Photosynthesis 2.0

Question 1

What is photosynthesis?

Answer 1

The way in which plants make their own food using light.

Question 2

What are plants classified as?

Answer 2

Autotrophs.

Question 3

Is photosynthesis anabolic or catabolic?

Answer 3

Anabolic.

Question 4

What is the aim of photosynthesis?

Answer 4

To get plants to make food.

Question 5

How is light absorbed in photosynthesis?

Answer 5

Chlorophyll in the leaf.

Question 6

What are the reactants of photosynthesis?

Answer 6

Carbon dioxide, water, and light.

Question 7

What are the products of photosynthesis?

Answer 7

Glucose and oxygen.

Question 8

Where does CO2 come from in photosynthesis?

Answer 8

Through stomata from the atmosphere.

Question 9

Where does water come from in photosynthesis?

Answer 9

Through roots - osmosis.

Question 10

Where does light come from in photosynthesis?

Answer 10

Sun and artificial light (lamps, etc.).

Question 11

What impacts the rate of photosynthesis?

Answer 11

Temperature (enzymes), light intensity, and CO2 levels.

Question 12

What is the effect of increasing light intensity in a greenhouse on plants?

Answer 12

Supplies more light which stimulates plant crop growth, increasing the growth rate for plants.

Question 13

What is the effect of adding artificial CO2 to a greenhouse on plants?

Answer 13

Supplies more carbon atoms to the dark stage of photosynthesis for glucose formation.

Question 14

What is the effect of increasing temperature of a greenhouse on plants?

Answer 14

Increases the rate of photosynthesis as it increases enzyme activity. Until enzymes are denatured

Question 15

What does ADP stand for?

Answer 15

Adenosine diphosphate.

Question 16

What is ADP?

Answer 16

Low energy molecule made from adenosine & 2 phosphates.

Question 17

How is ATP formed?

Answer 17

Add one phosphate to ADP.

Question 18

What is phosphorylation?

Answer 18

Adding a phosphate.

Question 19

What does ATP stand for?

Answer 19

Adenosine triphosphate.

Question 20

What is Stage 1 of photosynthesis?

Answer 20

The light stage (Cyclic phosphorylation).

Question 21

Why is the light stage called ‘the light stage’?

Answer 21

As it requires light.

Question 22

What is the summary of the light stage (Cyclic phosphorylation)?

Answer 22

Light energy is absorbed by chlorophyll molecules, high energy electrons leave chlorophyll, are passed through electron acceptors & lose energy, combining with ADP + P to form ATP, and low energy electrons return to chlorophyll.

Question 23

Why is it referred to as cyclic phosphorylation?

Answer 23

As electrons return to the chlorophyll at the end (low energy).

Question 24

What are the products formed in pathway 1 and their fate?

Answer 24

ATP (used in dark stage) ONLY

Question 25

Why is oxygen a waste product of the light stage?

Answer 25

As it is not needed for the light stage to occur.

Question 26

What is Pathway 2 of the light stage of photosynthesis?

Answer 26

Non-cyclic phosphorylation.

Question 27

What is the summary of the light stage (Non-Cyclic phosphorylation)?

Answer 27

1. Light splits water (Photolysis): → Produces electrons (e⁻), protons (H⁺), and oxygen (O₂). 2. Electrons go to chlorophyll 3. Oxygen is released as a waste gas. 4. Light excites the electrons in chlorophyll to a high energy level. 5. High-energy electrons leave chlorophyll and are passed to an electron acceptor. 6. Electrons pass along an electron transport chain: → Energy is released and used to make ATP from ADP + Pi (photophosphorylation). 7. Electrons reach Photosystem I, are re-energised by light, and passed to another electron acceptor. 8. NADP⁺ combines with the electrons and H⁺ (from the proton pool) to form NADPH. 9. ATP and NADPH move to the dark stage (Calvin Cycle).

Question 28

Why is it referred to as non-cyclic phosphorylation?

Answer 28

As electrons do not return to chlorophyll.

Question 29

What are the products formed during pathway 2

Answer 29

NADPH (supplies protons & electrons for dark stage), ATP (supplies energy for dark stage), and oxygen (used for respiration or released into the atmosphere).

Question 30

What is the fate of high energy electrons?

Answer 30

Used to make NADPH and return to chlorophyll.

Question 31

What are the two functions of NADPH?

Answer 31

Supply electrons and supply protons.

Question 32

What is the source of protons (+) to make NADPH?

Answer 32

Photolysis (4e+).

Question 33

Name another molecule other than chlorophyll that provides electrons in photosynthesis.

Answer 33

H2O.

Question 34

What is photolysis?

Answer 34

The splitting of water using light energy during photosynthesis.

Question 35

Why is it good that chlorophyll contains many chemicals?

Answer 35

Can absorb more energy.

Question 36

What is the role of stomata in photosynthesis?

Answer 36

Allows CO2 into the plant which is required for photosynthesis.

Question 37

What is the fate of the end products of the dark stage?

Answer 37

Return to light stage.

Question 38

What are the functions of glucose?

Answer 38

Food for the plant and respiration.

Question 39

What is the stage of photosynthesis controlled by enzymes?

Answer 39

The dark stage.

Question 40

What is the method for investigating the effect of light intensity on the rate of photosynthesis?

Answer 40

Cut stem of Elodea, attach a paperclip, switch off lights, use sodium hydrogen carbonate, place in water bath at 25 degrees, count bubbles for 1 min, and repeat.

Question 41

Why was Elodea used?

Answer 41

As it's a green aquatic plant that can produce bubbles underwater.

Question 42

Why was sodium hydrogen carbonate used?

Answer 42

To maintain CO2 levels.

Question 43

What is the optimum temperature for enzyme activity?

Answer 43

Water bath at 25 degrees.

Question 44

What factor was kept constant in the experiment?

Answer 44

CO2 levels - using sodium hydrogen carbonate.

Question 45

What factor was varied in the experiment?

Answer 45

Light intensity - moved lamp a set distance closer to the plant each time.

Question 46

Explain the shape of the graph drawn up from the experiment.

Answer 46

As light intensity increases, so does the number of bubbles, leveling off after reaching saturation point.

Question 47

What does saturation point mean?

Answer 47

Point where the plant cannot photosynthesize any faster.

Question 48

What is the importance of eliminating external light in the experiment?

Answer 48

To ensure the amount of bubbles produced is accurate due to the variable.

Question 49

What are the X and Y axes of the graph for the rate of photosynthesis light intensity experiment?

Answer 49

X = light intensity, Y = rate.

Question 50

What is the role of NADPH in the dark stage?

Answer 50

Supply protons & electrons. CO2 is reduced to glucose.

Question 51

What occurs in the dark stage

Answer 51

- Carbon Dioxide enters by diffusion from the atmosphere - NADPH transfers protons (H+) and energized electrons - The protons (H+) and energized electrons convert CO₂ to glucose - ATP is used to supply energy for glucose - NADP+ and ADP + P can be reused in the Light Phase