Question

What is the net yield of NADH when 26 moles of glucose are used to form pyruvate during glycolysis and the pyruvate is reduced during fermentation?

If a bacterial cell capable of aerobic respiration and fermentation has no oxygen available, which metabolic process could be used to regenerate NAD+ so glycolysis can continue producing ATP?

		Aerobic Respiration
		Glyoxylate Pathway
		Pentose 5 Phosphate Pathwway
		Fermentation
		Anaerobic Respiration

1. Which biochemical process puts electrons back on the same carbon source they came from?

   		fermentation
   		glycolysis
   		Tricarboxilic Acid Cycle
   		Glyoxylate Pathway

Answer 1

Sol.

(1)

When 26 moles of glucose are used to form pyruvate during glycolysis, 26×2=52 NADH and 26×2=52 ATP (net) are produced.

But when these pyruvate are reduced during fermentation,all NADH produced during glycolysis are consumed in fermentation, so there is no net NADH production and no NADH to enter into electron transport system (ETS) and produce more ATP.

(2)

If bacterial cell capable of aerobic respiration and fermentation has no oxygen available, the metabolic process used to regenerate NAD+ so that glycolysis can continue producing ATP is fermentation .

During fermentation all the NADH produced during glycolysis are consumed and are reoxidised to NAD+ , which is necessary for glycolysis and consequently these NAD+ are used in glycolysis to produce ATP.

Other options are incorrect because all of the options given except fermentation require final electron acceptor (sometimes oxygen while in some cases other than oxygen such as sulfate, nitrogen,etc). Only fermentation takes place in anaerobic condition i.e. when no oxygen is available..

Hence fermentation is the correct answer for this question.

(3)

The biochemical pathway which puts electrons back on the same Carbon source they came from is fermentation. During fermentation, electrons which comes with NADH are given back to the same Carbon source from which they came by reoxidising NADH to NAD+. Hence, fermentation is the correct answer for this question.

Other options are incorrect because they use up the electrons given to them.