Unit 2: Energetics and Muscle Metabolism

The type of substrate used during exercise depends on what 2 things?

Intensity and duration

What is the process of forming glycogen called?

glycogenesis

Where is excess glycogen stored?

liver and muscles

What is glycogenolysis?

Conversion of glycogen to glucose

What hormone and enzyme inhibit glycogen phosphorylase?

-insulin

-Protein phosphatase

What 2 hormones and enzyme inhibit glycogen synthase?

-glucagon, epinephrine

-Protein kinase A

What 2 hormones and 2 conditions as well as enzymes excite glycogen phosphorylase?

-Glucagon, Epinephrine

-Calcium, High ADP/AMP

-Phosphorylase Kinase

What hormone and 2 molecules as well as enzyme excite glycogen synthase?

-insulin

-glucose-6-phosphate, glucose

-protein phosphatase

In Kcals, how much glucose is typically stored?

2000-2500

What is lipolysis?

Breaking down a triglyceride into 3 fatty acids and a glycerol

What is lipogenesis?

Conversion of glucose to fat

What is gluconeogenesis?

Formation of glucose from proteins or fats (proteins mainly for this class)

What is the role of glycogen phosphorylase, what 2 enzymes interact with it and how?

-Breakdown of glycogen into glucose-1-phosphate

-phosphorylase kinase(activates it)

-protein phosphatase(inhibits it)

What is the role of glycogen synthase, what 2 enzymes interact with it and how?

-synthesizing of glycogen from glucose-1-phosphate

-protein kinase A (inhibitory)

-protein phosphatase (activating)

What hormone and 2 secondary messengers can activate protein phosphatase?

-insulin

-glucose

-glucose-6-phosphate

What 2 hormones activate protein kinase A and via what secondary messenger ?

-glucagon

-epinephrine

-cAMP

What 2 hormones and 2 secondary messengers can activate phosphorylase kinase?

-glucagon

—via cAMP

-epinephrine

—via cAMP

-calcium

-high ADP/AMP

What is the biggest rate limiting enzyme in glycogenolysis that is needed to know?

Glycogen-phosphorylase

What controls the rate of energy production?

substrate availability, enzyme activity

What is Mass Action Effect?

This is a term of the influence of substrate availability of the rate of metabolism.

-excess given substrate= cells rely mainly on that

what is a rate-limiting enzyme?

-the enzyme can create a bottle neck

-influenced by negative feedback, products of the reaction inhibit the enzyme

what is anaerobic metabolism and what is it also called?

-synthesis of ATP without oxygen

-substrate level phosphorylation

what is aerobic metabolism and what is it also called?

-synthesis of ATP with oxygen

-oxidative phosphorylation

What are the 3 systems that use energy and via what kind of metabolism?

-Na/K ATPase (anaerobic metabolism)

-SERCA ATPase (anaerobic metabolism)

-Myosin ATPase (aerobic metabolism)

Answer the following questions regarding the phosphocreatine pathway.

What enzyme catalyzes the reaction?

What would stimulate/inhibit the enzyme above?

During longer exercise what happens to the byproducts of this reaction and by what enzymes?

What type of phosphorylation is this?

1. creatine kinase

2A. stimulation:decrease ATP and increased ADP (low energy)

2B. inhibition:increased ATP and decreased ADP (high energy)

3. 2 ADPs combine together (adenylate kinase), AMP and hydrogen make IMP and ammonia (AMP Deaminase)

4. Substrate level phosphorylation

Where does the glycolytic system occur

Cytoplasm of the cell

How much ATP is generated from glycolysis

28-32

What are the 4 enzymes that are important to know, which steps are they involved and why are they important?

Hexokinase and glucokinase (step 1 in the liver)

Phosphofructokinase (PFK) (step 3)

Pyruvate Kinase (Step 10)

-catalyze irreversible reactions

what is the glycolitic yield of blood glucose and muscle glycogen

blood glucose: 2 ATP

Muscle glycogen: 3 ATP

what step is important to know for glycolysis and why?

-4th step

- Makes glycolysis economically advantageous since the rest of the steps occur twice.

what conditions would stimulate or inhibit Phosphofructokinase (PFK)?

-Stimulation: byproducts of exercise

--High: ADP, AMP, Ca2+,inorganic phosphate,Epinephrine, Temp, F-2 6-bisphosphate

-Inhibit: Products of rest/heavy exercise

--High: ATP, Citrate, H+(low pH), FFA Availability

what can pyruvate be converted to and what is this dependent on?

-Acetyl-CoA or Lactate

-determined by sufficient NAD+ mainly then O2

what enzyme changes pyruvate to Acetyl-CoA, what are the metabolic conditions required for this, what two reactants are required and where do these products go?

1. pyruvate is changed by pyruvate dehydrogenase to acetyl-coa

2. when sufficient NAD+ and O2 is around (low exs. intensity)

3. needs NAD+->NADH and CoA ->CO2

4. Acetyl- CoA->Krebs Cycle(mitochondria), CO2->exhaled, NADH->ETC (Mitochondria)

what enzyme plays a key role in regulating the integration between CHO and Fat oxidation during exercise?

pyruvate dehydrogenase

what enzyme changes pyruvate to Lactate, what metabolic conditions are required for this, what reactant is required and what is a main function of lactate?

1. pyruvate is changed by lactate dehydrogenase to Lactate

2. when pH is Low and insufficient NAD+ / O2

3. needs NADH->NAD+

4. Lactate is a weak buffer for H+ ions

what is the primary cause of acidosis in muscle and blood?

increase in Hydrogen ion concentration (lower pH)

why is the conversion of pyruvate to lactate so important?

continues glycolysis, buffers the acidity, allows for recycling of NADH to NAD+ by oxidation

what happens as we accumulate hydrogen ions in the blood (acidosis)?

-acidosis impairs performance (fatigue)

--metabolite build up depresses force production

what 2 things will stimulate Pyruvate dehydrogenase phosphatase (PDP) and what will it become?

-insulin(CHO intake)

-Ca2+ (exercise)

-PDC (active)

what 4 things will inhibit Pyruvate dehydrogenase kinase (PDK) and what will it become?

-Pyruvate

-CoA

-NAD+

-ATP

-(Acetyl-CoA and NADH surplus stimulate it)

major pro and con of glycolytic System

Pro: permits short term higher intensity exercise

Con: Inefficient and causes low pH which impairs glycolysis

3 steps of oxidation of CHOs and their NET ATP yield.

1. Glycolysis: 4 NET

2. Krebs Cycle: 2 NET

3. Electron Transport Chain (ETC): 28 NET

what does one glucose turn into and yield in the krebs cycle (important)?

- 1 glucose-> 2 pyruvate-> 2 Acetyl-CoA

-2 ATP, 2 FADH2, 6 NADH (cycle runs twice)

2 coenzymes of the ETC are?

NAD+ and FAD+

Answer the questions below regarding the ETC.

1. where does the proton motive force start?

2. what kind of gradient is formed

3. how much ATP does NADH yield(important)?

4. how much ATP does FADH2 yield(important)?

5. what is the final electron acceptor in the chain?

1. Location of the first NADH drop off point (integral protein FMN)

2. Hydrogen Ion concentration gradient

3. 2.5 ATP

4. 1.5 ATP

5. Oxygen,O2

how many ATP are produced oxidation of CHO?

33 ATP

2 important enzymes involved in lipolysis.

-ATGL: adipose triglyceride lipase

-HSL: Hormone sensitive lipase

why do we turn free fatty acids into Acyl-CoA?

to continue to transform it into Acetyl-CoA via beta oxidation for entry into the krebs cycle

-requires 2 ATP to accomplish

what is the ATP yield from the krebs cycle of 1 acyl unit?

10 ATP

how much ATP is yielded from glycerol oxidation(important)?

18.5 ATP

answer the following about the krebs cycle.

1. what is the rate limiting enzyme and step we need to know?

2. what stimulates the krebs cycle?

3. what inhibits the krebs cycle?

1. Isocitrate Dehydrogenase (step 3)

2. High: ADP, AMP, Inorganic phosphate, Ca2+

3. High ATP

Describe the Cori Cycle

lactate is converted to glucose in the liver which requires ATP. This is then transported back to the muscle for future use.

describe the cross over concept and what 3 conditions affect it.

1. cross over concept illustrates the relative balance of CHO and fat use during exercise

-increased training=more CHO and vice versa

2. Affected by

-exercise intensity

-training status

-nutrition

what are the 2 main reasons for decreased reliance on fats at a higher exercise intensities?

1. CHO are metabolized anaerobically, aerobically CHO requires less O2, CHO stores more readily

2. inhibition of carnitine acyltransferase due to acidosis and reduced free carnitine and malonyl CoA