5.6 PHOTOSYNTHESIS Flashcards

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1
Q

Structure of the chloroplast

A
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2
Q

What are thylakoids in the chloroplast?

A
  • Folded membranes which contain photosynthetic pigment (chlorophyll) and photosystems
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3
Q

What is stroma in the chloroplast?

A
  • fluid centre of the chloroplast with RUBISCO enzymes
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4
Q

What is the grana in the chloroplast?

A
  • stacks of thylakoids
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5
Q

What is the outer membrane of a chloroplast?

A
  • Highly permeable membrane that controls the entry/exit in chloroplast
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6
Q

What is a photosystem and where are they located?

A
  • Photosystems are a bunch of photosynthetic pigments found in the thylakoids
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7
Q

What is meant by a photosynthetic pigment?

A
  • Different pigments that absorb specific wavelengths of light
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8
Q

What are *accessory pigments**, where are they based in photosystems and what do they do?

A
  • Chlorophyll B/ Carotenoids
  • Light harvesting system
  • Light energy absorbed is passed to the reaction centres
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9
Q

Where is the *primary pigment**, where is it based in photosystems and what does it do?

A
  • Chlorophyll A
  • Reaction centres
  • Where light dependant stage happens
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10
Q

State the Rf value equation

A
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11
Q

Where does the light-dependant stage occur?

A
  • Thylakoids
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12
Q

What reactions does the light-dependant stage consist of? (4)

A

1) Non-cyclic photophosphporilation
2) Cyclic photophosphporilation
3) Photolysis
4) Chemiosmosis

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13
Q

What two things are produced by the light-dependant stage?

A
  • ATP
  • Reduced NADP/NADPH
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14
Q

Name the two photosystems used in the light-dependant stage.

A
  • PSII (used first) and PSI (used after)
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15
Q

Describe non-cyclic photophosphporilation

A
  • Light energy absorbed by photosynthetic pigments causes electrons in the reaction centre chlorophyll of PSII to become excited & released to electron carriers
  • Electron carriers combine with electron (to become reduced to Fe2+ then donates the electron to next electron carrier to become re-oxidised to Fe3+) which moves excited electrons along the electron transport system to PSI
  • The movement of electrons through the electron transport chain results in ATP production at the end via chemiosmosis
  • Electrons lost from the reaction centre chlorophyll of PSII are replaced by electrons from photolysis and electrons lost from reaction centre chlorophyll of PSI are replaced by electrons from PSII
  • At PSI reaction centre the electrons are released and accepted by the coenzyme NADP along with H+ protons from photolysis to produce reduced NAPD (NADPH)
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16
Q

Describe cyclic photophosphporilation

A
  • Some electrons released from the reaction centres of PSI are not picked up by the coenzyme NADP and are instead recyled back into PSI
  • The movement of electrons along the electron transport chain still results in ATP production by chemiosmosis
  • However reduced NADP (NADPH) is not produced
17
Q

Describe photolysis

A
  • Light energy absorbed by chlorophyll in PSII is used (along with an enzyme) to split water into oxygen, H+ and e-
  • The H+ proton is picked up by NADP to produce reduced NADP (NADPH)
  • The electron from this replaces the electrons lost from the reaction centre chlorophyll of PSII
  • The oxygen is used for respiration or diffuses out the leaf
18
Q

Describe chemiosmosis

A
  • When excited electrons move along the electron transport chain through the embedded electron carriers in thylakoid membrane energy is released
  • Some of this energy is used to pump H+ protons from photolysis across the thylakoid membrane from the stroma to the thylakoid space
  • This creates an electrochemical gradient as many H+ protons are now in the thylakoid space
  • As a result, H+ protons diffuse down the electrochemical gradient, back across the thylakoid membrane through the enzyme ATP synthase
  • When H+ protons pass through, ATP synthase converts ADP + Pi into ATP
  • The H+ protons now combine with the coenzyme NADP to form reduced NAPD (NAPH)
19
Q

Describe the three roles of water in photosynthesis

A

1) Source of H+ protons for photophosphorilation (NADPH production)
2) Replaces electrons lost from reaction centre chlorophyll of PSII
3) Keeps plant turgid

20
Q

Where does the light-independant stage occur?

A
  • Stroma
21
Q

What does the light-independant stage consist of?

A
  • The calvin cycle
22
Q

Draw and describe the calvin cycle

A
23
Q

What is produced in the light-independant stage?

A
  • Hexose sugar
24
Q

State the uses of TP during the calvin cycle

A
  • Can form the disaccarise sucrose
  • Can form the polysaccarides starch or cellulose
  • Can form amino acids
  • Can form lipids
  • Can regenerate RuBP for calvin cycle
25
Q

The three limiting factors of photosynthesis?

A
26
Q

How does decreasing light intensity affect levels of GP, TP and RuBP?

A
  • Lower light intensity reduces GP, TP and RuBP because ATP and NADPH is reduced during the light dependent stage
27
Q

How does **decreasing carbon dioxide* affect levels of GP, TP and RuBP?

A
  • Lower carbon dioxide increases RuBP but reduces GP, TP because RuBP accumulates as it cannot react with low levels of carbon dioxide meaning GP and TP cannot be produced.
28
Q

How does **increasing temperature* affect levels of GP, TP and RuBP?

A
  • Higher temperature increases GP, TP and RuBP as more kinetic energy means more successful collisions until temperature is too high, RuBP denatures