GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with the Calvin Cycle

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

varsity tutors app store varsity tutors android store

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept

Example Questions

Example Question #1 : Help With The Calvin Cycle

What molecule is remade in the Calvin cycle so that carbon dioxide can attach when entering?

Possible Answers:

Glyceraldehyde-3-phosphate

Ribulose-1,5-bisphosphate

Glucose-6-phosphate

1,3-bisphosphoglycerate

Correct answer:

Ribulose-1,5-bisphosphate

Explanation:

In order to keep the Calvin cycle going, the 5-carbon molecule that carbon dioxide attaches to in the first step must be remade at the end of the cycle. This molecule is called ribulose-1,5-bisphosphate, or RuBP.

Example Question #2 : Help With The Calvin Cycle

Which of the following is an advantage of C4 photosynthesis compared to C3 photosynthesis?

Possible Answers:

C3 plants fix carbon dioxide through rubisco; however, oxygen competes for rubisco binding, reducing the ability for C3 plants to fix carbon. C4 plants use phosphoenolpyruvate (PEP) carboxylase instead of rubisco, which binds carbon dioxide specifically.

The calvin cycle in C4 plants does not require NADPH; therefore, the light reactions are more efficient because they do not have to regenerate NADPH from NADP+

C3 plants physically separate carbon fixation and the Calvin cycle, whereas C4 plants execute both processes in the chloroplast stroma.

C3 plants have fewer photosystems than C4 plants; as a result, C4 plants are able to utlize a broader spectra of light in the light reactions of photosynthesis.

C3 plants are more suitable than C4 plants for growth in arid climates because they keep their stroma closed longer than C4 plants.

Correct answer:

C3 plants fix carbon dioxide through rubisco; however, oxygen competes for rubisco binding, reducing the ability for C3 plants to fix carbon. C4 plants use phosphoenolpyruvate (PEP) carboxylase instead of rubisco, which binds carbon dioxide specifically.

Explanation:

C3 plants use rubisco to fix carbon dioxide; however, oxygen also competes for binding. C4 plants have evolved to use PEP carboxylase, which only binds carbon dioxide, eliminating competition with oxygen. Furthermore, C4 plants separate carbon fixation and the Calvin cycle by location, but C3 plants do not. The light reactions of C3 and C4 plants are very similar, but C4 plants are more suited for arid climates due to their ability to close their stroma for longer periods of time to prevent water loss.

Example Question #3 : Help With The Calvin Cycle

Plants that utilize only the Calvin cycle to __________ carbon dioxide are known as __________ plants. 

Possible Answers:

fix . . . C3

phosphorylate . . . C3

oxidize . . . C3

oxidize . . . C2

fix . . . C2

Correct answer:

fix . . . C3

Explanation:

The purpose of the Calvin cycle is the fixation of carbon dioxide, which essentially turns inorganic carbon dioxide into an organic compound that can be used for energy production. C3 plants only use the Calvin cycle, whereas C4 plants can use a number of processes to fix carbon, including the use of phosphoenolpyruvate carboxylase (PEP carboxylase). 

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept
Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: