muscle metabolism and excercise Flashcards Preview

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

Flashcards in muscle metabolism and excercise Deck (61)
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1

sarcomeres

contractile fibers that make up myofibrils
contain actin-based thin filament and myosin-based thick filaments

2

actin

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

3

thin filament components

actin
tropobyosin
tropronin (C, I, T)

4

tropomyosin

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

5

troponin

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

6

Troponin C

calcium-binding protein

7

troponin I

binds both actin and troponin C

8

troponin T

binds troponin

9

myosin

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

10

steps in muscle contraction

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

11

tubule system

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

12

steps in activation of muscle contraction

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

13

non-sarcomeric cytoskeleton

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)

14

costameres

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

15

dystrophin

component of costameres
mutations result in muscular dystrophy

16

mitochondria in muscle

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

17

inter-myofibrillar mitochondria (IMF)

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

18

sub-sarcolemmal mitochondria (SS)

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

19

energy stores in muscle cells

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

20

skeletal muscle

striated
has two types: type 1 and 2

21

type I skeletal muscle

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

22

type II skeletal muscle

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

23

cardiac muscle

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

24

hypertrophic cardiomyopathy (HCM) (summary card)

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

25

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

muscle surrounding the left ventricle thickens
results in reduced chamber volume and arrythmia

26

how is HCM usually detected?

usually goes unnoticed until sudden cardiac arrest occurs

27

how common is HCM?

1/500

28

whom does HCM often affect?

major cause of death in young athletes

29

what causes the majority of HCM cases?

most have genetic component
over 400 mutations identified so far

30

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

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%