muscle contraction pt 2

Question 1

myosin filaments

Answer 1

globular heads that are hinged (back and forth)
heads have binding site for actin and ATP
actin filaments have binding site for myosin head called actin-myosin binding sites
protein tropomyosin between actin filaments helps myosin filaments move past eachother

Question 2

binding sites in resting muscles

Answer 2

actin-myosin binding site blocked by tropomyosin

filaments cant slide past eachother

Question 3

muscle contraction (AP stimulates muscle cell)

Answer 3

1. depolarises sarcomella. spreads down t-tubules to sarcoplasmic reticulum = release calcium ions into sarcoplasm
2. Ca2+ bind to protein attached to tropomyosin -> changes shape. pulls attached tropomyosin out of actin-myosin binding site
3. exposed binding site allows myosin head head to bind. actin-myosin cross bridge
4. calcium ions activate ATP hydrolase which breaks ATP down
5. energy released = myosin head bends pulls actin filament along in rowing action
6. ATP provides energy to break actin-myosin cross bridge. myosin head reattaches to different binding site further along actin filament. cycle repeated
7. many cross bridge form and break rapidly pulling actin filament long which shortens sarcomere and cause muscle to contract
8. continues as long as calcium present

Question 4

excitation stops / muscle stops being stimulates

Answer 4

Calcium ions leave binding sites moved ack into sarcoplasmic reticulum by ATP
causes tropomyosin molecules to move back blocking actin-myosin binding sites
actin filaments slide back to relaxed position - lengthens sarcomere

Question 5

ATP generated in respiration

Answer 5

aerobic respiration - most ATP. long period of low intensity excercise

anaerobic respiration - ATP made rapidly in glycolysis. lactate can quickly build up and cause fatigue. short periods of hard excerci

Question 6

ATP generated in ATP - phosphocreatine PCr system

Answer 6

ADP + PCr -> ATP + Cr 
PCr stored inside cells.
generates ATP very quickly 
runs out quickly 
short bursts of vigorous excercise 
anaerobic and alactic (no lactate)

Question 7

slow twitch vs fast twitch

Answer 7

S V F
contract slow. contract quickly

use for posture. use for fast movment

good for endurance. good for short bursts

long time without tiring. tire quickly

energy released slowly aerobic. energy released quickly anaerobic

redish - rich in myoglobin (stores O2). whitish in colour. dont have much myoglobin.
e.g. back. vs eyes