Cells biology AQA Additional Science

The cards contain information for animal and plant cells, specialised cells, osmosis and diffusion to help with AQA Biology Additional Science. You need to know: that cells may be specialised to carry out a particular function, dissolved substances pass into and out of cells by diffusion and water passes into and out of cells by osmosis.

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  • Created by: Rukhsar
  • Created on: 21-03-10 15:56

Cell parts

An animal and plant cells have a nucleus, cytoplasm, a cell membrane, mitochondria and ribosomes. A plant cell also has a cell wall, chloroplasts and a permanent vacuole. Here are the functions of each of the cell parts.

A nucleus contains genetic material, which controls the activities of the cell.

Cytoplasm is where most chemical processes take place, which are controlled by enzymes.

Cell Membrane controls what goes in and out of a cell.

Mitochondria is where most energy is released by respiration.

Ribosomes is where protein synthesis happens.

Cell wall strengthens the cell and supports the cell.

Chloroplasts contains chlorophyll for photosynthesis.

Permanent vacuole is filled with cell sap to help the cell turgid.

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Here are examples of specialised cells.

A leaf cell absorbs light energy for photosynthesis. It is packed with chloroplasts and is regular shaped. The closely packed cells form a continuous layer for efficient absorption for sunlight.

A root hair cell absorbs water and mineral ions from the soil. It has a long 'finger-like' process with a very thin wall, which gives a large surface area.

A sperm cell fertilises an egg cell which is a 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.

A red blood cell contains haemoglobin to carry oxygen to the cells. It has a thin outer membrane to let oxygen diffuse through easily. The shape increases the surface area to allow more oxygen to be absorbed efficiently. It has no nucleus, so the whole cell is full of haemoglobin.

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Diffusion and osmosis

Dissolve substances have to pass through the cell membrane to get into or out of a cell. Diffusion is one of the processes. Diffusion occurs when particles spread. They move from high concentration to low concentration. Examples of diffusion are:

  • The gut-particles move digested food products from the gut cavity to blood in capillary of villus.
  • The lungs-particles move oxygen from the alveolar air space to blood circulating around the lungs.

Diffusion is the random movement of molecules. The larger the concentration the faster the diffusion. Diffusion doesn't require energy. Particles move randomly through vibration. Water can move across cell membranes because of osmosis. For osmosis to happen you need two solutions with different concentrations and a partially permeable membrane to separate them. Osmosis is the movement of water from a less concentrated solution to a more concentrated solution through a partially permeable membrane. Osmosis is important in plants. they gain water by osmosis through their roots. Water moves into plant cells by osmosis, making them turgid or stiff so that they are able to hold the plant upright.

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