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Biochem Quiz 4 Winter > Muscle Metabolism > Flashcards

Muscle Metabolism Flashcards

1
Q

Explain the difference between

1) Sub-sarcolemma mitochondria
2) Intermyofibrillar (IMF) mitochondria

A

1) used for plasma Ca pumps

2) used for actin-myosin cross links

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2
Q

What are the qualities of Type I Slow Twitch muscle fibers?

A

high vascular
high mitochondria (more ox phos and b oxidation)
higher intramuscular triglycerides (IMTG)
higher lipoprotein lipase

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3
Q

What are the qualities of Type II fast twitch muscle fibers?

A

low vascularization
fewer mitrochondria
high glycolitic enzymes
major fuel source is glycogen, not TG

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4
Q

What are the qualities of cardiac muscle?

A 
high vascular
Lots of mitochondria
little glycogen
low glycolysis
FA and lactate are fuel sources
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5
Q

What are the two major fuel sources of the heart?

A

Fatty acids

Lactate

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6
Q

ATP can not be delivered through the blood

A

ATP can not be delivered through the blood

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7
Q

Where are the following found or sourced…

1) Glucose
2) Glycogen
3) Fatty acid
4) Ketone
5) Aminos
6) Phospo-creatinine
7) ADP

A

1) Blood and Liver
2) Muscle (local)
3) Muscle (local), Adipose Cells, Lipoproteins
4) LV
5) Blood and Liver
6) Muscle (local) generated by excess ATP and used as a storage of ATP
7) Muscle (Local) (adenylyl kinase) (note: AMP is then deaminated to IMP and NH3 through AMP deaminase)

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8
Q

What fuel source do muscles burn at rest?

A

mostly fatty acids

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9
Q

Why does muscle glycogen not contribute to blood glucose?

A

Muscle does not contain Glucose-6-phosphatase

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10
Q

What does muscle burn during activity?

A

Glucose
Glycogen
Fatty Acids
Ketones

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11
Q

What does the heart burn as fuel?

A

Fatty acids
Lactate
Also some Ketones
Some Glucose

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12
Q

Why is the heart good at using Lactate as a fuel source?

A

Lactate dehydrogenase converts lactate to pyruvate (then pyruvate dehydrogenase converts pyruvate to acetyl-CoA then to Citric Acid Cycle

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13
Q

How does insulin induce hypoglycemia and brain starvation?

A

Blocks…
gluconeogenesis
glycogenolysis
Ketone production from fatty acids

All fuel sources to brain are shut down.

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14
Q

In a well-fed well-fit individual, what are the fuel sources during exercise?

A

Glucose
Gluconeogenesis (from adipose)
glycogen
Local Triglycerides

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15
Q

General: In fasting individuals, What are the fuel sources during low activity
What is the fuel source during higher activity?
Highest activity?

A 
Low: plasma fatty acids
Higher: Muscle triglycerides
Highest: Glycogen
(and always some plasma glucose)
If you consume glucose, these will be burned preferentially.
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16
Q

Why are fatty acids not used during high intensity?

A

CAT I which binds carnitine to Acyl group for mitochondrial transfer is a rate limiting step. Although there are plenty of fat stores available for energy, they cannot make it into the mitochondria fast enough during high energy exercise.

17
Q

Remember: FA can enter cells through TG hydrolysis by Lipoprotein Lipase (look up term)

A

Remember: FA can enter cells through TG hydrolysis by Lipoprotein Lipase (look up term)

18
Q

What inhibits CAT I?
When is this relevant in exercise?
What activates CAT I?

A
  • ACC produces Malonyl CoA which is an inhibitor of CAT I.
  • When eat during exercise, insulin may be secreted, which will activate ACC ==> Malonyl CoA which blocks CAT I
  • Low ATP ==> AMP ==> AMPK phosphorylates ACC and inhibits ACC, therefore less malonyl CoA and then CAT I is activated.
19
Q

What is “hitting the wall”?

A

FA can only support 50% of max aerobic work due to rate-limiting CAT I.
Work above 50% max is supplied by glucose and glycogen.
When you run out of glycogen, exercise cannot continue.

20
Q

What are the fuel sources for sprinting and anaerobic exercise?
What are waste products?

A 
OxPhos and FA are NOT used
What is used:
Glycolysis (net 2 ATP)
Phosphocreatine
Glycogenolysis (produces glucose for glycolysis)
Adenylate Kinase
Waste products: Lactate, AMP/IMP
21
Q

What is the timeline for energy used in a sprint:
1 second?
5 Seconds?
10 Seconds?

A

1: ATP
5: phosphocreatinine
10: glycogenolysis and glycolysis

22
Q

What are the steps that encourage glycololysis via pathway of B-adrenergic receptor?

A

Gs ==> AC ==> cAMP ==> PKA ==> converts phosphorylase Kinase B to Phosphorylase Kinase A ==> breaks down glycogen

23
Q

What is the alternative pathway for glycogen release in muscles during sprinting?

A

increased Ca++ ==> Phosphorylase Kinase b ==> converts glycogen phosphorylase b to glycogen phosphorylase a ==> breaks down glycogen

24
Q

How is glycogen formation inhibited during exercise?

A
  • Heart and skeletal muscle has a special glycogen synthase isoform (Gys 1) that is inhibited by adrenaline via cAMP/PKA
  • AMP also allosterically stimulates glycogen phosphorylase
25
Q

PFK is activated during sprints and anaerobic exercise.

A

PFK is activated during sprints and anaerobic exercise.

26
Q

What is the fuel for replenishing after workout?

A

glucose and protein

27
Q

Why can we use medium chain tryglyerides as a fuel source during exercise?

A

They bypass the CAT I step (do not need CAT I to be transferred to mitochondria)

28
Q

What are the short term and long term benefits of exercise?

A

Short-term (allostery, phosphorylation):
Increased glucose uptake/oxidation
Increased FA oxidation

Long-term (transcription):
Increased glucose uptake
Increased # mitochondria
Increased mitochondrial activity
Increase FA storage in muscle?
29
Q

At low intensity, FA oxidation supplies most ATP
FA coming from muscle stores and adipose
FA oxidation can only supply about 50% of max. aerobic energy
Rate-limiting step in FA oxidation is CAT-1 activity
CAT-1 activity is decreased by insulin, increased by exercise
Glucose oxidation needed for maximum aerobic output
Glucose coming from muscle glycogen/blood glucose (liver)
Glycogen from other muscles is NOT available for working
muscle
“Hitting the wall” - run out of glycogen stores, only FA available
Sprint - all glycolysis, all local fuel sources:
a) cytosolic ATP = 1 sec
b) phosphocreatine = 4 sec
c) muscle glycogen thereafter
Glycogen is an important fuel store in both aerobic and anaerobic
work!

A

At low intensity, FA oxidation supplies most ATP
FA coming from muscle stores and adipose
FA oxidation can only supply about 50% of max. aerobic energy
Rate-limiting step in FA oxidation is CAT-1 activity
CAT-1 activity is decreased by insulin, increased by exercise
Glucose oxidation needed for maximum aerobic output
Glucose coming from muscle glycogen/blood glucose (liver)
Glycogen from other muscles is NOT available for working
muscle
“Hitting the wall” - run out of glycogen stores, only FA available
Sprint - all glycolysis, all local fuel sources:
a) cytosolic ATP = 1 sec
b) phosphocreatine = 4 sec
c) muscle glycogen thereafter
Glycogen is an important fuel store in both aerobic and anaerobic
work!

Biochem Quiz 4 Winter (6 decks)

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