BIO 201 Lectures 14-16

What is ∆G°' for the hydrolysis of ATP?

-7.3 kcal/mol

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

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

Activating Protein Kinase A and, therefore, glycogen breakdown

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

An odorant that binds to a G protein-coupled receptor

Which of the following is true for both GPCR signaling and steroid hormone signaling?

Both of the above (An extracellular signal is transduced to an intracellular response, They may have widespread effects because they may be secreted into the bloodstream)

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

Decreased structural stability

Which of the following is an advantage of multicellularity?

Increased mobility

Which of the following is an advantage of endocrine signaling?

It affects large numbers of cells.

Consider the reaction: A <=> B. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 1.5 M, and [B] = 0.5 M. Keq' for this reaction is ____ and ∆G°' is _____. (You should not need a calculator for this.)

<1; >0

Consider the reaction: A <=> B. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 0.1 M, and [B] = 1.1 M. Keq' for this reaction is ____ and ∆G°' is _____. (You do not need a calculator for this.)

> 1; < 0

The Krebs cycle involves the aerobic breakdown of glucose for energy. In the first reaction of the Krebs Cycle, the enzyme Aconitase converts Citric acid to its isomer, the molecule isocitrate. The Keq' for this reaction is approximately 0.1. ∆G°' for this reaction is therefore ____ and the reaction is ____.

>0; Endergonic

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? (Think very carefully before answering this question!)

A kinesin disorder

A mutation that causes a decrease in the GTPase activity of G-alpha in liver cells would have the effect of:

All of the above

Which of the following is NOT TRUE of a second messenger in signal transduction?

All of the above are TRUE (It is diffusible, It is produced when the "first messenger" binds to its receptor, It may activate enzymes)

Which adaptation specific to becoming multicellular compensates for the destabilizing effect of increased size? (Think carefully about answer choices!)

Both ECM and tight junctions

As we learned in Lecture 15, protein phosphatases catalyze removal of phosphate groups from proteins. How would the activity of a protein phosphatase affect liver cell responses to epinephrine?

Decrease glucose production

"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

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 reaction shown above is:

Exergonic

ATP hydrolysis is highly _____ because it involves _____.

Exergonic; separation of negatively charged phosphate groups

ras, a small GTPase, hydrolyzes GTP slowly on its own, but its enzymatic activity is increased significantly in the presence of GTPase activating proteins (GAPs). Imagine you discovered a novel mutation that prevents GAP from binding to ras. This mutation would have the effect of:

Increasing cell proliferation

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.

What happens to GTP in response to epinephrine binding to its receptor on liver cells?

It binds to G-alpha

Which of the following is a DISADVANTAGE of endocrine signaling?

It is relatively slow.

Dr. Hutson really likes coffee. Despite that, this is not a question about caffeine. How does a compound that inhibits the GTPase activity of Gα affect liver cell responses to epinephrine?

It would increase glucose production

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.

Which of the following is a disadvantage of being a multicellular organism specifically as opposed to unicellular? (read and think carefully!)

More difficult to absorb nutrients

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 alongside epinephrine. You observe that the cells fail to produce glucose. Which of the following could be how the compound acts?

None of the above (It could inhibit the GTPase activity of Gα, It could decrease the affinity of Gα for GDP, It could cause Gα to bind more tightly to adenylate cyclase)

If you wanted to decrease liver cell responses to epinephrine, which of the following classes of enzymes would you want to increase in activity?

Protein phosphatase (catalyzes dephosphorylation)

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

cyclic AMP

∆G°' for the hydrolysis of ATP is considered to be:

highly exergonic

The enzyme phenylalanine hydroxylase (PAH) catalyzes the conversion of the amino acid phenylalanine to tyrosine. If for this reaction, Keq' = 18.1, ∆G°' is ____ and the reaction is ____.

no idea!

Cell adhesion molecules are important components of:

tight junctions