Bio 201 block 2 hw 5

Collagen, an extremely important extracellular matrix protein, is constitutively secreted by fibroblast cells, a type of connective tissue cell. If you had a patient in which collagen is synthesized normally, but fails to be secreted into the extracellular matrix, which of the following would you examine as the likely cause of this problem?

A kinesin disorder

If you had a patient in which the lung epithelium was leaking fluids from the bloodstream into the lumen of the lung, which of the following is the most likely cause?

A mutation in a cell adhesion molecule

Which of the following correctly describes a second messenger?

A soluble cytoplasmic molecule produced in response to ligand binding that activates a cellular response.

If it were injected directly into liver cells, cAMP would have the effect of:

Activating Protein Kinase A and, therefore, glycogen breakdown

Protons (H+) are moved up their concentration gradients into the lysosome in order to activate lysosomal enzymes. This is an example of:

Active transport

Which of the following is NOT TRUE of a second messenger in signal transduction? It is diffusible It is produced when the "first messenger" binds to its receptor It may activate enzymes All of the above are TRUE

All of the above are TRUE

Shown below is a branched reaction pathway. Compounds are labeled A-E, and enzymes catalyzing each reaction are labeled E1-E4. Imagine that both D and E are useful to the cell but that E must always be maintained above a concentration of 2.0 mM for the cell to survive. If E is greater than 2.0 mM is it all right for the cell to shift some production to D. Which of the following is the simplest best way to regulate the pathway to keep the cell alive? (Always assume that any enzyme that is not subject to regulation is active; enzymes subject to inhibition are active unless the inhibitor is above the threshold concentration; and enzymes subject to activation are inactive unless the activator is above the threshold concentration.)

Allosteric activation of Enzyme 3 by E

Shown below is a branched reaction pathway. Compounds are labeled A-E, and enzymes catalyzing each reaction are labeled E1-E4. Imagine that both D and E are useful to the cell but that D must always be maintained above a concentration of 2.0 mM for the cell to survive. If D is greater than 2.0 mM is it all right for the cell to shift some production to E. Which of the following is the simplest best way to regulate the pathway to keep the cell alive? (Always assume that any enzyme that is not subject to regulation is active; enzymes subject to inhibition are active unless the inhibitor is above the threshold concentration; and enzymes subject to activation are inactive unless the activator is above the threshold concentration.)

Allosteric activation of Enzyme 4 by D

Shown below is a branched reaction pathway. Compounds are labeled A-E, and enzymes catalyzing each reaction are labeled E1-E4. Imagine that both D and E are necessary for the cell but that D is toxic above a threshold concentration of 100 mM. Which of the following is the simplest best way to regulate the pathway to keep the cell alive? (Always assume that any enzyme that is not subject to regulation is active; enzymes subject to inhibition are active unless the inhibitor is above the threshold concentration; and enzymes subject to activation are inactive unless the activator is above the threshold concentration.)

Allosteric inhibition of Enzyme 3 by D

Which of the following is/are likely to elicit a rapid, reversible response?

An odorant that binds to a G protein-coupled receptor

Which adaptation specific to becoming multicellular compensates for the destabilizing effect of increased size?

Both ECM and tight junctions

Which of the following is/are likely to elicit a slow, but long-lasting or even permanent cellular response?

Both growth factor signaling and steroid hormone signaling

Which of the following is true for both GPCR signaling and steroid hormone signaling? An extracellular signal is transduced to an intracellular response. They may have widespread effects because they may be secreted into the bloodstream. Both of the above They involve enzyme cascades

Both of the above OR They may result from endocrine signals.

Which of the following is a disadvantage of being a multicellular organism?

Decreased structural stability Greater energy needs More difficult to absorb nutrients Reproduction more complicated

"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?

Endocrine

Which of the following is a mechanism by which cells ensure a strong response to a small amount of ligand?

Enzyme cascades

One of the main differences between growth factor signaling (receptor tyrosine kinase receptors) and epinephrine signaling (G-protein coupled receptors) is that:

Epinephrine signaling is more likely to have a short-term, reversible effect.

The hormone glucagon is secreted by the pancreas in response to low blood sugar. Liver cells respond to glucagon by breaking down glycogen to form glucose, which is then release into the bloodstream for the other tissues. Based on this information, what mechanism is most likely used to transport glucose out of the cell into the bloodstream?

Facilitated diffusion

True or False: The concentration of K+ outside the cell is higher than it is inside.

False

True or False: The concentration of Na+ inside the cell is higher than it is outside.

False

Even though the blood glucose concentration may drop below the intracellular glucose concentration - for example, during a long fast - brain cells can still absorb glucose from the bloodstream. Under these circumstances, how does glucose get into the cells?

Indirect active transport

Unlike in animals, in which the Na+ gradient is used, it is the H+ gradient in some other species that fuels transport of other compounds up their concentration gradients. This type of transport is:

Indirect active transport

Oxidation of biological molecules, e.g. glucose:

Is exergonic

Which of the following is an advantage of endocrine signaling?

It affects large numbers of cells.

Which of the following is a DISadvantage of paracrine signaling?

It affects only a small number of cells.

Which of the following can be considered both an advantage and a disadvantage of juxtacrine signaling?

It affects only one or a very small number of cells.

Dr. Hutson really likes coffee. Caffeine is a xanthine, a class of molecules that are similar to purines. One of the mechanisms by which caffeine acts is to inhibit the enzyme cAMP phosphodiesterase, which converts cAMP to plain old AMP, which is inactive. How does caffeine alter liver cell responses to epinephrine?

It increases glucose production.

Which of the following is a DISADVANTAGE of endocrine signaling?

It is relatively slow. OR By the time it reaches the target cell, the ligand concentration is likely to be very low.

G-alpha is not only an activator of Adenylate cyclase, but it is a GTPase. How does mutation in G-alpha that decreases its GTPase activity affect liver cell responses to epinephrine?

It would increase glycogen phosphorylase activity.

Chloride ion (Cl-) concentrations must be maintained much higher outside of cells than inside of cells. How this gradient is maintained is complex, but a key transporter co-transports Cl- along with K+ ions. The name of this transport protein could be ____ and its mode of transport would be ____.

K+/Cl- symporter; indirect active transport

Which of the following enzymes catalyzes phosphorylation of proteins using a phosphate group from ATP?

Kinases

Pertussis toxin is produced by Bordetella pertussis, a bacterium that causes whooping cough. Pertussis toxin catalyzes the addition of ADP-ribose (structure below) to Gα, which prevents Gα from binding to GPCRs thus "locking" it in the GDP-bound state. If you could observe liver cells treated with epinephrine in real time, how would one infected with pertussis compare to a control (i.e. one treated with epinephrine alone)?

Less glycogen breakdown

Chloride ion (Cl-) concentrations are approximately 10x higher outside of cells than inside. Imagine you discovered a novel protein that is required in liver cells for transporting Cl- out of the cell up its concentration gradient, and further found that this protein only functions if the Na+/K+ ATPase is active. This suggests that the Cl- transport protein is a:

Na+/Cl- antiporter

Inhibition of which of the following would prevent indirect active transport of glucose into cells?

Na+/K+ ATPase

ATP hydrolysis provides the energy for the endergonic reaction: X + Y <=> Z . The mechanism by which this occurs is that compound X is phosphorylated using the phosphate group from ATP. dephosphorylation of X, which itself is exergonic, makes it possible for X and Y to combine to form Z. In this scheme X-P can be considered the transition state. The entire reaction, including ATP is as follows: X + Y + ATP <=> X-P + Y + ADP <=> Z + ADP + Pi Is ATP an enzyme for this reaction?

No, because it is irreversibly altered by the reaction

Which of the following enzymes catalyzes phosphorylation of proteins using inorganic phosphate, i.e. the phosphate buffering the cell?

Phosphorylases

Which of the following is true of steroid hormones but not a signaling molecule such as a ligand for G-protein coupled receptors?

Their receptors regulate gene transcription.

A major function of the epithelium in animals is to prevent entry of pathogens and toxins from the environment. Which of the following is common to all epithelial cells?

They are held together by tight junctions.

Cell adhesion molecules are important components of:

Tight junctions

True or False: The concentration of Ca++ outside the cell is higher than it is inside.

True

The Na+/K+ ATPase transports Na+ up its concentration gradient and K + ______ its concentration gradient. This is an example of ______ .

Up; Direct active transport

Liver cells respond to epinephrine by breaking down glycogen. What is the second messenger in this pathway?

cyclic AMP

Which of the following correctly describes a second messenger? a. A protein, such as a G-protein, that is switched 'on' upon ligand binding to receptor. b. An enzyme 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. None of the above

d. none of the above 2nd messengers are produced anew, i.e. from scrach and are not proteins that are simply switched on or off.

What is the second messenger in the receptor tyrosine kinase signaling pathway? a. The receptor b. The small GTPase ras c. The enzyme MAPK that gets transported into the nucleus to activate gene transcription d. None of the above

d. none of the above. involve only activation of proteins including enzymes

True or False: The concentration of Ca++ in the cytoplasm is higher than it is in the smooth ER.

false

True or False: The concentration of Ca++ inside the cell is higher than it is outside.

false

Which of the following is an advantage of multicellularity?

increased mobility Cellular specialization larger size

Which of the following is an advantage of juxtacrine signaling?

it is fast

Archeological evidence suggests that Neanderthals may have been aware of the medicinal properties of plants over 60,000 years ago. Imagine you are a modern-day ethnobotanist and have identified a compound from fossilized tree pollen that binds to the alpha subunit of the most common G-proteins. To test how the compound affects the activity of Gα, you treat liver cells with the compound and then epinephrine. You observe that the cells fail to produce glucose. Which of the following could be how the compound acts? It could inhibit the GTPase activity of Gα. It could increase the affinity of Gα for GTP. It could cause Gα to bind more tightly to adenylate cyclase. None of the above

none of the above

Archeological evidence suggests that Neanderthals may have been aware of the medicinal properties of plants over 60,000 years ago. Imagine you are a modern-day ethnobotanist and have identified a compound from fossilized tree pollen that binds to the alpha subunit of the most common G-proteins. To test how the compound affects the activity of Gα, you treat liver cells with the compound and then epinephrine. You observe that the cells fail to produce glucose. Which of the following could be how the compound acts? a. It could inhibit the GTPase activity of Gα. b. It could increase the affinity of Gα for GTP. c. It could cause Gα to bind more tightly to adenylate cyclase. d. None of the above

none of the above

"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?

paracrine

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

smooth er

True or False: The concentration of K+ inside the cell is higher than it is outside.

true

True or False: The concentration of Na+ outside the cell is higher than it is inside.

true