Photosynthesis Flashcards

1
Q

What is the equation for photosynthesis?

A

6CO2 + 6H2O + light energy → C6H12O6 + 6O2

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2
Q

What are the main functions of chloroplasts?

A
  • To absorb light energy to drive photosynthesis.
  • To convert light energy into chemical energy.
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3
Q

What are thylakoids?

A

Flattened sacs that contain pigments in their membranes to absorb light for the light dependent reaction.

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4
Q

What are grana?

A

Stacks of thylakoids

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5
Q

What are lamellae?

A

Membranous extensions that connect thylakoids

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6
Q

What is the stroma?

A

A fluid surrounding the thylakoids where the light independent reaction occurs.

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7
Q

What are chloroplast DNA used for?

A

Contain the genes that code for proteins involved in photosynthesis.

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8
Q

What is Chlorophyll a?

A

The main pigment that absorbs red and blue light and reflects green.

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9
Q

What is chlorophyll b?

A

An accessory pigment mostly found with chlorophyll a in light-harvesting complexes.

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10
Q

What are xanthophylls and carotenoids?

A

Absorb different wavelengths than chlorophyll, broadening the spectrum of light that can drive photosynthesis.

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11
Q

What are clusters of pigments called and where are they found?

A

Photosystems.
Found in the thylakoid membranes.

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12
Q

What does each photosystem have?

A

A light harvesting system that absorbs light energy which is then transferred to a reaction centre. This emits high energy electrons to drive light dependent reactions.

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13
Q

What is photophosphorylation?

A

Where ATP is formed using light energy.

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14
Q

What is non-cyclic photophosphorylation?

A

The use of water and light energy to produce ATP, reduced NADP and oxygen.

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15
Q

Describe the first stage in non-cyclic photophosphorylation?

A
  • Light energy is absorbed by pigments.
  • This excited electrons in the pigments in photosystem 1 and photosystem 2 reaction centres.
  • Electrons are lost from the pigments.
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16
Q

Describe the second stage in non-cyclic photophosphorylation?

A
  • Electrons are transferred to an electron carrier molecule.
  • They are passed along the chain, releasing energy as they go.
  • The electron from PSII replaces the lost electron from PSI.
17
Q

Describe the third stage of non-cyclic photophosphorylation?

A
  • The photolysis of water where light is used to split water into electrons, protons and oxygen.
  • 2H2O → 4H+ + 4e- + O2.
  • The electrons replace those lost from PSII.
  • The protons are used for ATP production and combine with electrons to reduce NADP.
18
Q

Describe chemiosmosis

A
  • The energy lost by electrons along the electron transport chain pumps protons across the thylakoid membrane.
  • This produces a proton gradient.
  • The protons diffuse through ATP synthase to produce ATP from ADP and an inorganic phosphate.
19
Q

How is NADP reduced?

A
  • NADP takes up protons and electrons from PSI in the stroma and is reduced.
  • Reduced NADP is carried into the light independent reaction.
20
Q

When is cyclic photphosphorylation used?

A

When NADP is not available.

21
Q

Describe cyclic photophosphorylation

A
  • Light energy is absorbed by pigments and excites electrons in the pigments in the PSI only.
  • Electrons are lost
  • They are transferred to an electron carrier molecule and passed along an electron carrier chain, releasing energy.
  • This powers proton transport across the thylakoid membrane.
  • ATP is produced as protons flow back into the stroma through ATP synthase.
  • Electrons are returned to the PSI so no NADP is reduced.