Redox Reactions

Q. How many redox equivalents are removed from one molecule of
3-phosphoglyceraldehyde during glycolysis?

1. 3
2. 4
3. 1
4. 2

Q. A biological redox reaction always involves:

1. loss and gain of electrons in different chemical species.
2. an oxidizing agent.
3. a reducing agent.
4. All of the above.