BS 161 Chapter 9: Homework

decrease

A mutation of the G protein−coupled receptor that removes the extracellular domain of the receptor. The amount of cAMP in cells will: stay the same decrease increase

decrease

A mutation in the α subunit of the G protein that prevents the release of bound GDP. The amount of cAMP in cells will: decrease stay the same increase

increase

A mutation in the α subunit of the G protein that prevents the release of bound GTP. The amount of cAMP in cells will: stay the same increase decrease

decrease

A mutation in the α unit of the G protein that prevents it from binding to adenylyl cyclase but not the receptor. The amount of cAMP in cells will: decrease increase stay the same

increase

A mutation of the G protein−coupled receptor that allows it to bind the α subunit of the G protein in the absence of ligand. The amount of cAMP in cells will: increase decrease stay the same

One adrenaline molecule can bind to and activate many receptors simultaneously.

According to Figure 9.11, which of the following is NOT responsible for amplifying the signal in a cell responding to adrenaline signaling? One adrenaline molecule can bind to and activate many receptors simultaneously. One molecule of protein kinase A can phosphorylate and activate many target proteins. One activated receptor can activate many G proteins. One molecule of adenylyl cyclase can produce many molecules of cAMP.

providing binding sites to recruit and activate signal-transduction proteins.

According to Figure 9.14, phosphate groups play a key role in receptor kinase activation by: activating the receptor, so that the receptor is capable of binding its signal. All of these choices are correct. providing binding sites to recruit and activate signal-transduction proteins. activating the dimerization of the receptor kinase proteins in the membrane. activating receptor kinase activity.

Cell-surface receptors bind polar signaling molecules; intracellular receptors bind nonpolar signaling molecules.

According to Figure 9.6, what is a key difference between cell signaling by a cell-surface receptor and cell signaling by an intracellular receptor? Cell-surface receptors bind polar signaling molecules; intracellular receptors bind nonpolar signaling molecules. Signaling molecules that bind to cell-surface receptors lead to cellular responses restricted to the cytoplasm; signaling molecules that bind to intracellular receptors lead to cellular responses restricted to the nucleus. Cell-surface receptors bind to specific signaling molecules; intracellular receptors bind any signaling molecule. Cell-surface receptors typically bind to signaling molecules that are smaller than those bound by intracellular receptors. None of the other answer options is correct.

fibroblasts cultured with serum

Based on the data provided in the two graphs shown in Figure 9.5, which method of culturing resulted in the greatest number of fibroblast cells on day 6? fibroblasts cultured with serum fibroblasts cultured with platelet proteins fibroblasts cultured with plasma The same results are obtained whether the fibroblasts are cultured with serum or with platelet proteins.

All of these choices are correct.

Defects in cell signaling can lead to a cancerous cell as a result of: All of these choices are correct. a defective receptor that stays in the activated state and triggers cell division continuously. overproduction of signals that trigger cell division. overproduction of a receptor that triggers cell division. a defective signal transduction protein that stays in the activated state and triggers cell division continuously.

The cascade serves to amplify the signal, so one activated receptor can have a significant response.

During the signal transduction process, the signal often triggers a signal transduction cascade. For example, an activated receptor activates hundreds of protein A. Each activated protein A activates hundreds of protein B and so on until a cellular response occurs. What purpose does this cascade serve? The cascade makes signaling easier to shut off or terminate. Having several intermediates allows for greater control of the response. Having a cascade allows the cell to respond to different signals. The cascade serves to amplify the signal, so one activated receptor can have a significant response.

the addition of a drug that prevents the final kinase from interacting with its target protein in the nucleus

Figure 9.15 shows how normal signaling works with a Ras protein acting downstream of a receptor kinase. You examine a cell line in which Ras is always activated even in the absence of a signaling molecule. This causes constant activation of the kinases in the MAP kinase pathway. Which of the following conditions would be MOST likely to turn off this abnormally active signaling pathway? the addition of a drug that prevents the final kinase from interacting with its target protein in the nucleus the addition of a drug that prevents the dimerization of the receptor kinase the addition of a drug that increases the binding affinity of Ras for MAP kinase enzymes in the cytoplasm the addition of a drug that prevents the phosphorylation of the receptor kinase

Both types undergo a conformational change when they bind to their ligand.

How are steroid hormone receptors and cell-surface receptors similar? Both types undergo a conformational change when they bind to their ligand. When activated, both types carry signals across the plasma membrane. When bound to their ligand, both types enter the nucleus to activate transcription. Both types cause G proteins to exchange GDP for GTP.

Phosphatases remove phosphate groups.

How do mitogen-activated protein (MAP) kinases become inactive? Ligand diffuses away from the ligand-binding site. Receptor kinases move apart in the membrane. Ras hydrolyzes GTP to GDP. Phosphatases remove phosphate groups.

The response of the cell would last longer than it normally would.

Phosphatases are a family of enzymes that remove phosphate groups from specific proteins; these phosphate groups had been added to the proteins by protein kinases. Vanadate is an inhibitor of phosphatases in eukaryotic cells. What effect would vanadate have on the response of cells to signals received by receptor kinases? The response of the cell would be shorter than it normally would. The signal would still bind the receptor, so there would be no effect. The response of the cell would last longer than it normally would.

paracrine

Platelet-derived growth factor (PDGF) is a signaling molecule that functions in which of the following types of cell signaling? endocrine paracrine All of these choices are correct. autocrine contact-dependent

All of these choices are correct.

Second messengers: All of these choices are correct. amplify the effects of the signal. are small intracellular molecules that participate in signal transduction. play a role in activation of intracellular signal transduction. are removed in order to terminate a cellular signaling response.

It would continue in the absence of ligand.

What would happen to the signaling cascade if phosphatases were nonfunctional? None of the other answer options is correct. It would continue in the absence of ligand. It would slow down in the absence of ligand. It would stop in the absence of ligand.

NOT adenylyl cyclase (activates) and phosphatase (terminates) protein kinase (activates) and phosphodiesterase (terminates)

Which of the following CORRECTLY pairs enzymes that activate and terminate the same step in a signaling event? (Select all that apply.) adenylyl cyclase (activates) and phosphatase (terminates) protein kinase (activates) and phosphodiesterase (terminates) protein kinase (activates) and phosphatase (terminates) adenylyl cyclase (activates) and phosphodiesterase (terminates)

autocrine

Which of the following is a type of cell communication where the signaling molecule is released by the same cell that responds to the signal? autocrine All of these choices are correct. endocrine contact-dependent paracrine

Receptor kinases

Which of the following receptors becomes phosphorylated when it is bound by its signaling molecule ligand? Ion channel receptors Receptor kinases G protein-coupled receptors Steroid receptors

All of these choices are correct.

Which of the following types of cellular activities can be a response to cell signaling? Cell signals are released to communicate with other cells. Gene expression patterns are changed. All of these choices are correct. Enzyme activities are changed. Cell division is triggered.

ligand-gated ion channel

Which type of receptor is involved in rapid responses of muscle cells and neurons? G protein-coupled receptor receptor kinase intracellular receptor ligand-gated ion channel

The receptor monomers must move together and dimerize to be activated

Why do the functions of many receptor kinases depend on the fluid nature of the plasma membrane? The generation of cAMP requires a fluid membrane. Binding of ligand to the receptor requires a fluid membrane. The receptor monomers must move together and dimerize to be activated. Phosphorylation requires a fluid membrane.

decrease

You are doing an experiment on a new class of G protein−coupled receptor. You make several cell lines that each express the receptor, the corresponding G protein, and adenylyl cyclase. Each cell line has different mutations in these components. You decide to measure cyclic AMP (cAMP) in the cells of each cell line to understand the effect of each of these mutations. Below is a list of mutations. For each, indicate whether the amount of cAMP in the cells will increase, decrease, or stay the same. A mutation in the G protein−coupled receptor that prevents it from binding to the G protein. The amount of cAMP in cells will: increase decrease stay the same