UWCSEA IGCSE Biology B2 - Diffusion and Osmosis

What would happen if a red blood cell was placed into concentrated sugar solution? Why?

When red blood cells are placed into concentrated sugar solutions, osmosis moves the water from the red blood cells out so they shrink.

semi permeable membrane

partially permeable membrane

Why is water important in diffusion in living things?

As water is the universal solvent, for the dissolving of a substance. A solute dissolves in a solvent. A concentrated solution has a large mass of solute dissolved in a given volume of the solvent.

What is diffusion? Define it

Diffusion is the movement of molecules from a place of higher concentration to a place of lower concentration.

What would happen if a plant cell was placed into a concentrated sugar solution (lots of sugar dissolved in water) Why?

For osmosis, there has to be a lower concentrated solution to higher concentrated solutions and since concentrated sugar solution is a higher so the process reverses and stops. It doesn't start reverse osmosis as that needs energy but it stops and nothing happens.

Give an example of diffusion of gases in living things- what is diffusing? From where to where? Why is this useful?

Gas exchange and respiration because we breath in oxygen which diffuses through a partially permeable membrane and then carbon dioxide is

What is a water potential gradient? How is it important in plants taking in water?

It is the difference in water potential between two regions. If there is a difference, water will move from a region of higher water potential to a region of lower potential. We call this 'going along the water potential gradient'.

How is osmosis important in plants taking water in? Explain

Osmosis in plants is vital because it helps in the uptake of water in plants, and water is essential for the plant to survive. It's how they gain the needed vitamins.

What is osmosis? Define it

Osmosis is a special kind of diffusion involving water molecules and occurs when 2 solutions are separated by a partially permeable membrane. A dilute solution into a more concentrated solution. It is from places of lower concentration to places of higher concentration. The solvent always.

What would happen if a plant cell was placed into a pure water? Why?

Plant cells become turgid. Turgid means swollen. When a plant cell is placed in water, the water enters the cell due to osmosis as the cell membrane is partially permeable. As the water enters the cell it swells up, and the cell becomes turgid.

What factors can speed up diffusion? How do they speed it up?

Temperature; Faster movement of molecules as well as more collisions. Higher temperature leads to a faster diffusion. The distance molecules have to travel. The size of the molecules; smaller molecules diffuse faster than larger ones. Surface area; larger surface area allows many molecules to cross. Concentration gradient; Higher the concentration gradient, the faster the diffusion/lower the concentration gradient, the slower the diffusion

What would happen if a red blood cell was placed into pure water? Why?

The red blood cell would burst as the concentration in the red blood cell is higher and it will fill up with water and burst. Water diffuses by osmosis from a region of high water potential to low water potential.

How is osmosis used in plants? Describe in detail.

The root hair cells absorbs the minerals and water through the osmosis problem. The cells in the root are more concentrated than the outside and since osmosis takes place from a place of lower concentration to a place of higher concentration through/via a semi permeable membrane.