Page 6 - Focus PT3 2020 Science ( BI Version )

Science PT3 Chapter 2 Cell as the Basic Unit of Life

2.1 Cell – Structure, Function and 5. When a cell divides rapidly without control,
it can form a tumour or cancer.
Organisation

What is a Cell? Form Form

A cell is the basic unit that makes up all Cell division
living things. Normal Cancer cell 1
cell
1. Cells are too small that they cannot be seen
with the naked eye; they can only be clearly
seen under a microscope.

Cell size and scale Normal cell division
stops
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SCIENCE INFO
SC I I I I I E N C E INFO Uncontrolled continuous
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cancer cell division
An English scientist, Robert Hooke was the Figure 2.2 Normal cell and cancer cell division
first person to discover cells. He was observing
a slice of cork under a simple microscope 6. If not destroyed, cancer cells will divide
made by him when he found the cork consisted uncontrollably to form a tumour, an
of an arrangement of small units which were
separated by walls. He named these small units abnormal lump of cells.
as cells, which means small rooms in Latin.
What is a cell? What is done by a cell? Formation of tumour
2. Cells carry out life processes like respiration,
growth, reproduction and excretion.
3. Cells also undergo cell division, a process by
which a single cell divides into two or more Cancer cell Normal cell
cells. division
Figure 2.3 The formation of tumour
7. Tumours can destroy surrounding cells.
8. A tumour can invade surrounding cells and
spread from one part of the body to another
which then leads to the malfunctions of the
body parts. This is called cancer.
Figure 2.1 Cell division
4. Cell division is essential for the growth of
living things and in producing new cells to
replace damaged or dead cells.
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