Cell Bio Exam 1 Banerjee

Viruses

a. are always alive

b. are Eukaryotic

c. need to live in host cells to reproduce

d. are Prokaryotic

e. always live in extreme conditions

If 1000 nm = 1 μm and a lymphocyte (blood cell) is 12 μm in diameter, then how many nm in diameter is a lymphocyte?

a. 12 nm

b. 12,000 nm 1nm/1000 = 12 nm/12000

c. 0.12 nm

d. 0.012 nm

e. 1.2 nm

M, P, Q, and R are four microscopes that can identify two distinct particles if the minimum distance between them is 2,4,6, and 8 mm, respectively. Which one has the least resolution?

a. R

b. Q

c.P

d.M

e. all have the same resolution

Hemoglobin protein typically consists of 2 pairs of polypeptides forming alpha and beta chains. Which protein structure best describes the hemoglobin molecule?

A. Primary
B. Secondary
C. Tertiary
D. Quaternary

ΔG = ΔH − TΔS, where ΔH = Enthalpy and ΔS = Entropy. Which of the following options are true for a chemical reaction that obeys the principles of thermodynamics?A non-spontaneous reaction will have high enthalpy.

1. A spontaneous reaction will increase entropy.

2. A non-spontaneous reaction will be exergonic.

3. A spontaneous reaction will have negative ΔG.

4. A spontaneous reaction will have negative ΔG

A. All 1 to 4 are true
B. Only 1, 2, & 3 are true
C. Only 3 & 4 are true
D. Only 1, 2, & 4 are true
E. None of 1 to 4 are true

Which of the following does NOT involve bonds/interactions among amino acid (R group/side chains)?

A. Protein secondary structure
B. Protein tertiary structure
C. Protein quaternary structure
D. Protein primary structure
E. A & D

What type of bond forms between a negatively charged amino acid R group/side chain (e.g., Aspartic acid) and a positively charged amino acid R group/side chain (e.g., Lysine) in making the protein tertiary and quaternary structure?

A. A hydrogen bond
B. An ionic bond
C. A covalent bond
D. A hydrophobic interaction

What type of amino acid is generally found at the core of a soluble protein, and helps to drive protein folding by participating in hydrophobic interactions?

A. Polar and positively charged amino acid
B. Polar uncharged amino acid
C. Nonpolar amino acid
D. Polar and negatively charged amino acid
E. All of the above

How do cells “get around” the 1st and 2nd laws of thermodynamics?

A. Cells are open systems and so can absorb energy from their surroundings to carry out energetically unfavorable processes
B. Cells are capable of creating new energy in the universe
C. Cells are capable of decreasing entropy in the universe
D. Cells are capable of carrying out energetically unfavorable processes without any input of energy

ΔG is:

A. The energy available to do work inside a cell
B. Negative for an energetically favorable process
C. Positive for an energetically favorable process
D. Positive for an exergonic reaction
E. A and B

The transition state in an enzymatic biochemical reaction:

A. Involves only the reactants
B. Involves only the enzyme
C. Is a chemical transition between the reactants and products when covalent bonds are being broken and new ones are being made in the enzyme-substrate complex
D. Is stabilized by the enzyme to reduce the activation energy and speed up the reaction
E. C and D

Which of the following statements are TRUE? Enzymes reduce the activation energy to:

1. Convert a non-spontaneous reaction into a spontaneous reaction

2. Convert a spontaneous reaction into a non-spontaneous reaction

3. Initiate a spontaneous reaction

4. Inhibit a non-spontaneous reaction

5. Increase the speed of a reaction

A. Only 5 is true
B. Only 1 & 3 are true
C. Only 2 & 4 are true
D. Only 3 is true
E. All 1 to 5 are true

Which of the following promotes a small GTPase (such as Ran) to bind GTP?

A. A GAP
B. An effector
C. A GEF
D. Laminin
E. Importin

When a small GTPase is bound to GDP:

A. It binds to an effector
B. It is in the inactive conformation
C. It is in the active conformation
D. A and C

Glycolipids:

A. Are lipids that are attached to either a mono- or an oligosaccharide
B. Are lipids that are attached with an oligopeptide (small protein)
C. Are enriched in the extracellular leaflet of the plasma membrane
D. Are enriched in the intracellular leaflet of the plasma membrane
E. A and C

A membrane protein has an alpha-helical transmembrane domain. It is a(n):

A. Glycoprotein
B. Peripheral membrane protein
C. Integral membrane protein
D. Cytoplasmic protein
E. All of the above

Which type of amino acid is most common in a transmembrane domain of a protein?

A. Polar charged amino acid
B. Polar uncharged amino acid
C. Nonpolar amino acid
D. All of the above

Detergents help remove integral membrane proteins from membranes and release them into an aqueous solution because:

A. They are completely hydrophobic
B. They are completely hydrophilic
C. They are amphipathic
D. Their hydrophobic regions can bind to the transmembrane domain(s) while their hydrophilic regions can interact with the water in the aqueous solution
E. C and D

The following reaction shows the ATP hydrolysis and standard free energy related to ATP breakdown (ATP hydrolysis):

ATP + H₂O → ADP + Pi
ΔG° = −7.3 kcal/mole

A non-spontaneous reaction (X → Y) is coupled with ATP breakdown to occur. Thus, the ΔG° for that reaction (X → Y) can only be:

A. Positive and less than or equal to +7.3 kcal/mole
B. Positive and more than +7.3 kcal/mole
C. Negative
D. Negative and less than −7.3 kcal/mole
E. Only C and D

Which amino acid is involved in making the only type of covalent bond between amino acid side-chains that participates in protein tertiary and quaternary structure, AND what is the name of this type of covalent bond?

A. Alanine, Peptide bond
B. Cysteine, Disulfide bond
C. Methionine, Disulfide bond
D. Aspartic acid, Ionic bond
E. Histidine, Ionic bond

What would happen to ATP production during the electron transport chain if the NADH dehydrogenase in complex I cannot function at all (abnormal mitochondria)? Will there be any ATP produced during ETC in the above case?

A. There will be no change in ATP production in a given time in the abnormal mitochondria relative to normal mitochondria by ETC
B. There will be an increase in ATP production in a given time in the abnormal mitochondria relative to normal mitochondria by ETC
C. There will be a reduction in ATP production in a given time in the abnormal mitochondria relative to normal mitochondria by ETC
D. There will be no ATP production in a given time in the abnormal mitochondria relative to normal mitochondria by ETC
E. Any of the above can take place

Scientists found a new unicellular living species with ribosomes from hot springs (80°C). The species is most likely to be a/an:

A. Eukaryote
B. Bacteria
C. Archaea
D. Any of the above

Why is the TCA cycle considered the central pathway in the energy metabolism of a cell

A. Because it is the step of aerobic cell respiration that produces the highest amount of ATP compared to the other two stages (e.g., glycolysis and electron transport chain)
B. Because it is the step of aerobic cell respiration that produces the least amount of ATP compared to the other two stages (e.g., glycolysis and electron transport chain)
C. Because it is the only step of aerobic cell respiration that produces NADH
D. Because it is the only step of aerobic cell respiration that produces Acetyl-CoA
E. Because it is the only step of aerobic cell respiration which oxidizes metabolites produced from amino acids, fats, and carbohydrates catabolism into carbon dioxide, and produces precursor molecules (like NADH, FADH₂) for ATP production during the electron transport chain

The concentration of Ran-GTP is:

A. Higher inside cytoplasm
B. Higher inside the nucleus
C. The same inside and outside of the nucleus
D. Higher outside of cell
E. None of the above

Which of the traits below is/are characteristic(s) of the classical nuclear localization signals in a protein?

A. Possession of large numbers of hydrophobic amino acids
B. Possession of one or two short stretches of negatively charged amino acids
C. Possession of one or two short stretches of positively charged amino acids
D. Twisted backbones
E. Double-helical regions

Due to mutation in a specific gene, it can no longer produce a functional protein associated with nuclear import and export cycle. As a result, high concentration of Ran-GTP bound with nuclear export cargo is present in the cytoplasmic side of the nuclear membrane (instead of high concentration of Ran-GDP). Thus, the mutated gene is likely to code the:

A. Importin proteins
B. GEF protein
C. Ran protein
D. GAP protein
E. Nucleoporins

Why doesn’t the rate of an enzyme-catalyzed reaction increase indefinitely as the substrate concentration [S] increases in a test tube?

A. Because at equilibrium, with a constant amount of enzyme in the test tube, once the active sites of all the enzymes are bound with substrate and saturate the enzymes, the additional substrate cannot be broken down further
B. Because at equilibrium, enzymes are inactivated
C. Because at equilibrium, all products are converted into substrate again

An enzyme converts the substrate “A” into products “B” and “C”. During this process, ΔG = +4.3 kcal/M energy is required to run the reaction. In addition, “C” inhibits the enzyme function in a feedback reaction, although C is structurally different than A. Which is correct?

A. The reverse reaction (B + C → A) is non-spontaneous, and C is a competitive inhibitor
B. The reverse reaction (B + C → A) is spontaneous, and C is a competitive inhibitor
C. The reverse reaction (B + C → A) is spontaneous, and C is a non-competitive inhibitor
D. The reverse reaction (B + C → A) is non-spontaneous, and C is a non-competitive inhibitor
E. None of the above is true

Enzyme A and its synthetic version Enzyme A′ have differences in their Michaelis constant (Km) values. A has a lower Km compared to A′. Thus:

A. Enzyme A′ has the same substrate affinity as Enzyme A
B. Enzyme A′ has more substrate affinity than Enzyme A
C. Enzyme A′ has less substrate affinity than Enzyme A
D. Enzyme A′ requires relatively less substrate molecules to reach Vmax/2 compared to Enzyme A
E. C and D

Trypsin, a digestive enzyme, functions within a range of pH 7.5–10. Trypsin does not work in a highly acidic environment like in the stomach (pH = 2) because:

A. Acidic pH hydrolyzes trypsin into its component amino acids and breaks down the enzyme
B. Acidic pH interferes with and distorts bonds that are essential for Trypsin to maintain its functional conformation
C. Acidic pH enhances the production of Trypsin inhibitors in cell
D. Acidic pH makes the reaction endergonic
E. None of the above

Enzyme X converts Substrate S into Product P (S → P). The inhibitor of this enzyme is I. In the presence of I, a higher concentration of S is needed for the reaction to reach the same Vmax as in the absence of I. Thus, the inhibitor:

A. Is non-competitive
B. Is competitive
C. Is either non-competitive or competitive
D. Binds at the allosteric site of the enzyme
E. Both A & D

Which of the following are ion channels found in the cell membrane?Voltage-gated ion channel

• Ligand-gated ion channel

• Aquaporin channel

• Na⁺/K⁺ ATPase pump

• Mechanically gated ion channel

A. All 1 to 5 are ion channels
B. Only 3 is an ion channel
C. Only 3 & 4 are ion channels
D. Only 1, 2, & 5 are ion channels
E. None of 1 to 5 is an ion channel

At high altitudes, the concentration of oxygen gas is considerably lower in the environment than at sea level. Tourists who normally live near sea level, when visiting high mountains and remaining very active, often feel muscle fatigue and lack of energy. This muscle fatigue and lack of energy are observed because:

A. At high altitudes, limited ATP is produced in the cells
B. At high altitudes, lactic acid fermentation is triggered in the muscle, which is toxic for the muscle cells
C. At high altitudes, the rate of occurrence of the TCA cycle in the cell is lower
D. At high altitudes, the rate of occurrence of the Electron Transport Chain in cells is very low
E. All of the above are true

What composition of fatty acids and cholesterol would you expect to find in an animal cell isolated from an animal that lives in a temperate zone (high temperature)?

A. High amount of saturated fatty acids, low amount of short-tail fatty acids, and high amount of cholesterol
B. High amount of saturated fatty acids, low amount of short-tail fatty acids, and low amount of cholesterol
C. High amount of unsaturated fatty acids, high amount of short-tail fatty acids, and low amount of cholesterol
D. Low amount of saturated fatty acids only
E. C and D

TFIID, a general transcription factor, is a protein molecule. It binds with DNA and other transcription factors to trigger gene transcription in the nucleus. Due to a specific mutation in the gene that encodes TFIID, it has been found that the mutant TFIID protein is present in a significantly higher concentration in the cell cytoplasm, but it is completely absent in the nucleus where it normally functions. When this mutant TFIID is isolated and added to a test tube with all necessary components for transcription, the overall rate of transcription becomes normal. Thus, the mutation in TFIID disrupted the:

A. Nuclear Localization Signal (NLS)
B. Nuclear Export Signal (NES)
C. DNA binding domain
D. Protein binding domain
E. None of the above

“An un-spliced mRNA either is blocked from transportation through Nuclear Pore Complex (NPC), or gets destroyed in the cytoplasm as soon as it appears through NPC in the cytoplasm by nonsense-mediated decay.” This statement is:

A. True
B. False

Movement of lipids from the inner leaflet to the outer leaflet of the cell membrane requires:

A. Integral membrane protein
B. Peripheral membrane protein
C. Flippase and ATP breakdown
D. Flippase and ATP synthesis
E. Na⁺/K⁺ ATPase pump

“In the presence of a non-competitive inhibitor, an enzymatic reaction can reach the same Vmax as in the absence of the inhibitor.” This statement is:

A. True
B. False

Protein A interacts with five different protein partners, one at a time, in the cytoplasm and performs different cellular functions. Due to a mutation that changes one amino acid in protein A, it is still present in the cytoplasm, but cannot bind with any of its partners. Thus, protein A:

A. Has one single domain to bind with the different partners
B. Has several different domains to bind with the different partners
C. Binds with its partners by transient non-covalent bonds
D. A and C
E. None of the above is correct

The cellular solute concentration of a red blood cell is 0.7%. If the red blood cell is kept in a 0.9% solution, what will happen to it?

A. The cell will shrink
B. The cell will swell
C. There will be no change in the cell volume and shape
D. The cell will first shrink, and then it will swell
E. None of the above

Which of the following is/are true about Na⁺/K⁺ ATPase pump?

1. It is an example of passive transport.

2. It exports 3 K⁺ ions outside of the cell and imports 2 Na⁺ ions inside the cell.

3. This pump moves ions across the cell membrane along their concentration gradients.

4. Movement of ions through this pump triggers ATP synthesis.

A. Only 2 is true
B. Only 4 is true
C. Only 1 and 3 are true
D. All of the 1 to 4 are true
E. None of the 1 to 4 are true

Acetylcholine binds with the receptor on the post-synaptic membrane and opens the Ca²⁺ ion channels. Thus, this ion channel is an example of:

A. Proton pump
B. Ligand-gated ion channel
C. Ion-gated ion channel
D. Voltage-gated ion channel
E. Mechano-gated ion channel

Which of the following is the final acceptor of the electrons in the Electron Transport Chain?

A. Acetyl CoA
B. NADH
C. NADH dehydrogenase
D. Oxygen
E. FADH₂

Find the correct sequential events that take place in the membrane of neurons during the movement of an Action Potential:

1. When the membrane potential reaches a threshold, voltage-gated Na⁺ ion channels open, and Na⁺ ions move rapidly from the cell exterior to the interior.

2. Sodium-potassium pump helps restore the voltage to its resting potential in the nerve membranes after the action potential is triggered.

3. Membrane depolarization happens due to an influx of sodium (Na⁺) or another positive ion inside the cell, which makes the membrane potential relatively more positive.

4. After 1 msec, voltage-gated K⁺ channels open. It polarizes the neuron again by relatively slow transport of K⁺ out of the cell to the extracellular region.

A. 1 → 2 → 3 → 4
B. 2 → 1 → 4 → 3
C. 3 → 1 → 4 → 2
D. 3 → 4 → 1 → 2
E. 4 → 3 → 2 → 1

Phosphoglycerides:

A. Are completely hydrophilic
B. Are completely hydrophobic
C. Have a glycerol backbone
D. Can have a net negative charge or can be net neutral
E. C and D

Which amino acid(s) would you likely find in the extra-cellular domain of an integral membrane protein?

A. Ala (nonpolar amino acid)
B. Lys (positively charged amino acid)
C. Asn (polar uncharged amino acid)
D. Glu (negatively charged amino acid)
E. B to D

The stomach is a highly acidic environment that is further acidified after ingestion of food, which triggers a hormone-stimulated cascade. This hormone stimulation results in the activation of H⁺/K⁺ ATPase channels (“proton pump”) that release additional protons into the stomach cavity. Heartburn occurs when acid in the stomach undergoes reflux and backs up into the esophagus.

Due to a mutation in the gene that encodes the hormone receptor, the hormone receptor becomes hyperactive and triggers the pump even in the absence of food and receptor agonists. The mutation ultimately results in continuous heartburn. What would NOT be a suitable strategy to treat such heartburn?

A. Use the antacid
B. Use receptor antagonists
C. Use proton pump inhibitors
D. Use A and C
E. None of the above is suitable

Which of the following cell membrane components are involved in cell signaling pathways?

A. Phosphatidyl inositol (PI)
B. Phosphatidyl serine (PS)
C. Phosphatidyl choline (PC)
D. Phosphatidyl ethanolamine (PE)
E. A and B

Liposomes are used to carry and deliver drugs in cells because:

A. Liposomes are the genes that encode the protein drugs
B. Liposomes are isotonic to the cell
C. Liposomes are made of lipids; thus, they can fuse with the cell membrane to deliver the drugs inside the cell
D. Liposomes contain importins
E. B and D

Which amino acids in a protein are normally phosphorylated by a kinase enzyme?

A. Ser, Tyr, Thr
B. Arg, Lys, Val
C. Gly, Pro, Glu
D. ADP, GDP, TDP
E. Glycerol backbone of fatty acids

A transcription factor (TF) (a protein molecule) binds to a specific DNA sequence and recruits other transcription factors. Which of the following is false for a TF?

A. TF is imported into the nucleus from the cytoplasm to do its job
B. TF is exported into the cytoplasm from the nucleus to do its job
C. TF contains a Nuclear Localization Signal (NLS)
D. TF can bind with importins
E. TF contains different domains like DNA binding and protein binding domain