Cell Biology - Passive and active transport T1

Question 1

Concentration Gradient

Answer 1

The difference between two concentrations is known as the concentration gradient.

Question 2

Passive Transport

Answer 2

Passive transport of materials can occur across a cell membrane. This process does not require energy to take place because the substances move down the concentration gradient – from high concentration to low concentration.

Question 3

Diffusion

Answer 3

Diffusion is the movement of molecules down a concentration gradient from a region of high concentration to a region of low concentration until the concentrations are equal.

Question 4

Diffusion in cells

Answer 4

In cells, diffusion occurs as molecules move down a concentration gradient from a higher concentration to a lower concentration. This is important to cells as it enables useful substances to enter the cell and waste substances to leave. As your cells respire they use up oxygen and as a result the concentration of oxygen in your blood is higher than in your cells and oxygen continually diffuses in. As carbon dioxide is produced as a product of respiration the concentration in your cells is higher than in your blood and carbon dioxide continually diffuses out.

Question 5

Osmosis

Answer 5

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

Question 6

Animal Cell Shrinks

Answer 6

When there is a lower water concentration outside the cell – water moves out of the cell and the cell shrinks.

Question 7

No Net Movement

Answer 7

When water concentrations are equal outside and inside of the cell there is no net (overall) movement of water.

Question 8

Animal Cell swells and bursts

Answer 8

When there is a higher water concentration outside the cell – water moves into the cell and the cell swells and then bursts.

Question 9

Plant cell is Plasmorysed

Answer 9

When there is a lower water concentration outside of the cell – water moves out of the cell, causing the vacuole to shrink and cell contents to shrink away from the cell wall. Cell is plasmolysed.

Question 10

Plant cell is turgid

Answer 10

When there is a higher water concentration outside of the cell – water moves into the cell, causing the vacuole to swell and cell contents to push against the cell wall. Cell is turgid.

Question 11

Active Transport

Answer 11

Active transport is the movement of molecules and/or ions by membrane proteins from a region of low concentration to a region of high concentration. As this movement goes against the concentration gradient it requires energy in the form of ATP.