All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Questions
Example Question #11 : Cellular Structures And Functions
Which of the following transport mechanisms requires ATP hydrolysis to move a molecule against its concentration gradient?
Secondary active transport
Facilitated diffusion
Cotransport
Active transport
Passive diffusion
Active transport
Secondary active transport and cotransport are the same thing, and while solutes can be moved against their concentration gradient, ATP is not used. Passive and facilitated diffusion do not require ATP either. Active transport is the only transport mechanism that uses ATP to move molecules against their concentration gradient.
Example Question #11 : Cell Membrane And Cell Wall
Which of the following is not a method used to transport substances into a cell?
Exocytosis
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis
Exocytosis
Endocytosis is the process by which substances from the external environment are encapsulated in vesicles and brought into the cell. Receptor-mediated endocytosis uses membrane receptors to help localize the formation of the trasnport vesicle. Pinocytosis uses vesicles to transport fluids into the cell, while phagocytosis uses vesicles to bring pathogenic debris into the cell for digestion.
Exocytosis, in contrast, is the expulsion of substances from the cell via a transport vesicle.
Example Question #221 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology
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?
I'm A People Person
SOAP
HIKIN'
KADE
TIRE
HIKIN'
"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 : Nucleus And Ribosomes
What is the main function of the nucleolus in eukaryotic cells?
To facilitate nuclear transport of proteins and mRNA from the nucleus to the cytoplasm
The site of microtubule assembly during mitosis
To promote the transcription, processing, and assembly of rRNA genes into ribosomes
Eukaryotic cells do not have a nucleolus
Storage site for transcription factors, RNA polymerases, DNA polymerases, and other transcriptional machinery until transcription occurs
To promote the transcription, processing, and assembly of rRNA genes into ribosomes
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 : Nucleus And Ribosomes
The nuclear lamina is generally associated with __________.
ribosome synthesis and assembly
heterochromatin and transcriptionally active genes
chromatin containing transcriptionally inactive genes
chromatin containing transcriptionally active genes
euchromatin and transcriptionally inactive genes
chromatin containing transcriptionally inactive genes
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 #3 : Nucleus And Ribosomes
What is the function of RanGAP in relation to nuclear import and export?
Bind cargo proteins
Bind importins/exportins and bring them through the nuclear pore complex
Attach GTP to Ran
Maintain a gradient of GTP/GDP bound Ran
Maintain a gradient of GTP/GDP bound Ran
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 #4 : Nucleus And Ribosomes
Which of the following choices would have the biggest effect on nuclear transport?
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
A non-functional copy of the gene that encodes CRM1
A mutated, non-functional copy of RanGAP
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?
Smooth endoplasmic reticulum
Nucleolus
Nucleus
Golgi apparatus
Nucleolus
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.
1
6
0
3
2
1
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?
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
Provide a large surface area for chemical reactions
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.