The Student Room Group

Hard Biology question

2. Melvin Calvin studied the light-independent reaction (Calvin cycle) in plant cells.
He used radiolabelled 14CO2 to measure the production of organic molecules in chloroplasts.

He placed an aquatic plant in water.
The plant was given light for 20 minutes.
The light was then turned off (dark conditions) for a further 30 seconds.

He measured the radioactivity of the solutions produced and used these values to calculate the number of
molecules of triose phosphate (TP) and ribulose bisphosphate (RuBP) present.

The results are shown in the table below.

Activity of 14C (x10^27 Bq)
After 20 minutes light / 30 seconds dark conditions

TP 5.5 10.1
RuBP 4.9 0.6

Assuming 8.5 × 10^18 Bq are generated by each 14C atom in the molecule, how many new TP molecules are
produced after 30 seconds in the dark

A 6.47 × 10^8
B 1.80 × 10^8
C 1.83 × 10^27
D 3.37 × 10^27

(by the way ^ means to the power of in this context)
Reply 1
Activity of 14C (x10^27 Bq)

For TP After 20 minutes in the light was 5.5 , in the dark was 10.1
For RuBp it was 4.9, then 0.6

(edited 9 months ago)

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