Gas exchange in plants

Question 1

What is Diffusion?

Answer 1

Movement of molecules from a region of high concentration to low concentration down a concentration gradient

Question 2

What is the role of Diffusion?

Answer 2

Diffusion (in the alveoli) allows oxygen into the blood and carbon dioxide into the alveoli.

Question 3

Pathway of carbon dioxide from atmosphere to chloroplasts by diffusion.

Answer 3

atmosphere → air spaces around spongy mesophyll tissue → leaf mesophyll cells → chloroplast

Question 4

What are the adaptations of leaves to maximise gas exchange?

Answer 4

• They are thin which gives a short diffusion distance.
• They are flat which provides a large surface area to volume ratio.
• They have many stomata which allow movement of gases in and out of the air spaces inside the leaf to maintain a steep concentration gradient.

Question 5

What are the adaptations of the internal leaf structure?

Answer 5

• Air spaces to allow gas movement around the loosely packed mesophyll cells.
• Many stomata in the lower epidermis open in sunlight to allow gas movement in and out of the leaf.
• Thin cell walls allow gases to move into the cells easily.
• Moist air which gases can dissolve into for easier movement into and out of cells.
• The close contact between the cells and the air spaces allows efficient gas exchange for photosynthesis and respiration.

Question 6

What is the stomata?

Answer 6

Stomata are spaces found in between the guard cells on the lower epidermis of the leaf.

Question 7

What is the role of guard cells?

Answer 7

They are responsible for the opening and closing of the stomatal pore which controls gas exchange and water loss.

Question 8

How does the plant cell become turgid?

Answer 8

When the stomata open when water moves (by osmosis) into the guard cells. They become turgid.

Question 9

How does the plant cell become flaccid?

Answer 9

When the stomata close when the guard cells lose water (by osmosis) to the neighbouring epidermal cells.

Question 10

Aerobic respiration equation

Answer 10

Glucose + Oxygen -> carbon dioxide + water

C6H12O6 + 6O2 -> 6CO2 + 6H2O

Question 11

Where does the oxygen diffuse in the leaf during respiration?

Answer 11

The oxygen diffuses down the concentration gradient from a high concentration (outside the leaf) to a low concentration (inside the leaf).

Question 12

Where does carbon dioxide diffuse in the leaf during respiration?

Answer 12

The carbon dioxide diffuses down the concentration gradient from a high concentration (inside the leaf) to a low concentration (outside the leaf).

Question 13

Respiration process:

Answer 13

Requires the uptake of oxygen and the release of carbon dioxide.

Question 14

Photosynthesis process:

Answer 14

Requires the uptake of carbon dioxide and release of oxygen

Question 15

Where does carbon dioxide diffuse in the leaf during photosynthesis?

Answer 15

carbon dioxide diffuses down the concentration gradient from a region of high concentration (outside the leaf) to a region of low concentration (inside the leaf).

Question 16

Where does oxygen diffuse in the leaf during photosynthesis?

Answer 16

The oxygen diffuses down the concentration gradient from a high concentration (inside the leaf) to a low concentration (outside the leaf).

Question 17

What happens to the plant during the daytime?

Answer 17

The plant both respires and photosynthesize. However, the rate of photosynthesis is higher than the rate of respiration. Therefore, there is a net diffusion of carbon dioxide into the plant and net diffusion of oxygen out of the plant.

Question 18

What happens to the plant during nighttime?

Answer 18

Plant only respires, this means there is a net diffusion of oxygen into the plant and a net diffusion of carbon dioxide out of the plant.

Question 19

What happens when there is low light intensity?

Answer 19

The rate of photosynthesis is equal to the rate of respiration. This means that there is no net movement of oxygen and carbon dioxide.