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

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

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Example Question #1 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

Which of the following techniques would be most useful for a researcher who is trying to determine the structure of a protein?

Possible Answers:

Equilibrium centrifugation

LCMS

FPLC

X-ray crystallography

Correct answer:

X-ray crystallography

Explanation:

X-ray crystallography is a very powerful technique used to determine the structure of proteins. It involves first obtaining a crystal of your protein and then shooting x-rays through the sample and observing the resulting diffraction pattern.

Equilibrium centrifugation is a separation technique. FPLC is used to purify proteins. LCMS is used to analyze large samples of peptides quickly.

Example Question #2 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

What does a microarray allow you to visualize?

Possible Answers:

All of these

The genome size of an organism

The base pair sequence of a gene

Expression levels of multiple genes

The level of cellular replication in a sample

Correct answer:

Expression levels of multiple genes

Explanation:

A microarray is a chip with many copies of short segments of DNA that allows you to visualize the expression level of potentially unlimited genes simultaneously. It only informs you on how many copies of the gene are present in a sample, and does not give any information on gene sequence/length, etc.

Example Question #3 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

Which type of microscopy is needed to study subcellular structures like organelles?

Possible Answers:

Scanning electron microscopy

Light microscopy

Both light microscopy and scanning electron microscopy

Transmission electron microscopy

Both scanning and transmission electron microscopy

Correct answer:

Both scanning and transmission electron microscopy

Explanation:

Light microscopy can magnify a sample up to 1000X. this is not enough to visualize subcellular structures like organelles in cells. Electron microscopy can magnify a sample much higher than 1000X and so can be used to visualize subcellular structures. Both scanning and transmission electron microscopy magnify to this extent.

Example Question #4 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

What type of microscopy would you use if you want to get a topographical/3D image of your sample?

Possible Answers:

Transmission electron microscopy

Scanning electron microscopy

Fluorescence microscopy

Both scanning and transmission electron microscopy

Light Microscopy

Correct answer:

Scanning electron microscopy

Explanation:

Scanning electron microscopy runs a beam of electrons over the surface of a specimen. This beam changes in length as the specimen changes in height off the slide. The microscope can detect the change in beam length and generate a 3D image of the specimen. All of the other forms of microscopy listed produce 2D images.

Example Question #5 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology

Which of the following is true concerning light microscopy?

Possible Answers:

It can only be performed on living material

It provides greater resolution than an electron microscope

It uses a light source and a glass lens to magnify images

It works via a magnetic force that depends on electron concentration

It can produce three dimensional images of living material

Correct answer:

It uses a light source and a glass lens to magnify images

Explanation:

Light microscopy uses light and a glass lens to magnify images. The higher the magnification, the more blurry the image. Special staining techniques are used to produce images via light microscopy. Electrons are not utilized in light microscopy.

Example Question #1 : Laboratory Practices

Light microscopy and electron microscopy are used for the same purpose: to magnify very small objects for further examination by using radiation. The fundamental difference is that light microscopes use radiation of visible light, and electron microscopes use radiation of electron beams. This technical difference impart different properties on each type of microscopy. Each of the following describes a difference between light and electron microscopy, except __________.

Possible Answers:

"electron microscopy has a much higher resolution than light microscopy."

"usage of a vacuum tube is required in electron microscopy to prevent electrons from escaping."

"electron microscopy permits much higher magnification than light microscopy."

"light microscopy requires only a tungsten coil to produce a light beam, while electron microscopy couples a tungsten coil and magnetic lenses to produce and focus the electron beam."

"light microscopy specimens can be alive because they do not need to be dehydrated, as is the case with electron microscopy."

Correct answer:

"light microscopy requires only a tungsten coil to produce a light beam, while electron microscopy couples a tungsten coil and magnetic lenses to produce and focus the electron beam."

Explanation:

Light microscopy does not need a tungsten coil to produce visible light, only a strong but simple light source is required. Electron microscopy does employ a tungsten coil and magnets for this purpose. Each other answer choice describes a difference between the two types of microscopy. 

Example Question #6 : Laboratory Practices

A scientist wants to observe the localization of a particular protein within a tissue sample. Which of the following tags would be most useful for accomplishing this task?

Possible Answers:

TRX

GFP

His

FLAG

Correct answer:

GFP

Explanation:

Fluorescent tags are incredibly powerful tools for observing protein localization. GFP (green fluorescent protein) is a widely used fluorescent tag for just this purpose. All of the other answers are tags used for various functions. His and FLAG tags are commonly used to purify recombinant proteins. TRX tags are used for solubilization and to assist in recombinant protein folding in organisms that are chaperone-deficient. 

Example Question #8 : Laboratory Practices

Which of the following describes information that might be obtained from a successful FRET (fluorescence resonance energy transfer) experiment? 

Possible Answers:

Protein localization

Distance between two interacting proteins in vivo

All of the answers

Distances between domains on the same protein

Correct answer:

All of the answers

Explanation:

FRET is a widely used technique to study protein-protein interactions as well as reaction kinetics. The technique works by attaching fluorophores to proteins that produce fluorescent light when stimulated by light of the appropriate wavelength. When attempting to detect distances between two objects, two fluorophores are used. The first one is stimulated by an external source and the second is stimulated by the light produced from the excited fluorophore. The presence or absence of the light produced by the second excited fluorophore can then help determine protein-protein interactions. The technique is also applicable to protein localization and detecting distances between domains. 

Example Question #9 : Laboratory Practices

A scientist performs a FRAP (fluorescence recovery after photobleaching) experiment. To do so he labeled a protein with a fluorescent probe. Originally, the fluorescent color was ubiquitous throughout the entire sample. His results indicate that fluorescence did not return to anywhere near the normal level after bleaching his sample. What information can be concluded from this experiment?

Possible Answers:

The protein is embedded in a lipid raft

The protein is being held in place by the cytoskeleton

The protein is unstable

The protein is immobile

Correct answer:

The protein is immobile

Explanation:

During FRAP experimentation, a section of membrane is labeled with fluorophores. High intensity exposure to a small region of the membrane is used to "bleach" this region, resulting in a small region of zero fluorescence. The lack of recovery of the fluorescence only gives us information about the mobility of the protein: it is immobile. If the protein were mobile, then tagged proteins would be able to move into the bleached region, returning it to fluorescence.

While it may be true that the protein is anchored to the cytoskeleton or part of a lipid raft, the result of the experiment does not directly lead to these conclusions. It does, however, point the researcher in the right direction about learning more about the functionality of his protein. FRAP does not tell us anything about the stability of the protein.

Example Question #7 : Laboratory Practices

Which of the following tags would help a researcher locate a protein in vivo?

I. GFP

II. GST

III. His

IV. myc

Possible Answers:

I, II, and III

I, II, III, and IV

I only

II and III

Correct answer:

I only

Explanation:

GFP is a fluorescent tag that is incredibly useful in helping visualize a protein in vivo. The tag will glow green in the tissue where the protein is present.

All of the other choices describe tags that help purify recombinant proteins. Because all of these tags isolate proteins from a sample of lysed cell, they would not be useful in following a protein in vivo

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