3.5.1.2 - Photosynthesis (Calvin Cycle) Flashcards

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1
Q

The diagram shows Melvin Calvin’s Lollipop experiment for identifying the products of the Calvin Cycle. Why was radioactive hydrogen carbonate supplied to the algae?

A

So that the substances into which the CO2 is incorporated can be identified.

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2
Q

Describe the Calvin Cycle

A
  1. CARBON FIXATION - Rubisco enzyme catalyses the reaction of RuBP with CO2 to produce 2x Glycerate-3-Phosphate (G-3-P).
  2. REDUCTION - NADPH reduces G-3-P into 2x Triose Phosphate (TP) with energy being provided by ATP.
  3. REGENERATION - 2 x TP are converted into orgnaic compounds e.g. glucose OR ATP is used to convert TP into RuBP for more turns of the Calvin cycle.
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3
Q

How many carbon aotms in Ribulose Bisphosphate (RuBP)?

A

5

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4
Q

Name the enzyme that catalyses the fixation of carbon dioxde into RuBP to produce glycerate-3-phosphate.

A

Rubisco

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5
Q

How many turns of the calvin cycle take place to produce 1 molecule of glucose?

A

6

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6
Q

How many carbon atoms in glycerate-3-phosphate?

A

3

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7
Q

What are the proudcts of every 6 turns of the carbon cycle?

A

1 x glucose molecule

5 x RuBP

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8
Q

What are the light independent reactions of photosynthesis sometimes referred to as?

A

The Calvin Cycle

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9
Q

What are the products of the Calvin cycle (LIR)?

A

Organic compounds e.g. glucose, amino acids, lipids

RuBP (Ribulose Bisphosphate)

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10
Q

How many carbon atoms in triose phosphate?

A

3

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11
Q

The diagram shows Melvin Calvin’s Lollipop experiment for identifying the products of the Calvin Cycle. Why is a fast flow tap used in this experiment?

A

To terminate the reactions immediately.

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12
Q

The diagram shows Melvin Calvin’s Lollipop experiment for identifying the products of the Calvin Cycle. Why is hot methanol supplied to the algae?

A

High temp will denature enzymes that catalyse reactions.

Methonal could denature the enzymes.

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13
Q

Does the Calvin Cycle require light to function?

A

No

BUT

The reactions will stop eventually in the absence of light because essential ATP and NADPH from light reactions will run out.

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14
Q

During the light-independent reaction of photosynthesis, carbon dioxide is converted into organic substances. Describe how. (6 marks)

A
  1. Carbon dioxide combines with ribulose bisphosphate / RuBP;
  2. Produces two glycerate-3-phosphate / GP;
  3. GP reduced to triose phosphate / TP;
  4. Using reduced NADP; and…
  5. …Using energy from ATP;
  6. Triose phosphate converted to glucose / RuBP / ribulose bisphosphate
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15
Q

Heat stress decreases the LDR - why does this lead to a decrease in the LIDR?

A

Less ATP

Less reduced NADP

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16
Q

A decrease in the activity of the enzyme rubisco would limit photosynthesis - why?

A

Less carbon dioxide reacts with RuBP

so

Less GP

17
Q

where is rubisco found?

A

stroma (of chloroplast)