Muscle metabolism Flashcards
What are the two major (90%) energy sinks in muscle?
1) sarcomeric myosin motor activity - uses ATP for contraction
2) Ion pump activity - uses ATP to keep Ca levels low inside cell
Type 1 skeletal muscle also known as:
slow twitch
Type 2 skeletal muscle also known as:
fast twitch
3 muscle types
skeletal type 1 - slow twitch
skeletal type 2 - fast twitch
cardiac
aerobicity of 3 muscle types
type 1 - predominantly aerobic
type 2 - predominantly anaerobic
cardiac - very aerobic
vascularization of 3 muscle types
type 1 - high
type 2 - low
cardiac - high
mitochondrial content of 3 muscle types
type 1 - high
type 2 - low
cardiac - high
glycogen stores in 3 muscle types
type 1 - lower
type 2 - high
cardiac - low
primary energy source in 3 muscle types
type 1 - triglycerides via LPL
type 2 - glycolysis, glycogenolysis
cardiac - fatty acid and lactate oxidation
sources of blood glucose
- diet
- liver through glycogenolysis or gluconeogenesis
sources of local glycogen
muscle glycogen stores
sources of blood FA
adipose
sources of local triglyceride
intracellular TG
sources of blood triglyceride
- diet - chylomicrons
- liver - VLDL
sources of blood ketone bodies
liver - B-oxidation
sources of blood amino acids
diet
sources of local phospho-creatine
creatine kinase
sources of local ADP
adenylate kinase
how do muscles access FA from trigycerides?
from chylomicrons and VLDL using lipoprotein lipase (LPL)
what are the two mechanisms for muscle to supply ATP very rapidly?
1) adenylate kinase - makes one ATP from two ADPs when cellular ADP levels are high (squeezes energy from the system)
- This also produces AMP which activates AMPK
- AMPK makes more ATP, inhibits ATP using processes, and in muscle activates FA oxidation
2) creatine kinase - in times of need, can re-convert creatine-phosphate to ATP very rapidly
why is FA metabolism the predominant energy source at ow intensity exercise?
- because FA catabolism is slow
- it is slow because carnitine acyltransferase I (CAT-1) is a slow rate-limiting step
what is the action of ACC?
- produces malonyl-CoA which inhibits CAT-1
action of AMPK on ACC?
- AMPK inhibits ACC, activating CAT-1 and FA oxidation
four muscle mechanisms that boost ATP generation during glycolysis:
1) creatine kinase - converts creatine-phosphate to ATP
2) adenylate kinase - converts two ADP to ATP and AMP
3) rapid activation of muscle glycogenolysis through PKA independent pathways
4) rapid activation of glycolysis via PFK
two molecules that rise during muscle contraction and activate glycogenolysis:
- AMP - allosterically activates glycogen phosphorylase
- calcium ion - activates phosphorylase kinase
increasing AMP levels _________ PFK
activate
increasing phophate levels ___________ PFK
activate
increasing ammonia/ammonium levels _________ PFK
activate
decreasing ATP levels ____________ PFK
inhibit
decreasing creatine-phosphate levels __________ PFK
inhibit
why is refueling right after exercise so beneficial?
1) because AMPK is highly active, opening GLUT 4 glucose channels independently of insulin (high benefit for type II diabetics)
2) will cause an insulin spike that will stimulate muscle protein synthesis
