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Biology: Module 5 > 5.5: Photosynthesis (new) > Flashcards

5.5: Photosynthesis (new) Flashcards

1
Q

What are the organelles that make up a chloropast?

A
  • Thylakoids
  • Grana
  • Lamellae
  • Stroma
  • Strarch grains
  • Ribosomes
  • Chloropast DNA
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2
Q

What are the main roles of the chloroplast?

A
  • Absorb light energy to drive photosynthesis
  • Convert light energy into chemical energy
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3
Q

What are thylakoids?

A

Flattened sacs that contain complexes of pigments like chlorphyll 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

Membraneous extentions that connect thylakoids

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6
Q

What are stroma?

A

Fluid surrounding the thylakoids where the light dependent reaction occurs

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7
Q

What are starch grains?

A

Store sugars

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8
Q

What are chlorplast DNA?

A

Genes that code for protein involved in photosynthesis

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9
Q

List the four main photosynthetic pigments?

A
  • Chlorophyll A
  • Chlorophyll B
  • Xanthophylls and caretenoids
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10
Q

What is chlorophyll a?

A

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

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11
Q

What is chlorophyll b?

A

An accessory pigment mostly found with chlorophyll a

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12
Q

What is xanthophyll and carotenoids?

A

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

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13
Q

Where are photosystems?

A

Embedded in the thylakoid membrane

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14
Q

What do photosystems contain?

A
  • A light harvesting system - contains pigments
  • A reaction centre - contains two chlorophyll a molecules
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15
Q

What is the balanced photosynthesis equation?

A

6CO2 + 6H2O → C6H12O6 + 6O2

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16
Q

What is the direction of the light in the photosystem?

A

Light harvesting system absorbs light energy
This is transferred to the reaction center which emits high energy electrons to drive the light dependent reactions

17
Q

What are photosystems?

A

A protein/antenna commplex in the membrane that contains pigments

18
Q

What are the adaptations of photosystems?

A
  • Large antenna complex - increases the area over which photons can be harvested
  • Accessory pigments - can catch a greater range of wavelengths of light
19
Q

What is a photon?

A

A particle of light, each contains a quantam of energy

20
Q

What is a compensation point?

A

When photosynthesis and respiration are equal

21
Q

What is a compensation period?

A

Time taken to reach compensation point
Different in different species
Shade adpated plants reach theirs later (when light is dim)

22
Q

What is part of the light dependent stage and where does it occur?

A

Happens in the thylakoid membrane

  1. The light harvesting photosystem
  2. Photolysis
  3. Photophosphorylation (cyclic and non cyclic)
  4. Formation of NADPH and oxygen (waste product of photosynthesis)
23
Q

What are the two photosystems and their wavelengths?

A
  • Photosystem I -700nm
  • Photosystem II - 680nm
24
Q

What are the steps of non cyclic photophosphorylation?

6 steps

A
  1. Energy from photons is transferred to chla in PSII
  2. The energy excites electrons, causing two electrons to leave chla in photosystem II
  3. Electrons flow down the e.t.c via acceptors and lose energy as they do. Energy is used to phosphorolyse ADP
  4. Electrons flow to PSI chla where they replace electrons that have also been excited by light
  5. Electrons leave PSI with more energy than PSII (some is used for photolysis
  6. The excited electron pair are passed on to the final electron acceptor molecule NADP. Reduces NADP into NADPH
25
Q

What are the steps of chemiosmosis?

6 steps

A
  1. The energy lost by electrons along the electron transport chain is used to pump protons across the thylakoid membrane into the thylakoid space
  2. This produces a proton gradient, where they are in a higher concentration in the thylakoid space.
  3. The protons then diffuse through ATP synthase into the stroma
  4. This movement powers ATP synthase to produce ATP from ADP and an inorganic phosphate
  5. NADP takes up protons and electrons from PSI in the stroma and is reduced.
  6. Reduced NADP is carried into the light-independent reaction
26
Q

What is cyclic phosphorylation?

4 steps

A
  1. Energy from photons is transerred to chla in PSI
  2. Energy excites electrons, causing 2 electrons to leave chla in PSI
  3. Electrons flow down e.t.c via accepters and lose energy. Energy is used to phosphorolyse ADP
  4. The electrons then return to PSI and begin the cycle again
27
Q

What is photolysis and where is it?

A
  • Energy from photons split water
  • Only at PSI
  • Oxygen evolving complex - special enzyme that can split water

It is only found in PSII which is why we start there

28
Q

Compare cyclic and non cyclic photophosphorylation:

  • Photosystem
  • Products
  • Photolysis
A

Cyclic:

  • PSI
  • ATP
  • No

Non cyclic

  • PSII & PSI
  • ATP and reduced NADP
  • Yes
29
Q

What is part of the light independent reaction and where does it occur?

A
  • Happens in the stroma of the chloroplast
  1. Calvin cycle
  2. Formation of carbohydrate
30
Q

What happens in the Calvin cycle?

5 steps

A
  1. CO2 (1C) reacts with RuBP (5C) which is catalysed by the enzyme Rubisco
  2. Forms an unstable 6 carbon compound that then splits into 2GP (3C)
  3. GP is then reduced into TP, using the energy from ATP being hydrolysed into ADP + Pi
  4. Also using the protons from NADP being reduced
  5. In 10 of every 12 TP molecules, the atoms are rrearranged to regenerate 6 molecules of RuBP
31
Q

What is glucose and TP used for?

A

Glucose:

  • Converted to sucrose
  • Starch
  • Cellulose

TP

  • Synthesise amino acids
  • Fatty acids
  • Glycerol

Biology: Module 5 (10 decks)

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