1. How can we smell our dinner being made in the room next door? diffusion diffusion diffusion

2. Diffusion Diffusion is the movement of particles from a region where they are concentrated to a region where they are less concentrated Diffusion is the movement of particles from a region where they are concentrated to a region where they are less concentrated No energy is needed for Diffusion to take place. It is a Passive process. No energy is needed for Diffusion to take place. It is a Passive process.

3. It is important in the movement of substances between cells and inside cells (occurs only over short distances, no more than 1mm) It is important in the movement of substances between cells and inside cells (occurs only over short distances, no more than 1mm) Hence, larger organisms will require Transport systems as well i.e. circulatory system in humans Hence, larger organisms will require Transport systems as well i.e. circulatory system in humans

4. Osmosis Osmosis is the movement of water molecules across a semi-permeable membrane, from an area of high concentration of water molecules to an area of low concentration of water molecules. Osmosis is the movement of water molecules across a semi-permeable membrane, from an area of high concentration of water molecules to an area of low concentration of water molecules.

5. Cell Membrane & Osmosis The cell membrane controls movement of substances into and out of the cell The cell membrane controls movement of substances into and out of the cell It is semi-permeable i.e. it allows small molecules like water, carbon dioxide and oxygen through by diffusion but stops larger ones. It is semi-permeable i.e. it allows small molecules like water, carbon dioxide and oxygen through by diffusion but stops larger ones. Where energy is required to move molecules in and out of cells is called Active transport Where energy is required to move molecules in and out of cells is called Active transport

6. Osmoreregulation Our cells contain sugar and salt at certain concentrations. Our cells contain sugar and salt at certain concentrations. If these concentrations change, action is taken by cells to counteract the changes and return to the normal balanced state. If these concentrations change, action is taken by cells to counteract the changes and return to the normal balanced state. This balancing action is called Osmoregulation. This balancing action is called Osmoregulation.

7. Osmosis in Animal Cells Animal Cells in Pure water Red blood cells have 1% salt concentration in them. Red blood cells have 1% salt concentration in them. What would happen if a red cell is placed in pure water? What would happen if a red cell is placed in pure water? The Cytoplasm swells up with water and eventually the cell may burst and die. The Cytoplasm swells up with water and eventually the cell may burst and die. Animal cells in Salt water What would happen if a red cell is placed in a very salty solution? What would happen if a red cell is placed in a very salty solution? Experiences a loss of water which causes the cell to shrivel up. Experiences a loss of water which causes the cell to shrivel up.

8. Osmosis in Plant Cells Plant Cells in Pure Water Onion cells have Salt and Sugar in their cytoplasm. Onion cells have Salt and Sugar in their cytoplasm. What happens if an onion cell is placed in pure water? What happens if an onion cell is placed in pure water? The cytoplasm & vacuole fill up with water, which stretches the cell. The cytoplasm & vacuole fill up with water, which stretches the cell. The cell wall prevents the cell from bursting and the cell is said to be Turgid. The cell wall prevents the cell from bursting and the cell is said to be Turgid. Plant Cells in Salt Solution What happens if an onion cell is placed in a very salty solution? What happens if an onion cell is placed in a very salty solution? The cytoplasm & vacuole lose water. The cytoplasm & vacuole lose water. The cell membrane comes away from the cell wall, the cell is said to be Plasmolysed. The cell membrane comes away from the cell wall, the cell is said to be Plasmolysed.

9. Turgid describes a plant cell in which the cell wall is rigid, due to the cytoplasm pushing out against it as it fills with water. Osmotic pressure is the main cause of support in plant leaves (Without water the cell walls are not strong enough to support the weight of the plant, and so it Wilts)

10. Osmosis in Food Preparation Naturally occurring chemicals like salt, sugar and fruit juice will preserve foods by osmosis. Naturally occurring chemicals like salt, sugar and fruit juice will preserve foods by osmosis. Salt is the oldest and most common method of preserving fish and meats. Salt is the oldest and most common method of preserving fish and meats. Water moves, by osmosis, from the cells into the salt solution, causing the tissues to become dehydrated, which destroys bacteria. Water moves, by osmosis, from the cells into the salt solution, causing the tissues to become dehydrated, which destroys bacteria. Sugars are used to preserve fruits (jams/tinned fruit) Sugars are used to preserve fruits (jams/tinned fruit)

11. Active Transport In order for Large molecules to move across the cell membrane they must do so at certain ‘gates’ and the In order for Large molecules to move across the cell membrane they must do so at certain ‘gates’ and the cell has to use energy to do this. These ‘gates’ are proteins within the cell These ‘gates’ are proteins within the cell membrane, which pump the molecules across, often against the concentration gradient (from where there is less to where there is more of the substance) Active Transport is the movement of substances across a cell membrane against a concentration gradient, using energy from respiration. Active Transport is the movement of substances across a cell membrane against a concentration gradient, using energy from respiration. SOLUTE CONCENTRATION GRADIENT Fewer solute molecules More solute molecules Active transport of solute molecules