Biochemistry Glycolysis/Gluconeogenesis

[JOJOwwwAiri]

Homework Statement

Avidin, a 70-kd protein in egg white, has very high affinity for biotin. In fact, it is a highly specific inhibitor of biotin enzymes. Which of the following conversions would be blocked by the addition of avidin to a cell homogenate?
(a) Glucose & pyruvate
(b) Pyruvate & glucose
(c) Oxaloacetate & glucose
(d) Malate & oxaloacetate
(e) Pyruvate & oxaloacetate
(f) Glyceraldehyde 3-phosphate & fructose 1,6-bisphosphate

Relevant Equations

N/A

The answer is that reactions in parts b and e would be blocked but I don't understand why the answer is that and what's the logic involved in getting the correct answer. Could somebody explain the general approach in understanding and solving this type of question to me? Thanks in advance!

 

[Ygggdrasil]

I guess the answer requires knowing two key facts:
1) The enzyme pyruvate carboxylase (which converts pyruvate to oxaloacetate) uses biotin as a cofactor (hence reaction e is blocked).
2) For pyruvate to be converted to glucose (via gluconeogenesis), pyruvate must be able to be converted to oxaloacetate via pyruvate carboxylase (so reaction b is also blocked).

The other reactions are not catalyzed by biotin enzymes and hence would not be affected by avidin.