Lecture 10 Flashcards
How does glycogen phosphorylase respond to glucagon signal in the liver tissue?
It gets activated by glucagon because that’s the signal that glucose stores are low and more needs to be made. Glycogen phosphorylase catabolized glycogen into glucose
Where is HKIV found in the cell when blood glucose concentrations are high?
It’s in the cytosol. When glucose levels are low, then it’s in the nucleus
How are glycolysis and gluconeogenesis prevented from extensive futile cycling?
The enzymes are coordinated in a reciprocal manner. Most reactions take place in the same compartments, with a few exceptions (matrix and ER lumen)
What is the purpose of carbon assimilation in C3 plants?
It converts CO2 into triose phosphates, which can be used to regenerate ribulose 1,5-BP OR to make starch, cellulose, and sucrose
What is step 1 in carbon assimilation?
The carboxylase aspect of the rubisco enzyme catalyzed the covalent attachment of CO2 to ribulose 1,5-BP, and a it also cleaves an unstable 6-C intermediate into two 3-PG molecules
What is step 2 in carbon assimilation?
3-PG gets converted into glyceraldehyde 3-P.
3-PG + ATP -> 1,3-BPG + NADPH -> glyceraldehyde 3-P + Pi + (NADP+)
The conversion of 3-PG to glyceraldehyde 3-P is energetically unfavorable. What makes it favorable anyway?
The high concentrations of ATP and NADPH Le Chat the rxn forward
What is step 3 of carbon assimilation?
5 triose phosphates regenerate ribulose 1,5-BP and 1 triose phosphate is used to make starch, cellulose, or sucrose
Which enzyme from gluconeogenesis is involved in step 3 of carbon assimilation and how?
FBPase-1.
glyceraldehyde 3-P -> fructose 1,6-BP -> fructose 6-P ->… 2 pentose phosphates -> ribulose 5-P -> ribulose 1,5-BP
Each triose phosphate needs how many ATP and NADPH?
9ATP and 6 NADPH
3 turns of the Calvin cycle yields…?
3CO2 + 1 phosphate -> 1 triose phosphate
What is the stoichiometry of carbon fixation?
3CO2 + H2O -> 6 (3-PG) -> 6 (1,3-PG) -> 6 glyceraldehyde 3 -P + 6 DHAP -> 1 glyceraldeyde 3- P net for use to make starch, cellulose, or sucrose, rest of 5 glyc. 3-P regenerate 3 ribulose 1,5-BP molecules
Why is rubisco infamous?
It is inefficient at its job (only processes like 3 CO2 per second at room temp, so plants need lots of the enzyme. That’s why it’s the most abundant enzyme on Earth
What is a trash product that rubisco produces upon CO2 fixation?
2-PG + CO2 (it regenerates a reactant!)
Which pathway salvages 2-PG?
The glycoxylate pathway
