Cells

Both: - Nucleus: Control centre

            - Cytoplasm: chemical reactions

            - Cell membrane: controls movement of materials

            - Mitochondria: energy released during aerobic respiration

            - Ribosomes: proteins are made

Only Plant cells: - Cell wall: support

                                 - Chloroplasts: contain chlorophyll for photosynthesis

                                 - Vacuole: cell sap

Materials that move across membrane E.G.s: CO2, glucose, oxygen

Red Blood Cells: - No nucleus

                              - Contains haemoglobin

            Neurone: - Send electronic signals

       Sperm Cells: - Enzymes in head to eat away at egg cell layer

                              - Tail to swim

                              - Lot's of Mitochondria for oxygen for energy

     Muscle Cells: - Contract

                             - Lot's of Mitochondria

       Gland Cells: - Secrete hormones and fluids in the body

          Egg Cells: - Very large

  Root Hair Cell: - Thin membrane so water and nutrients is easily absorbed

Epidermal Cell: - Waxy layer to reduce water loss

   Palaside Cell: - Top of leaf 

                           - Lot's of chloroplasts

            Fat Cell: - Contain less cytoplasm so they can store a lot of fat

      Guard Cell: - Bottom of leaf in pairs

                          - Open to let water and gas out of the plant

      Xylem Cell: - Hollow

                          - Transport water around the plant

Diffusion: The random movement of molecules from an area of high concentration to an area of lower concentration (down a concentration gradient)

The rate is quicker if: bigger difference of concentration, shorter distance, higher temperature

Examples:

- Diffusion of oxygen into cells of the body from the blood stream as the cells are respiring (using up oxygen)

- Diffusion of carbon dioxide into actively photosynthesising plant cells

- Diffusion of simple sugars and amino acids from the gut through cell membranes

• THE MOVEMENT OF WATER!

• The movement is random and requires no energy from the cell

• The diffusion of water across a partially permeable membrane into or out of a cell (depending on concentration of inside and outside of the cell)

• From a dilute solution to a more concentrated solution:

• From a high to low concentration of water

• No solute molecules can move across the mebrane

• Water is needed to support cells and because chemical reactions take place in solution