Question

1. (a) How many phosphoanhydride bond(s) are present in each of the following biomolecules? ADP:_____________________ AMP:_____________________ 1,3-Bisphosphoglycerate:______________________ Glucose-6-phosphate:_____________________ Glyceraldehyde-3-phosphate:_____________________ Fructose-1,6-bisphosphate:_____________________ Pyrophosphate (PPi) :______________________ (b) Using chemical names and structures write out the substrate-level phosphorylation steps (and not the full pathway) in glycolysis. Name the enzymes catalyzing these reactions. (c) Which enzyme catalyzes substrate-level phosphorylation in the citric acid cycle? d) Write the reaction using names and structures of the metabolites. (Note: no need to give the full chemical structures of the "activated carriers".)

Answer 1

1.
P-O-P bond = Phosphoanhydride bond

Number of Phosphoanhydride bonds:
1. ADP = 1
2. AMP = 0
3. 1,3-Bisphosphoglycerate = 1
4. Glucose-6-phosphate = 0
5. Glyceraldehyde-3-phosphate = 0
6. Fructose-1,6-bisphosphate = 0
7. Pyrophosphate = 1

2.
Direct phosphorylation of ADP to produce ATP instead going through oxidative phosphorylation via ETC = Substrate level phosphorylation.
There is one substrate level phosphorylation reaction in glycolysis.

1,3-Bisphosphoglycerate + ADP --------> 3-phosphoglycerate + ATP
This reaction is catalyzed by Phosphoglycerate kinase

3.
There is one substrate level phosphorylation reaction in TCA cycle.

Succinyl COA + GDP + Pi --------> Succinate + GTP + CoASH
This reaction is catalyzed by Succinyl CoA synthetase