chapter 16 molecular cell biology

(Q016) Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase, the enzyme that breaks down glycogen, as depicted in Figure 16-16. Which of the following statements is FALSE? A constitutively active mutant form of PKA in skeletal muscle cells would not increase the affinity of adrenaline for the adrenergic receptor. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glucose available. A constitutively active mutant form of PKA in skeletal muscle cells would lead to a decrease in the amount of unphosphorylated phosphorylase kinase. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.

A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.

(Q032) The last common ancestor to plants and animals was a unicellular eukaryote. Thus, it is thought that multicellularity and the attendant demands for cell communication arose independently in these two lineages. This evolutionary viewpoint accounts nicely for the vastly different mechanisms that plants and animals use for cell communication. Fungi use signaling mechanisms and components that are very similar to those used in animals. Which of the phylogenetic trees shown in Figure 16-32 does this observation support? a) plants and fungi together, animals along b)Plants alone on left, fungi and animals connected on right c) plants and animals together and fungi alone

B Plants alone on left, fungi and animals connected on right

(Q034) Figure 16-34 shows that intracellular signaling pathways can be highly interconnected. Figure 16-34 From the information in Figure 16-34, which of the following statements is FALSE? CaM-kinase is only activated when the GPCR is active and not when the RTK is active. Ras is activated only when the RTK is active and not when the GPCR is active. The GPCR and the RTK both activate phospholipase C. Activation of either the GPCR or the RTK will lead to activation of transcriptional regulators.

CaM-kinase is only activated when the GPCR is active and not when the RTK is active.

(Q031) Which of the following statements is FALSE? Some signal molecules can bind directly to intracellular proteins that bind DNA and regulate gene transcription. Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids. Some signal molecules are transmembrane proteins. Nucleotides and amino acids can act as extracellular signal molecules.

Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids.

(Q006) Which of the following statements is TRUE? a. Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior. b. To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol. c. A cell-surface receptor capable of binding only one type of signal molecule can mediate only one kind of cell response. d. Any foreign substance that binds to a receptor for a normal signal molecule will always induce the same response that is produced by that signal molecule on the same cell type.

Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.

(Q005) Acetylcholine is a signaling molecule that elicits responses from heart muscle cells, salivary gland cells, and skeletal muscle cells. Which of the following statements is FALSE? Heart muscle cells decrease their rate and force of contraction when they receive acetylcholine, whereas skeletal muscle cells contract. Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family. Heart muscle cells, salivary gland cells, and skeletal muscle cells all respond to acetylcholine within minutes of receiving the signal. Active acetylcholine receptors on salivary gland cells and heart muscle cells activate different intracellular signaling pathways.

Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family.

(Q028) Akt promotes the survival of many cells by affecting the activity of Bad and Bcl2, as diagrammed in Figure 16-28. Figure 16-28 Which of the following statements is FALSE? In the presence of a survival signal, the cell-death inhibitory protein Bcl2 is active. In the absence of a survival signal, Bad is phosphorylated. In the absence of a survival signal, Bad inhibits the cell-death inhibitor protein Bcl2. In the presence of a survival signal, Akt is phosphorylated.

In the absence of a survival signal, Bad is phosphorylated.

(Q007) Which of the following statements about molecular switches is FALSE? Serine/threonine kinases are the most common types of protein kinase. Protein kinases transfer the terminal phosphate from ATP onto a protein. Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off. A GTP-binding protein exchanges its bound GDP for GTP to become activated.

Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off.

(Q009) Cell lines A and B both survive in tissue culture containing serum but do not proliferate. Factor F is known to stimulate proliferation in cell line A. Cell line A produces a receptor protein (R) that cell line B does not produce. To test the role of receptor R, you introduce this receptor protein into cell line B, using recombinant DNA techniques. You then test all of your various cell lines in the presence of serum for their response to factor F, with the results summarized in Table 16-9. Table 16-9 Which of the following cannot be concluded from your results above? Receptor R binds to factor F to induce cell proliferation in cell line A. Cell line A expresses a receptor for factor F. Factor F is not required for proliferation in cell line B. Binding of factor F to its receptor is required for proliferation of cell line A.

Receptor R binds to factor F to induce cell proliferation in cell line A.

(Q011) Which of the following statements about G-protein-coupled receptors (GPCRs) is FALSE? GPCRs are found in yeast, mice, and humans. GPCRs are the largest family of cell-surface receptors in humans. The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains. GPCRs are used in endocrine, paracrine, and neuronal signaling.

The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains.

(Q003) Which of the following statements is TRUE? a. The axons of neurons typically signal target cells using membrane-bound signaling molecules that act on receptors in the target cells. b. The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling. c. Paracrine signaling involves the secretion of signals into the bloodstream for distribution throughout the organism. d. Because endocrine signals are broadcast throughout the body, all cells will respond to the hormonal signal.

The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling.

(Q010) The following happens when a G-protein-coupled receptor activates a G protein. The β subunit exchanges its bound GDP for GTP. The GDP bound to the α subunit is phosphorylated to form bound GTP. It activates the α subunit and inactivates the βγ complex. The α subunit exchanges its bound GDP for GTP.

The α subunit exchanges its bound GDP for GTP.

(Q020) Figure 16-20 shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine? a smooth muscle cell that has a defect in guanylyl cyclase such that it cannot bind NO a drug that blocks an enzyme involved in the metabolic pathway from arginine to NO a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP a muscle cell that has cyclic GMP phosphodiesterase constitutively active

a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP

(Q015) You are interested in how cyclic-AMP-dependent protein kinase A (PKA) functions to affect learning and memory, and you decide to study its function in the brain. It is known that, in the cells you are studying, PKA works via a signal transduction pathway like the one depicted in Figure 16-15. Furthermore, it is also known that activated PKA phosphorylates the transcriptional regulator called Nerd that then activates transcription of the gene Brainy. Which situation described below will lead to an increase in Brainy transcription? 1. a mutation in the Nerd gene that produces a protein that cannot be phosphorylated by PKA 2. a mutation in the gene that encodes cAMP phosphodiesterase that makes the enzyme inactive 3. a mutation in the gene that encodes adenylyl cyclase that renders the enzyme unable to interact with the α subunit of the G protein 4. a mutation in the nuclear import sequence of PKA from PPKKKRKV to PPAAAAAV

a mutation in the gene that encodes cAMP phosphodiesterase that makes the enzyme inactive

(Q021) The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? a mutation that prevents the binding of the normal extracellular signal to the receptor a mutation that prevents dimerization of the receptor a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor a mutation that destroys the kinase activity of the receptor

a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor

(Q022) The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine kinase called RGFR. Which of the following types of alteration would be most likely to prevent receptor dimerization? changing the tyrosines that are normally phosphorylated on RGFR dimerization to glutamic acid changing the tyrosines that are normally phosphorylated on RGFR dimerization to alanines a mutation that increases the affinity of RGFR for RGF a mutation that prevents RGFR from binding to RGF

a mutation that prevents RGFR from binding to RGF

(Q013) Acetylcholine binds to a GPCR on heart muscle, making the heart beat more slowly. The activated receptor stimulates a G protein, which opens a K+ channel in the plasma membrane, as shown in Figure 16-13. Which of the following would enhance this effect of the acetylcholine? 1. mutations in the acetylcholine receptor that weaken the interaction between the receptor and the G protein 2. addition of a high concentration of a nonhydrolyzable analog of GTP 3. mutations in the acetylcholine receptor that weaken the interaction between the receptor and acetylcholine 4. addition of a drug that prevents the α subunit from exchanging GDP for GTP

addition of a high concentration of a nonhydrolyzable analog of GTP

(Q002) During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in __________ signaling. paracrine neuronal endocrine contact-dependent

contact-dependent

(Q001) When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a neurotransmitter. hormone. scaffold. dissolved gas.

hormone.

(Q023) A protein kinase can act as an integrating device in signaling if it catalyzes its own phosphorylation. is activated by two or more proteins in different signaling pathways. initiates a phosphorylation cascade involving two or more protein kinases. phosphorylates more than one substrate.

is activated by two or more proteins in different signaling pathways.