C3, C4 and CAM plants

Question 1

What is the structure of a leaf?

Answer 1

Mesophyll Cell: Can absorb CO2 - has Rubisco
Bundle-Shealth cell : Cannot absorb CO2

Question 2

What are the two components of the light independent cell?

Answer 2

Carbon fixation and the remainder of the Calvin Cycle

Question 3

The light dependent cell is identical in all three plantgroups, true or false?

Answer 3

True, the light independent stage slightly differs in each group of plants

Question 4

C3 plants

Answer 4

• Carbon Fixation and the remainder of the the Calvin Cycle occur in the mesophyll cell
• ‘Normal’ plants
• No adaption to limit photorespiration

Question 5

What makes C4 plants different to C3 and CAM?

Answer 5

• Carbon fixation occurs in the MESOPHYLL CELLS
• Remainder of the Calvin Cycle occurs in the BUNDLE SHEATH CELLS

Question 6

How do C4 plants avoid photorespiration?

Answer 6

Due to the constant pumping of CO2 into the bundle sheath cells, there is always a higher concentration of CO2 as Rubisco cannot make contact with O2

Question 7

Steps of C4 plants

Answer 7

• Co2 enters the mesophyll cells
• CO2 converted into malate
• Malate moves to bundle sheath and calvin cycle occurs
• Malate is concerted back into CO2 to act as the substrate for Rubisco

Question 8

What makes CAM plants different to C3 and C4?

Answer 8

• Carbon fixation during the night
• Calvin cycle occurs at day
• All in mesophyll cell

Question 9

How do CAM plants avoid photorespiration?

Answer 9

Uses energy to store CO2 as malate for use during the day

Question 10

CAM PLANTS: Carbon fixation

Answer 10

• Carbon fixation occurs during the night as it is cooler
• Stomata open, allowing CO2 in and to prevent water loss
• CO2 is converted into Malate and stored in the vacuole until the daytime…

Question 11

CAM PLANTS: Calvin Cycle

Answer 11

• Malate wakes up and is converted back into CO2 to act as a substrate for Rubisco

Question 12

How does light affect photosynthesis?

Answer 12

Light is required for the light dependent stage as it excites the water electrons to split it into Oxygen and Hydrogen ions

Question 13

How does temperature/pH affect photosynthesis?

Answer 13

Temperature and pH levels can act on the enzymes that catalyse the photosynthesis reactions as enzymes have optimal temperature/pH levels

Question 14

How does CO2 concentration affect photosynthesis?

Answer 14

It is required in the Light Independent stage for the production of glucose
Lower levels of CO2 will also cause Rubisco to use O2 as a substrate, causing photorespiration

Question 15

How does water availability affect photosynthesis?

Answer 15

It is an input in the Light Dependent stage
It also influences the opening and closing of the stomata