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A- Level Biology - Photosynthesis > Light indepdent reaction > Flashcards

Flashcards in Light indepdent reaction Deck (29)
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What are the products of light-dependent reaction

e.g ATP and reduced NADP used in light independent reaction?

To reduce glycerate 3-phosphate in the second stage of photosynthesis


Why is light independent reaction different from light-dependent reaction?

Does not require light directly and in theory occurs whether light is available or not


What does it require?

The products of light-dependent stage and so rapidly cases when light is absent


Where does it take place?

In the stroma of the chloroplasts


What is the details of this stage worked out by?

Melvin Calvin


Calvin Cycle


What is the first step of light independent (LIR)?

  • The carbon dioxide from the atmosphere diffuses into the leaf through the stomata
  • It dissolves in water around the walls of the mesophyll cells
  • It diffuses through the cell-surface membrane, cytoplasm and chloroplast membrane into stroma of the chloroplast


What is the second step of lihgt independent reaction?

  • In the stroma, carbon dioxide reacts with 5-carbon compound of RuBP
  • A reaction catalysed by an example called rubsico


What is the full name of RuBP?

Ribulose Bisphosphate


What is full name of rubsico?

Rublose bisphosphate carboxylase


What is the third stage of light independent reaction?

The reaction between carbon dioxide and RuBP produces two molecules of 3-carbon GP


What is full name of GP?

Glycerare 3-phosphate


What is fourth stage of light independent reaction?

Reduced NADP from LDR is used to reduce GP to TP using energy supplied by ATP


What is the full name of TP?

Triose phosphate


What is the fifth step  of LIR?

NADP is re-formed and goes back to the LDR reaction to be reduced again by accepting more protons


What is the sixth step of LIR?

Some TP molecules are converted to organic substances that plant requires such as starch, cellulose, lipids, glucose , amino acids and nucleotides


What is the seventh step of LIR?

Most TP molecules are used to regenerate RP using ATP from LDR


What proportion of TP is used to regenerate RuBP?


(1/6 - used to make organic molecules)


Why Calvin Cycle needs to turn six times to make one hexose sugar?

  • Three turns of cycle produce six TP because 2 TP made for one CO2 used
  • 5/6 of TP used to regenerate RuBP
  • Three turns of cycle only one TP is produced thats for hexose sugar
  • A hexose has six carbons , two TP need to form one hexose sugar
  • Cycle turn six times to make two molecules of TP used to make sugar
  • Six out of the cycle need 18 ATP and 12 NADPH from LDR


What keeps the cycle going?

Make sure there is enough RuBP

ready to combine with CO2 in atmosphere


Diagram of Calvin Cycle


Diagram of total no in Calvin Cycle


What is carbon fixation?

Addition of C02 to RuBP


What is Calvin cycle the starting point for?

Making all organic substances a plant needs

Tp and GP molecules are used to make carbohydrates, lipids and amino acids?


How are carbohydrates made?

Hexose sugar e.g glucose

Joined two TP molecules together 

Larger carbohydrate made (e.g sucrose, cellulose) by joining hexose sugar in different ways


How are lipids made?

Made from using glycerol which is synthesised from TP and fatty acids which are synthesised from GP


How are amino acids made?

Some are made from GP


How is the fluid of the stroma adapted for LIR?

It is membrane bound in the chloroplast

Chemical envirnoment has high concentration of enzyme and subtrates be maintined within it

Distinct from the envirnoment of the cytoplasm


How is the stroma fluid surrounding grana adapted?

Products of LDR reaction in grana can readily diffuse in the stroma


How chloroplats containg DNA and ribosomes adapted for LIR?

Quickly manfacture some proteins involed in LIR