B3- Transport in Cells

Question 1

Definition - Diffusion

Answer 1

A net movement of particles from an area of higher concentration to an area of lower concentration.

Question 2

Main factors that affect diffusion (3)

Answer 2

• Concentration gradient (larger gradient, faster diffusion)
• Temperature (higher temperature, faster diffusion)
• SA:V ratio (larger surface area, faster diffusion)

Question 3

Examples of diffusion (2)

Answer 3

• Lungs- Oxygen diffuses into the blood from the lungs (alveoli) and carbon dioxide diffuses from the blood back into the lungs (alveoli) to be exhaled out of the body
• Kidneys- Urea diffuses from cells into blood plasma so it can be excreted in urine.

Question 4

How are haploid celled organisms adapted for diffusion?

Answer 4

Large SA:V ratio - maximises rate of diffusion across a short diffusion distance to meet the organism’s needs.

Question 5

How is SA:V ratio calculated?

Answer 5

SA = No. of sides x (side width x side length)

Question 6

Factors that increase the effectiveness of a gas exchange surface (4)

Answer 6

• Large Surface Area
• Thin membrane (short diffusion pathway)
• Efficient blood supply (animals)
• Ventilation (animals)

Question 7

Definition - Osmosis

Answer 7

Movement of water from a dilute solution to a concentrated solution through a partially permeable membrane.

Question 8

Definition- Isotonic

Answer 8

The concentration inside and outside the cell are equal.

Question 9

Definition- Hypertonic

Answer 9

The concentration is higher OUTSIDE the cell.

Question 10

Definition- Hypotonic

Answer 10

The concentration is higher INSIDE the cell.

Question 11

What would happen if an animal was placed in a very hypotonic solution?

Answer 11

Water moves into the cell, causing it to burst.

Question 12

What would happen if an animal was placed in a very hypertonic solution?

Answer 12

Water moves out of the cell, causing it to shrivel up.

Question 13

How do plants leaves and stems remain rigid?

Answer 13

Turgor pressure- water moves in by osmosis, causing the vacuole to swell and the cytoplasm to press against the cell wall.

Question 14

What would happen if a plant was placed in a very hypertonic solution?

Answer 14

The water moves out of the cell via osmosis and the vacuole and cytoplasm shrink (decrease in size). The cell membrane may pull away from the cell wall, causing the cell to be plasmolysed.

Question 15

Definition- Active Transport

Answer 15

Movement of molecules from a low (more dilute) concentration to a high (more concentrated) concentration using energy from respiration.

Question 16

Example of Active Transport - Root Hair Cell

Answer 16

Takes up mineral ions from the ground into the roots of the plant. Ions like magnesium and nitrate ions are required for healthy growth.

Question 17

Example of Active Transport - Gut to blood

Answer 17

Transports glucose from a lower concentration in the gut to a higher concentration in the blood. Glucose is then transported to the tissues where it can be used for respiration.