Muscle contractions

Question 1

Describe the whole troponin and tropomyosin thing.

Answer 1

1. muscle is relaxed, tropomyosin blocks the myosin binding sites on actin
2. when calcium ion levels are high enough and ATP is present, calcium ions bind to troponin, which displaces tropomyosin
3. myosin binding sites on actin are exposed
4. myosin can bind to actin

Question 2

Which one’s which? Troponin & tropomyosin?

Answer 2

Tropomyosin is the molecule that blocks the binding site
Long, thin and wrapped round actin

Troponin is the one that is attached to the tropomyosin and is where Ca binds

Question 3

Where is Ca stored in the muscle cell?

Answer 3

Sarcoplasmic reticulum

Question 4

What happens after muscle cell membrane has been depolarised to cause a contraction?

Answer 4

Electrical impulse travels down T-tubules and opens calcium stores in the sarcoplasmic reticulum

Ca goes and causes a contraction

Question 5

What happens to sarcomeres during contraction?

Answer 5

Shorten

Z lines and M lines move closer together