Biochemistry Practice Questions XI with Answers


What is chromatin, and what does it look like in eukaryotes?
A. Chromatin is a single chromosome that floats freely in the cytoplasm rather than the cell nucleus. It is circular in shape.
B. Chromatin is a naked piece of double-stranded DNA that is uncondensed and pulled taut. It is long, thin, and straight.
C. Chromatin is a complex that consists of DNA and its associated packaging proteins. Within eukaryotes, chromatin usually folds into characteristic formations called chromosomes.
D. Chromatin is a single strand of DNA that functions as a template during replication. It forms a large loop that doubles back on itself.

The final and most complex phase of DNA organization is known as:
B. “beads on a string” chromatin
C. Packed nucleosomes
D. Metaphase chromosome

In the Guillermo del Toro movie, Pacific Rim, humans are attacked by gigantic monsters called Kaijus. One of the characters is a scientist who discovers that all the Kaijus are clones even though they look different from one another. Is this possible? (Select the best explanation from the choices below).
A. Possibly. Assuming there are a very small percentage of mutations in DNA sequences that regulate gene expression then these could affect the timing and intensity of transcription which would result in morphological differences between individual Kaijus.
B. Why not? Maybe the Kaijus don’t have mitochondria.
C. No way. If the genomes are 100% identical then they should all look very similar to each other if not exactly alike.

How do you think the scientist in Pacific Rim separated the nuclei from the mitochondria so that he could extract gDNA for sequencing?
A. Differential centrifugation
B. Immunihistochemistry
C. Western Blot

In this same movie, humans fight the Kaijus using massive robots or “mechs, known as Jaegers, which are controlled simultaneously by two or three pilots whose minds are locked in a neural bridge; sharing the mental strain which would overwhelm a single pilot.” Unfortunately, we don’t actually have this technology. How could we use our knowledge of biology to fight Kaijus while protecting humans in 2017?
A. Hit them with a nuclear weapon and accept the collateral damage.
B. Hit them with smallpox and hope for the best.
C. Compare the Kaiju genome with that of animals that are phylogenetically distant from humans, i.e. birds, reptiles, etc. Look for similarities in druggable targets and develop a toxin that would kill them but not humans.

What are the protein complexes that provide the first level of DNA organization?
A. Histones
B. Scaffold proteins
C. Heterochromatin
D. Euchromatin

What does a GTPase do?
A. Hydrolyzes NADH.
B. Hydrolyzes GTP to GDP.
C. Hydrolyzes GDP to GTP.
D. Hydrolyzes ATP to ADP.
E. Hydrolyzes ADP to ATP.

Ran is a GTPase involved in what transport process?
A. Peroxisome transport
B. Nuclear transport
C. Enterprise transport
D. Mitochondrial transport

When is Ran is bound to GDP, what state is it in?
A. Off
B. Neither
C. On
D. Both

Scientists working for U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) have discovered a new virus that only attacks and kills mitochondria. It’s isolated to bats right now, but it could jump to humans. Should scientists and governments be worried about this disease if jumps to humans?
A. No, the mitochondria would perish, however the cell could rely on its chloroplasts to live because this other energy-production machinery could take over the mitochondrial functions quite easily.
B. No, the mitochondria would perish, however the cell would continue to live because its other energy-production machinery could take over the mitochondrial functions quite easily.
C. Yes, human cells infected with this disease would die because they cannot survive over time as they have become dependent on mitochondrial energy production for survival.

Which mitochondrial protein complex imports proteins from the cytoplasm?
A. The TOM complex.
B. The Nuclear Transport Complex.
C. The sodium transporter.
D. The Translocase of the Inner Membrane complex.

Where in the mitochondria are the proteins that carry out electron transport?
A. The inner membrane.
B. The intermembrane space.
C. The matrix.
D. The outer membrane.

What mitochondrial protein complex imports proteins for the electron transport machinery?
A. The Nuclear Transport Complex
B. Sodium transporter
D. The TIM complex

A doctor is trying to figure out the cause of a young child’s sudden deafness. She appears to be recovering her hearing after being treated with a drug known to assist with protein folding within the matrix of the mitochondria. She did not respond to a previous treatment with a drug that stimulates the pathway responsible for bringing proteins to the mitochondria. Doctors know the she inherited the disease from her mother, who is also deaf. Apparently, the maternal grandmother and maternal great-grandmother also had sudden onset of deafness. Where do you think the mutated gene is located?
A. Nuclear genome
B. Prokaryotic genome
C. Mitochondrial genome
D. Chloroplast genome

Alzheimer’s and Parkinson’s disease do not have measurably disturbed mitochondrial function.
A. True
B. False

Which of the following best describes the functionality of the mitochondrial genome as compared to that of modern prokaryotes?
A. The mitochondrial genome is only partially functional in comparison to the prokaryotic genome because it encodes only some of the proteins needed by the mitochondrion itself.
B. The mitochondrial genome is equally functional in comparison to the prokaryotic genome because it encodes all of the proteins needed by the mitochondrion itself.
C. The mitochondrial genome is more functional in comparison to the prokaryotic genome because it encodes proteins for both the mitochondrion and the rest of the cell.
D. The mitochondrial genome is nonfunctional in comparison to the prokaryotic genome because it encodes no proteins for the mitochondrion or for the cell as a whole.

Which of the following athletes is probably going to have more mitochondria in their leg muscles?
A. Johnathan Wendel, considered to be the one of the best video game players in the world, earning over $450,000 last year.
B. Rafal Majka, professional cyclist and winner of the Polka dot jersey in 2014, which is given to the best climber in the mountain stages of the Tour de France.
C. Viktor Testsov, ranked number 1 by the International Powerlifting Federation in Bench Press in 2013.
D. Magnus Carlsen, current Chess World Champion.

Glycosylation is a common protein modification essential for folding of many proteins.
A. True
B. False

In a healthy cell, misfolded proteins accumulate in the cytoplasm.
A. True
B. False

Which of the following is the most direct for a cell to clear misfolded proteins?
A. Transcription
B. Refolding
C. Translation
D. Degradation

Phospholipids have a hydrophilic phosphate head and two hydrophobic hydrocarbon tails. Under normal circumstances, both a cell’s cytoplasm and its exterior environment contain water-based materials. Given this information, what can you infer about the structure of the phospholipid bilayer?
A. The two phospholipid layers must stand tail-to-tail so that their water-loving heads face the cytoplasm and exterior and their water-fearing tails are tucked between the two layers.
B. The two phospholipid layers must stand head-to-tail so that the water-loving heads can contact the cytoplasm and the water-fearing tails can move freely on the exterior of the cell.
C. The two phospholipid layers must stand side-by-side with a head-to-tail orientation, forming broad sheets that exhibit both water-loving and water-fearing characteristics on both sides.
D. The two phospholipid layers must stand head-to-head with their water-fearing tails moving freely in the cytoplasm and on the exterior of the cell.

Very few molecules can cross the membrane bilayer by passive diffusion?
A. True
B. False

Which of the following does not work by passive diffusion?
A. Potassium channel
B. Voltage sensitive sodium channel
C. ABC transporter

You are an ethnobiologist studying voodoo in Haiti. One of your interests is zombification which uses coupre poudre to induce total paralysis in the victim while the brain and senses remain intact. The victim is thought to be dead and is buried alive. How do you think coupre poudre works?
A. Activates the potassium channel which kills the neurons.
B. Blocks activation of the voltage sensitive sodium channel which prevents neuron activation.
C. Stimulates the ABC transporter, which promotes lysine entry into the cell.

How do proteins get targeted to the nucleus?
A. Prenyl groups
B. Nuclear localization signal
C. None of the above
D. Phosphorylation

Your friend’s company is hosting a group of entrepreneurs who are trying to raise money for a joint venture to start a biotech company. There is no formal pitch from either side. It is more of a first meeting opportunity. However, your friend’s department head is trying to get more information about the entrepreneurs’ technology. They claim they have a blockbuster drug against cancer that interferes with nuclear transport but they won’t divulge any more information. Your friend tells you that she went online and Googled the names of the visitors before the meeting and she realized that only one of them was a scientist. She guessed that this individual will have detailed knowledge of the technology so she spends the day talking with the visiting scientist. Without asking directly about the drug your friend discovers that the visiting scientist was hired because of her expertise in GTPases. Your friend doesn’t know how this information is useful but if she could help her supervisor figure out what these entrepreneurs are up to, then it would really be a feather in her cap as she climbs the corporate ladder. Can you help her? What do you think the technology is?

You’ve recently joined the CIA as Technical Analyst in the agency’s Directorate of Science & Technology. On your first day you are asked to take a look at cyber crime case involving ransomware. Normally the FBI would handle this but they are stumped and they have begrudgingly reached out to the CIA for help. Your first thought is, “Why I am being given a cyber crime case? My expertise is biology.” Unfortunately, the new guy gets all the cases nobody else wants, so you are stuck with it. You open the case file and start looking through the details and you notice something very interesting. First, unlike other ransomware attacks, this hacker specifically went after computers in academic labs at the Scripps Research Institute. The infected labs seem random but one name stands out: Paul Schimmel. You remember he has been the world leader in translation research for 40 years, but he is also one of the most outstanding bioentrepreneurs in the United States. He has founded a dozen companies that currently employ thousands of people in the States and in China, and he was recognized in 2007 as the bioentrepreneur of the year in the United States. You start reading some of the interviews that the FBI conducted with his postdocs and you realize that Schimmel was developing a new cancer drug. Based on his published research and the case file notes, you can determine that the protein based drug, or biologic, is an enzyme that cleaves a glycosidic bond within the large rRNA of the 60S subunit of eukaryotic ribosomes. The key to its therapeutic use is being able to target the drug to cancer cells so that it doesn’t destroy healthy cells. It appears that the lab hadn’t quite perfected the targeting capability but they had optimized its activity to an amazing level. A single drug molecule in the cytosol is capable of depurinating approximately 1500 ribosomes per minute. As you come to this conclusion, your supervisor sticks his head in your office to let you know that the FBI cyber crime unit has tracked the source of the hack to North Korea and that you can dump the case because it appears to be nothing more than an attempt to extract money from easy targets. Your intuition tells you that this may be more than an attempt to steal money but before you say anything you need to justify your hunch. What scientific basis could you use to justify contradicting your supervisor?

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