Plant cells
Cells
If you study a plant by observing part of it through a microscope, you will see that it is made up of a very large number of tiny ‘boxes’. These are called cells. All living organisms are made of cells.
Cells are so small that you cannot see them with your eyes alone. The photograph of the plant cells was taken through a microscope. The microscope magnifies the view of the cells, so that they look much bigger than they really are.
Parts of a plant cell
The diagram shows a plant cell from a leaf.
cell wall
Every plant cell has a cell wall. The cell wall is strong and stiff. It holds the plant cell in shape. Plant cell walls are made of a substance called cellulose.
cell membrane
All cells have a cell membrane. The cell membrane is very thin and flexible. It is like the thin skin of a soap bubble. It lies along the inner edge of the cell wall. The cell membrane controls what goes in and out of the cell.
cytoplasm
All cells have cytoplasm. Cytoplasm is like clear jelly. Chemical reactions happen inside the cytoplasm. These reactions keep the cell alive.
nucleus
Most cells have a nucleus. The nucleus controls the activities of the cell.
sap vacuole
This is a large, fluid-filled space inside a plant cell. The liquid inside it is a solution of sugars and other substances dissolved in water. The solution is called cell sap.
chloroplast
Plant cells that are in the sunlight often contain chloroplasts. This is where plants make their food. Chloroplasts look green because they contain a green substance called chlorophyll.
mitochondrion
All plant cells have mitochondria (singular: mitochondrion). Inside mitochondria, energy is released from food.
Questions
Look at the photograph of the plant cells on this page.
What do you think the little green circles inside the cells are?
Why are they green? What happens inside them?
Show Answer
The little green circles are chloroplasts. They appear green because they contain chlorophyll, a green pigment that absorbs light for photosynthesis. Inside them, the plant makes its own food by converting sunlight, water, and carbon dioxide into sugars.
Describe four differences between a cell wall and a cell membrane.
Show Answer
1. The cell wall is rigid and provides structural support; the cell membrane is flexible.
2. The cell wall is made of cellulose; the cell membrane is made of lipids and proteins.
3. The cell wall is only found in plant cells; the cell membrane is found in all cells.
4. The cell wall does not control entry/exit of substances; the cell membrane regulates what enters and leaves the cell.
Microscopes
Scientists who study living organisms often use microscopes to help them to see very small things.
The diagram shows a microscope. Look at a real microscope and find all of these parts on it.
