ZIMSEC O Level · Combined Science · Form 1
All living things are made of cells. Living things carry out seven life processes: movement, respiration, sensitivity, growth, reproduction, excretion and nutrition (MRS GREN).
Animal and plant cells
- Both have: a cell membrane (controls what enters and leaves), cytoplasm (where reactions happen), a nucleus (controls the cell and carries genetic information) and mitochondria (release energy in respiration).
- Plant cells also have: a cellulose cell wall (support), chloroplasts (photosynthesis) and a large permanent vacuole filled with cell sap.
Levels of organisation
Cells → tissues → organs → organ systems → organism. For example, muscle cells form muscle tissue; tissues form the heart; the heart and blood vessels form the circulatory system.
Specialised cells
- Red blood cells have no nucleus and contain haemoglobin to carry oxygen.
- Root hair cells have a long extension that increases the surface area for absorbing water.
- Sperm cells have a tail for swimming.
Using a microscope
Total magnification = eyepiece magnification × objective magnification. Start with the lowest power objective and focus with the coarse knob, then the fine knob.
Exam tip: In exams, “compare” means give similarities AND differences, usually in a table.
Check yourself
- Name two structures found in plant cells but not in animal cells.
- State the function of the nucleus.
- An eyepiece of ×10 is used with an objective of ×40. What is the total magnification?
Show answers
- Any two of: cell wall, chloroplasts, large permanent vacuole.
- It controls the activities of the cell and carries genetic information.
- ×400
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