GRE Subject Test: Biology : Understanding Plant Metabolism and Photosynthesis

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #2 : Plant Nutrition And Hydration

The Calvin cycle takes place in the __________ and occurs __________.

Possible Answers:

cytoplasm . . . only during the absence of light

stroma . . . whenever the appropriate nutrients are present

cytoplasm . . . whenever the appropriate nutrients are present

stroma . . . only during the absence of light

Correct answer:

stroma . . . whenever the appropriate nutrients are present

Explanation:

The Calvin cycle takes place in the stroma of the chloroplast, which is the region in the chloroplast lumen outside of the thylakoids. It does not actually matter whether or not light is present for the reactions of the Calvin cycle to take place. They are light independent, but light will not prevent the reactions from occurring, similar to how glycolysis is independent of oxygen. As long as the appropriate nutrients and reactants are present, including ATP and NADPH generated from the light reactions, the Calvin cycle will occur. 

Example Question #3 : Plant Nutrition And Hydration

What is the purpose of photosystem II in photosynthesis? 

Possible Answers:

Donate electrons to NADP+ reductase

Sequester carbon dioxide and facilitate its binding to rubisco

Split water to create a high concentration of hydrogen ions

Donate electrons to ATP synthase 

None of the other answers

Correct answer:

Split water to create a high concentration of hydrogen ions

Explanation:

Photosystem II splits water into hydrogen and oxygen. Hydrogen ions accumulate in the thylakoid space, creating an electrochemical concentration gradient. Due to this gradient, hydrogen ions pass through ATP sythase, powering the synthesis of ATP from ADP + Pi

Example Question #1 : Cellular Structures

Which of the following structures is unique to plant cells?

Possible Answers:

Chloroplasts

Endoplasmic reticulum

Mitchondria

Lysosomes

Vacuoles

Correct answer:

Chloroplasts

Explanation:

Chloroplasts are organelles in plant cells that conduct photosynthesis; therefore they are unique to plant cells. All the other mentioned organelles can be found in both animal and plant cells.

Example Question #1 : Understanding Plant Metabolism And Photosynthesis

Which of the following can be found in plant cells, but not animal cells?

Possible Answers:

Chloroplasts

Mitochondria

Ribosomes

Cell membrane

Correct answer:

Chloroplasts

Explanation:

Chloroplasts, the site of photosynthesis, are only in plant cells and are not found in animal cells. Ribosomes, a cell membrane, and a mitochondria, however, can be found in both animal and plant cells.

The other structure that may be found in plant cells, but not animal cells, is a cell wall.

Example Question #1 : Plant Structures

Where in the chloroplasts does the Calvin Cycle of photosynthesis take place?

Possible Answers:

Grana

Thylakoid membrane

Stroma

Intermembrane space

Thylakoid lumen

Correct answer:

Stroma

Explanation:

The Calvin Cycle occurs in the stroma, the aqueous fluid-filled area of the chloroplast. The stroma can be seen as analogous to the cytoplasm of a cell, in that it is the liquid in which all other substructures reside. The other processes of photosynthesis, the light-dependent reactions, take place in the thylakoid, a membrane-bound substructure within the chloroplast.

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