DD - Intro to Cell Metabolism 2 Flashcards
Describe the open glucose structure
- Aldehyde group on carbon 1
- All hydroxyl groups are on the right side apart from on carbon 3 (on left side)
What are the 3 irreversible steps involved in glycolysis?
- Glucose –> Glucose-6-Phosphate
- Fructose-6-Phosphate –> Fructose-1,6-Bisphosphate
- Phosphoenolpyruvate –> Pyruvate
How does the structure of fructose differ from that of glucose?
Aldehyde group on C1 is changed to a Ketone group on C2
Hydroxyl group changes from C2 to C1
Why are some steps in glycolysis irreversible?
Due to a large negative gibbs value
What are coenzymes?
An organic non-protein component of enzymes
Where are coenzymes derived from?
Vitamins
e.g. NAD+ - Niacin
FAD - Riboflavin
CoA - Pantothenic acid
What are some roles of coenzymes in metabolism? (4)
- Involved in catabolism of glucose
- Involved in delivery of chemical groups/atoms
- NAD+ involed in the transfer of protons
- ATP involved in the transfer of phosphate
Describe the structure of NAD+
ADP-Ribose-Nicotinamide
What does coupling 2 reactions involve?
If one reaction is positive gibbs it cannot occur spontaneously
However, if coupled with a large negative gibbs reaction, the overall reaction will occur spontaneously
What are energy transducers?
- Transfer energy between reactions
- Not a store
- Produced on demand
Which 2 coenzymes act as energy trasnducers?
ATP and GTP
Are phosphorylation reactions endergonic or exergonic?
Endergonic (Gibbs >0) and so must be coupled
What is the structure of pyruvate?
Carboxylate
I
Carbonyl
I
Methyl
Are oxidation reactions endergonic or exergonic?
Exergonic (Gibbs <0)
What are the 2 steps involved in the tricky reversal of Pyruvate –> Phosphoenolpyruvate?
STEP 1 -
- Carboxylation (endergonic)
STEP 2 -
- De-carboxylation (exergonic)
- Phosphorylation (endergonic)
