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Biology A2 Rafa > 5.6 Photosynthesis > Flashcards

5.6 Photosynthesis Flashcards

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1
Q

What is the compensation point?

A

When photosynthesis and respiration proceed at the same rate so there is no net gain or loss of carbohydrate

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2
Q

What is the compensation period?

A

The time taken to reach the compensation point

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3
Q

Does a sun plant or a shade plant have a higher compensation point?

A

The sun plant is higher

Because the shade plant begins to photosynthesise at a much lower light intensity than the sun plant

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4
Q

Define granum

A
  • Inner part of chloroplasts made of stacks of thylakoid membranes
  • where the light dependent stage takes place
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5
Q

Define photosynthetic pigment

A
  • Pigment that absorbs specific wavelengths of light and traps the energy associated with light
  • chlorophylls a and b, carotene and xanthophyll
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6
Q

Define photosystem

A
  • System of photosynthetic pigments found in thylakoids of chloroplasts
  • each photosystem contains about 300 molecules of chlorophyll that trap photons and pass their energy to a primary pigment reaction centre, a molecule of chlorophyll a, during the light dependent stage of photosynthesis
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7
Q

Define stroma

A

fluid-filled matrix of chloroplasts, where the light independent stage of photosynthesis takes place

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8
Q

Define thylakoid

A

Flattened membrane-bound sac found inside chloroplasts; contains photosynthetic pigments/photosystems and is the site of the light-dependent stage of photosynthesis

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9
Q

What is the reaction centre

A

Its at the bottom of all of the photosynthetic pigments and it contains a type of chlorophyll

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10
Q

Describe chlorophyll a

A
  • there are two forms
  • both appear blue green
  • both absorb red light
  • different absorption peaks
  • both have porphyrin group
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11
Q

Describe P680

A
  • PSII

- peak absorption of light at 680nm

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12
Q

Describe P700

A
  • PSI

- peak absorption at 700nm

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13
Q

Describe chlorophyll b

A

400-500nm and 640nm

appears yellow/green

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14
Q

Describe carotenoids

A
  • accessory pigment
  • blue light
  • 400-500nm
  • appear orange
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15
Q

Describe xanthophylls

A
  • accessory pigment
  • blue and green light
  • wavelength 375-550nm
  • appear yellow
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16
Q

Difference between primary and accessory pigments

A
  • primary pigments act as reaction centres

- accessory pigments surround the reaction centre and transfer energy to primary pigments

17
Q

What is photophosphorylation?

A

Generation of ATP from ADP and Pi in the presence of light

18
Q

What do electron carriers consist of?

A

Fe3+ which are reduced to Fe2+ and reoxidised to Fe3+ as e- moves on

19
Q

Products of non-cyclic photophosphorylation of light dependent stage

A

ATP and reduced NADP

20
Q

Products of cyclic photophosphorylation

A

ONLY ATP

21
Q

Which cells use cyclic photophosphorylation?

A

Guard cells

  • only have PSI
  • ATP moves K+ into guard cell and water follows and swells
22
Q

Where does reduction of NADP occur?

A

Stroma

23
Q

Where does the light-independent stage occur?

A

Stroma

24
Q

Why does the Calvin cycle only occur during the day?

A
  • ATP and NADPH are used from the light dependent stage
  • H+ ions that are pumped out of the stroma increase the pH to 8 which is the optimum for RuBisCo
  • Extra ATP in the stroma which activates RuBisCo
  • Mg2+ increase in daylight and are cofactors of RuBisCo
  • Ferredoxin (reduced by e- in the light) activates enzymes in the Calvin cycle
25
Q

What factors could limit the rate of photosynthesis?

A
  • light intensity
  • carbon dioxide concentration
  • temperature
  • water stress
26
Q

How does decreasing amount of water affect the plant?

A

1) plasmolysis, flaccid tissues, wilting
2) roots produce absisic acid, stomata close, decrease in gaseous exchange
3) rate of photosynthesis greatly reduces

27
Q

Easiest ways to measure rate of photosynthesis?

A

measure rate of CO2 uptake

measure O2 production

28
Q

What are the limitations of measuring productions of oxygen?

A
  • some O2 used in respiration

- some dissolved nitrogen may be in gas collected

29
Q

What do you use to measure rate of photosynthesis?

A

A photosynthometer/ Audus microburette

30
Q

How does a photosynthometer work?

A

Bubbles of gas collect in funnel, use syringe to draw bubble out, measure the length of bubble and work out volume

31
Q

Uses of triose phosphate (TP)

A

Starting material for the synthesis of carbohydrates, lipids and amino acids
Recycling to generate RuBP

32
Q

What is a limiting factor?

A

factor that determines the rate when at low levels

Biology A2 Rafa (14 decks)

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