Specialised animal cells

Question 1

Red blood cells

Answer 1

Red blood cells carry oxygen around the body, which is needed for respiration.They are well suited to this function because:

They contain haemoglobin, which carries oxygen molecules.
They don’t have a nucleus, allowing more space to carry oxygen.
They are a flat disc shape with dips on both sides (biconcave). This gives them a large surface area, and the best chance of absorbing as much oxygen as they can in the lungs.

Question 2

Sperm cells

Answer 2

Sperm are the male sex cell. They are made in the testes after puberty. They join with an egg cell during fertilisation to form an embryo which can then develop into a new life. The following features make them well suited to this function:

A tail moves them towards an egg cell.
Many mitochondria release energy for movement.
Part of the tip of the head of the sperm, called the acrosome, releases enzymes to digest the egg membrane to allow fertilisation to take place.
The haploid nucleus contains the genetic material for fertilisation.
Sperm are produced in large numbers to increase the chance of fertilisation.

Question 3

Egg cell

Answer 3

Eggs are the female sex cell. They are made in the ovaries before birth. Usually, one egg is released each month during the menstrual cycle, but sometimes this number may be higher. They join with a sperm cell during fertilisation to form an embryo which can then develop into a new life. They are well suited to this function because:

The egg cell’s cytoplasm contains nutrients for the growth of the early embryo.
The haploid nucleus contains genetic material for fertilisation.
The cell membrane changes after fertilisation by a single sperm so that no more sperm can enter.

Question 4

Nerve cells

Answer 4

Nerve cells transmit electrical signals in the nervous system. They are well suited to their function because:

They are thin, and can be more than one metre long in your spinal cord. This means they can carry messages up and down the body over large distances very quickly.
Nerve cells have branched connections at each end. These join to other nerve cells, allowing them to pass messages around the body.
They have a fatty (myelin) sheath that surrounds them. The fatty sheath increases the speed at which the message can travel.

Question 5

Muscle cells

Answer 5

Muscles cells are found in bundles which make up our muscles. These cells are able to contract (get shorter) and relax (return to original length). There are different types of muscle cell, each perfectly adapted to its function:

Cardiac (heart) muscle cells contract and relax to pump blood around our bodies for our entire lives. They never get tired.
Smooth muscle cells make up thin sheets of muscle, such as the stomach lining. They can also be arranged in bundles, or rings, like that in the anus.
Skeletal muscle is joined to bones. Its cells contract to make bones move and joints bend.

Question 6

Ciliated cells

Answer 6

Ciliated cells are found in the airways. They have tiny hairs on their tops called cilia which beat in a rhythm. These hairs move mucus containing dust and other particles upwards and out of the airways. Ciliated cells are also found in the oviducts. Here the tiny hairs beat to move the egg from the ovaries to the uterus.

Question 7

Villi

Answer 7

Villi are structures about one millimetre long in the small and large intestines. Millions of them poke out to absorb digested food and water into the blood. They are well suited to this function because:

They have a large surface area.
They have thin walls which are only one cell thick.
The cells of the lining have tiny hairs to absorb more food and water.