Muscles

Question 1

Fast or slow twitch: Fatigue slowly

Answer 1

Slow

Question 2

Fast or slow twitch: Builds up lactic acid quickly.

Answer 2

Fast

Question 3

What is the sacroplasm?

Answer 3

The cytoplasm of the muscle cell.

Question 4

What is actin?

Answer 4

Thinner, two strands twisted around one another.

Question 5

What is myosin?

Answer 5

Thicker, long rod-shaped fivres with bulbous heads that project from the side.

Question 6

Why do myofibrils appear striped?

Answer 6

Alternating light and dark bands. The light bands are called isotropic bands and they are light because the actin and the myosin don’t overlap. The dark bands are called anisotropic bands and they are dark because the myosin and actin overlap.

Question 7

What is the light region in the middle of the anisotropic called?

Answer 7

H-zone

Question 8

What is a Z-line?

Answer 8

The centre of a isotropic band.

Question 9

What is the sacromere?

Answer 9

The sarcomere is the distance between adjacent Z-lines.

Question 10

What is tropomyosin?

Answer 10

A protein that forms a fibrous strand around the actin filament.

Question 11

Describe and draw out the process of contraction of skeletal muscle.

Answer 11

1. Tropomyosin molecule prevents the myosin head from attaching to the binding site on the actin molecule.
2. Calcium ions released from the endoplasmic reticulum cause the tropomyosin molecule to pull away from the binding sites on the actin molecule.
3. Myosin head attaches to the binding site.
4. Head of myosin changes angle, moving the actin filament along, and as it does this an ADP molecule is released.
5. ATP molecule fixes to the myosin head, causing it to detach from the actin filament.
6. Hydrolysis of ATP to ADP by ATPase provides the energy for the myosin head to resume its normal position.
7. The head of the myosin reattaches to a binding site further along the actin filament and the cycle is repeated.