Life Processes, Cells and Cell Organisation

Question 1

How do you use a microscope to view slides?

6 marks

Answer 1

1. Move the stage (the flat ledge the slide sits on) down to its lowest position.
2. Place the glass slide onto the stage. Be careful pushing it under the clips that the cover slide doesn’t move or crack.
3. Select the lowest power objective lens.
4. Turn the coarse focus knob slowly until you are able to see the cells.
5. Turn the fine focus knob slowly until the cells are in focus and you can see them clearly.
6. Repeat steps 1-5 using the higher power magnification to see the cells in more detail.

Question 2

List and describe the 7 Life Processes.

14 marks

Answer 2

M - Movement - All living things move, even plants
R - Respiration - Getting energy from food
S - Sensitivity - Detecting changes in the surroundings
G - Growth - All living things grow
R - Reproduction - Making more living things of the same type
E - Excretion - Getting rid of waste
N - Nutrition - Taking in and using food

Question 3

List at least five specialised cells and explain how they are adapted to their function.

10 marks

Answer 3

Red Blood Cells

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.

Sperm Cells

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.

Egg Cells

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.

Nerve Cells

Nerve cells (neurons) 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.

Muscles

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 Muscles

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 4

Describe how organisms are organised and give examples.

4 marks

Answer 4

Cell -> Tissue -> Organ -> Organ system -> Organism

Muscle cell -> Muscle -> Muscular system -> Human

Question 5

List four main plant organs and describe how they are adapted to their function.

8 marks

Answer 5

1. The stem holds the plant up and delivers all the water and nutrients.
2. The roots suck water and nutrients out of the ground.
3. The leaves photosynthesise.
4. The petals attract pollinating insects.

Question 6

Name the main food groups, giving examples of what they are needed for in the body.

10 marks

Answer 6

1. Carbohydrates provide the body with glucose.
2. Fat helps the body absorb vitamin A, vitamin D and vitamin E.
3. Dairy products provide the body with a source of calcium, essential for strong bones.
4. Protein is essential for growing, making new cells and repairing cells.
5. Fruit and vegetables provide vitamins and minerals, including folate, vitamin C and potassium. They also provide the body with dietary fibre.

Question 7

What is meant by a balanced diet?

2 marks

Answer 7

A balanced diet means that you are getting the correct amount of all food groups, and not too much or too little of any one group.

Question 8

Describe the food test.

4 marks

Answer 8

1. Crush the solid food into small pieces.
2. Add a few drops of iodine solution.
3. A blue-black colour means that the food has starch.
4. You can test liquid foods too.