Muscle Metabolism Flashcards
Explain the difference between
1) Sub-sarcolemma mitochondria
2) Intermyofibrillar (IMF) mitochondria
1) used for plasma Ca pumps
2) used for actin-myosin cross links
What are the qualities of Type I Slow Twitch muscle fibers?
high vascular
high mitochondria (more ox phos and b oxidation)
higher intramuscular triglycerides (IMTG)
higher lipoprotein lipase
What are the qualities of Type II fast twitch muscle fibers?
low vascularization
fewer mitrochondria
high glycolitic enzymes
major fuel source is glycogen, not TG
What are the qualities of cardiac muscle?
high vascular Lots of mitochondria little glycogen low glycolysis FA and lactate are fuel sources
What are the two major fuel sources of the heart?
Fatty acids
Lactate
ATP can not be delivered through the blood
ATP can not be delivered through the blood
Where are the following found or sourced…
1) Glucose
2) Glycogen
3) Fatty acid
4) Ketone
5) Aminos
6) Phospo-creatinine
7) ADP
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)
What fuel source do muscles burn at rest?
mostly fatty acids
Why does muscle glycogen not contribute to blood glucose?
Muscle does not contain Glucose-6-phosphatase
What does muscle burn during activity?
Glucose
Glycogen
Fatty Acids
Ketones
What does the heart burn as fuel?
Fatty acids
Lactate
Also some Ketones
Some Glucose
Why is the heart good at using Lactate as a fuel source?
Lactate dehydrogenase converts lactate to pyruvate (then pyruvate dehydrogenase converts pyruvate to acetyl-CoA then to Citric Acid Cycle
How does insulin induce hypoglycemia and brain starvation?
Blocks…
gluconeogenesis
glycogenolysis
Ketone production from fatty acids
All fuel sources to brain are shut down.
In a well-fed well-fit individual, what are the fuel sources during exercise?
Glucose
Gluconeogenesis (from adipose)
glycogen
Local Triglycerides
General: In fasting individuals, What are the fuel sources during low activity
What is the fuel source during higher activity?
Highest activity?
Low: plasma fatty acids Higher: Muscle triglycerides Highest: Glycogen (and always some plasma glucose) If you consume glucose, these will be burned preferentially.
Why are fatty acids not used during high intensity?
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.
Remember: FA can enter cells through TG hydrolysis by Lipoprotein Lipase (look up term)
Remember: FA can enter cells through TG hydrolysis by Lipoprotein Lipase (look up term)
What inhibits CAT I?
When is this relevant in exercise?
What activates CAT I?
- 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.
What is “hitting the wall”?
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.
What are the fuel sources for sprinting and anaerobic exercise?
What are waste products?
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
What is the timeline for energy used in a sprint:
1 second?
5 Seconds?
10 Seconds?
1: ATP
5: phosphocreatinine
10: glycogenolysis and glycolysis
What are the steps that encourage glycololysis via pathway of B-adrenergic receptor?
Gs ==> AC ==> cAMP ==> PKA ==> converts phosphorylase Kinase B to Phosphorylase Kinase A ==> breaks down glycogen
What is the alternative pathway for glycogen release in muscles during sprinting?
increased Ca++ ==> Phosphorylase Kinase b ==> converts glycogen phosphorylase b to glycogen phosphorylase a ==> breaks down glycogen
How is glycogen formation inhibited during exercise?
- 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
