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Biology A Level Unit 3 > 3.2 Photosynthesis > Flashcards

3.2 Photosynthesis Flashcards

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1
Q

What is a chloroplast?

A

An organelle found in plants and algae that is the site of photosynthesis

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2
Q

Describe the structure of a chloroplast

A
  • double membrane
  • Grana - stacks of thylakoids that contain photosystems, ETC, ATP synthase
  • Grana are connected by 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 the mesophyll layers

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4
Q

How are chloroplasts adapted for photosynthesis ?

A
  • thylakoids give large surface area for light-independent reactions
  • photosynthetic pigments to maximise light absorption
  • inner membrane less permeable to control movement of substances
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5
Q

What is a transducer?

A

Something that converts one type of energy to another, chloroplasts transducer light energy into chemical

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6
Q

What is a photosynthetic pigment?

A

Absorbs certain wavelengths of light

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7
Q

Give some examples of photosynthetic pigment

A
  • Chlorophylls a and b
  • beta carotene
  • xanthophylls
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8
Q

What is the purpose of chromatography

A

To separate different products from a mixture

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9
Q

State the equation used to calculate retention value (Rf)

A

Distance travelled by component ÷ distance travelled by solvent

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10
Q

What is photosynthesis

A

A complex metabolic pathway that synthesised organic molecules in the presence of light

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11
Q

What is the equation for photosynthesis

A

Carbon dioxide + water -> glucose + oxygen

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12
Q

Name the two stages of photosynthesis

A

Light dependant stage and light independent stage

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13
Q

What is a photo system?

A
  • protein complex
  • consists of antenna complex and reaction centre
  • absorbs light and transfers electrons
  • photo system I and II
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14
Q

How do photosystems I and II differ?

A

They absorb different wavelengths of light

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15
Q

Describe the process of light harvesting

A
  • The antenna complex absorbs light energy and transfers it to the reaction centre
  • energy is absorbed by two chlorophyll a molecules which emits excited electrons
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16
Q

What is an absorption spectra?

A

A graph showing the wavelengths of light absorbed by a pigment

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17
Q

What is an action spectra?

A

A graph of the rate of photosynthesis against each wavelength of light absorbed by a pigment

18
Q

Describe the light dependant- stage of photosynthesis

A
  • first stage of photosynthesis
  • takes place in the thylakoids of the chloroplast
  • uses light energy to produce ATP, reduced NADP and oxygen
19
Q

State the sources of electrons for the electron transport chain

A

Cyclic and non cyclic photo phosphorylation

20
Q

Define cyclic photophosphorylation

A

The formation of ATP involving photosystem I only.

21
Q

Outline cyclic photo phosphorylation

A
  • Photosystem I only

- excited electrons enter the ETC to produce ATP and then return to photosystem I

22
Q

What is the purpose of cyclic photo phosphorylation

A

Produces additional ATP to meet surplus energy demands of the cell

23
Q

Define non-cyclic photophosphorylation

A

The formation of ATP and reduced NADP involving both Photosystems

24
Q

Outline non-cyclic photophosphorylation

A
  • both photosystems
  • excited electrons enter the ETC to produce ATP
  • NADP acts as final electron acceptor
  • water is photolysed to replace electrons
25
Q

What is the purpose of non-cyclic photophosphorylation

A

Produces ATP and reduced NADP for Calvin cycle

26
Q

How does chemiosmosis produce ATP in the light-dependant 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
27
Q

Describe photolysis

A

Splitting of water molecule in the presence of light during light-dependant stage. Produces protons, electrons and oxygen.

28
Q

What happens to the products of photolysis

A
  • H+ used in proton pumping and to reduce NADP
  • electrons replace those lost in photosystem II
  • oxygen diffuses out of leaf as waste
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-dependant stage to build organic molecules
30
Q

Name the three main stages of the light-independent stage

A
  1. Carbon fixation
  2. Reduction
  3. Regeneration
31
Q

What is carbon fixation

A

It is a reaction between CO2 and RuBP catalysed by RuBP carboxylase. It forms an unstable 6C compound that breaks down into to molecules of glycerate 3-phosphate

32
Q

What happens during reduction of the Calvin cycle

A
  • 2x GP are reduced to 2x triode phosphate (TP)
  • Requires 2x reduced NADP and 2x ATP formed during the light-dependant reaction
  • Forms 2x NADP and 2x ADP that enter the light-dependant reaction
33
Q

What happens during regeneration of the Calvin cycle

A
  • After 1C leaves the cycle, the 5C compound RuP forms
  • RuBP is regenerated from RuP using 1 ATP
  • Forms 1 ATP
34
Q

How are nutrients produced as a result of photosynthesis?

A
  • formation of amino acids from GP (requires nitrates and sulfates)
  • TP molecules used to produce sugars e.g glucose, fructose, sucrose
35
Q

What is a limiting factor?

A

A variable that limits the rate of a particular reaction

36
Q

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

A
  • light intensity - light dependant state
  • CO2 levels - light-independent stage
  • temperature/ pH - enzyme-controlled reactions
37
Q

Describe the role of nitrogen in plant metabolism

A

Synthesis of amino acids, nucleotides and chlorophyll

38
Q

What does nitrogen deficiency in plants cause?

A
  • stunted growth

* chlorosis ( yellowing of leaves )

39
Q

Describe the role of magnesium in plant metabolism

A

Synthesis of chlorophyll

40
Q

What does magnesium deficiency in plants cause?

A

Chlorosis (yellowing of leaves)

Biology A Level Unit 3 (4 decks)

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