2.15-2.17 Movement of Substances In and Out of Cells

What is diffusion?

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

What is osmosis?

Osmosis is the movement of water molecules from a region of higher water concentration to a region of lower water concentration through a partially permeable membrane.

What happens to animal cells in a strong sugar solution?

Animal cells lose water and become (shrivelled).

What is the effect of osmosis on plant cells in distilled water?

Plant cells gain water, making them turgid as the vacuole expands.

What is active transport?

Active transport is the movement of particles across a cell membrane from a region of lower concentration to a region of higher concentration, requiring energy.

How does temperature affect diffusion?

Higher temperatures result in faster movement of molecules, increasing the rate of diffusion.

What is a key requirement for active transport?

Energy as it moves particles up a concentration gradient

What is the significance of a partially permeable membrane in osmosis?

Partially permeable membranes allow the movement of water while preventing larger molecules from passing through.

How does surface area to volume ratio affect diffusion?

A larger surface area to volume ratio increases the rate at which substances can diffuse across a cell's surface.

What is the result of osmosis in potato cylinders placed in strong sucrose solution?

They lose mass as water moves out of the cells, making them flaccid.

What effect does diffusion distance have on the rate of diffusion?

The smaller the distance molecules have to travel, the faster the rate of diffusion.

How can you measure the impact of temperature on the rate of diffusion?

You can investigate by using beetroot cells and observing the pigment leakage at different temperatures.

What is the outcome of a potato cylinder in a solution with the same solute concentration as the cytoplasm?

There will be no net movement of water, meaning the mass of the potato cylinder will remain unchanged.

What is required to conduct an experiment investigating factors affecting osmosis?

You need potato cylinders, sucrose solutions of varying concentrations, and measurements before and after immersion.

Hypertonic(Concentration)

Water potential is higher inside the cell so net movement of water out. This causes cells to be shrivelled

Hypotonic (Dilute)

Water potential is higher outside the cell so net movement of water is in. This cause cells to be turgid(cell swelling and may burst)

Describe an example where diffusion of gases is important in mutli-cellular organisms?

Gas exhange in lungs for respiration. Oxygen moves from alveoli into blood. While carbon dioxide moves from the blood into the alveoli.

3 features of gas exchange that maximises diffusion(3)

short diffusion distance, steep concentration gradient, large surface area for exchange

How does temperature affect the rate of movement of substances

Higher the temperature → More kinectic energy → faster the molecules move as they have high energy

How does the concentration gradient affect the movement of substances?

Steeper the concentration gradient, faster the diffusion