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Biology Paper 2 (5-8) > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

First step of light dependent stage (non-cyclic photo phosphorylation)

A
  • photons of light absorbed by chlorophyll in photosystem 2 (PS2)
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2
Q

Second step of light dependant stage (non-cyclic photo phosphorylation)

A
  • increases kinetic energy in electrons and chlorophyll undergoes photoionisation
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3
Q

Third step of light dependant stage (non-cyclic photo phosphorylation)

A
  • photosystems are linked by proteins called electron carriers and form electron transport chain. Electrons leave chlorophyll and move to photosystem 1 (PS1)
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4
Q

Forth step of light dependant stage (non-cyclic photo phosphorylation)

A
  • light energy can split water by photolysis forming protons (H+), electrons and oxygen. Electrons can be used to replace those lost in photosystem 2 (PS2)
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5
Q

Fifth step of light dependant stage (non-cyclic photo phosphorylation)

A
  • electrons lose energy as they move down the electron transport chain. This energy is used to actively pump protons against their electrochemical gradient from the stroma to the thylakoid space
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6
Q

Sixth step of light dependant stage (non-cyclic photo phosphorylation)

A
  • hydrogen ions move down the concentration gradient back out into the stroma via the embedded enzyme ATP synthase. This allows ATP to form
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7
Q

Seventh step of light dependant stage (non-cyclic photo phosphorylation)

A
  • steps 1 and 2 are repeated in photosystem 1 with electrons leaving the chlorophyll molecules of photosynthesis 1 (PS1)
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8
Q

Eighth step of light dependant stage (non-cyclic photo phosphorylation)

A
  • Using enzyme NADP reductase, electrons from photosystem 1 (PS1) are transferred to NADP along with a proton from the stroma to form NADPH. Electrons from photosystem 2 (PS2) that moved along the electron transport chain replace those lost from photosystem 1 (PS1)
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9
Q

First step of light independent stage (cyclic photo phosphorylation/calvin cycle)

A
  • carbon dioxide enters chloroplast by diffusion and passes into the stroma, combining with intermediate compound ribulose bisphosphate (RuBP) and catalysed by enzyme rubisco in carbon fixation producing 2 molecules of glycerate 3 phosphate (G3P)
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10
Q

Why are large quantities of enzyme rubisco required in calvin cycle

A
  • slow process
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11
Q

Second step of light independent stage (cyclic photo phosphorylation/calvin cycle)

A
  • Energy from ATP and hydrogen from reduced NADP (from light dependant stage) is used to reduce glycerate 3 phosphate (G3P) to form triose phosphate (TP)
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12
Q

Third step of light independent stage (cyclic photo phosphorylation/calvin cycle)

A
  • 1/6 of triose phosphate (TP) is used to make glucose phosphate and in turn, glucose.
  • condensation of many glucose molecules in the stroma forms starch
  • glycerol is synthesised from triose phosphate (TP) and fatty and amino acids from glycerate 3 phosphate (G3P)
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13
Q

Forth step of light independent stage (cyclic photo phosphorylation/calvin cycle)

A
  • 5/6 of triose phosphate must be used to regenerate ribulose bisphosphate (RuBP) using ATP
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14
Q

Limiting factors of photosynthesis

A
  1. Carbon dioxide concentration
  2. Light intensity
  3. Temperature
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15
Q

Limiting factor definition

A
  • something present in the environment in such short supply that it restricts life processes, slowing rate of reaction
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16
Q

Rate limiting step

A
  • step in a process proceeding most slowly at a given time
17
Q

Carbon dioxide concentration

A
  • low carbon dioxide concentration causes NADPH and RuBP to accumulate so the rate limiting step is carbon fixation stage of the Calvin cycle
18
Q

Temperature

A
  • low temperature causes the enzymes catalysing the whole of the Calvin cycle to slow down, especially the activity of rubisco
19
Q

Light intensity

A
  • low light intensity causes a shortage of products of light dependant reaction (NADPH and ATP) so rate limiting step is when glycerate 3 phosphate (G3P) is reduced in the light independent stage as those products are required
20
Q

Explanation of curved graph section A

A
  • as (x axis) increases, so does the rate of photosynthesis. (X axis) is limiting factor. … reaction occurs producing…
21
Q

Explanation of curved graph section B

A
  • graph starts to plateau as some other factor is starting to become limiting
22
Q

Explanation of curved graph section C

A
  • (x axis) is no longer a limiting factor; now (other 2 limiting factors). Rate of photosynthesis won’t increase more. … step has become rate limiting step overall
23
Q

How to isolate a sample of chloroplasts from leaves?

A
  • break open cells and filter
  • in cold, isotonic, pH controlled solution
  • centrifuge and remove cell debris
  • spin at higher speeds until chloroplasts settle out
24
Q

Photoionisation

A
  • light energy absorbed by chlorophyll releasing electrons and causing them to pass to an electron acceptor at the start of the electron transport chain
25
Q

Chemiosmosis

A
  • movement of electrons along the electron transport chain creating a proton gradient across the membrane to drive ATP synthase
26
Q

Photolysis

A
  • process of splitting water molecules using light energy to reduce electrons, oxygen and hydrogen ions
27
Q

Electrochemical gradient

A
  • difference in charge and chemical concentration across a membrane
28
Q

Explain how to use chromatography to separate photosynthetic pigments

A
  • draw pencil line with ruler to mark origin
  • using paint brush, apply pigment in origin mark and mark solvent front
  • place solvent in tube and place chromatogram below the origin line
  • measure the rf value
29
Q

Why use propanone for chromatography?

A
  • breaks down cells, chloroplasts and thylakoids to release pigment
  • dissolves chlorophyll to isolate from plant tissues

Biology Paper 2 (5-8) (4 decks)

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