL): epinephrine regulates lipolysis through HSL

protein structure

how is protein “turned over”

anabolism: building up tissue, protein synthesis

catabolism: breakdown of tissue, protein degradation (increases with aging)

protein catabolism for energy

• impractical fuel source

• ammonium ions (NH4+) are toxic to cells

• proteins are the most important structural and functional components of cells

what is a ketone and how can it be used at fuel?

• carbon-containing molecules that can be transformed into ATP-producing substrates

• increase production during prolonged exercise and exercise while fasted

• ketones can also fuel the CNS when blood glucose is low

• when carb storage is low, ketones enter citric acid cycle to produce ATP

what is respiratory exchange ratio (respiratory quotient)?

• RQ = VCO2/VO2

• RQ provides an index of the relative use of CHO and fat

• RQ = 0.70-1.0 —> 0.70 is all fat, 1.0 is all carbs, 0.85 is roughly 50/50

• RQ = RER

draw the relationship between energy supply and time for the three main ATP supply chains (3)

when is ATP-PCr used as a fuel source?

• quick energy

• short, intense bout (predominantly <10s)

when is glycolysis used as a fuel source?

• breakdown of glucose to pyruvate

• endpoint (aerobically): pyruvate —> acetyl CoA —> TCA —> ETC

  • moderate duration/intensity

• endpoint (anaerobically): pyruvate —> lactate —> H+ ions

  • short duration/higher intensity

when is oxidative phosphorylation used as a fuel source?

• acetyl-coa derived from either CHO or lipid sources

• generate reducing equivalents (NADH and FADH2) to drive the electron transport chain (ETC) and generate lots of ATP

• in general, endless supply for lower intensity (rest and low intensity/long duration)

can all ATP-generating systems occur at the same time?

YES! All of the ATP-generating systems are active in cells at all times

factors that impact substrate choice (4)

• intensity (endurance exercise)

• duration (endurance exercise)

• diet/meals

  • fasted vs fed state

  • timing of last meal

  • high vs. low CHO diet/meal

• hormones

  • epinephrine

  • insulin and glucagon

draw and explain the fed state vs. fasted state pathways within the liver

what two metabolic byproducts are used in gluconeogenesis?

lactate and alanine are substrates for gluconeogenesis/

what are the preferred substrates for skeletal muscles at rest and during exercise?

rest: fatty acids

exercise: fatty acids and glucose/glycogen (intensity and duration dependent)

what are the preferred substrates for brain at rest and during exercise?

rest: blood glucose, can use lactate and ketones —> fatty acids are too big to pass the BBB

exercjse: blood glucose, can use lactate and ketones

what are the preferred substrates for red blood cells at rest and during exercise?

rest: blood glucose

exercise: blood glucose

what are the preferred substrates for liver at rest and during exercise?

rest: fatty acids

exercise: fatty acids, blucose, and amino acids (intensity, duration, and nutrition dependent)

what are the preferred substrates for the heart at rest and during exercise?

rest: fatty acids, glucose (depending on time of last meal)

exercise: fatty acids, glucose, and lactate (intensity dependent)

what is the ATP : ADP ratio?

• this ratio is critical to the energy status of a cell

• Metabolic byproducts are key messengers in cells

  • in a typical cell, 500 ATP molecules to 1 ADP molecule per cell

  • 500:1

• ATP levels are steady (even during exercise!!)

• byproducts do accumulate

  • break down of one ATP causes a decrease in ATP by 1 (500 to 499)

  • but, 2x change in the number of molecules of ADP (1 to 2)

  • ratio is how 499:2

what is the importance of the ATP : ADP ratio? why is it so large?

• allows cells to be highly sensitive to changes in byproducts of ATP breakdown while being able to recycle ATP rapidly

• relevant for how cells regulate which substrates to utilize

  • slowly producing byproducts: use slow energy source (lipid)

  • quickly producing byproducts/need ATP quickly: use quick energy source (glycogen)

• quick build-up of ADP triggers use of glycogen as energy source!

what action occurs when AMPK targets Acetyl CoA carboxylase (ACC)

INC fatty acid entry into mito

INC fat oxidation

what action occurs when AMPK targets FAT/CD36

INC fatty acid transport

what action occurs when AMPK targets GLUT4

INC glucose transport

what action occurs when AMPK targets glycogen synthase

inhibits glucogen synthesis

draw stimulation and inhibition pathways by AMPK

explain the six steps of the contraction cycle

what are the most common sources of fuel for carbs and fats?

carbs: muscle glycogen

fats: plasma FFA

What are the three irreversible, regulated steps of glycolysis?

Hexokinase, PFK-1, and pyruvate kinase

hexokinase purpose in glycolysis

converts glucose to G6P

hexokinase stimulators

glucose, insulin, Ca2+, epinephrine

hexokinase inhibitors

high levels of G6P, F6P

phosphofructokinase (PFK) purpose in glycolysis

converts F6P to F1,6 bisphosphate

phosphofructokinase (PFK) stimulators

ADP, Pi, AMP, high pH

phosphofructokinase (PFK) inhibitors

high ATP/ADP, citrate, low pH

pyruvate kinase purpose in glycolysis

converts phosphoenolpyruvate to pyruvate

pyruvate kinase stimulators

F16DP, insulin

pyruvate kinase inhibitors

high ATP/ADP, acetyl-coA, glucagon

what cell conditions and energy state stimulates glycolysis

high AMP, low ATP, low citrate, low energy state

what cell conditions and energy state inhibit glycolysis

high ATP, high citrate, fasting with high glucagon, high energy state

what are the regulatory enzymes of glycogenolysis

glycogen phosphorylase

glycogen phosphorylase purpose in glycogenolysis

converts glycogen to G1P to G6P

glycogen phosphorylase stimulators

ADP, Pi, AMP, Ca2+, epinephrine

glycogen phosphorylase inhibitors

high ATP/ADP, citrate

Describe the mechanism of muscle glycogenolysis regulation (hormonal + Ca²⁺ + AMP pathway)

1. Epinephrine/norepinephrine binds a β-adrenergic receptor

2. activating a Gs protein

3. which activates adenylate cyclase to convert ATP to cAMP

4. cAMP activates protein kinase A, which phosphorylates and activates phosphorylase kinase (Ca²⁺ released during muscle contraction also directly activates phosphorylase kinase).

5. Active phosphorylase kinase phosphorylates glycogen phosphorylase, converting it from inactive phosphorylase b to active phosphorylase a (AMP can also promote this and blocks the reverse reaction).

6. Active phosphorylase a then cleaves glucose units off glycogen using Pi,

7. producing glucose-1-phosphate, the first and rate-limiting step of glycogen breakdown.

what are liver and muscle glycogen used for?

liver: maintain blood glucose

muscle: provide glucose for muscular contraction

steps of liver glycogenolysis

1. Glucagon binds its receptor on the liver cell membrane

2. activating adenylate cyclase to convert ATP to cAMP

3. cAMP activates protein kinase A, which phosphorylates and activates phosphorylase kinase

4. Active phosphorylase kinase then phosphorylates glycogen phosphorylase, converting it from inactive phosphorylase b to active phosphorylase a

5. Active phosphorylase a cleaves glucose units off glycogen using Pi, producing glucose-1-phosphate.

which two gluconeogenic pathways are reciprocally regulated

glycolysis and gluconeogenesis

what are the 3 ways glucose enters the muscle INSULIN-DEPENDENT

1. resting conditions

2. post-meal

3. rest/digest

what are the 3 ways glucose enters the muscle INSULIN-INDEPENDENT

1. exercise

2. muscle contraction

3. energetic stress (AMPK)

mechanistic steps of glucose uptake during exercise

1. muscle contraction

2. increased intramuscular Ca2+ levels

3. energetic stress (sensed by AMPK, energy demands are inc)

4. GLUT4 vesicles moving to the muscle fiber membrane

5. glucose removed from the plasma and into the muscle fiber

6. glucose “trapped” in muscle fiber by hexokinase (rate-limiting enzyme) converting glucose to glucose-6-phosphate

how do glucose transport protein (GLUT4) levels relate to exercise duration

longer you exercise, more transport of glucose into the muscle (insulin independent), which leads to a greater expression of GLUT4 over time