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Biology Unit 3 > 3.2 Photosynthesis 5 > Flashcards

3.2 Photosynthesis 5 Flashcards

1
Q

What is a cholorplast?

A

An organelle found in plants and algae, site of photosynthesis

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2
Q

Describe structure of chloroplast

A

Double membrane
Grana - stacks of thylakoids that contain photosystems, electron transport chains, ATP Synthase
Grana connected by Intergranal lamellae
Stroma - fluid filled matrix containing enzymes

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3
Q

Where are chloroplasts located in an angiosperm leaf?

A

Mainly found in mesophyll layers

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4
Q

How are chloroplasts adapted for photosynthesis?

A
  • Thylakoids have large surface area for light dependent reactions
  • Photosynthetic pigments arranged into photosystems to maximise light absorption
  • Stroma directly surrounds grana - products of photosynthesis diffuse directly into stroma
  • Contain their own DNA and ribosomes
  • Inner chloroplast membrane less permeable than outer allows control over the movement of substances
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5
Q

How are angiosperm leaves adapted for photosynthesis?

A
  • Large surface area to maximise light absorption
  • Upper epidermis transparent to allow light to strike mesophyll layers
  • Palisade layers densely packed to contain many chloroplasts
  • Vein network - transports water and minerals to leaf and takes away sugars
  • Air spaces reduce diffusion distance for CO2
  • Thin to reduce diffusion distance for CO2
  • Stomata - allows CO2 to diffuse into the leaf
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6
Q

What is a transducer? Why are chloroplasts described as transducers?

A

Something that converts one form of energy into another
Chloroplasts convert light energy into the chemical energy of ATP

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7
Q

What is a photosynthetic pigment?

A

A molecule present in chloroplast that absorb certain wavelengths of light

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8
Q

Examples of photosynthetic pigments

A

Chlorophyll a
Chlorophyll b
Xanthophyll
Beta Carotene

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9
Q

Purpose of chromatography?

A

To separate different products from a mixture

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10
Q

Equation used to calc the retention value (Rf)

A

Retention value (Rf)= distance travelled by component/ distance travelled by solvent

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11
Q

What is photosynthesis?

A

Complex metabolic pathway that synthesises organic molecules in the presence of light: 6CO2+6H2O -> C6H12O6 + 6O2

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12
Q

Two stages of Photosynthesis:

A

Light dependent stage
Light independent stage

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13
Q

What is a Photosystem?

A
  • Two types: Photosystem I and Photosystem II
  • Protein complex consisting of an antenna complex and a reaction centre
  • Involved in the absorption of light and transfer of electrons in photosynthesis
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14
Q

Difference between Photosystems I & II

A

They absorb different wavelengths of light

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15
Q

Describe the process of light harvesting:

A

Antenna complex absorbs light energy of varying wavelengths and transfers to the reaction centre
Energy absorbed by two chlorophyll a molecules which emit excited electrons.

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16
Q

Absorption Spectra?

A

Graph showing wavelengths of light absorbed by a pigment

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17
Q

Action Spectra?

A

Graph of the rate of photosyntesis against each wavelength of light absorbed by a pigment

18
Q

The sources of electrons for the electron transport chain

A

cyclic and non-cyclic photophosphorylation

19
Q

Define cyclic photophosphorylation

A

The formation of ATP invovling Photosystem I only

20
Q

Outline cyclic photophosphorylation

A

Involves only Photosystem I
Excited electrons enter the electron transport chain to produce ATP and return to Photosystem I
No reduction of NADP and no water required to replace lost electrons

21
Q

What is the purpose of cyclic photophosphorylation

A

Produces additional ATP to provide surplus energy demands of the cell

22
Q

Define non-cyclic photophosphorylation

A

The formation of ATP and reduced NADP involving both Photosystems I and II

23
Q

Outline non-cyclic photophosphorylation

A

Involves Photosystems I and II
Excited electrons enter the electron transport chain to produce ATP
NADP acts as a final electron acceptor and is reduced
Water is photolysed to compensate for electrons lost from Photosystem II

24
Q

What is the purpose of non-cyclic photophosphorylation?

A

Produces ATP and reduced NADP for the Calvin cycle

25
Q

How does chemiosmosis produce ATP in the light dependent stage?

A

Protons flow down their concentration gradient from the thylakoid space into the stroma via ATP synthase
ATP synthase phosphorylates ADP to form ATP as protons flow through it

26
Q

Describe photolysis

A

The splitting of a water molecule in the presence of light that occurs during the light dependent stage of photosynthesis producing protons electrons and oxygen
H2O -> 2H+ + 2e- + 1/2O2

27
Q

What happens to the products of photolysis?

A

H+ - used in proton pumping and to reduce NADP
e- - replaces electrons lost from chlorophyll a in PSII
O2 - by-product used in respiration or diffuses out of leaf as waste gas.

28
Q

Explain how the electron transport chain results in the production of reduced NADP.

A

NADP acts as a final electron acceptor, is subsequently reduced

29
Q

Describe the light-independent stage of photosynthesis

A

Second stage of photosynthesis
Does not require light energy and takes place in the stroma
Uses carbon dioxide and the products of the light-dependent stage to build organic molecules

30
Q

What is the light-independent stage also known as?

A

The Calvin Cycle

31
Q

The three main stages of the Calvin Cycle:

A
  1. Carbon fixation
  2. Reduction
  3. Regeneration
32
Q

What happens during the carbon fixation of the Calvin Cycle?

A
  • Reaction between CO2 and ribulose biphosphate (RuBP) catalysed by the enzyme RuBisCo
  • Forms unstable 6C intermediate that breaks down into two molecules of glycerate 3-phosphate (GP)
33
Q

What happens during the reduction of the Calvin Cycle?

A

2x GP are reduced to 2x triose phosphate (TP)

Requires 2x reduced NADP and 2x ATP formed during the light-dependent reaction

Forms 2x NADP and 2x ADP that enter the light dependent reaction

34
Q

What happens during the regeneration of the Calvin Cycle?

A

After 1C leaves the cycle the 5C compound RuP forms

RuBP is regenerated fron RuP using 1x ATP

Forms 1x ADP

35
Q

How are nutrients produced as a result of photosynthesis?

A

Formation of amino acids from GP (required nitrates and sulfates)

TP molecules used to produce sugars e.g. glucose, fructose, sucrose

36
Q

What is a limiting factor?

A

A variable that limits the rate of a particular reaction

37
Q

Name the factors that limit the rate of photosynthesis. What stage do they limit?

A

Light intensity - light-dependent stage
Light wavelength - absorption of chlorophyll
CO2 levels - light-independent stage
Temperature - enzyme-controlled reactions
pH - enxyme-controlled reactions

38
Q

Describe the role of nitrogen in plant metabolism.

A

Synthesis of amino acids, nucleotides and chlorophyll.

39
Q

What does nitrogen deficiency in plants cause?

A

Stunted growth
Chlorosis (yellowing of the leaves)

40
Q

Describe the role of magnesium in plant metabolism.

A

Synthesis of chlrophyll

41
Q

What does magnesiumdeficiency in plants cause?

A

Chlorosis (yellowing of the leaves)

Biology Unit 3 (8 decks)

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