Metabolism of skeletal muscle Flashcards
Diagram of Metabolism of skeletal muscle
Compare the Glycolytic activity/Glycogen store between skeletal muscle fibers I, IIA, IIB
I - Low
IIA - Moderate
IIB - High
Compare the Capillary supply/ Myoglobin content between skeletal muscle fibers I, IIA, IIB
I - Good
IIA - Moderate
IIB - Poor
Compare the Oxidative capacity between skeletal muscle fibers I, IIA, IIB
I - high
IIA - moderate
IIB - low
Compare the Speed of contraction Myosin ATPase activity between skeletal muscle fibers I, IIA, IIB
I - slow
IIA - fast
IIB - fast
Compare the Triacylglycerol usage between skeletal muscle fibers I, IIA, IIB
I - High
IIA - Moderate
IIB - Low
Compare the Speed of contraction Myosin ATPase activity between skeletal muscle fibers I, IIA, IIB
I - slow
IIA - fast
IIB - fast
Does Carbohydrate metabolism in skeletal muscle consist of glucagon receptor?
NO
Does Carbohydrate metabolism in skeletal muscle consist of glucose-6- phosphatase?
No
The role of hexokinase during Carbohydrate metabolism in skeletal muscle
Glucose ➔ glucose-6-phosphate
fructose ➔ fructose-6-phosphate
Characteristics of the activity of Pentose phosphate cycle during Carbohydrate metabolism in skeletal muscle
very low activity (2% of G6P) (no fatty acid synthesis)
What is Phosphorolysis?
The cleavage of a bond by the addition of orthophosphate
The role of glycogen phosphorylase
Removal of a terminal glucose residue from the nonreducing end of a glycogen chain by glycogen phosphorylase
Why is the phosphorolytic cleavage of glycoge advantageous?
because the released sugar is already phosphorylated.
During exercise, which enzyme is activated in the process of Glycogen metabolism in muscle?
Activation of muscle glycogen phosphorylase during exercise
Glycogen metabolism in muscle doesn’t have glucagon receptor.
-> What is the consequence?
glycogen levels in muscle do not vary with the fasting/feeding state.
Does glucose inhibit glycogen phosphorylase in muscle?
No
Does glucose inhibit glycogen phosphorylase in muscle?
No
Why are the glycogen stores in skeletal muscle limited?
because an efficient feedback- mediated inhibition of glycogen synthase prevents accumulation
The role of AMP during glycogen metabolism in muscle
an allosteric activator of the muscle isozyme of glycogen phosphorylase (but not liver glycogen phosphorylase)
The role of Ca2+ during glycogen metabolism in muscle
binds to the delta-subunit (calmodulin) of phosphorylase kinase and activates it
What does Reciprocal regulation of glycolysis and glyconeogenesis in liver cells mean?
where glycolysis and gluconeogenesis occur
Reciprocal regulation of glycolysis and glyconeogenesis in liver cells
-> Which enzymes are the same bifunctional enzyme (whose function is reversed by phosphorylation by protein kinase A)?
Fructose bisphosphatase-2 (FBPase-2) and phosphofructokinase-2 (PFK-2)
Reciprocal regulation of glycolysis and glyconeogenesis in liver cells
-> Fructose bisphosphatase-2 (FBPase-2) and phosphofructokinase-2 (PFK-2) enzymes are the same bifunctional enzyme whose function is reversed by phosphorylation by___ (which enzyme?)
protein kinase A
Reciprocal regulation of glycolysis and glyconeogenesis in liver cells
-> What happen during starvation?
Starvation
➔ glucagon level elevates
➔ cAMP level elevates
➔ PKA active
➔ phosphofructokinase-2 is phosphorylated
➔ it has phosphatase activity (A phosphatase is an enzyme that removes a phosphate group from a protein.)
➔ fructose 2,6 BP level drops
➔ glycolysis is inhibited, gluconeogenesis is active
Regulation of acetyl-CoA-carboxylase-2 (ACC2) in skeletal and cardiac muscle
-> The role of Malonyl-CoA
the regulator of fatty acid synthesis and oxidation
Regulation of acetyl-CoA-carboxylase-2 (ACC2) in skeletal and cardiac muscle
-> What are the Souces of FA?
Well-fed state: LIPI inactive (but: intensive muscle work)
Short-term starvation: Lipoprotein lipase (LPL) active (VLDL)
Long-term starvation: FFA and ketone bodies
Regulation of acetyl-CoA-carboxylase-2 (ACC2) in skeletal and cardiac muscle
-> The role of Malonyl-CoA
the regulator of fatty acid synthesis and oxidation
Regulation of acetyl-CoA-carboxylase-2 (ACC2) in skeletal and cardiac muscle
-> What is the source of FA during short-term starvation?
LPL active (VLDL)
Regulation of acetyl-CoA-carboxylase-2 (ACC2) in skeletal and cardiac muscle
-> What is the source of FA during long-term starvation?
Free fatty acids (FFA) and ketone bodies
How does Amino acid metabolism in skeletal muscle occur? (GENERALLY)
Starvation➔ DECREASED insulin ➔ proteolysis
General description of alanine cycle
In the case of starvation or increased energy requirements,
-> protein breakdown in the muscle increases
-> the release of alanine increases.
Alanine serves ammonia elimination and gluconeogenesis in the liver.
How does METABOLISM OF BRANCHED CHAIN AMINO ACIDS
(BCAA transaminase is missing from liver) occur?
Branched chain amino acids are first transaminated (1) and then oxidized to succinyl- CoA and/or acetyl-CoA.
Where is the ammonia coming from?
PURINE NUCLEOTIDE CYCLE
What is the aim of purine nucleotide cycle?
aim: anaplerosis (fumarate is synthetised) (PC, GDH activity is low in muscle)
PURINE NUCLEOTIDE CYCLE
-> What happen if If GTP level is low?
AMP level elevates
How is uric acid produced in purine nucleotide cycle?
AMP →IMP→ uric acid
How is hyperuricemia occurred in term of purine nucleotide cycle?
Chronic ATP deficiency
Name of these structures (in red circles)
Role of Liver During Excercise
Continued exercise→Increased Epinephrine
+Gluconeogenetic precursors from periphery increases
What are Liver adrenergic receptors and their roles?
α1➔Ca2+
β2➔cAMP
What are the enzymes participating in Energy Provision in Skeletal Muscle during Exercise?
creatine kinase (CK)
adenylate kinase (AK)
What is Muscle Fatigue?
a reduction in the maximal voluntary force-generating capacity of the muscle,
as inability to maintain power output.
What does Fatigue depend on?
Highly dependent on the capacity of the aerobic metabolic system (slow oxidative fibers are more fatigue-resistant)
What are the 2 types of fatigue?
Central vs. peripheral fatigue
What is Manifestation of fatigue?
- Decreased isometric force production
- Reduced shortening speed
- Slowed relaxation
What are Major metabolites in peripheral fatigue?
Pi (creatine phosphate breakdown), protons, glycogen
What are Major metabolites in central fatigue?
Serotonin?
What is 5 Metabolic reasons for fatigue?
- Phospho-creatine depletion (ATP depletion), [Pi] level increase
- Proton accumulation in the muscle
- Glycogen depletion in the muscle
- Hypoglycemia
- tryptophan/branched chain aminoacid ratio elevates
Metabolic reasons for fatigue
-> How can proton accumulation in the muscle contribute to fatigue?
- Lactate (lactic acid) levels increase
➔pH decreases - (in muscle: 7,2➔6,2)
- Actin-myosin interaction slows down
- impaired enzyme activity
Metabolic reasons for fatigue
-> How can Hypoglycemia contribute to fatigue?
Hypoglycemia
➔ FFAlevel is elevated
displace tryptophan bound to albumine
➔ free tryptophan level elevates *
Is hypoglycemia a central or peripheral effect?
Central
What can help with hypoglycemia?
high carbohydrate containing drinks
Metabolic reasons for fatigue
-> How can elevation of tryptophan/branched chain aminoacid ratio contribute to fatigue?
*brain tryptophan level elevates -> serotonin level elevates
*Tryptophan inhibits branch chain aa uptake into the brain competitively
➔ mental fatigue can be delayed with the help of bcaa containing drinks.
