5C FACTOS AFFECTING THE RATE OF PHOTOSYNTHESIS

Question 1

Light:

factors that affect the rate of photosynthesis: light availability

Answer 1

Rate of photosynthesis increases as light intensity increases up until a plateau/it reaches saturation.

Question 2

rate 

Answer 2

the speed at which a chemical reaction proceeds.

Question 3

plateau

Answer 3

to reach a state where no further change occurs. Eg, after point x the rate of photosynthesis does not increase as light continues to increase. Instead, the rate of photosynthesis remains high, yet constant.

Question 4

enzyme

Answer 4

an organic molecule, typically a protein, that catalyses (speeds up) specific reactions.

Question 5

saturation point

Answer 5

the point at which a substance (e.g. an enzyme) cannot receive more of another substance (e.g. a substrate)

Question 6

limiting factor

Answer 6

a factor that prevents the rate of reaction from increasing

Question 7

limiting reagent

Answer 7

a reactant that prevents the rate of reaction from increasing.

Question 8

C3 plants 

Answer 8

plants with no evolved adaptation to minimise
photorespiration.

Question 9

C4 plants

Answer 9

plants that minimise
photorespiration by separating
initial carbon fixation and the
remainder of the Calvin cycle
over space.

Question 10

CAM plants

Answer 10

plants that minimise
photorespiration by separating
initial carbon fixation and the
remainder of the Calvin cycle
over time.

Question 11

wavelength of light

Answer 11

the wavelength (colour) of light can affect photosynthesis, not just the intensity.

Question 12

optimal

Answer 12

the point at which for
a given condition (e.g.
temperature), the maximum
function of an enzyme occurs.
Also known as optimum.

Question 13

denature

Answer 13

the disruption of a molecule’s structure by an external factor such as heat.

Question 14

Carbon dioxide:

Answer 14

Ac CO2 (carbon dioxide) concentration increases so does the rate of photosynthesis until a plateau is reached.

Question 15

Comparing the effect on C3, C4, and CAM plants: Carbon Dioxide

Answer 15

C4 and CAM plants have evolved adaptations to counter photorespiration and expose
Rubisco to greater levels of CO2. Because of this, C4 and CAM plants are less susceptible to
the impacts of low CO2 concentration on the rate of photosynthesis compared to C3 plants, which have no strategy to combat photorespiration.

Question 15

What are the things that can cause the plateau on the CO2 graph:

Answer 15

• Maximum rate of photosynthesis is reached.
• All enzymes involved in using CO2 are currently being used.
• not enough of a factor other than CO2
• We can say that CO2 was the
  limiting factor before the plateau but now it could be light, water, or temperature.

Question 16

stoma (pl. stomata)

Answer 16

a small pore on the leaf’s surface that opens and closes to regulate gas exchange.

Question 17

photorespiration

Answer 17

a wasteful process in plants initiated by Rubisco that limits photosynthesis.

Question 18

Rubisco

Answer 18

a pivotal enzyme involved
in initial carbon fixation during
the light-independent stage of
photosynthesis.

Question 19

Affinity

Answer 19

the tendency of a
molecule/atom to bind or react
with another molecule/atom

Question 20

Enzyme inhibition 

Answer 20

• Enzyme inhibitors influence the function of enzymes and, as a result, the rate of photosynthesis.
• Competitive inhibitors bind to the active sites of enzymes to prevent the catalysis of substrates.
• Meanwhile, non-competitive inhibitors bind to an allosteric site of an enzyme causing a conformational change to the active site meaning the substrate can no longer bind.
• This inhibition can also be classified as either reversible or irreversible.

Question 21

enzyme inhibitor

Answer 21

a molecule that binds to and prevents an enzyme from functioning.

Question 22

competitive inhibitor

Answer 22

a molecule that hinders an enzyme by blocking the active site and preventing the substrate from binding.

Question 23

non-competitive inhibitor

Answer 23

a molecule that hinders an
enzyme by binding to an allosteric site and changing the shape of the active site to prevent the substrate
from binding.

Question 24

allosteric site

Answer 24

a region on an enzyme that is not the active site.

Question 25

reversible inhibition

Answer 25

enzyme inhibition that involves weaker bonds that can be overcome.

Question 26

irreversible inhibition

Answer 26

enzyme inhibition that involves stronger bonds that cannot be broken.