W2 - Chapter 3 - Fuel Sources for Muscle & Exercise Metabolism

Question 1

What surrounds the myofibrils of a muscle?

Answer 1

Sarcoplasmic reticulum

Question 2

How is energy stored in the sarcoplasm?

Answer 2

Triacylglycerol droplets

Glycogen

PCr

small pool of aa

ATP

Question 3

What are myofibrils composed of?

Answer 3

Thick + thin filaments

Question 4

What ATPase in the muscle breaks ATP down?

Answer 4

Myosin ATPase

Question 5

G-actin

Answer 5

Its monomers are polymerised into long strands of fibrous actin (F-actin)

Question 6

F-actin

Answer 6

2 F-actin strands twist together to form thin filament backbone.

Question 7

What spirals around the F-actin chains?

Answer 7

Rod-shaped tropomyosin molecules

Question 8

3 sub units of troponin

Answer 8

Troponin - I

Troponin - T

Troponin - C

Question 9

What does Troponin - I bind to?

Answer 9

Actin

Question 10

What does Troponin - T bind to?

Answer 10

Tropomyosin

Question 11

What does Troponin - C bind to?

Answer 11

Ca2+

Question 12

Define a sarcomere

Answer 12

Smallest contractile unit of a muscle fibre + is the region between 2 z-lines.

Question 13

What happens when there’s a sufficient amount of Ca2+ + ATP present in the muscle?

Answer 13

Actomyosin is formed

Question 14

When does sliding of the filaments in the muscle happen?

Answer 14

When myosin heads form cross-bridges w/ active sites of actin.

Question 15

What happens in the muscle without Ca2+

Answer 15

Tropomyosin blocks myosin binding sites on actin.

Question 16

How is Ca2+ released from the sarcoplasmic reticulum and into the sarcoplasm of a muscle?

Answer 16

AP along sarcolemma + down T-tubules

Question 17

What does Ca2+ do once released into the sarcoplasm of a muscle?

Answer 17

Bind to troponin = change shape = tropomyosin moves away from myosin binding sites.

Question 18

How is muscle excitation initiated?

Answer 18

By arrival of a nerve impulse at muscle membrane via motor end plate.

Question 19

What do the activated/cocked myosin heads do?

Answer 19

Bind to actin

Myosin head then changes to a bent shape = head pulls on thin filament = slides towards centre of sarcomere.

== Power stroke

Question 20

What also happens during the power stroke?

Answer 20

ADP + Pi are released from myosin head.

Question 21

What happens when a new ATP binds to the myosin head at the ATPase activity site?

Answer 21

Myosin cross-bridge detaches from actin.

Question 22

Energy released per mole of PCr

Answer 22

43kJ/mol

Question 23

What does it mean that PCr has a higher free energy of hydrolysis than ATP?

Answer 23

Its P is donated directly to ADP.

Question 24

When is PCr broken down?

Answer 24

When ATP content ⬇️

Question 25

What is an additional pathway to regenerate ATP when ATP + PCr stores are depleted?

Answer 25

Kinase reaction -- ONLY important during high intensity exercise.

Question 26

When can the total adenylate pool decline rapidly?

Answer 26

If AMP conc. of cell ⬆️ during muscle force generation

Question 27

What is the principal reason for why the total adenylate pool declines rapidly when AMP conc of cell ⬆️ during muscle force generation?

Answer 27

By deamination of AMP to IMP ALSO, by dephospho rylation of AMP --> adenosine.

Question 28

When does the deamination of AMP to IMP occur?

Answer 28

Under low ATP:ADP

Question 29

When is adenine nucleotide loss important to muscle function?

Answer 29

During cond of metabolic crisis i.e max exercise or later stages of prolonged submax exercise when glycogen stores become depleted.

Question 30

What carries glucose across cell membrane?

Answer 30

Transporter protein - GLUT4

Question 31

What happens once the glucose molecule has been transported into the muscle cell?

Answer 31

1. Irreversibly phosphorylated | 2. Catalyzed by hexokinase

Question 32

What does attaching a P group to glucose to prod G-6-P mean?

Answer 32

Now trapped in cell

Question 33

Do the liver + skeletal muscle contain the G-6-P enzyme?

Answer 33

No, just liver.

Question 34

When is hexokinase inhibited?

Answer 34

By accumulation of G-6-P

Question 35

What enzyme helps conversion of glucose-1-phosphate to G-6-P?

Answer 35

Phosphoglucomutase

Question 36

IN MITOCHONDRIA Reaction for pyruvate to Acetyl-CoA

Answer 36

Pyruvate + CoA + NAD+ -- (Pyruvate dehydrogenase) --> AcetylCoA

Question 37

What does insulin promote in regards to fat?

Answer 37

Triacylglycerol synthesis

Question 38

What does insulin inhibit in regards to fat?

Answer 38

Lipolysis

Question 39

When does adipose tissue bf increase?

Answer 39

During prolonged exercise at around 50% of vo2 Max

Question 40

What does sympathetic vasoconstriction during intense exercise cause?

Answer 40

⬇️ in adipose tissue bf = accumulation of FA w/in adipose tissue + limits entry of FFAs + glycerol into circulation.

Question 41

Where is glycerol readily soluble?

Answer 41

Plasma

Question 42

What can happen to the glycerol in the plasma?

Answer 42

Taken up into the liver + phosphorylated to G-3-P

Question 43

What can glycerol-3-phosphate be used for in the liver?

Answer 43

To form triacylglycerol OR oxidised to dihydroxyacetone P

Question 44

What can happen to dihydroxyacetone P

Answer 44

Enter glycolytic pathway OR be converted to glucose

Question 45

How are most FAs in plasma transported?

Answer 45

Loosely bound to albumin

Question 46

What is the uptake of FA by muscle directly related to?

Answer 46

Plasma FA conc

Question 47

What must FFAs do to be taken up by muscle?

Answer 47

Dissociate from albumin Then pass through: - Endothelial lining of capillary - Interstitial fluid - Sarcolemma

Question 48

What happens to the FA-albumin complex at the endothelial lining of the blood capillary?

Answer 48

Binds to albumin-binding proteins (ABPs) = allow FAs to be released from albumin = facilities entry into muscle

Question 49

When will FA uptake into muscle only occur?

Answer 49

IF ICF FFA conc is less than that in the true aqueous solution in ECF

Question 50

How is the low intracellular FFA conc maintained?

Answer 50

By the cytoplasmic FA-binding protein

Question 51

Where does beta-oxidation of FAs occur?

Answer 51

Mitochondria

Question 52

What does beta-oxidation of FAs do?

Answer 52

Removes 2-C units from FA chain in the form of ACoA. -- ACoA can then enter TCA cycle.

Question 53

How are the fatty ACoA molecules in the muscle sarcoplasm transported into the mitochondria?

Answer 53

w/ carnitine.

Question 54

Where is carnitine synthesised?

Answer 54

Liver

Question 55

Where is carnitine usually abundant?

Answer 55

Tissues that are able to oxidise FAs

Question 56

What enzyme regulates the transport of FA by carnitine?

Answer 56

Carnitine acyl-transferase (CAT)

Question 57

What are the forms of CAT found in the muscle?

Answer 57

CAT-I CAT-II

Question 58

CAT-I in the muscle Where is it located? What does it do?

Answer 58

Outer surface of membrane Generates acyl-carnitine

Question 59

CAT-II in the muscle Where is it located? What does it do?

Answer 59

Inner surface of inner mitochondrial membrane Regenerates ACoA + free carnitine

Question 60

What are CAT-I and CAT-II also referred to as?

Answer 60

Carnitine palmitoyl transferase I + II | CPT 1 + CPT 2

Question 61

Why has carnitine been promoted as a dietary supplement?

Answer 61

Weight loss by ⬆️ fat oxidation ⬆️ endurance exercise by promoting fat use = sparing limited glycogen stores.

Question 62

What must happen before aa can be oxidised?

Answer 62

Removal of amino group

Question 63

Activators of liver glycogen to plasma glucose

Answer 63

Glucagon Epinephrine Norepinephrine

Question 64

Inhibitors of liver glycogen to plasma glucose

Answer 64

Insulin

Question 65

Activators of muscle glycogen to glucose-1-phosphate

Answer 65

AMP Pi Ca2+ Epinephrine

Question 66

Inhibitors of muscle glycogen to glucose-1-phosphate

Answer 66

ATP

Question 67

Activators of muscle protein to aa

Answer 67

Cortisol

Question 68

Inhibitors of muscle protein to aa

Answer 68

Insulin

Question 69

Activators of pyruvate to ACoA

Answer 69

Ca2+ ADP CoA NAD+

Question 70

Activators of adipose tissue + muscle triacylglycerol to FAs

Answer 70

Epinephrine Glucagon Cortisol

Question 71

Inhibitors of adipose tissue + muscle triacylglycerol ---> FAs

Answer 71

Insulin

Question 72

What are the catecholamines?

Answer 72

Epinephrine Norepinephrine

Question 73

Where is insulin secreted from?

Answer 73

Beta cells of pancreatic islets

Question 74

Where is glucagon secreted from?

Answer 74

Alpha cells of pancreatic islets

Question 75

Where is epinephrine secreted from?

Answer 75

Adrenal medulla

Question 76

Where is norepinephrine secreted from?

Answer 76

Sympathetic nerve endings

Question 77

Where is cortisol secreted from?

Answer 77

Adrenal cortex

Question 78

Where is the growth hormone secreted from?

Answer 78

Anterior pituitary gland

Question 79

Metabolic changes in response to endurance training

Answer 79

⬆️ fat oxidation ⬇️ muscle glucose + glycogen use Small ⬆️ in circulating hormones ⬆️ FFA transporters in muscle membrane ⬇️ Lactate accumulation