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AQA GCSE Biology 8461

1. Cell Biology

Cell biology

Every living thing is built from cells, and every cell is one of two kinds. The dividing line is simple: is the DNA shut inside a nucleus, or not?

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156 questions5 subtopicsFoundation tier1 required practical

What cell biology covers

Every subtopic below has its own questions, mark schemes and notes.

4.1.1.1Eukaryotes & prokaryotes

Every living thing is built from cells, and every cell is one of two kinds. The dividing line is simple: is the DNA shut inside a nucleus, or not?

4.1.1.2Animal & plant cells

Plant cells contain everything an animal cell has, plus three extras. Learn the animal list first, then add the three.

4.1.1.3Cell specialisation

A specialised cell has a shape and a set of structures that suit one particular job. Six examples are needed: three animal, three plant.

4.1.1.4Cell differentiation

Differentiation is a cell becoming specialised. It is not the same as cell division, which is a cell making more cells.

4.1.1.5Microscopy

Microscopes have improved as technology has, letting us see more detail. Two ideas run through this topic: magnification and resolution are different things, and units must always match before you calculate.

Key terms

The definitions examiners expect, in the wording that earns the mark.

Eukaryote — An organism whose cells keep their genetic material inside a nucleus.
Prokaryote — A single-celled organism whose genetic material is not enclosed in a nucleus.
Plasmid — A small ring of DNA, separate from the main DNA loop, found in some bacteria.
Chlorophyll — The green pigment inside chloroplasts that absorbs light for photosynthesis.
Cell sap — The weak solution of sugar and salts filling a plant cell's permanent vacuole.
Cellulose — The material a plant cell wall is made from.
Specialised cell — A cell whose structure is adapted to carry out one particular function.
Differentiation — The process by which a cell changes to become specialised for a specific function.
Stem cell — An undifferentiated cell.
Magnification — How many times larger the image is than the real specimen.
Resolution — How well a microscope can distinguish between two points that are very close together.
Stain — A liquid such as iodine solution that adds colour to structures so they are easier to see.

Where marks get lost

The mistakes that come up again and again in this topic.

  • 'Bacteria have no DNA' is wrong and costs marks. They have DNA — it just isn't in a nucleus.
  • Ribosomes are never a valid difference between prokaryotes and eukaryotes: both have them.
  • Bacteria do have a cell wall. The structures they lack are the nucleus, mitochondria and chloroplasts.
  • Chloroplast is the structure; chlorophyll is the pigment inside it. Mixing the words up loses the mark.
  • The word 'permanent' matters — animal cells can have small temporary vacuoles.
  • The nucleus controls the cell through its genetic material; the enzymes in the cytoplasm control the chemical reactions.
  • Adaptation questions want the feature AND why it helps. 'It has lots of mitochondria' alone is half an answer.
  • The tail makes a sperm swim, but the mitochondria supply the energy. Check which the question asks for.
  • A specialised cell only keeps the structures its job needs — that reasoning works on unfamiliar cells too.
  • Differentiation = becoming specialised. Division = making more cells. Examiners test that you can tell them apart.
  • The animal/plant comparison is worth two marks: say what happens in each, not just one.
  • Check units first, calculate second.
  • Start on the lowest-powered objective lens. Starting high risks hitting the slide and makes the specimen hard to find.
  • A light microscope can show mitochondria as blobs — it is their internal structure that needs an electron microscope.

Other topics

Transport in cells Cell division Organisation in animals Enzymes and the human digestive system Plant tissues, organs and systems Non-communicable disease Communicable disease and plant defences Preventing and treating disease Monoclonal antibodies Photosynthesis Respiration Homeostasis and the nervous system Hormonal coordination DNA, genes and variation Reproduction Evolution and Classification Adaptations, interdependence and competition Organisation of an ecosystem Humans and biodiversity Working scientifically Practical skills

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