The enzyme, decarboxylase, catalyses the following step :
1. conversion of citric acid to cis aconitic acid
2. fumaric acid to malic acid
3. oxalosuccinic acid to $\mathrm{\alpha }$-ketoglutaric acid
4. malic acid to oxaloacetic acid

Pyruvate is transported into the mitochondria by:
1. Simple diffusion
2. Facilitated diffusion
3. Active transport
4. Either 2 or 3, depending on the availability of oxygen

Match the following and choose the correct option from those given below.

Options :

A reducing agent in a redox reaction:
1. gains electrons and gains energy.
2. loses electrons and loses energy.
3. gains electrons and loses energy.
4. loses electrons and gains energy.

When an electron is shifted to a more electronegative atom, its potential energy:

By the end of glycolysis, most of the original energy in the glucose molecule is:
1. utilized to form ATP.
2. retained in the pyruvate.
3. stored in the NADH produced.
4. lost as heat.

The number of molecules of carbon dioxide produced by three turns of the Krebs cycle would be:

What is the total number of NADH and ${\mathrm{FADH}}_2$ molecules produced for each molecule of glucose metabolized by glycolysis and the citric acid cycle?

The correct sequence of electron flow during aerobic respiration would be:
1. food → Krebs cycle → ATP → NAD⁺
2. food → NADH → electron transport chain → oxygen
3. glucose → pyruvate → ATP → oxygen
4. glucose → ATP → electron transport chain → NADH

Electron is donated to the mitochondrial ETC at the lowest energy level by: