1. The unit of life
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2. Questions to think about…
How is an animal cell different from a plant cell?
What are the different parts of a plant cell and an animal cell and what are their functions?
What are the different types of cells?
What forms the basic unit of life?
How do cells produce new cells?
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3. Cells All living things are made of cells.
A cell is the smallest unit of life in the body.
Most living things like people, cows and trees are made up of millions of cells.
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4. Cells
We can look at cells and study them with the help of a powerful microscope.
an optical microscope
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5. Cells
Some living things are made of fewer cells, like certain algae, mosses and anemones.
moss
anemone
algae
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6. Cells Some other living things are made up of only one cell.
These are single-cell organisms, such as bacteria, yeast and paramecium.
The cells can only be seen under a microscope.
paramecium
bacteria
yeast
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7. Different types of cells
Plants are made up of cells too.
There are cells in all parts of a plant – the leaves, the stem, the roots.
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8. Different types of cells
Some cells in a leaf make food for the plant.
These cells contain chlorophyll.
Chlorophyll traps light energy from the Sun to allow plants to carry out photosynthesis.
There are also cells that control the size of the stoma.
stoma
cells in a leaf
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9. Different types of cells
Some cells in the stem transport food and water within the plant.
The xylem and phloem tubes are made up of such cells.
xylem
phloem
cells in a stem
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10. Non-living things
Unlike living things, non-living things do not have cells.
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11. Different types of cells
What is inside a typical animal cell?
Nucleus
In both plant and animal cells, there is a nucleus found in the cytoplasm.
The nucleus is a very important part of a cell.
It controls everything that happens inside the cell.
Cytoplasm
All cells is made up of a jelly-like substance called the cytoplasm.
The cytoplasm allows substances such as food and oxygen to move around within the cells.
Many activities of the cells take place in the cytoplasm
Cell membrane
Surrounding the cytoplasm is a soft and thin cell membrane.
The cell membrane holds the cytoplasm inside it.
It also controls substances that go in or out of a cell.
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12. Different types of cells
What is inside a typical plant cell?
A plant cell has cytoplasm, a cell membrane, and nucleus, just like the animal cell.
However, a plant cell has other parts that are not found in an animal cell.
nucleus
cytoplasm
cell membrane
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13. Different types of cells
What is inside a typical plant cell?
Sap
A liquid which fills the cavity in the centre of most plant cells.
The sap keeps the cell firm.
Firm cells help the plant to stand upright as plants do not have a skeletal system to provide support.
Animal cells do not have such cavities in them.
Cell wall
A plant cell has a cell wall outside the cell membrane.
The cell wall is made up of a stiff material that gives a plant cell its shape.
Cell walls are not found in animal cells.
Chloroplast
A chloroplast is a tiny green structure that is found in the cytoplasm of a plant cell.
Chloroplasts contain chlorophyll, a pigment that traps sunlight for photosynthesis.
Chloroplasts are not present in animal cells.
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14. Different types of cells
Cells come in different shapes and sizes.
Different types of cells have different functions.
In the human body, cells work in groups, like those in the heart and the brain.
They form the organs in the body.
a brain cell
heart muscle cells
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15. Different types of cells
Other cells such as red and white blood cells travel within the body to do their jobs.
red blood cells
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16. Producing new cells Our bodies increase in size as we grow.
This is due to an increase in the number of cells in the body.
Cells increase in number by dividing themselves.
The nucleus and cytoplasm of one cell divide to produce two cells.
The two new cells later divide into four cells.
These four cells can divide to form more cells.
This process is known as cell division.
It takes place all the time to allow cells to multiply.
cell division
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17. Producing new cells
Single-cell organisms, such as paramecium, yeast and bacteria, multiply by cell division.
The new cells produced are identical to the original cell.
Yeast multiplies by a special cell division method called budding (see below).
In budding, a small bud grows from a yeast cell.
The bud slowly increases in size and then breaks away.
bud growing
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18. Producing new cells Cells do not live forever.
Old cells die and new ones are produced to replace them.
This takes place in our bodies all the time.
Our skin cells can live for 3 weeks while the cells lining out intestines are replaced after 3 days.
Some cells also divide to help repair damaged parts of our bodies.
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19. The end
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