Cells - Plants, Animals & Bacteria Quiz

Structure and Function of Animal and Plant Cells

Understanding animal and plant cells’ basic structure and function is essential for GCSE biology. Both types of cells have the same sub-cellular structures, but plant cells have some extras and you need to know which are found where.

Sub-Cellular Structures in Animal Cells

1. Nucleus: The nucleus is the control centre of the cell. It contains genetic material (DNA) that directs all cell activities and controls cell growth, reproduction, and the synthesis of necessary molecules.
2. Cytoplasm: This jelly-like substance fills the cell and is where most chemical reactions happen. These reactions are essential for the cell’s survival and are controlled by enzymes present within the cytoplasm. One important reaction that takes place here is anaerobic respiration.
3. Cell Membrane: The cell membrane acts as a selective barrier that surrounds the cell, controlling the movement of substances in and out. It helps maintain the cell’s internal environment and protects it from the external surroundings. 
4. Mitochondria: Sometimes known as the powerhouse of the cell, mitochondria are the site of aerobic respiration. They convert glucose and oxygen into adenosine triphosphate (ATP), which is then used for energy around the body.
5. Ribosomes: These are the sites of protein synthesis. Ribosomes can be found floating within the cytoplasm or attached to a structure called the endoplasmic reticulum (but you don’t need to know about this for GCSE). Proteins created by ribosomes are essential for various cellular functions, including repair and growth.

Additional Sub-cellular Structures in Plant Cells

Plant cells share all the components found in animal cells but also have unique structures that support their specific roles.

1. Chloroplasts: These organelles are where photosynthesis occurs, allowing plants to produce glucose using sunlight, carbon dioxide, and water. Chloroplasts contain chlorophyll, the green pigment that captures light energy and makes plants look green.
2. Permanent Vacuole: The permanent vacuole is a large, fluid-filled sac that helps maintain cell rigidity and stores cell sap—a mixture of water, sugar, and other substances. The pressure from the vacuole helps keep the plant cell turgid, which is vital for supporting the plant structure.
3. Cell Wall: In addition to the cell membrane, plant and algal cells have a cell wall made of cellulose. This rigid structure strengthens the cell and provides additional support, helping the plant maintain its shape and resist external pressures.

Size and Measurement of Sub-Cellular Structures

Units of Measurement

Cells and their components are often measured using small units:

• Centimetre (cm): 1 cm = 10 millimetres.
• Millimetre (mm): 1 mm = 1,000 micrometres.
• Micrometre (μm): 1 μm = 1,000 nanometres.
• Nanometre (nm): This is one-billionth of a metre.

To convert between these units (except centimetres which are not commonly used in science) you can simply divide or multiply by 1000 depending on which direction you want to go. To convert metres to millimetres you can times by 1000, so in 5 m there are 5000 mm. If there are two or more steps simply do it again as many times as necessary. Learn more about this and get some practice in our quiz on Unit Conversions. Another important page you should check out after this is our quiz on Microscopy

One more thing, in the AQA specification it says you’re supposed to understand “Order of magnitude calculations”. That just means converting between metres and millimetres for example or from grams to kilograms. You also need to know how to use standard form and you can practice that here in our quiz on Standard Form. 

Practical Estimation

When analysing cell images or diagrams, estimating the size of sub-cellular structures can be useful for comparisons. For example, mitochondria are typically 0.5-10 μm (micrometres) long, while ribosomes are much smaller at around 20-30 nm (nanometres). Estimation allows students to make quick, logical judgments when exact measurements are unavailable.

When you take a second to use logic to check your answers, you can catch some basic errors and get a few extra marks for a little more effort.

Learn more about this topic on our page on Cells – Plants, Animals and Bacteria.