Cell structure and organisation for N(A)-Level Science (Biology): the parts of animal and plant cells, how cells are specialised, levels of organisation, and using the light microscope to calculate magnification

What this module covers

Cell structure and organisation is the starting point of N(A)-Level Science (Biology). The cell is the basic unit of all living things, so you need to know the parts of animal and plant cells and what each one does, how cells are specialised for particular jobs, how cells build up into the whole organism, and how to use a light microscope and work out how much bigger the image is. These ideas underpin almost every later topic.

This overview links every dot point in the module. Work through them in order, then check yourself with the questions at the end. See the full set at /sg-n-level/biology/syllabus.

The parts of animal and plant cells

Begin with the structures inside a cell. The page on animal and plant cell structure names the parts of each cell and states the function of each: the cell membrane controls what enters and leaves, the cytoplasm is where reactions happen, the nucleus holds the genetic information, and the mitochondria are the site of respiration. A plant cell has three extra features: a cell wall for support, chloroplasts for photosynthesis, and a large vacuole that stores cell sap. Learn each part with its job, because questions often give a diagram and ask you to label and explain.

Specialised cells and levels of organisation

Cells are not all the same. The page on specialised cells and organisation explains how a cell's structure suits its job, with examples such as the red blood cell, the root hair cell and the nerve cell. It then climbs the ladder of organisation: similar cells form a tissue, tissues form an organ, organs form an organ system, and organ systems form the whole organism.

Using the light microscope and magnification

Finally, the practical skill. The page on using the light microscope and magnification explains how to prepare a simple slide, how to focus from low to high power, and how to calculate magnification from the image size and the actual size. The formula is the part most often tested, so practise rearranging it and converting units.

How this module is examined

At N(A) level there is no standalone pure Biology paper. Biology is taken as part of a combined Science subject, either Science (Physics, Biology) syllabus 5106 or Science (Chemistry, Biology) syllabus 5107, so this module is examined within whichever combination your school offers.

• Label and explain. A diagram of a cell may be given; name each part and state its function, and remember the three features unique to plant cells.
• Match structure to job. For specialised cells, link one named feature to the function it makes possible.
• Use the formula carefully. Convert both measurements to the same unit before dividing, and remember magnification has no units.

Check your knowledge

A mix of recall, comparison and calculation questions. Attempt them, then check against the solutions.

1. State three parts found in a plant cell but not in an animal cell. (3 marks)
2. Explain how a red blood cell is adapted to carry oxygen. (2 marks)
3. A cell is drawn 40 mm wide at a magnification of 200. Calculate its actual size in micrometres. (2 marks)
4. Put these in order, smallest first: organ, cell, organism, tissue, organ system. (1 mark)