we Are ForMeD of CeLLS

Refresh What different types of cells are there?

4 What is a cell?

A cell is the most basic unit in living organisms: they are made up of cells. Cells are microscopic and we can only see them with a microscope. Cells perform the three vital functions. Living organisms are unicellular when they are made up of only one cell (such as bacteria and yeast). Other living organisms are multicellular and they are made up of more than once cell. Human beings, for example, have got more than 100 trillion cells. Cells contain the genetic material necessary to keep an organism alive. Cells are different shapes and sizes depending on what type of cell they are.

Bacteria are unicellular.

Plants are multicellular.

1 In your notebook, correct these false statements about cells.

a) All cells are similar in shape and size.

b) Cells do not contain genetic material.

c) All living organisms consist of a variety of cells.

d) Cells are not alive.

• Search online and find microscopic images of cells in different living organisms. Prepare a presentation with the pictures and the name of each living organism.

5 Types of cells

There are two types of cells.

• Eukaryotic cells have got a nucleus which contains the genetic material.

• Prokaryotic cells haven’t got a nucleus. The genetic material is in the cytoplasm.

Parts of a cell

All cells have the same basic components: a membrane, cytoplasm and genetic material.

• The cell membrane is a thin wall that surrounds and protects the cell. It controls the substances that enter and leave the cell.

• The cytoplasm is the fluid that fills the inside of the cell. It contains the organelles, which perform different functions.

• Genetic material controls the cell’s activity.

2 Answer the following questions in your notebook: a) What is a multicellular living organism? b) Are bacteria unicellular or multicelullar? c) What is an eukaryiotic cell? d) Where is the genetic material in a prokaryotic cell?

3 Draw and label a diagram of a eukaryotic cell and a prokaryotic cell in your notebook.

4 Explain the function of the cell membrane, the cytoplasm and the genetic material.

5 With a classmate, identify the basic components in the following cells.