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Biology > Topic 11 - Photosynthesis > Flashcards

Topic 11 - Photosynthesis Flashcards

1
Q

What are the two stages of photosynthesis called

A

The light dependent reaction
The light independent reaction (the Calvin cycle)

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2
Q

What is the purpose of photosynthesis?

A

So energy from light is used to make glucose

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3
Q

What is the general equation for photosynthesis

A

6H20 + 6C02 + energy –> C6H1206 +6O2

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4
Q

What are the 6 stages of the light dependent reaction?

A
  1. Photoionisation of PSII
  2. Photolysis of water
  3. Photoionisation of PSI
  4. Active transport of H+ions
  5. Oxidative phosphorylation
  6. Reducing NADP
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5
Q

Describe what happens during photoionisation of PSII

A

Chlorophyll absorbs light
Electrons excited and move to higher energy level
Electrons move down electron transport chain to PSI

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6
Q

Describe what happens during photolysis of water

A

Light energy splits water molecules into H+, e- and oxygen.
The electrons replace those lost from PSII during photoionisation

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7
Q

Explain how H+ ions are moved across the thylakoid membrane

A

The excited electrons from photoionisation lose energy as they move down the electron transport chain
The energy is used to actively transport H+ into the chloroplast

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8
Q

Explain how H+ are involved in the synthesis of ATP in chloroplasts

A

H+ move down their concentration gradient into the stroma
This is via ATP synthase in the thylakoid membrane
The energy synthesises ATP from ADP and Pi

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9
Q

Explain why the photoionisation of PSI is important

A

The excited electrons are transferred to NADP with H+ to form reduced NADP.
This is needed for the light independent reaction

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10
Q

What is chemiosmosis

A

Electrons move down the electron transport chain and creating a proton gradient
This drive ATP synthesis

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11
Q

Which molecules from the light-dependent reaction are needed in the light independent reaction?

A

ATP
reduced NADP

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12
Q

Where does the light dependent reaction take place

A

(acrid) thylakoid membranes of chloroplasts

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13
Q

Where does the light independent reaction take place

A

Stroma of chloroplasts

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14
Q

What are the three stages of the light independent reaction?

A
  1. Formation of glycerate 3-phosphate
  2. Formation of triose phosphate
  3. Regeneration of ribulose bisphosphate
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15
Q

Explain how glycerate 3-phosphate (GP) is formed

A

Ribulose bisphosphate (RuBP) combines with CO2
Forms unstable 6 carbon compound which breaks down to give 2 molecules of glycerate 3-phosphate
Catalysed by Rubisco

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16
Q

How does CO2 enter the stroma from the atmosphere

A

Diffusion through the stomata
Diffusion into the stroma

17
Q

Which enzyme catalyses the reaction of CO2 with ribulose bisphosphate (RuBP)?

A

Rubisco

18
Q

How many molecules of glycerate 3-phosphate (GP) are produced from 1 molecule of CO2 and 1 molecule of ribulose bisphosphate (RuBP)?

A

2

19
Q

How many carbon atoms are in RuBP?

A

5

20
Q

How many carbon atoms are in glycerate 3-phosphate (GP)?

A

3

21
Q

Explain how triose phosphate (TP) is formed glycerate 3-phosphate (GP)

A

Glycerate 3-phosphate (GP) is reduced to triose phosphate (TP) using hydrogen from NADP

22
Q

How is glycerate 3-phosphate (GP) reduced to triose phosphate (TP)?

A

Hydrolysis ATP from the light dependent reaction provide energy
Reduced NADP releases H+ to form NADP

23
Q

What two things can triose phosphate (TP) be used for?

A
  1. Regenerating ribulose biphosphate (RuBP)
  2. Converted to useful organic substances
23
Q

How many of the carbon atoms in 2 molecules of triose phosphate (TP) are used to regenerate ribulose bisphosphate (RuBP)?

A

5/6 carbon atoms

24
Q

How many of the carbon atoms in 2 molecules of triose phosphate (TP) are converted to useful organic substances?

A

1/6

24
Q

Which two stages in the light independent reaction is ATP hydrolysed

A

Reduction of glycerate 3 - phosphate (GP) to triose phosphate (TP)
Regeneration of ribulose bisphosphate (RuBP)

25
Q

Which three factors can limit the rate of photosynthesis

A

Light intensity
Temperature
CO2 Concentration

26
Q

Why is it important that RuBP is regenerated

A

So that GP is formed and the light independent reaction can continue
Photosynthesis can continue

27
Q

What are the 4 optimum conditions for photosynthesis

A

High light intensity of a certain wavelength (red and blue chlorophyll a/b)
25 C
0.4% CO2
Water of the right volume

Biology (20 decks)

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