Animal and plant cells: structures and functions

Not every plant cell has chloroplasts: root cells, which grow in the dark, don't. See our guide to the photosynthesis equation.

Bacteria are much smaller than animal and plant cells. They have cytoplasm, a cell membrane, a cell wall (not made of cellulose) and ribosomes, but no nucleus: their DNA is a single circular loop in the cytoplasm, and many also have small rings of DNA called plasmids. Some have a flagellum to help them move.

Many cells are adapted for a particular job:

• Red blood cells: no nucleus, leaving more room for haemoglobin to carry oxygen.
• Sperm cells: a tail to swim and many mitochondria for energy.
• Root hair cells: a long extension with a large surface area for absorbing water.
• Palisade cells: packed with chloroplasts for photosynthesis.

Light microscopes show cells, nuclei and chloroplasts. Electron microscopes have much higher magnification and resolution, revealing ribosomes and the inside of mitochondria. Work out sizes with our magnification calculator and practise with our magnification questions.

• Saying plant cells have a cell wall instead of a membrane (they have both).
• Saying mitochondria "make energy" (they release it, in respiration).
• Forgetting that bacteria have DNA, just not in a nucleus.

Learn how cells divide in our guide to mitosis and meiosis.

Cells are measured in micrometres (µm), thousandths of a millimetre. A typical animal cell is roughly 10 to 30 µm across, plant cells are often larger, and bacteria are usually a few micrometres long, around a tenth of the size of an animal cell. That's why you need a microscope to see them, and why the units in magnification questions matter.

1. Which cell structure is the site of photosynthesis?
2. Name three structures found in plant cells but not animal cells.
3. Why do red blood cells have no nucleus?
4. Where is the genetic material in a bacterial cell?

Answers: 1. Chloroplasts. 2. Cell wall, chloroplasts, permanent vacuole. 3. To leave more room for haemoglobin, so they can carry more oxygen. 4. In a single DNA loop in the cytoplasm, and in plasmids.

• When drawing a cell from a microscope, use clear, continuous lines, no shading, and label with ruled lines.
• Learn each structure as a pair: structure and function.
• Read whether the question asks about a plant cell, an animal cell or a bacterium, since each has different structures.