Question

1. In a cell, a thermodynamically unfavorable process can occur if

1. the process is coupled to a thermodynamically favorable process.
2. the process is thermodynamically favorable outside the cell.
3. an enzyme gives energy to the reacting substances.
4. the cell as a whole is close to equilibrium.

2. In an active transport protein,

1. ATP hydrolysis creates a channel through the membrane.
2. ATP uses the protein to move across the membrane.
3. ATP hydrolysis causes the protein to change shape.
4. ATP carries a substance across a membrane.

3. The NAD+ molecules that become reduced during operation of the citric acid cycle

1. are converted to ATP by the electron transport chain.
2. transfer their electrons to other substances.
3. are regenerated by accepting electrons from another source.
4. are degraded by cellular enzymes.

4. The reaction ATP + H2O ADP + Pi

1. generates products with less free energy than the reactants.
2. requires the input of free energy.
3. is endergonic under cellular conditions.
4. has a positive value of ΔG.

Answer 1

1. A. Many unfavorable reactions in our cell occurs by coupling it with a thermodynamically favourable processes such as ATP hydrolysis. So the energy released by favourable processes are used by the unfavorable reactions.

2. C. Active transport utilizes ATP to transport the molecules across the membrane. By ATP hydrolysis the confirmation of membrane protein changes due to which the molecules are transported easily.

3. B. NADH produced in citric acid cycle transfer it's electron to the other electron acceptors in a process called electron transport chain. Finally this electron is transferred to oxygen to produce water molecule.

4. A. ATP hydrolysis is an exergonic reaction in which energy is released. That why in spontaneous reaction or exergonic reaction products energy state is less than that of the reactants. It's delta d value is always negative.