Cells and Organisms
Cells are the smallest units of life; all living organisms are made of cells, which carry out essential life processes.
What You Need to Know
Key Concept Diagram
The cell is the basic structural and functional unit of all living things
Unicellular organisms (e.g. bacteria, amoeba) consist of a single cell; multicellular organisms (e.g. humans, trees) consist of many cells
Plant cells have a cell wall, chloroplasts, and a large vacuole; animal cells do not have these features
Cells are organised into tissues, tissues into organs, and organs into organ systems that work together
Key Vocabulary
Cell
The smallest unit of life capable of carrying out basic life processes
Unicellular
Made up of only one cell (e.g. bacteria, amoeba)
Multicellular
Made up of many cells working together (e.g. humans, plants, animals)
Cell membrane
A thin, flexible layer surrounding all cells that controls what enters and leaves the cell
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
Which structure is found in plant cells but NOT in animal cells?
Question 2
A bacterium is an example of which type of organism?
Question 3
In what order are cells organised from smallest to largest level?
Key Concepts Summary
- ●The cell is the basic structural and functional unit of all living things
- ●Unicellular organisms (e.g. bacteria, amoeba) consist of a single cell; multicellular organisms (e.g. humans, trees) consist of many cells
- ●Plant cells have a cell wall, chloroplasts, and a large vacuole; animal cells do not have these features
- ●Cells are organised into tissues, tissues into organs, and organs into organ systems that work together