B2

Animal Cells- all cells have some feature in connom. We can see these clearly in animal cells, all cells in the body have these features:

1) A nucleus: controls all the activities of the cell. It also contains the instructions for making new cells or new organisms.

2) Cytoplasm: liquid gell in which most of the chemical reactions needed for life take place. E.g. repiration where oxygen and sugar react to release energy the cell needs.

3) Cell membrane: controls the passage of substances in and out of the cell.

4) mitochondria: strucutres in the cytoplasm where most of the energy is released during respiration

5) Ribosomes: where protein synthesis takes place. All the protein needed in the cell is made here.

Plants Cells- plants make their own food by photosynthesis. So, plant cells have all features of a typical animal cell, and also certain structures which help them live.

ALL PLANTS HAVE:

Cell wall: made of cellulose which strengthens the cell and gives it support.

MANY PLNATS HAVE:

Chloroplasts: they are found in all green plants. Plants are green due to the green substance chlorophyll which gives the plants its colour. They absorb light energy to make food by photosynthesis.

A permanent vacuole: (a space in the cytoplasm filled with cell sap) this is important for keeping the cells rigid to support the plant.

Cell chemistry works because each reaction is controlled by an enzyme.

Each enzyme is a protein which controls the rate of a very specific reaction.

Makes sure that reations take place without mixing up with any other reactions.

Find enzymes throughout the strucutre of a cell, but paticularly in the mitochondria (and chloroplasts in plants)

The enzymes involved in different chemical processes are usually found in different parts of cells. For example, most enzymes controlling reactions of:

respiration are found in the mitochondria

photosynthesis are found in chloroplasts

protein synthesis are found on the surface of the ribosomes.

Some cells in body have become specialised so that they carry out a certain job, examples being, sperm cells (stream line and long tail so can swim to egg), root hair cells, (increase surfave area for water to move into cell and have a large permanent vacuole which affects the movement of water from the soil across the root hair cell).

When a cell become specialised its structure is adapted to suit the paticular job it does. As a result, specialised cells become so specialised that they can only have on function within the body.

Good examples are:

sperm, eggs, red blood cells and nerve cells.