Chapter 7

The second stage of the Calvin cycle needs an input of energy to reduce the 3PG molecules that resulted from the first stage. Where does this energy input come from?

ATP and NADPH that were supplied through the light reactions

Which of the following is the enzyme used to synthesize ATP?

ATP synthase

Photosystem I occurs before photosystem II during the light reactions.

False

The energy that is released when hydrogen ions pass through ATP synthase provides the energy needed to form ADP and phosphate from ATP.

False

Heterotrophs and autotrophs

Organisms that produce their own food are called autotrophs. One process that some organisms use to make this food is called photosynthesis. This process converts solar energy, carbon dioxide gas, and water into a carbohydrate called glucose and oxygen gas. The products of this reaction are consumed by organisms called heterotrophs that must take in pre-formed organic molecules for energy. These organisms transform the energy found in ____________ and oxygen gas to usable energy, releasing carbon dioxide gas and water.

In which of the following ways is photosystem I different than photosystem II?

Photosystem I uses the high-energy electrons to reduce NADP+ to NADPH, whereas photosystem II uses them to convert ADP into ATP.

The last stage of the Calvin cycle acts to recycle _____, sending it back to aid in _____ again.

RuBP; carbon fixation

As the hydrogen ions move down their concentration gradient, energy is released.

True

A photosystem can best be described as

a collection of pigments that trap solar energy and focus it on reaction centers, releasing high-energy electrons.

After their generation during the light reactions, NADPH and ATP

are used in the Calvin cycle reactions to help form carbohydrates.

Because the reactions aren't cyclic, over time photosystem II would lose all its electrons. This does not happen because

energy from photosystem II is used to split water molecules, releasing electrons.

As protons move through the proton pump,

they build up on one side of the membrane, producing a concentration gradient.

The overall goal of the Calvin cycle is to

use carbon dioxide gas and energy to produce carbohydrates.

Proton pumps are protein complexes that

move hydrogen ions across cell membranes.

After high-energy electrons leave photosystem II, they proceed directly to _____, where their energy is used to _____.

the electron transport chain; convert ADP into ATP