Give three features of a skeletal muscle fibre that distinguish it from an ordinary cell.

It contains many nuclei because it is formed by the fusion of several cells, it can be several centimetres long, and its cytoplasm is packed with myofibrils and mitochondria.

What is stored in the sarcoplasmic reticulum, and why is that important?

It stores calcium ions, which are released into the sarcoplasm to trigger contraction and pumped back to allow relaxation.

What are T-tubules and what is their function?

T-tubules are inward folds of the sarcolemma that run deep into the fibre, so that an action potential reaches the sarcoplasmic reticulum throughout the fibre at almost the same instant.

A sarcomere is the repeating functional unit of a myofibril, extending from one Z line to the next.

Describe what is meant by the A band and the I band of a sarcomere.

The A band is the dark region occupied by the full length of the thick myosin filaments, including where actin overlaps them, and the I band is the light region containing only thin actin filaments.

OCR A-Level Biology B H422

The Developing Cell: Cell Division and Cell Differentiation

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Cells and Microscopy

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Water and Its Importance in Plants and Animals

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Metabolism and Exercise

The structure of skeletal muscle

3 things to know
Components 01, 02 and 03

Overview

Recall questions on muscle fibres, the sarcolemma, sarcoplasm, sarcoplasmic reticulum and T-tubules, the sarcomere and its A band, I band and H zone, thick and thin filaments, slow and fast twitch fibres, and preparing, measuring and testing chicken muscle fibres with ATP.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Describe how a piece of muscle from a chicken leg can be prepared to show its striations under a light microscope.

Key term

Name the cell surface membrane and the cytoplasm of a muscle fibre.

Key term

What is a sarcomere?

Questions from this subtopic

Each one with the model answer underneath.

1
Give three features of a skeletal muscle fibre that distinguish it from an ordinary cell.
Model answer
It contains many nuclei because it is formed by the fusion of several cells, it can be several centimetres long, and its cytoplasm is packed with myofibrils and mitochondria.
2
Name the cell surface membrane and the cytoplasm of a muscle fibre.
Model answer
The membrane is the sarcolemma and the cytoplasm is the sarcoplasm.
3
What is stored in the sarcoplasmic reticulum, and why is that important?
Model answer
It stores calcium ions, which are released into the sarcoplasm to trigger contraction and pumped back to allow relaxation.
4
What are T-tubules and what is their function?
Model answer
T-tubules are inward folds of the sarcolemma that run deep into the fibre, so that an action potential reaches the sarcoplasmic reticulum throughout the fibre at almost the same instant.
5
What is a sarcomere?
Model answer
A sarcomere is the repeating functional unit of a myofibril, extending from one Z line to the next.
6
Describe what is meant by the A band and the I band of a sarcomere.
Model answer
The A band is the dark region occupied by the full length of the thick myosin filaments, including where actin overlaps them, and the I band is the light region containing only thin actin filaments.

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The Developing Cell: Cell Division and Cell Differentiation

The Developing Individual: Meiosis, Growth and Development

The Development of Species: Evolution and Classification

Cells and Microscopy

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measles and .

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