Photosynthesis in C3 and C4 Plants (5B)

Question 1

Which type of plant uses the least amount of energy to undertake photosynthesis?

Answer 1

C3 plants as they do not undergo extra process to lower the affinity of photorespiration

Question 2

Explain how C4 plants have evolved adaptations to maximise photosynthesis.

Answer 2

C4 plants separate the initial carbon fixation from the remainder of the Calvin cycle in photosynthesis between cells. Initial carbon fixation occurs in a mesophyll cell whilst the remainder of the Calvin cycle takes place in a bundle-sheath cell.1This separation allows for a high concentration of around Rubisco, encouraging it to bind rather than, which decreases photorespiration and increases photosynthesis.

Question 3

Explain the differences between C4 and CAM photosynthesis.

Answer 3

C4 photosynthesis separates initial carbon fixation from the remainder of the Calvin cycle over space, between a mesophyll cell and a bundle-sheath cell.Conversely, CAM photosynthesis separates these two steps over time, between day and night with the use of a vacuole.

Question 4

Cereal crops like wheat and barley grow well in Victoria. Explain why sugarcane would likely be outcompeted by other cereal crops if it were introduced into a similar Victorian environment.

Answer 4

As sugarcane undertakes C4 photosynthesis to cope with hot environments, it expends more energy compared to the standard C3 photosynthesis.1Whilst this payoff is advantageous in hot environments, in colder environments such as Victoria, the sugarcane is now expending significantly more energy than other C3 plants to undertake photosynthesis.2This likely means the other cereals would outcompete sugarcane as it costs them less energy to photosynthesise.3