UNIT 3 5B: Factors Affecting the rate of photosynthesis

Question 1

Rate

Answer 1

The speed at which a process occurs, or how quickly the reactants are used up and the products are created

Question 2

Limiting Factor

Answer 2

Any factor that slows down the rate of a reaction when there is not enough of it,

Question 3

C3 Plants

Answer 3

Plants that fix CO2 from the atmosphere to form 3-phosphoglycerate or PGA, which contains three carbon atoms; are better suited to cooler and temperate climates

Question 4

Photorespiration

Answer 4

The series of reactions that occur as a consequence of Rubisco using O2 as a substrate instead of CO2; an inefficient process that cannot produce glucose

C3 plants have no special adaptations to reduce such competition

Question 5

C4 Plants

Answer 5

Plants that fix CO2 to form malate, which contains four carbon atoms; better suited to grasslands

Question 6

CAM plants

Answer 6

Plants that fix CO2 to form malate, which contains four carbon atoms; better suited to deserts

Question 7

Why is it called a C3 plant?

Answer 7

Because they form the 3C compound PGA during carbon fixation

Question 8

Disadvantages of photorespiration

Answer 8

1. Forms a product that cannot be used to make glucose
2. It Is an inefficient pathway, as it wastes energy
3. Reduces the efficiency of the Calvin Cycle, reducing the levels of photosynthesis by close to 25% in C3 Plants

Question 9

How does photorespiration occur?

Answer 9

At low temperatures, the rate of photorespiration in C3 plants is low and the rate of photosynthesis is high. However, as the temperature increases, the stomata close to conserve water, leading to a buildup of oxygen from the light dependent stage. More oxygen and less CO2 binds to rubisco and thus the rate of photorespiration increases and the rate of photosynthesis decreases.

Question 10

Difference between C4 plants and CAM plants

Answer 10

In C4 plants, carbon dioxide is stored as a 4C compound and is only released to the Calvin Cycle WHERE OXYGEN LEVELS are low, whereas in CAM plants, it is released WHEN oxygen levels are low

Question 11

What enzyme is used to combine Carbon dioxide with a 3C compound to make the 4C compound

Answer 11

PEP Carboxylase

Question 12

PEP Carboxylase

Answer 12

Used to combine carbon dioxide with a 3C compound to make the 4C compound, and this enzyme has a high affinity for carbon dioxide. This means it can extract a greater proportion of it from the air, and makes it more efficient that the C3 process.

Question 13

what is the event through which the adaptations in C4 and CAM plants arisen to prevent photorespiration

Answer 13

Natural selection

Question 14

Examples of C3 plants

Answer 14

Rice, cotton, wheat, soybean and trees

Question 15

Examples of C4 plants

Answer 15

Corn, sorghum and sugar cane

Question 16

Examples of CAM plants

Answer 16

Cacti, agave, pineapple