Most human and animal cells have the following parts in their bodies. They are very important:
- Nucleus-Contains genetic material that controls the activities of the cell.
- Cytoplasm-Gel-like substance where most of the chemical reactions happen, it contains enzymes that control the chemical reactions.
- Cell membrane-Holds the cell together and controls what goes in and out.
- Mitochondria-These are where most of the reactions for respiration take place. Respiration releases energy that the cell needs to work.
- Ribosomes-These are where proteins are made in the cell.
Plant cells usually have all the bits that animal cells have, plus a few extra things that animal cells don't have:
- Rigid cell wall-Made of cellulose. It supports the cell and strengthens it.
- Permanent vacuole-Contains cell sap, a weak solution of sugar and salts.
- Chloroplasts-These are where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll.
Palisade Leaf Cells
Palisade leaf cells are adapted for photosynthesis. They are grouped together to give the palisade layer of a leaf-this is the leaf tissue where most of the photosynthesis happens.
- The cells are packed with chloroplasts for photosynthesis. More of them are crammed at the top of the cell-so they are nearer the light.
- Tall shape means a lot of surface area exposed down the side for absorbing CO2 from the air in the leaf.
- Thin shape means that you can pack loads of them in at the top of a leaf.
Guard cells are adapted to open and close pores. They are adapted to their function of allowing gas exchange and controlling water loss within the leaf organ.
- Special kidney shape which opens and closes the stomata (pores) in a leaf.
- When the plant has lots of water the guard cells fill with it and go plump and turgid. This makes the stomata open so gases can be exchanged for photosynthesis.
- When the plant is short of water, the guard cells lose water and become flaccid, making the stomata close. This helps stop too much water vapour escaping.
- Thin outer walls and thickened inner walls make the opening and closing work.
- They're also sensitive to light and close at night to save water without losing out on photosynthesis.
Red Blood Cells
Red blood cells are adapted to carry oxygen. They are an important part of the blood.
- Concave shape gives a big surface area for absorbing oxygen. It also helps them pass smoothly through capillaries to reach body cells.
- They're packed with haemoglobin-the pigment that absorbs the oxygen.
- They have no nucleus, to leave even more room for haemoglobin.
Sperm and Egg Cells
Sperm and egg cells are specialised for reproduction. They are extremely important in the reproductive system.
- The main functions of an egg cell are to carry the female DNA and to nourish the developing embryo in the early stages. The egg cell contains huge food reserves to feed the embryo.
- When a sperm fuses with the egg, the egg's membrane instantly changes its structure to stop any more sperm getting in. This makes sure the offspring end up with the right amount of DNA.
- The function of a sperm is basically to get the male DNA to the female DNA. It has a long tail and a streamlined head to help it swim to the egg. There are a lot of mitochondria in the cell to provide the energy needed.
- Sperm also carry enzymes in their heads to digest through the egg cell membrane.