Page 128 - Knowledge Organiser Yr9 24-25

Knowledge Base: Science B1: Cell Biology Year 9
7. Osmosis
7.1
What is osmosis?
The movement of water particles from a dilute solution to a concentrated solution through a partially permeable membrane.
7.2
How can you calculate the percentage change in mass?
change in mass x 100 starting mass
8.6
Explain what is happening to the carrot cell in Figure 6 at salt concentration of 0.8 mol/dm3
Mass of the carrot decreased, as the cells lost water due to osmosis. The water moved out of the cell as the concentration of the salt within the carrot cells is greater than the concentration of the salt solution.
8.7
Use the graph (Figure 6) to determine the salt concentration in the plant cell. Explain why.
Q = 0.3 mol/dm3
There is no overall movement of water, showing that the concentration of the salt solution is equal to the concentration of salt inside the cell.
8. Osmosis in Plant Tissues
8.1
When preparing plant tissue to investigate osmosis, why should you use a cork borer to cut the plant tissue (e.g. potato)?
So each piece of plant tissue has the same diameter (to act as a control variable).
8.2
What measurements should be taken to investigate osmosis in plant tissue?
So each piece of plant tissue has the same diameter (to act as a control variable).
8.3
Name two ways to reduce error when investigating osmosis in plant tissue.
• Blot the plant tissue dry so excess water/solution is removed before making measurements.
• Place a bung on the tube to prevent the evaporation of water (which would change the concentration of the solution).
8.4
Why is it important to calculate the percentage change in mass of the plant tissue when investigating osmosis?
Difficult to control the starting mass of the plant tissue.
8.5
Explain what is happening to the carrot cell in Figure 6 at salt concentration of 0.1 mol/dm3
Mass of the carrot increased, as the cells gained water due to osmosis. The water moved into the cell as the concentration of the salt solution is greater than the concentration of salt in the carrot cells.
9. Active Transport
9.1
What is active transport?
The movement of substances from a dilute solution to a more concentrated solution (against a concentration gradient).
9.2
What does active transport require? Why?
Energy from respiration - moving against the concentration gradient.
9.3
Name an example of a substance that is moved by active transport in plants.
Mineral ions moving from dilute solutions in the soil into the root hair cell.
9.4
Name an example of a substance that is moved by active transport in animals.
Sugar molecules moving from lower concentrations in the gut to higher concentrations in the blood.
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