Calvin cycle

Question 1

How is Rubisco activated?

Answer 1

-light dependent rxns create a pmf across the thylakoid membrane, making the stroma more alkaline (increasing pH) and increasing the stromal conc of Mg2+
-alkaline conditions of stroma allow the Lys residue in the active site of Rubisco to interact with CO2 to form a carbamate ion (COO-)
-carbamate ion binds Mg2+ (active form of Rubisco!)

Question 2

What is the structure of Rubisco?

Answer 2

octamer
-8 large catalytic subunits and 8 small regulatory subunits

active site contains a Lys residue
-when activated, has COO- and Mg2+ bound

Question 3

What does thioredoxin do?

Answer 3

-thioredoxin detects changes in the redox potential of the stroma (caused by the reduction of ferredoxin and NADP+ in the light dependent rxns)
-thioredoxin interacts with Calvin cycle enzymes (eg. phosphoribulokinase) to active them by reducing them

Question 4

What do the sugars produced from the Calvin cycle go onto in plants?

glyceraldehyde-3-phosphate

Answer 4

diff sugars made via pentose phosphate pathway go onto diff metabolic pathways
-aa production
-lipid synth
-nt synth