11.3 light-independent reaction Flashcards

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1
Q

light independent reaction

A

doesn’t require light directly

Uses products of ldr so ceases when light is absent

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2
Q

first step

A

CO2 from atmosphere diffused through stomata into leaf

dissolves in water around the walls of mesophyll cells

diffused through csm, cytoplasm and chloroplast membranes into stroma of chloroplast

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3
Q

second step

A

CO2 reacts with 5-carbon compound ribuslose bisphosphate(RuBP)

reaction catalysed by enzyme ribuisco(ribuslose bisphosphate carboxylase)

produces 2 molecules of 3-carbon glycerate 3-phosphate(GP)

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4
Q

third step

A

reduced NADP from ldr reduces glycerate 3-phosphate to triose phosphate(TP)

uses energy supplied by ATP

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5
Q

fourth step

A

NADP is re-formed

Goes back to ldr to be reduced again by accepting more protons

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6
Q

fifth step

A

some triose phosphate molecules converted to organic substances plant needs
-e.g. starch, cellulose, lipids, glucose, amino acids and nucleotides

most used to regenerate ribulose bisphosphate using ATP from ldr

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7
Q

site of light independent reaction

A

stroma

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8
Q

3 adaptions of chloroplast

A
  1. stroma surrounds grana so products of ldr can readily diffuse into stroma
  2. contains both DNA and ribosomes so can quickly manufacture some proteins involved
  3. fluid of stroma contains all enzymes needed to carry out reaction. It is membrane bound in chloroplast and separate to chloroplast so chemical environment with high conc of enzymes and substrates can be maintained
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9
Q

Limiting factors

A
  1. light intensity
  2. availability of water
  3. temperature
  4. carbon dioxide concentration
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10
Q

light intensity

A

-less light for ldr
-fewer electrons excited
-less ATP and reduced NADP for lir
-less photolysis
-fewer electrons released to replace those lost from photosystems
-less o2 is produced
-fewer stomata open so less co2 for lir

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11
Q

temperature (too cold)

A

-less kinetic energy for rubisco reactions in lir if too cold
-less RuBP carboxylated
-less GP and TP generated
-less complex molecules produced
-less ADP + Pi and NADP for LDS
-less kinetic energy for enzyme involved in photolysis if too cold

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12
Q

co2 concentration

A

-less co2 for lir
-less available to carboxylate RuBP
-less GP and TP generated
-fewer complex molecules produced
-less ADP + Pi and NADP for ldr

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13
Q

temperature too hot

A

–rubisco enzyme denatures
-electron carries in ldr renature
-proteins holding photosystems in place denature

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14
Q

No limiting factors

A

rate of photosynthesis doubles every 10 degrees between 0-25

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15
Q

water availability

A

-less h20 available for photolysis
-less o2 produced
-fewer electrons released to replace those lost from photosystems
-less ATP and reduced NADP for lir
-less H20 h20 available for guard cells to swell and stomata to open
-less co2 available for lir
-plant wilts so less SA exposed to sun for ldr

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