Gas exchange (plant)

Question 1

Describe how the structure of the leaf is adapted for gas exchange.

Answer 1

• Broad so large surface area for diffusion
• Thin so short diffusion distance
• Air spaces allow gases to move to all cells easily
• lots of stomata that open to let gases(oxygen and carbon dioxide) diffuse in and out
• Plants can control the opening and closing of stomata using the guard cells
• Spongy mesophyll - to allow for the interchange of gases (CO2)/gas exchange that is needed for photosynthesis

Question 2

Describe an investigation to show how light affects gas exchange

Answer 2

METHOD:

• Put three leaves all of the same size into tubes with the same volume of hydrogen-carbonate indicator.
• Have a fourth tube with the indicator in but no leaf as a control experiment
• Wrap one tube in aluminum foil
• Wrap another in muslin
• Now shine a bright light onto the tubes and leave them for 45 minutes

RESULTS:

• The tube which was covered with foil had no light and therefore the leaf had not been photosynthesizing but only respiring. Therefore producing CO2.
• The tube with no cover has been photosynthesizing a lot and therefore using up the CO2 in the tube.
• The tube with muslin has had some light so overall no change in CO2.
• The control tube has had no leaf in it and therefore no change in CO2.

Question 3

What is diffusion?

Answer 3

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

Question 4

How do single-celled organisms exchange gases?

Answer 4

Single-celled organisms such as amoeba exchange gases sufficiently by simple diffusion through the cell membrane

Question 5

Name the gas exchange organs in fish

Answer 5

Gills

Question 6

Describe gas exchange during respiration.

Answer 6

• During respiration, cells uptake oxygen and release carbon dioxide.
• Oxygen diffuses into the cells down its concentration gradient, while carbon dioxide diffuses out of the cells.

Question 7

Explain gas exchange during photosynthesis.

Answer 7

• During photosynthesis, plants uptake carbon dioxide and release oxygen.
• Carbon dioxide diffuses into the photosynthesizing cells, while oxygen diffuses out

Question 8

How does gas exchange vary between day and night in plants?

Answer 8

• During the day, plants both respire and photosynthesize, leading to net diffusion of carbon dioxide into the plant and net diffusion of oxygen out.
• At night, plants only respire, resulting in net diffusion of oxygen into the plant and carbon dioxide out.