Muscle metabolism

Question 1

What are the two major (90%) energy sinks in muscle?

Answer 1

1) sarcomeric myosin motor activity - uses ATP for contraction
2) Ion pump activity - uses ATP to keep Ca levels low inside cell

Question 2

Type 1 skeletal muscle also known as:

Answer 2

slow twitch

Question 3

Type 2 skeletal muscle also known as:

Answer 3

fast twitch

Question 4

3 muscle types

Answer 4

skeletal type 1 - slow twitch
skeletal type 2 - fast twitch
cardiac

Question 5

aerobicity of 3 muscle types

Answer 5

type 1 - predominantly aerobic
type 2 - predominantly anaerobic
cardiac - very aerobic

Question 6

vascularization of 3 muscle types

Answer 6

type 1 - high
type 2 - low
cardiac - high

Question 7

mitochondrial content of 3 muscle types

Answer 7

type 1 - high
type 2 - low
cardiac - high

Question 8

glycogen stores in 3 muscle types

Answer 8

type 1 - lower
type 2 - high
cardiac - low

Question 9

primary energy source in 3 muscle types

Answer 9

type 1 - triglycerides via LPL
type 2 - glycolysis, glycogenolysis
cardiac - fatty acid and lactate oxidation

Question 10

sources of blood glucose

Answer 10

• diet

- liver through glycogenolysis or gluconeogenesis

Question 11

sources of local glycogen

Answer 11

muscle glycogen stores

Question 12

sources of blood FA

Answer 12

adipose

Question 13

sources of local triglyceride

Answer 13

intracellular TG

Question 14

sources of blood triglyceride

Answer 14

• diet - chylomicrons

- liver - VLDL

Question 15

sources of blood ketone bodies

Answer 15

liver - B-oxidation

Question 16

sources of blood amino acids

Answer 16

diet

Question 17

sources of local phospho-creatine

Answer 17

creatine kinase

Question 18

sources of local ADP

Answer 18

adenylate kinase

Question 19

how do muscles access FA from trigycerides?

Answer 19

from chylomicrons and VLDL using lipoprotein lipase (LPL)

Question 20

what are the two mechanisms for muscle to supply ATP very rapidly?

Answer 20

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

Question 21

why is FA metabolism the predominant energy source at ow intensity exercise?

Answer 21

• because FA catabolism is slow

- it is slow because carnitine acyltransferase I (CAT-1) is a slow rate-limiting step

Question 22

what is the action of ACC?

Answer 22

• produces malonyl-CoA which inhibits CAT-1

Question 23

action of AMPK on ACC?

Answer 23

• AMPK inhibits ACC, activating CAT-1 and FA oxidation

Question 24

four muscle mechanisms that boost ATP generation during glycolysis:

Answer 24

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

Question 25

two molecules that rise during muscle contraction and activate glycogenolysis:

Answer 25

• AMP - allosterically activates glycogen phosphorylase

- calcium ion - activates phosphorylase kinase

Question 26

increasing AMP levels _________ PFK

Answer 26

activate

Question 27

increasing phophate levels ___________ PFK

Answer 27

activate

Question 28

increasing ammonia/ammonium levels _________ PFK

Answer 28

activate

Question 29

decreasing ATP levels ____________ PFK

Answer 29

inhibit

Question 30

decreasing creatine-phosphate levels __________ PFK

Answer 30

inhibit

Question 31

why is refueling right after exercise so beneficial?

Answer 31

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