BIO201 Exam 2: Practice Questions

b

"During embryonic development red blood cells begin to develop in patches called blood islands. The blood cells secrete growth factors that diffuse only to nearby cells, signaling differentiation into endothelial cells. The endothelial cells eventually form the linings of the blood vessels." The growth factor described in the passage is involved in what type of signaling? A. Autocrine B. Paracrine C. Juxtacrine D. Endocrine

increasing

A mutation in G-alpha that inactivates its GTPase will have the effect of ------ a liver cell's response to epinephrine.

increasing

A mutation in ras that inactivates its GTPase will have the effect of ----- the cell's response to growth factors.

d

A reaction in which Keq < 1 is: a. exothermic b. endothermic c. exergonic d. endergonic

inhibit cell migration

A toxin that blocks integrin-laminin interactions is likely to:

no

ATP makes the reaction X -> Y possible through energy coupling as shown. For this reaction, is ATP a catalyst?

d

After you eat, insulin is secreted by pancreatic Beta cells into the bloodstream, where it diffuses throughout the body to bind to receptors on target cells, telling them to take up glucose. This mode of signaling is referred to as: A. Autocrine B. Paracrine C. Juxtacrine D. Endocrine

a

An exergonic reaction is ... a. Favorable b. Unfavorable

facilitated diffusion

Ca++ flowing down its concentration gradient through a Ca++ channel is an example of:

c

Cells shrink when you place them in a solution with a high concentration of the amino acid glycine. This indicates that the cell membrane: A. IS permeable to BOTH glycine and water. B. IS permeable to glycine but NOT to water. C. Is NOT permeable to glycine but IS permeable to water. D. Is permeable to NEITHER glycine NOR water.

b

Chloride ion (Cl-) concentrations are approximately 10x higher outside of cells than inside. Imagine you discovered a new protein that was required in liver cells for transporting Cl- out of the cell, and further found that this protein was only active when the Na+/K+ ATPase was active. Which of the following might you reasonably conclude about the Cl- transport protein? A. It could be a Na+/Cl- symporter. B. It could be a K+/Cl- symporter. C. It could be glucose/Cl- antiporter. D. It must be a ligand-gated Cl-channel.

d

Collagen is constitutively secreted by fibroblasts, which help to maintain the ECM. If you had a patient in which collagen was synthesized normally, but failed to get secreted into the ECM, which of the following would you look to as the likely cause of this problem? A. A Ca++ deficiency B. A failure of the Na+/K+ ATPase C. A H+ pump disorder D. None of the above

b

Compared to GPCR-mediated signal transduction, steroid hormone signaling tends to: a. have more signal amplification. b. have more permanent effects. c. be more easily reversible. d. all of the above

a

Compared to paracrine signaling, endocrine signaling tends to: a. be slow b. have long-term effects c. affect only specific cells d. all of the above

2

Consider the reaction A <--> B . If, at equilibrium, [A] = 0.25 M and [B] = 0.5 M, what is Keq?

a

Dr. Hutson really likes coffee. Caffeine is a chemical called a xanthine, which is a class of purine. One of the mechanisms by which caffeine acts is to inhibit cAMP phosphodiesterase. How does caffeine alter how Dr. Hutson's liver cells respond to epinephrine? A. It would increase glucose production. B. It would decrease glucose production. C. Neither A nor B

a

Enzymes NEVER... a. provide energy to make unfavorable reactions go. b. interact chemically with their substrate(s). c. have multiple substrates. d. alter the activation energy of the reaction.

increasing

Factors that increase membrane fluidity have the effect of ___________ membrane permeability:

low to high

For solutes that cannot diffuse through the membrane, water diffuses across the membrane from a region of ______ to a region of ______ solute concentration.

d

G-protein coupled receptors have ____ transmembrane domains. A. 1 B. 2 C. 5 D. 7

d

Glycolysis takes place in the ----- in eukaryotic cells and in the ------ in prokaryotes. a. mitochondria; mitochondria b. mitochondria; cytoplasm c. cytoplasm; mitochondria d. cytoplasm; cytoplasm

b

How would this affect liver cell behavior? A. It would decrease contraction. B. It would decrease glucose production. C. It would decrease glycogen production. D. It would decrease endocytosis.

b

If Keq = 2, what is delta G? a. > 0 b. < 0 c. = 0 d. > 1

A

If you had a patient in which the lung epithelium was leaking fluids into the lumen of the lung, which of the following could be the cause? A. Defective tight junctions B. Defective gap junctions C. An unusually high number of lipid rafts D. Excessive cholesterol E. All of the above

b

If you treated liver cells with epinephrine first and then homogenized and centrifuged them, in what fraction would you find cAMP? a. Membranes b. Cytoplasm c. Other

c

If you wanted to decrease liver cell responses to epinephrine, which of the following classes of enzymes would you want to increase in activity? A. Cyclases B. Kinases C. Phosphatases D. Phosphorylases

Cyclic AMP (cAMP)

In addition to everything described in the previous question, liver cells respond to epinephrine by breaking glycogen down to glucose. What is the second messenger in this patway?

d

Inhibition of which of the following would prevent glucose transport in the context of the previous question? A. GluT1 B. Ca++ ATPase C. Ligand-gated ion channels D. Na+/K+ ATPase

are not

Membranes are/are not permeable to large, polar solutes.

low [solute] to high [solute]

Osmosis occurs when water flows from an area of ----- [solute] to an area of ----- [solute] across a semi-permeable membrane.

c

Pertussis toxin is produced by Bordetella pertussis, the bacterium that causes whooping cough. Pertussis toxin catalyzes the addition of ADP-ribose (structure at right) to Gα, which prevents Gα from binding to GPCRs thus "locking" it in the GDP-bound state. Which of the following would you expect to see in liver cells treated with pertussis toxin? A. A decrease in Ca++ released in response to epinephrine B. Inhibition of ACh-mediated sodium channel opening C. A decrease in Adenylate Cyclase activity D. An increase in Protein Kinase A activity

direct active transport

Protons (H+) must be moved up their concentration gradients in order to activate lysosomal enzymes. This is an example of:

190

Say that you do all of the above, and find that the temperature is 25°C; the density of is 2.0 g/mL; the concentrations of the compounds are [A] = 0.1 M, [B] = 0.1 M, [C] = 1.9 M; and the pH is 10.0. What is Keq for the reaction?

a

Shown at right below is a hypothetical single-subunit enzyme. The first domain, represented by the rectangle on top, is called the regulatory domain, and the middle section is the catalytic domain with the active site on the right. The P in the red circle refers to a phosphate group. This enzyme is active when: A. it is phosphorylated. B. it is dephosphorylated.

a

The compound DPF is an insecticide that binds covalently to the active site of the enzyme Acetylcholinesterase, preventing binding of ACh. This is an example of: A. Competitive inhibition B. Covalent modification C. Allosteric inhibition D. Zymogen activation

a

The enzyme Succinate dehydrogenase (SDH) converts succinate to fumarate in the Citric Acid Cycle. The compound malonate, whose structure is similar to succinate, can bind to the active site of SDH, preventing succinate from binding. This is an example of: A. Competitive inhibition B. Covalent modification C. Allosteric inhibition D. Zymogen activation

a

The enzyme phenylalanine hydroxylase (PAH) catalyzes the conversion of the amino acid phenylalanine to tyrosine (the first step of the breakdown pathway for phenylalanine, but also they way tyrosine is made!). For this reaction, ΔG = -1.7 kcal/mol. This reaction is: A. Exergonic B. Neither exergonic nor endergonic C. Endergonic

1:1

The lipid:protein ratio in red blood cell membranes (a typical plasma membrane) is approximately:

b

The reaction above, conversion of a 5-pointed star into an 8-pointed star, is endergonic and only happens in the presence of ATP, which is involved in energy coupling in this reaction. Which of the following best describes how energy coupling works? A. The thermal energy supplied by ATP hydrolysis increases the probability that the reactants will interact, speeding up the rate of the forward reaction. B. ATP changes the transition state of the reaction by transferring some chemical energy to the reactant. This makes conversion to the product energetically favorable. C. Phosphorylation by ATP changes the conformation of the enzyme thereby converting it to an active state. D. ATP catalyzes the reaction.

false

True or false: ATP is an enzyme in the reaction catalyzed by a kinase.

true

True or false: During energy coupling ATP changes the transition state of a reaction.

false

True or false: Mutations in genes encoding enzymes general have LITTLE EFFECT on enzyme activity UNLESS they affect amino acid residues in the active site.

true

True or false: a receptor tyrosine kinase is an enzyme.

false

True or false: if ΔH < 0, the reaction is definitely exergonic.

false

True or false: if ΔS > 0, the reaction is definitely exergonic.

true

True or false: the Na+/K+ ATPase is an enzyme.

a

What is the role of an enzyme that catalyzes this reaction? A. The enzyme lowers the activation energy of the reaction. B. The enzyme lowers ΔG of the reaction. C. The enzyme captures the energy of ATP to drive the reaction. D. The enzyme is phosphorylated using a phosphate from ATP.

d

What is the second messenger in the pathway described in the previous question? A. GTP B. GDP C. Adenylate cyclase D. cAMP E. Gα F. Glucose

b

What is ΔG°' for the hydrolysis of ATP? A. +7.3 kcal/mol B. -7.3 kcal/mol C. O D. +1

Smooth ER

Where in the cell would you expect to see a Ca++ ATPase?

c

Which of the following best explains why we can safely say, "Diamonds are forever"? A. The conversion of diamonds into charcoal is highly exergonic. B. The conversion of diamonds into charcoal is highly endergonic. C. The conversion of diamonds into charcoal has an extremely high activation energy. D. The conversion of diamonds into charcoal needs to be catalyzed by an enzyme.

d

Which of the following is true of both GPCR ligands and steroid hormones? A. An extracellular signal is transduced to an intracellular response. B. Their receptors are usually transcription factors. C. They may have widespread effects because they may be secreted into the bloodstream. D. Both A and C

a

Which of the following is/are likely to elicit a rapid, reversible response? A. An odorant that binds to a G protein-coupled receptor B. A growth factor that binds to a receptor tyrosine kinase C. A steroid hormone D. Both A and B

d

Which of the following is/are likely to elicit a slow, but long-lasting or even permanent cellular response? A. An odorant that binds to a G protein-coupled receptor B. A growth factor that binds to a receptor tyrosine kinase C. A steroid hormone D. Both B and C

a

Which of the following may be true for an enzyme? A. It may form a covalent bond with its substrate. B. It may be permanently altered by the reaction. C. It may provide the energy for an endergonic reaction. D. All of the above

Laminin

Which of the following molecules is described in this passage: "ECM protein that is most commonly associated with activation of amoeboid cell migration"? (*Note not the only ECM protein that promotes migration but it is the most important one*)

unsaturated

fluidity: high melting temp: low

saturated

fluidity: low melting temp: high

covalent modification

mode of regulation where a enzyme is active when phosphorylated

lipid rafts

proteins with related function co-localize in __________ _________ which leads to an improved effect.

extracellular matrix

proteoglycans are part of the

high

saturation of fatty acid chains is associated with _____ melting temperature

low

saturations of fatty acid chains is associated with ____ fluidity

kinase

type of enzyme that activates the enzyme in covalent modification

b

ΔG°' for the hydrolysis of ATP is considered to be: A. highly endergonic B. highly exergonic C. slightly endergonic D. slightly exergonic

d

Guanine is produced from adenine through a series of enzyme-catalyzed chemical reactions as shown below. Inhibitors of enzymes in this pathway are used as immune suppressants to prevent organ transplant rejection and to treat autoimmune disorders because they slow production of white blood cells by inhibiting proliferation of blood stem cells. (Without guanine, cells cannot make all of the nucleotide building blocks of DNA and cannot, therefore, proliferate.) These types of inhibitors would be expected to have which of the following cellular side effects? A. Decreased muscle contraction B. Rigor mortis C. Decreased glucose import when the blood glucose concentration is low D. Decreased liver cell responses to epinephrine E. all of the above

d

He was awakened in the middle of the night by a low growling that sounded as if it was coming from just outside his tent. In response, the cells of his adrenal medulla began to secrete epinephrine, causing his palms to sweat, his heart to race, and his hair to stand on end." Epinephrine is involved in what type of signaling as described in this passage? A. Autocrine B. Paracrine C. Juxtacrine D. Endocrine E. Contact Mediated

c

If delta G < 0, the reaction is ... a. Exothermic b. Endothermic c. Exergonic d. Endergonic

a

If you were able to examine cells with a mutation in Integrin that prevented it from binding to laminin, which of the following would you expect to see? A. Failure of cells to migrate using laminin as a substrate. B. Bone weakness. C. Poor cushioning in the joints due to failure to absorb water. D. All of the above

c

Imagine that you walk into lab after spring break and your T.A. hands you a beaker and tells you that before spring break the beaker contained a solution of three compounds, A, B, and C each at 1 M. A, B, and C are represented by the equilibrium shown below, and by now, they have had time to come to equilibrium. Your job is to calculate ΔG for the forward reaction. What is the first thing that you do? A + B-->C A. Measure the temperature of the beaker. B. Weigh the beaker and calculate the density of the solution. C. Measure the concentrations of A, B, and C. D. Measure the pH.

a

In response to low blood glucose, pancreatic α-cells secrete the hormone Glucagon into the bloodstream. Glucagon binds to a GPCR on liver cells, which results in glycogen breakdown using the same mechanism as epinephrine. Which of the following describes how the G- protein downstream of the GPCR is activated? A. GDP is replaced by GTP on the α-subunit of the G-protein B. GDP is replaced by GTP on the α-subunit of the receptor C. GTP is hydrolyzed by the α-subunit of the G-protein D. The α-subunit of the G-protein is phosphorylated by Protein Kinase A

b

In what circumstances is the mechanism in the previous question most likely seen? A. Toxic compounds like pesticides and chemical weapons B. Direct feedback inhibition C. End product inhibition D. Positive feedback

d

Shown at right are the results of two fluorescence recovery after photobleaching (FRAP) experiments. Which of the following could explain the difference between the data plotted with the solid line and the data plotted with the dashed line? A. The membrane indicated by the dotted line is more fluid than the membrane indicated by the solid line. 2 B. The membrane indicated by the dotted line has fewer proteins than the membrane indicated by the solid line. C. The membrane indicated by the dotted line could have more unsaturated phospholipids than the membrane indicated by the solid line. D. The membrane indicated by the dotted line could contain lipid rafts.

Glycosylation

What property of proteoglycans makes them attract water molecules and provide cushioning in tissues like cartilage?

facilitated diffusion

What type of transport brings glucose into your cells when the concentration of glucose in your bloodstream is higher than the concentration inside cells?

a

When glucose is converted to pyruvate, this is ---- and it is ----. a. Oxidation; exergonic b. Oxidation; endergonic c. Reduction; exergonic d. Reduction; endergonic

b

When liver cells produce glucose in response to Glucagon, what type of transport is most likely responsible for getting the glucose back out into the bloodstream? A. Simple diffusion B. Facilitated Diffusion C. Direct active transport D. Indirect active transport

b

When liver cells produce glucose in response to Glucagon, what type of transport is most likely responsible for getting the glucose back out into the bloodstream? A. Simple diffusion B. Facilitated diffusion C. Direct active transport D. Indirect active transport

indirect active transport

When you haven't eaten for a long time, the concentration of glucose in your drops below the intracellular glucose concentration. In these circumstances, how does glucose get into cells?

a

When you place cells in a solution containing a high concentration of fructose, the cells shrink. This indicates that: a. Cell membranes are not permeable to fructose. b. Cell membranes are not permeable to water. c. Both A and B d. Neither A nor B

d

Which of the following correctly describes a second messenger? A. A protein, such as a G-protein, that is activated upon ligand binding to receptor. B. An enzyme such as Adenylate Cyclase that is activated upon ligand binding to receptor. C. An enzyme responsible for the cellular effects of a signal transduction pathway, like Protein Kinase A or Glycogen Phosphorylase. D. A soluble cytoplasmic molecule produced in response to ligand binding that activates a cellular response.

c

Which of the following correctly is true of steroid hormones but not a signaling molecule such as a GPCR ligand? A. An extracellular signal is transduced to an intracellular response. B. Their cellular effects are strong due to signal amplification. C. Their receptors regulate gene transcription. D. They may have widespread effects because they may be secreted into the bloodstream.

a

Which of the following correctly states the difference between active transport and facilitated diffusion? a. Active transport requires energy while facilitated diffusion does not. b. Active transport can involve movement of ions while facilitate diffusion cannot. c. Active transport proteins are ATPases while facilitated diffusion proteins are not. d. All of the above.

b

Which of the following enzymes catalyzes phosphorylation of proteins using a phosphate group from ATP? A. Cyclases B. Kinases C. Phosphatases D. Phosphorylases

e

Which of the following has the effect of INCREASING a cell's response to epinephrine? a. cAMP phosphodiesterase activity b. G-alpha GTPase activity c. Phosphatase activity d. All of the above e. None of the above

d

Which of the following is NOT a tenet (i.e. principle) of the fluid mosaic model? A. Proteins and lipids are oriented asymmetrically in the membrane. B. Membranes are amphipathic: regions of both lipids and proteins are in the membrane interior with hydrophilic regions on the outside C. The lipid bilayer is fluid enabling protein mobility in the membrane like "icebergs floating in a lipid sea" D. Many different lipid rafts create a mosaic of signaling modules in membranes.

d

Which of the following is NOT needed for glycolysis? a. glucose b. ATP c. ADP d. O2

b

Which of the following is an advantage of endocrine signaling? A. It is fast B. It affects a large number of cells C. It can be bidirectional D. all of the above

a

Which of the following is an advantage of juxtacrine signaling? A. It is fast B. It affects a large number of cells C. It can be bidirectional D. all of the above

b

Which of the following is never true of enzymes? A. They change the transition state of a reaction. B. They lower ΔG of a reaction. C. They interact chemically with the reactants. D. They are restored to their original form at the end of the reaction.

c

Which of the following is true of all enzymes? A. They provide energy for endergonic reactions. B. They stabilize the transition state. C. They alter the transition state. D. They harness energy from ATP.

c

Which of the following molecules is described in this passage: "Extracellular matrix (ECM) protein important for structural support; comprised of three intertwined polypeptide chains that bundle together to form a rigid macromolecular fiber; the most abundant protein in the body"? A. Microtubules B. Proteoglycan C. Collagen D. Integrin

d

Which of the following molecules is described in this passage: "Transmembrane receptor for ECM proteins"? A. Microtubules B. Proteoglycan C. Collagen D. Integrin

a

Which of the following never uses simple diffusion to pass through the cell membrane? A. Ions B. Small polar uncharged molecules C. Small hydrophobic molecules D. Large hydrophobic molecules.

Proteoglycan

Which of the following proteins is characterized by being heavily glycosylated, which causes it to attract large amounts of water, providing cushioning in tissues such as cartilage?

b

Which of the following statements is NOT true? A. The entropy of a closed system never decreases. B. If entropy decreases, the reaction is exergonic. C. In order to decrease entropy, energy must be provided. D. An exergonic reaction is one that releases energy.

c

Which of the following statements is TRUE? a. ALL signaling pathways involve a second messenger. b. Cyclic AMP is the second messenger for ALL signaling pathways. c. A second messenger is produced ONLY in response to the "first messenger." d. All of the above

Cholesterol

Which of the following would you expect to be found in lipid rafts at a HIGHER concentration that in the surrounding membrane?

b/c all cells would die

Why do you suppose we don't use inhibitors of the production of all purines, including adenine?

Smooth ER

You are most likely to find Ca++ channels in the membranes of what organelle?