iGCSE Biology Section A

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

(MRS GREN)

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.

Animal + plant cells

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

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

Absorbs water and mineral ions from the soil.

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.

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.

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-
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.