IGCSE Biology Section A (Organisms and Life processes)

IGCSE Section A Biology Notes :)


Characteristics of living things

  • Nutrition ( needing food )
  • Excretion ( removing waste products )
  • Movement ( of all or part of organism )
  • Growth and development
  • Respiration ( getting energy from food )
  • Response to stimuli ( changes )
  • Reproduction ( producing offspring )
  • Controlling internal environment


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Animal Cell


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Plant Cell


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Enzymes are biological catalysts that control all the reactions in a cell. A catalyst speeds up a reaction without being used up or changing the reaction. Enzymes are made of proteins which are made in the ribosomes.


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Table of what cells do

nucleus contains genetic material, which controls the activities of the cell cytoplasm most chemical processes take place here, controlled by enzymes cell membrane controls the movement of substances into and out of the cell mitochondria most energy is released by respiration here ribosomes protein synthesis happens here

Plant cells also have extra parts:

cell wall strengthens the cell chloroplasts contain chlorophyll, which absorbs light energy for photosynthesis permanent vacuole filled with cell sap to help keep the cell turgid

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Leaf Cell

Absorbs light energy for photosynthesis.

Packed with chloroplasts. Regular shaped, closely packed cells form a continuous layer for efficient absorption of sunlight.


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Root hair cell

Absorbs water and mineral ions from the soil.

Long 'finger-like' process with very thin wall, which gives a large surface area.


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Sperm Cell

Fertilises an egg cell - female gamete.

The head contains genetic information and an enzyme to help penetrate the egg cell membrane. The middle section is packed with mitochondria for energy. The tail moves the sperm to the egg.


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Red Blood Cell

Contain haemoglobin to carry oxygen to the cells.

Thin outer membrane to let oxygen diffuse through easily. Shape increases the surface area to allow more oxygen to be absorbed efficiently. No nucleus, so the whole cell is full of haemoglobin.


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Variety of living organisms

Bacteria- All bacteria have the same basic structure. Most bacteria cells have a cell wall. The cell wall is rigid and provides protection for the bacteria cell.Beneath the cell wall is the cell membrane.Since bacteria cells do not have a nucleus, DNA floats around in cytoplasm. 


Fungi are eukaryotes like plants and animals so they have the same cell structure however,unlike plants and animals; fungi have some special characteristics which plants and animals do not.

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