Biology Unit 2: Variation in Cell Structure

Most have the following parts - make sure you know them all:

1. Plasma membrane - holds the cell together and controls what goes in and out.

2. Cytoplasm - gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions.

3. Nucleus - contains genetic material that controls the activities of the cell.

4. Mitochondria - where most of the reactions for respiration take place. Respiration releases energy hat the cell needs to work.

5. Ribosomes - where proteins are made in the cell.

They usually have all the bits that animal cells have, plus...

1. Rigid cell wall - made of cellulose. It supports and strengthens the cell.

2. Permanent vacuole - contains cell sap, a weak solution of sugar and salts.

3. Chloroplasts - where photosynthesis occurs, which makes food for the plant. They contain chlorophyll.

   - Chloroplasts are surrounded by a double membrane, and also have membranes inside called thylakoid membranes. These membranes are stacked up in the chloroplast to form grana.

   - Grana are linked together by lamellae - thin, flat pieces of thylakoid membrane

   - Some parts of photosynthesis happen in the grana, and other parts in the stroma (a thick fluid found in chloroplasts).

You might get a question where you need to apply your knowledge of organelles to explain why its particularly suited to its function...

Think about where the cell's located in a plant - if it's exposed to light, then it's have lots of chloroplasts to maximise photosynthesis.

Think about what the cell needs to do its job - if the cell uses a lot of energy, it'll need lots of mitochondria. If it makes lots of proteins, it'll need lots of ribosomes.

Good luck on your exams!