Chemiosmosis

Part A

Which term describes ATP production resulting from the capture of light energy by chlorophyll?

	Dephosphorylation
	Oxidative phosphorylation
	Substrate-level phosphorylation
	Photophosphorylation

Correct

The excitation of chlorophyll by light energy initiates a chain of events that leads to ATP production.

Part B

True or false? The chemiosmotic hypothesis states that the synthesis of ATP generates a proton gradient that leads to electron flow through an electron transport chain.

	True
	False

Correct

The chemiosmotic hypothesis states that the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP.

Part C

According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?

	Electrons
	Proton gradient
	Temperature gradient
	Osmotic gradient

Correct

A proton gradient across chloroplast and mitochondrial membranes drives ATP synthesis by the enzyme ATP synthase.

Part D

Which of the following particles can pass through the ATP synthase channel?

	ADP
	Inorganic phosphate
	Protons
	ATP

Correct

The channels formed by ATP synthase are specific for protons.

Part E

True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.

	True
	False

Correct

The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span, the chloroplast membrane; the region that spans the membrane is an ion channel through which protons can pass.

Part F

Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5. The solution is then adjusted to pH 8. Which of the following conclusions can be drawn from these experimental conditions?

	Protons will not diffuse toward the outside of the vesicles.
	ATP will be produced because the proton gradient favors proton movement through the ATP synthase channels.
	The change in the solution's pH results in a gradient across the chloroplast membranes such that there is a lower concentration of protons inside the vesicles and a higher concentration outside.
	ATP will not be produced because there is no ADP and inorganic phosphate in the solution.

Correct

This statement is true; although the proton gradient is present, ADP and inorganic phosphate are required to make ATP and were not added to the reaction.