Cell Bio Exam 3 Questions

Which of the following polypeptides is most likely to bind to a receptor in the nucleus?

a nonpolar polypeptide

Cellular responses depend on the type of receptor present; the same signaling molecule can elicit different responses depending on the receptors present.

True

Selective serotonin reuptake inhibitors (SSRIs) can increase the time serotonin, a signaling molecule, spends outside of cells. What effect do SSRIs likely have on the serotonin-receptor equilibrium?

More serotonin receptors will be bound.

Which of the following are likely to increase the strength and length of a signal?

All of these are likely to increase the strength and length of a signal.

Which of the following best explains the benefit of signal amplification?

It allows for a small amount of signaling molecule to generate a large and/or prolonged cellular response.

Which of the following is NOT a form of cell-to-cell signaling?

Simulacrine signaling

Which of the following is NOT a feature of G-Protein coupled receptors (GPCRs)?

GPCRs are active when they are bound by GDP and inactive when they are bound by GTP.

Above is a dissociation graph of hemoglobin and myoglobin, two proteins capable of binding oxygen. Hemoglobin (show as the red curve) dissociates carbon monoxide (CO), a toxic gas, about 200 times less than it does oxygen. What would the curve for carbon monoxide-bound hemoglobin look like?

The curve would shift upward, more closely resembling the myoglobin curve.

Some G-Protein coupled receptors cause ion channels to open.

True

Which of the following pathways is most likely going to result in a short-term, rapid response by a receiving cell?

Norepinepherine (triggers fight-flight-freeze response)

Cytokine receptors can activate many of the same kinase pathways as RTKs.

True

Which of the following is the most common cellular response from RTKs?

Changes in transcription rates

Which of the following best explains why the Wnt pathway is not used by unicellular eukaryotes?

It wastes molecular resources by constantly being "on."

Arrange the following events in the Ras/MAP Pathway.

Receptor protein dimerizes and is phosphorylated.
GDP is swapped for GTP in Ras, activating it.
Raf is phosphorylated and activated.
MEK is phosphorylated and activated.
MAP is phosphorylated and activated.

Which of the following best describes what kinases do?

Act as enzymes, transferring a phosphate from ATP to a substrate

PI3 kinases are activated by the same receptors as many tyrosine kinase pathways.

True

Which of the following best describes the relationship between insulin and glucagon?

Inhibitory: The signals initiate opposite responses in the cell

The figures above are from Meier (2012) of glucose or insulin over time under fasting or fed conditions. Patients in the trial were given 0.4 pmol, 0.8 pmol, or 1.2 pmol of GLP-1 or a placebo (0 pmol of GLP-1). Which of the following best explains why administration of GLP-1 in these patients resulted in lower blood glucose levels while fasting?

GLP-1 stimulated insulin production.

What is the cellular response of the insulin pathway in fat cells?

Increase GLUT4 transporter in membrane

What is the cellular response of the insulin pathway in liver cells? Select ALL that apply.

Phosphorylation of GSK3 for glycogen synthesis

Which of the following is NOT a requirement for a cellular response pathway (such as responding to blood sugar or low oxygen) for a cell to maintain homeostasis?

All of these are required

Which of the following environments would signal the pancreas to STOP releasing insulin?

Low glucose levels in the blood

What type of signal transduction pathway best describes the insulin receptor pathway in fat and muscle cells?

Enzyme receptor

In most signal transduction pathways, the receptor activates one response protein per signal received.

False

BRET (Bioluminescence Resonance Energy Transfer) is a technique very similar to FRET, except is uses a bioluminescent tag instead of a fluorescent tag. Jang et al (2023) used BRET to observe the binding of an incorrect G-protein coupled receptor (GPCR) with either a wildtype G-protein (Midi Gs wtct; thinner lines) or a mutant G-protein (Midi Gs; thicker lines). Each graph shows the amount of BRET generated by a different incorrect GPCR: M3R activated by Ach or TP activated by U46619. Which of the following statements is true about the G-protein pathway in the figure below?

The mutated G-proteins are not selective about the GPCR they bind with.

Carlessi et al (2017) investigated the mechanism by which Ex-4 stimulated the insulin receptor pathway. They measured the amount of mRNA of HIF-1a and mTOR produced in the presence of three solutions: "vehicle" (an aqueous solution with no inhibitors), torin1 (inhibitor of mTOR), and LY294002 (inhibitor of PI3 kinase). Based on the results above, what is the sequence of protein activations in the pathway?

PI3K activates mTOR which activates HIF-1a.

Which of the following is the most likely outcome for the organism if a cytokine receptor (such as IL-5R) is overexpressed in the gut?

Frequent irritation of the gut lining from inflammation

Bahar et al (2023) summarized the current understanding of the Ras/MAPK pathway in mammalian cells to identify suitable targets for cancer therapy. Given the diagram above, which would be the best target in this pathway?

RAF

NOTCH signaling pathways are important for which type of cellular regulation? Select ALL that apply.

Epithelial cell response to damage
Cancer cell prolific growth
Immune cell recognition of self

The figures above are from Meier (2012) of glucose or insulin over time under fasting or fed conditions. Patients in the trial were given 0.4 pmol, 0.8 pmol, or 1.2 pmol of GLP-1 or a placebo (0 pmol of GLP-1). Which of the following best explains why administration of GLP-1 in these patients resulted in lower blood glucose levels while fasting?

GLP-1 stimulated insulin production.

Above is an image from Carrell et al (2017) of a Drosophila embryo releasing a signaling molecule to be received by the same cells that produced the signal. This best describes which type of signaling pathway?

autocrine

Gagliani et al (2022) generated a Drosophila model (K195E) of a NOTCH genetic disease. The authors then compared the binding between ligand and receptor of the Drosophila line to an existing mouse model (E89G) as well as to a wildtype (WT) system. Which of the following conclusions can be made from the data presented? Select ALL that apply.

The mutation causes NOTCH receptor to bind poorly to the signaling ligand.
The signal will be weaker in carriers of the mutations.

Renal fibrosis is a kidney disease in which thick, rigid cells grow in the kidneys, ultimately reducing their capacity to function. Renal fibrosis is the result of excess inflammation caused by overstimulation of the hedgehog, Wnt and NOTCH pathways. Which of the following statements is/are TRUE given your prior knowledge of these pathways? Select ALL that apply.

All three pathways are defaulted to be "on" so that activation of the pathway stops the signal transduction from being broken down.
These pathways tend to involve post-translational protein regulation.
Signaling amplification is NOT a feature of any of these pathways.

Most enzyme kinase receptors and cytokine receptors bind to a very narrow and specific group of 1-4 molecules.

False

Which type of cell signaling pathway is represented by the diagram above?

Which type of cell signaling pathway is represented by the diagram above?

Zhang et al (2015) wanted to know what pathways herpesvirus activated in tumor cells. To study this, the team performed a Western blot (left) of several proteins, fluorescence microscopy (center) of fluorescently tagged GPCRs (kGPCR) and measured the fluorescence intensity (right) in uninfected (HUVEC/Vec) and infected (HUVEC/kGPCR) cells. Which of the following conclusions is supported by the figure above?
DMSO and CsA are reagents used to dissolve compounds and carry them across the membrane. The numbers in E indicate relative intensity of the bands. COX-2 and RCAN1 are both intracellular proteins. Beta-globulin is a control for Western blots.

Infection with herpesvirus results in gain-of-function changes in the GPCR pathway.

Edelstein et al (2024) wanted to make a enzyme-kinase receptor "switch." They wanted their "switch" to be active only when both receptors were bound. However, as shown in the diagram above, their "switch" continued to produce the product (although at a lower rate) even if only one receptor was activated. Which of the following best explains why this occurred?

Enzyme-kinase pathways crosstalk; many receptors target the same enzymes during the transduction of the cell signal.

BRET (Bioluminescence Resonance Energy Transfer) is a technique very similar to FRET, except is uses a bioluminescent tag instead of a fluorescent tag. Jang et al (2023) used BRET to observe the binding of a G-protein coupled receptor (GPCR) with either a wildtype G-protein (thinner lines) or a mutant G-protein (thicker lines). Each graph shows the amount of BRET generated by the GPCR and the G-protein when the GPCR is bound by ICl or Rauw, two signaling molecules that normally deactivate the GPCR. Which of the following statements is true about the G-protein pathway in the figure below?

The mutant G-protein is unable to dissociate from the GPCR after swapping out its GDP for GTP.

Apical periodontitis (AP) is inflammation of the gums caused by plaque buildup on teeth near the gumline. Which of the following conclusions are supported by the graph above? Select ALL that apply.

These data do not show a dose-dependent response.
Wnt and b-catenin have similar expression profiles.
There is a greater expression of Wnt in AP patients than in control patients.

Cells can become desensitized to a signal that has been activated too strongly. The process of adjusting the number of receptors at the cell surface to reduce the signaling strength is referred to as ______________.

cellular adaptation

Venerando et al (2011) used a literature review to understand the role of the S120 kinase on the CFTR transporter. The diagram above illustrates their findings. The left portion of the diagram ("High Energy Active...") is their understanding of the normal/healthy pathway. The right portion of the diagram ("Low Energy Inactive...") is their understanding of a mutated S120 kinase on this pathway. Which of the following statements is TRUE given the model above?

The S120 mutant is unable to phosphorylate the H118 residue.

Which of the following best explains why microfilaments are used for phagocytosis (ingestion of bacteria)?

Actin is more flexible than microtubules or intermediate filaments. - they are able to shape and change the cell membrane

Which of the following functions of microfilaments is most likely to be in the elongation phase?

contractile ring

Which of the following functions of microfilaments is/are most likely to be treadmilling? Select ALL that apply.

Moving vesicles

Sen et al (2012) identified an adherens tight junction protein (PATJ) essential for Drosophila growth. To determine the mechanistic role of PATJ, the authors measured the mortality of different life stages of Drosophila larvae. During embryonic development, adherens junctions establish the polarity of epithelial cells. During larval growth, adherens junctions maintain the integrity of the cuticle. During pupation, adherens junctions facilitate the mobility of epithelial cells for adult structures. According to the graph to the right, what is the role of PATJ in Drosophila growth? Black bars are PATJ mutants. Gray bars are cadherin mutants.

Assist myosin movement along actin filaments

If you wanted to identify where in the cell the centrosomes form during mitosis, which protein would you target for immunofluorescence?

γ-TuRC

Neutrophils are a specialized type of white blood cell that possess nuclei with multiple lobes. What role does vimentin, a Type III IF, play in determining the number of lobes in neutrophils?

Vimentin affects the number of lobes in neutrophils, but must work with other proteins to determine the exact number.