The cell is the basic structural and functional unit of living organisms. Some organisms, such as an amoeba, carry out life processes within a single cell. Multicellular organisms contain many cells, often with specialised structures that help them perform particular jobs.
Parts of a typical cell
The cell membrane forms a boundary and regulates the movement of substances into and out of the cell. The cytoplasm contains cell components and is the site of many reactions. In a typical plant or animal cell, a nucleus contains genetic material and helps control cell activities.
Not every cell has all the structures shown in a simple textbook diagram. Bacteria, for example, do not have a membrane-bound nucleus. A diagram is a useful model, rather than a picture of every possible cell.
- A group of similar cells working together forms a tissue.
- Cells differ in shape and size according to their roles.
Plant and animal cells
Plant cells have a cell wall outside the cell membrane. Many have a large central vacuole. Chloroplasts in green plant parts contain chlorophyll and carry out photosynthesis. Typical animal cells lack a cell wall and chloroplasts.
A root cell usually does not contain chloroplasts, even though it is a plant cell. When comparing cells, separate features that are common to most cells from those found only in particular tissues.
Put it into practice
A worked example
A diagram shows a rigid outer wall and a large central vacuole. Is it more likely a plant or animal cell?
- Identify the labelled structures rather than relying only on the outline.
- A cell wall and a large central vacuole are typical features of plant cells.
Answer: It is more likely a plant cell.
Try it yourself
Have a go before revealing the answer.
Which boundary regulates movement into and out of a cell?
Show answer
The cell membrane.
Answer: The cell membrane.
Why is ‘all plant cells have chloroplasts’ incorrect?
Show answer
Many non-green plant cells, such as typical root cells, do not have chloroplasts.
Answer: Many non-green plant cells, such as typical root cells, do not have chloroplasts.
Watch out for these
- Do not use cell wall and cell membrane as interchangeable names.
- The nucleus is a cell component, not a separate cell inside the cell.
Continue with official resources
Match these concept notes to your current textbook and syllabus. They are independent explanations, not official board publications.
