a-Which of the following statements about enzymes is true?

1. Different types of cells contain different sets of enzymes.

2. Substrates can induce a better fit with their enzyme.

3. Different enzymes have different optimal temperature and pH requirements.

4. All of these are true.

5. None of these are true.

b-Why is there a reduction reaction every time there is an oxidation reaction?

1. because energy cannot be created or destroyed

2. to maintain heat gradients in cells

3. every time and electron is lost by an atom, it is gained by another atom

4. because energy levels of electrons must always remain constant