Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

biochem term 2 quiz 4 > muscle metabolism and excercise > Flashcards

muscle metabolism and excercise Flashcards

1
Q

sarcomeres

A

contractile fibers that make up myofibrils

contain actin-based thin filament and myosin-based thick filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

actin

A

monomeric globular protein that polymerizes into double helical filaments
polar filaments
plus end at z line
minus end toward center of sarcomere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

thin filament components

A

actin
tropobyosin
tropronin (C, I, T)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

tropomyosin

A

elongated protein that fits into a groove in the actin filament
bound along entire length of actin filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

troponin

A

complex of 3 polypeptides
bind both actin and tropomyosin at point where two tropomyosins overlap
C, I, and T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Troponin C

A

calcium-binding protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

troponin I

A

binds both actin and troponin C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

troponin T

A

binds troponin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

myosin

A

motor protein
hydrolyzes ATP to move along actin filament
results in contraction
one of the reasons muscle has large energy requirement
has two regions: head - has motor activity
tail - controls myosin oligomeritization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

steps in muscle contraction

A

1: motor binds ATP, releasing it from the actin filament
2: motor hydrolyzes ATP to ADP + Pi - still released from actin filament at this point
3: Pi product is released => motor binds tightly to actin filament
4: ADP released => motor takes step toward plus end = power stroke

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

tubule system

A

T tubules = plasma membrane invaginations
SR = sarcoplasmic reticulum = specialized endoplasmic reticulum
work together to stimulate contraction by releasing Ca into sarcomere
pumps required to maintain the ca gradients in muscle are the second main energy sink

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

steps in activation of muscle contraction

A

1: motor neurons release AcTH at neuromuscular junction
2: AcTH binds receptors = non-selective cation channels
3: channels open => depolarization
4: voltage sensitive Na channels open => depolarization of entire cell
5: calcium enters cytosol from voltage-sensitive ca channels in T tubule and from calcium release channels in smooth ER (SR)
6: Ca binds troponin C
7: troponin complex changes binding state o thin filament
8: tropomyosin shifts location on actin filament
9: change in tropomyosin binding allows myosin to bind actin filament
10: => motor activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

non-sarcomeric cytoskeleton

A

actin filaments radiate from z-discs
actin filaments interact with plasma membrane at costameres - contain dystrophin
(these actin filaments are different from the ones in the sarcomere)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

costameres

A

groups of protein where actin filaments interact with plasma membrane
contain dystrophin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

dystrophin

A

component of costameres

mutations result in muscular dystrophy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

mitochondria in muscle

A

two categories:
inter-mylofibrillar mitochondira (IMF)
sub-sarcolemmal mitochondria (SS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

inter-myofibrillar mitochondria (IMF)

A

closely associated with sarcomeres
supply ATP for myosin function
85-90% of muscle mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

sub-sarcolemmal mitochondria (SS)

A 
between myofibrils and plasma membrane
supply ATP for non-myosin functions
s.a. ion pump activity, costamere maintenance
number and properties change dramatically due to exercise training
function affected by obesity - may contribute to obesity-induced type II diabetes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

energy stores in muscle cells

A

glycogen granules and intra-muscular lipid droplets (full of TG) reside between myofibrils and plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

skeletal muscle

A

striated

has two types: type 1 and 2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

type I skeletal muscle

A 
aerobic, slow twitch
used for sustained, repetitive contraction of moderate forces
specialized for oxidative phosphorylation of glucose and beta-oxidation of FA
- has high vascularization
- lots of myoglobin
- lots of mitochondria
- TG stores
- secrete lipoprotein lipase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

type II skeletal muscle

A

anaerobic, fast twitch
used for rapid but transient contraction of high force
specialized for anaerobic catabolism of glucose
- low vascularization
- few mitochondria
- high concentration of glycolytic enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

cardiac muscle

A

highly aerobic
more vascularized than type I skeletal
can take lactate into citric acid cycle because has a special lactate dehydrogenase enzyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

hypertrophic cardiomyopathy (HCM) (summary card)

A

muscle surrounding left ventricle thickens +> reduced chamber volume and arrythmia
often goes unnoticed until sudden cardiac arrest
occurs in 1/500 people - major cause of death in young athletes
most cases have a genetic component

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is the problem in HCM and what difficulties does it cause?

A

muscle surrounding the left ventricle thickens

results in reduced chamber volume and arrythmia

26
Q

how is HCM usually detected?

A

usually goes unnoticed until sudden cardiac arrest occurs

27
Q

how common is HCM?

A

1/500

28
Q

whom does HCM often affect?

A

major cause of death in young athletes

29
Q

what causes the majority of HCM cases?

A

most have genetic component

over 400 mutations identified so far

30
Q

what proteins are affected by the mutations that cause HCM? what percentage of cases are due to each mutation type?

A

mutations in:

  • cardiac myosin (heavy or light chains) found in 48% of cases
  • cardiac troponin T - 10%
  • cardiac troponin I - 9%
  • tropomyosin - 4%
  • cardiac actin - 2%
31
Q

what are common characteristic in the mutations that cause HCM?

A

1: dominant - only on copy of the mutant is needed
2: missense mutations (point mutations)
3: don’t inactivate protein, just change its ability to do its job

32
Q

what is the predominant theory for disease progression in HCM myosin mutants? (ie how does this mutation lead to hypertrophy of the muscle?)

A

1: mutant protein incorporates into sarcomere - represents about half of the protein (since other half made from non-mutant gene)
2: mutant causes contraction to occur sub-optimally (may be “out of phase” with the normal copy of the protein)
3: sub-optimal contraction => heart muscle to hypertrophy in effort to compensate

33
Q

what are the two things ATP is needed for during exercise?

A

muscle myosin and ion channels

34
Q

where does muscle ATP come from?

A

ATP can’t travel through blood so must be made in muscle

35
Q

what are the main storage forms of fuel for muscle?

A

glycogen and FA

36
Q

what are the chemical sources of energy in muscle cells? how much ATP can be acquired per mole from each of these sources?

A

1: glucose:
- anaerobic to lactate => 2 ATP/mole
- aerobic to CO2 => 32 ATP/mole
2: fatty acids => 106 ATP/mole (palmitate)
3: ketone bodies => 18 ATP/mole
4: AA => variable ATP output
- muscle predominantly uses branched chain AA => 15 ATP/mole
5: creatine phosphate => 1 ATP/mole
6: ADP (through adenylate kinase_ => .5 ATP/mole

37
Q

how does muscle acquire and use glucose?

A

1: muscle has its own glycogen stores - breaks these down using glycolysis
2: liver supplies glucose through gluconeogenesis and glycogenolysis

38
Q

how does muscle acquire and use FA?

A

1: has its own TG stores - breaks these down to FA via triglyceride lipase
2: FA come through blood from adipose tissue, liver, intestine

39
Q

what are the sources of FA that the muscle uses?

A

1: adipose tissue - releases FA into blood through hormone-sensitive lipase - FA circulate bound to albumin
2: liver secretes TG in VLDL
muscle uses lipoprotein lipase (LPL) to release FA from TG
3: intestine secretes TG in chylomicron - muscle again uses LPL to release FA

40
Q

which muscle types store and use FA?

A

type I burns appreciable FA

type II does not burn fat appreciably, has little or no fat stores

41
Q

what are the proportions of aerobic and anaerobic glucose catabolism dependent on?

A

a: muscle type (fast twitch or slow twitch)
b: activity intensity

42
Q

can muscle use glycogen?

A

no. glycogen stores in resting muscle are’t available to active muscle because there’s no glucose-6-phosphate in muscle

43
Q

describe what happens when a type I diabetic injects too much insulin. what are the mechanisms by which this occurs?

A

brain only burns glucose (can burn ketone during starvation)
insulin will cause inappropriate drop in blood glucose and inhibit ketone body production
results in impaired mental function but muscle can still function relatively well
mechanisms of insulin action:
1: inhibiting PEPCK transcription in liver => inhibiting gluconeogenesis
2: inhibiting glycogenolysis in liver
3: inhibiting transcription of glucose-6-phosphatase => inhibition of dephosphorylation of glucose-6-phosphate generated by gluconeogenesis or glycogenolysis
4: inhibiting ketone body production in liver
5: increasing GLUT4 on plasma membrane of muscle cells

44
Q

how can excess AA in the blood be used if the body needs fuel?

A

1: muscle can catabolize branched AA (Leu, Ile, Val)
2: liver good at converting alanine to glucose - major source of energy for brain during starvation - derived from breakdown of muscle proteins

45
Q

what are 4 conditions that alter the anabolism/catabolism balance of protein? what is the effect of these?

A

1: type I diabetes => increased protein catabolism (melting of flesh into urine)
2: growth hormone treatment => increases anabolism (for patients who have lost muscle mass during injury)
3: anabolic steroids => increases anabolism
4: B-adrenergic agaoinsts => increased anabolism (clenbuterol)

46
Q

what are the differences between FA and glucose storage and catabolism? (ie which is stored more, how long does catabolism take, which energy source is used when?)

A

much more FA than glycogen
but FA oxidation slow - inefficient to support maximal exertion and requires some glucose oxidation
fatty acid catabolism dominates at low intensity
glucose catabolism dominates at high intensity
muscle glycogen is the dominant source for anaerobic work

47
Q

how are plasma FA taken up by muscle? (steps)

A

1: plasma FA releases from albumin and incorporates into the PM outer leaflet
2: the FA flipflops to the PM inner leaflet
3: FA diffuses in cytoplasm to mitochondria outer membrane
4: fatty acyl-coA ligase in outer membrane converts FA to acyl-CoA - transports it to inner membrane space
5: acyl-coA in inner membrane space onverted to acyl-carnitine by CAT-1 (aka CPT-1) rate limiting
6: carnitine translocase transports acyl-carnitine across inner mitochondrial membrane
7: acyl-carnitine in mitochondrial matrix is converted to acyl-CoA by CAT-II
8: acyl-coA in mitochondrial matrix is oxidized for ATP production

48
Q

how are LVDL and chylomicron FA taken up by muscle? (steps)

A

1: lipoprotein lipase (LPL) on endothelial cell surface hydrolyzes lipoprotein TG to FA
2: FA finds albumin and is taken up the same way as plasma FA

49
Q

where is LPL attached?

A

non-covalently attached to heparin-sulfate proteoglycans on endothelial cell PM - can be washed off with heparin

50
Q

what determines LPL’s preference for VLDL and chylomicrons?

A

LPL binds apo CII on surface of the lipoproteins

51
Q

what factors drive FA uptake?

A

rate of blood flow (increases several fold during exercise)

2: concentration gradient (gradient driven by conversion of acyl-CoA in muscle

52
Q

how is conversion of acyl-CoA to acyl-carnitine regulated?

A

in liver:

  1. malonyl CoA negatively regulates CAT-1 - increased hepatic FA synthesis => decreased FA oxidation
    2: insulin stimulates ACC activity => increased malonyl-CoA synthesis => synthesis of FA and decrease FA oxidation

in muscle:

1: ACC-derived malonyl-CoA negatively regulates CAT-1 => muscle favors glucose oxidation over FA oxidation
2: insulin stimulates ACC activity
3: ACC activity also regulated by AMPK = phosphorylates and inhibits ACC

53
Q

how is AMPK activated by exercise?

A

1: exercise increases muscle contraction => more ATP converted to ADP
2: adenylate kinase converts 2 ADPs to 1 ATP and 1 AMP
3: AMP is an allosteric activator of AMPK

therefore, exercise stimulates muscle FA oxidation by inhibition of ACC

54
Q

what systems can be activated to supply large amounts of ATP rapidly in situations requiring intense contraction (processes used to fuel aerobic contraction are too slow)? (list)

A

1: phosphocreatine used to generate ATP from ADP
2: adenylate kinase converts 2 ADPs to ATP and AMP
3: glycogenolysis activated to supply glucose-6-phosphate
4: glycolysis activated to generate ATP and lactate fro G6P

55
Q

when is phospho-creatine used? how much energy will it create?

A

in situations requiring intense contraction
generates ATP from ADP
provides about 4 seconds of energy before glycogenolysis/glycolysis needed

56
Q

when is adenylate cyclase needed to generate energy? what does it do?

A

in situations requiring intense contraction
provides some ATP as a “stop-gap” measure during initial contraction
generates AMP => allosteric activator of glycogen phosphorylase and phosphofructokinase (PFK)
generates NH3/NH4 => allosteric activator of PFK

57
Q

how can muscle contraction increase glycogenolysis rate? when does this occur?

A

occurs in situations requiring intense contraction

1: ca influx directly activates phosphorylase kinase b=> phosphorylation of glycogen phosphorylase b => conversion to active glycogen phosphorylase a
2: myosin activity generates Pi = necessary substrate for glycogen phosphorylase a
3: ADP generated by myosin activity can be converted to ATP and AMP by adenylyl cyclase => AMP activates muscle-specific glycogen phosphorylase b

58
Q

how does adrenaline affect glycogen synthesis in muscle?

A

muscle has special isoform of glycogen synthase

inhibited by adrenaline

59
Q

how is glycolytic rate increased in muscle? when does this occur?

A

occurs in situations requiring intense contraction

1: inorganic phosphate, AMP, and ammonia/ammonium levels all go up => PFK activation
2: ATP and phospho-creatine levels decrease => PFK activation

60
Q

what are acute responses to exercise that allow for muscle to re-fueled?

A

1: increased FA oxidation
2: increased glucose uptake

61
Q

what are long-term responses to exercise that allow for muscle to re-fueled?

A

1: increased synthesis of GLUT4 to allow more glucose transport
2: increased synthesis of many enzymes involved in glucose and FA oxidation
3: increase in number of mitochondria
4: increased FA storage in active muscles (in elite athletes)

biochem term 2 quiz 4 (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions