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

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

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

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Example Questions

Example Question #1 : Help With Other Membrane Functions

Every cell membrane has protein channels that allow certain molecules to pass through.

Which acronym is used to explain the concentration gradient of sodium (Na+) and potassium (K+) inside and outside the cell membrane?

Possible Answers:

HIKIN'

KADE

TIRE

I'm A People Person

SOAP

Correct answer:

HIKIN'

Explanation:

"HIKIN'" represents the statements "there is a HIgh K concentration INside the cell."

"KADE" is used to remember the vitamins that are fat soluble: vitamins K, A, D, and E. "I'm A People Person" refers to the four-point physical assessment of a disease: Inspection, Auscultation, Percussion, Palpation. SOAP is the acronym for Subjective, Objective, Assessment, and Plan—a way to organize patient examination information. TIRE is an mnemonic for remembering the four abdominal muscles: transversus abdominis, internal abdominal oblique, rectus abdominis, external abdominal oblique.

Example Question #1 : Help With Nuclear Structure

What is the main function of the nucleolus in eukaryotic cells?

Possible Answers:

To facilitate nuclear transport of proteins and mRNA from the nucleus to the cytoplasm

Eukaryotic cells do not have a nucleolus

Storage site for transcription factors, RNA polymerases, DNA polymerases, and other transcriptional machinery until transcription occurs

The site of microtubule assembly during mitosis

To promote the transcription, processing, and assembly of rRNA genes into ribosomes

Correct answer:

To promote the transcription, processing, and assembly of rRNA genes into ribosomes

Explanation:

The correct answer is that the nucleolus is the site of ribsome synthesis and assembly. Chromosomes containing rRNA (ribosomal RNA genes) are clustered within the nucleolus, which facilitates rapid transcription and processing of rRNA genes and assembly of rRNA subunits into ribosomes. 

Example Question #2 : Help With Nuclear Structure

The nuclear lamina is generally associated with __________.

Possible Answers:

ribosome synthesis and assembly 

chromatin containing transcriptionally inactive genes

heterochromatin and transcriptionally active genes

euchromatin and transcriptionally inactive genes

chromatin containing transcriptionally active genes

Correct answer:

chromatin containing transcriptionally inactive genes

Explanation:

The correct answer is chromatin and transcriptionally inactive genes. The nuclear lamina provides support and structure to the nucleus and binds transcriptionally inactive regions. Euchromatin is loosely packed chromatin and is, therefore, associated with transcriptionally active genes. Alternatively, heterochromatin is densely packed chromatin and implies inactive genes. Ribosome synthesis and assembly occurs in the nucleolus.

Example Question #1 : Nucleus And Ribosomes

What is the function of RanGAP in relation to nuclear import and export?

Possible Answers:

Maintain a gradient of GTP/GDP bound Ran 

Attach GTP to Ran

Bind cargo proteins

Bind importins/exportins and bring them through the nuclear pore complex

Correct answer:

Maintain a gradient of GTP/GDP bound Ran 

Explanation:

RanGAP is notable for its ability to activate the GTPase function of the Ran protein. This allows for the hydrolysis of the third phosphate of GTP-bound Ran and the maintenance of a Ran-GDP/Ran-GTP gradient that is used to control nuclear import and export. RanGAP does not directly associate with cargo proteins or importins/exportins.

Example Question #2 : Nucleus And Ribosomes

Which of the following choices would have the biggest effect on nuclear transport?

Possible Answers:

A non-functional copy of the gene that encodes CRM1

An inhibitor that globally targets exportins at their cargo binding sites

A mutated, non-functional copy of RanGAP

An inhibitor that globally targets importins at their cargo binding sites

Correct answer:

A mutated, non-functional copy of RanGAP

Explanation:

Because the question is asking which will have the largest effect, it makes sense that the answer should affect import and export globally.

Importins and exportins only work in one direction. While mutations to either of these protein classes would greatly affect nuclear transport, each is only responsible for "half" or the transport across the membrane. CRM1 is a well characterized exportin.

RanGAP, however, is responsible for helping maintain the gradient of Ran bound to GTP or GDP. The gradient of RanGTP/GDP is what provides global directionality to nuclear import and export. Loss of RanGAP would affect both import and export, having the largest detrimental effect on nuclear transport.

Example Question #3 : Nucleus And Ribosomes

What is the site of ribosomal subunit synthesis in the cell?

Possible Answers:

Smooth endoplasmic reticulum

Nucleolus

Nucleus

Golgi apparatus

Correct answer:

Nucleolus

Explanation:

Ribosomal subunits are created in the nucleolus, a small area found inside of the nucleus.

Example Question #1 : Help With Ribosome Structure

How many RNA molecules are found in the small ribosomal subunit.

Possible Answers:

1

6

0

3

2

Correct answer:

1

Explanation:

The small subunit of the ribosome contains only one RNA molecule; the 16S rRNA in prokaryotes and the 18S rRNA in eukaryotes.

Example Question #1 : Help With Mitochondria Structure

What is the primary purpose of cristae in the mitochondria?

Possible Answers:

Protect the mitochondrial genome

Prevent the mitochondria from folding in on itself

Provide a large surface area for chemical reactions

No purpose has yet been identified; they are likely an evolutionary remnant 

Correct answer:

Provide a large surface area for chemical reactions

Explanation:

The importance of the cristae comes from the fact that they greatly increase the surface area of the inner membrane of the mitochondria. This is important because this membrane houses the electron transport chain proteins. A larger surface area allows reactions to occur at a higher rate and, thus, more ATP can be generated. The cristae are not essential to protecting the mitochondrial genome or maintaining shape.

Example Question #2 : Help With Mitochondria Structure

Where does the Krebs cycle take place in the mitochondria?

Possible Answers:

Outer mitochondrial membrane

Inner mitochondrial membrane

Intermembrane space

Mitochondrial matrix

Correct answer:

Mitochondrial matrix

Explanation:

The mitochondrion is a double-membraned organelle responsible for generating ATP for the cell. The Krebs cycle is the middle step of cellular respiration, and takes place in the mitochondrial matrix.

Example Question #1 : Mitochondria And Chloroplasts

In what part of mitochondria does the electron transport chain take place?

Possible Answers:

Intermembrane space

Thylakoid space

Matrix

Outer membrane 

Inner membrane 

Correct answer:

Inner membrane 

Explanation:

While the matrix, outer membrane, and intermembrane spaces are components of mitochondria, the correct answer is inner membrane. The thylakoid space is found in chloroplasts not mitochondria. Compounds are embedded in the inner membrane and transfer electrons from electron donors to electron acceptors by redox reactions. The final enzyme in the chain is ATP synthase, which generates ATP from ADP and inorganic phosphate. 

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

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