12/3 Muscle Metabolism

Question 1

Illustrate an approximate time course of how exercising muscles regenerate ATP from the inital few seconds of exercise through one or more hours

Answer 1

Exercising muscle will initally use Adenaline Kinase and Creatine Kinase to generate ATP from stores of ADP and Creatine Phosphate respectively! Longer course: breakdown Glycogen to glucose for glycolysis (anarobic transitioning to arobic) Then long course use Fat oxydation to provide energy.

Question 2

A reserve of High energy bonds in the muscles:

Answer 2

Creatine phosphate

Question 3

How does the muscle take advantage of creatine phosphate to maintain ATP levels in the muscle during the first few seconds of activity?

Answer 3

creatine phosphate plus ADP plus creatine kinase will give creatine and ATP!

Question 4

How Could the muscle use ADP as a source of ATP during and initial burst of exercise?

Answer 4

it could use Adenaline kinase to convert two ADP to one ATP and one AMP!

Question 5

What are the the two different types of muscle fibers?

Answer 5

Slow Twitch (Type I) and Fast Twitch (Type IIa, IIb)

Question 6

Characterize Type I fibers

Answer 6

Type I: lots mitochondria/myoglobin; respiration/oxydative phosphorylation and resist fatigue, low glycogen content, develop force slowly but maintain longer than fast-twitch

Question 7

Characterize Type IIa/IIb fibers

Answer 7

IIb(fast-glycolytic) -few mitochondria, low myoglobin, righ in glycogen and use glycogenolysis and glycolysis as primary energy source. Fatigue easily because lactic acid levels rise. Develop force greater and more quickly! (IIA are fast-oxidative glycolytic and are an inbetween)

Question 8

What type of muscle fiber (IIa, IIb, I) would have more glycogen content

Answer 8

IIb! and IIa that is the fast glycolytic

Question 9

what type of muscle fiber (I,IIa,IIb) would have higher myoglobin content

Answer 9

The type I because they are dowing more oxidation so more oxygen buffer provided by myoglobin content being high!

Question 10

What type of muscle fiber (I,IIa,IIb) would have a highter lipoprtein lipase level?

Answer 10

Type I that is slow oxidative…using more fat oxydation for energy and therefore it would need to be trafficing more fat to themselves…(lipoprotein lipase is in the endothelial cells near them)

Question 11

What type of muscle fiber (I,IIa,IIb) would have higher resisitance to fatigue?

Answer 11

The type I would be more resistant because they would need to act longer and they use fat stores for fuel.

Question 12

what is the molecule that breaks and releases the fatty acids from fat stores in adipocytes?

Answer 12

hormone sensitive lipase is the most well known.

Question 13

Case of very high creatine kinase, and dark urine with exercise and little food intake, trouble doing exercise for long periods…

Answer 13

This sounds like a type I muslce fiber problem in metabolizing fatty acids. Specifically it is a Carnitine palmitoyl transferase defect. (this gets the fatty acids into the mitochondria to metabolize them)

Question 14

what type of muslces are type I?

Answer 14

they are the large, strong muscles that support stature and movement of limbs etc.

Question 15

why would the urine be very dark when you have a break down of muscle cells?

Answer 15

they would release myoglobin into the blood and this would make the urine very dark!

Question 16

what would indicate muscle damage in the blood and urine?

Answer 16

High Creatine kinase in the blood and high myogloblin in the urine.

Question 17

When contrasting exercise at different VO2 max levels which level would be using more total calories?

Answer 17

when you are at higher VO2 max then you are using up more calories i.e. you are burning more caloreis and using more oxygen!

Question 18

in a situation of burning more carbs or more fats when would the respiratory quotient be higher?

Answer 18

RQ = CO2 eliminated / O2 consumed So if the energy source is more reduced it will take more O2 to produce CO2 and the quotient would decrease (fats = 0.7; carbs = 1)

Question 19

Why would AMP activate both glycogen phosphorylase and phosphofructokinase-1?

Answer 19

AMP is indicating that ATP is low therefore: glycogen phosphorylase activated to break off glucose from glycogen. Then phosphofructokinase commits us to glycolysis so now we have an energy source and a commited process.

Question 20

High AMP would act to phosphorylate both acetyl CoA ccarboxylase and malonyl CoA decarboxylase how does the phosphorylation most likely affect the activity of these two enzymes

Answer 20

Acetyl CoA can be carboxylated to produce Malonyl CoA. Malonyl CoA inhibits the transfer of fatty acids into the mitochondria. if high AMP want low Malonyl CoA to up fatty acid metabolism in mitochondria. Therefore, deactivate the carboxylase and activate the decarboxylase.

Question 21

what is phosphofructokinase 1?

Answer 21

Phosphofructokinase-1 (PFK-1) is one of the most important regulatory enzymes of glycolysis. It is an allosteric enzyme made of 4 subunits and controlled by many activators and inhibitors. PFK-1 catalyzes the important “committed” step of glycolysis, the conversion of fructose 6-phosphate and ATP to fructose 1,6-bisphosphate and ADP

Question 22

what happens in the liver to PFK-1 when blood glucose is high?

Answer 22

it is phosphorilated and deactivated

Question 23

what happens in muscle cells to PFK-1 when blood glucose is high

Answer 23

Skeletal: nothing; Cardiac: phosphorilated and upregulated (heart can do glycolysis when blood glucose is high).

Question 24

How does the heart muscle get most energy?

Answer 24

aerobic metabolism, oxidizing fatty acids, glucose, and lactate, and they contain many mitochondria, with very little glycogen.

Question 25

What chemical signal is sent out by the mitochondria to down regulate fatty acid import by up reg. the produciton of malonylCoA?

Answer 25

Citrate!

Question 26

What do muslces use as fuel at rest?

Answer 26

what is available in the blood (glucose, amino acids, fatty acids)

Question 27

What do muscles use as fuel during starvation?

Answer 27

fatty acids are the preferred energy source (even over ketone bodies)

Question 28

What do muscles use as fuel during exercise

Answer 28

stored glycogen, blood glucose, and blood fatty acids

Question 29

what would stimulate muscle building?

Answer 29

Exercise; Insulin; Testosterone (steroid horomone).

Question 30

what would inhibit muscle synthesis and cause breakdown

Answer 30

fasting: insulin low and cortisol high (stressed too)

Question 31

how can increased muscle activity combat the effects of obesity?

Answer 31

Exercise up glut 4 activation (increase glucose uptake-as is normally induced by insulin) and lowers triglycerol in the blood.