Which type of respiration is a slow twitch fibre adapted for, and give two features that show it.

It is adapted for aerobic respiration, and this shows in its very large number of mitochondria and the dense network of capillaries that supplies it with oxygen.

What is the function of myoglobin in a muscle fibre?

Myoglobin binds oxygen more strongly than haemoglobin does, so it holds a store of oxygen in the fibre and releases it only when the oxygen concentration in the muscle falls very low.

Give three features that adapt a fast twitch fibre to short bursts of powerful activity.

A fast twitch fibre holds a large store of glycogen and creatine phosphate, it has a high concentration of the enzymes of glycolysis and a rapidly acting myosin ATPase, and it has an extensive sarcoplasmic reticulum that floods the fibre with calcium ions very quickly.

Why does a fast twitch fibre fatigue so quickly?

It relies on anaerobic respiration, which yields very little ATP for each glucose used, so its glycogen store is soon spent and the lactate that accumulates lowers the pH and interferes with contraction.

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Human Musculoskeletal Anatomy: Skeletal TissuesMusculoskeletal

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Human Musculoskeletal Anatomy: Skeletal Tissues

Fast and slow twitch fibres, and energy for contraction

3 things to know
Component 3

Overview

Function of myoglobin in a muscle fibre and role of creatine phosphate in a working muscle.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why does the build-up of lactate cause fatigue and pain?

Key term

How do fast twitch and slow twitch fibres differ in the speed and duration of their contraction?

Key term

Why is slow twitch muscle darker in colour than fast twitch muscle?

Questions from this subtopic

Each one with the model answer underneath.

1
How do fast twitch and slow twitch fibres differ in the speed and duration of their contraction?
Model answer
A fast twitch fibre contracts rapidly and powerfully but can sustain that effort for only a short time, whereas a slow twitch fibre contracts more slowly and less forcefully but can keep working for a long period without tiring.
2
Which type of respiration is a slow twitch fibre adapted for, and give two features that show it.
Model answer
It is adapted for aerobic respiration, and this shows in its very large number of mitochondria and the dense network of capillaries that supplies it with oxygen.
3
Why is slow twitch muscle darker in colour than fast twitch muscle?
Model answer
Slow twitch fibres contain a high concentration of the red oxygen-storing pigment myoglobin and are supplied by more blood vessels.
4
What is the function of myoglobin in a muscle fibre?
Model answer
Myoglobin binds oxygen more strongly than haemoglobin does, so it holds a store of oxygen in the fibre and releases it only when the oxygen concentration in the muscle falls very low.
5
Give three features that adapt a fast twitch fibre to short bursts of powerful activity.
Model answer
A fast twitch fibre holds a large store of glycogen and creatine phosphate, it has a high concentration of the enzymes of glycolysis and a rapidly acting myosin ATPase, and it has an extensive sarcoplasmic reticulum that floods the fibre with calcium ions very quickly.
6
Why does a fast twitch fibre fatigue so quickly?
Model answer
It relies on anaerobic respiration, which yields very little ATP for each glucose used, so its glycogen store is soon spent and the lactate that accumulates lowers the pH and interferes with contraction.

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