Chapter 9 & 10 Homework

Consider the steps in activation of a cellular response.I. Protein kinase A is activated.II. Ligand binds to G protein‑coupled receptor.III. ATP is converted into cAMP.IV. The alpha subunit of the G protein activates adenylyl cyclase.V. GDP is replaced by GTP in the G protein. In what order do the steps for the activation of a cellular response take place? a. II > V > IV > III > I b. V > I > III > II > IV c. I > III > II > IV > V d. III > IV > I > V > II e. IV > II > V > I > III

a. II > V > IV > III > I

What happens if the conversion of GTP into GDP by the G protein is inhibited? a. The amplification reaction continues until ATP levels are too low. b. Polar ligands stop binding G protein‑coupled receptors. c. Phosphatases dephosphorylate the target proteins of protein kinase A. d. cAMP molecules are degraded into AMP.

a. The amplification reaction continues until ATP levels are too low.

Which answer choice is true about the motor proteins myosin and kinesin? a. They both use the energy of ATP. b. They both move along microfilaments. c. They both move cargo along microtubules. d. They both move chromosomes along spindle fibers during mitosis.

a. They both use the energy of ATP.

The ligand for a G protein‑coupled receptor is added to cells, but they exhibit no cellular response. After some tests, you identify ATP levels are lower than normal but GTP levels are not lower than normal. Which process(es) are likely to be affected by this? Select all that apply. a. activation of adenylyl cyclase b. activation of G protein‑coupled receptor c. activation of protein kinase A d. activation of G protein

a. activation of adenylyl cyclase, c. activation of protein kinase A

Cellular responses that result from receptor kinase activation tend to: a. involve changes in gene expression. b. be short term. c. involve changes in metabolism. d. involve ion channels.

a. involve changes in gene expression.

Which would be more likely to cause development of a microvillus on an intestinal epithelial cell? a. plus (+) end growth of microfilaments at the tip of the microvillus but no shrinkage at the minus (−) end b. plus (+) end growth of microfilaments at the tip of the microvillus and shrinkage at the minus (−) end c. minus end growth of microfilaments at the tip of the microvillus and shrinkage at the plus (+) end

a. plus (+) end growth of microfilaments at the tip of the microvillus but no shrinkage at the minus (−) end

What is the end-result of activating the MAP kinase pathway? a. phosphorylation of multiple cytosolic proteins b. a change in gene expression c. ion flow d. synthesis of second messenger molecules

b. a change in gene expression

Microtubules can grow by addition of tubulin dimers to ______ , and they can shorten by removal of dimers from ______. a. the plus end; the minus end b. both plus and minus ends; both plus and minus ends c. the plus end; both plus and minus ends d. both plus and minus ends; the minus end e. the minus end; the plus end

b. both plus and minus ends; both plus and minus ends

Why are some mutations of Ras associated with cancer? a. Ras binds to growth factor receptors. b. Ras is a type of second messenger. c. Ras activates the MAP kinase signal transduction pathway that regulates cell division. d. Ras alters ion flow across the cell membrane.

c. Ras activates the MAP kinase signal transduction pathway that regulates cell division.

Which type of reaction is carried out by adenylyl cyclase? a. hydrolysis of ATP into ADP b. phosphorylation of GDP into GTP c. cyclization of ATP into cAMP d. phosphorylation of a protein target

c. cyclization of ATP into cAMP

A specific ligand is polar in nature. Where is the ligand‑binding portion of the receptor most likely to be located? a. lumen (interior) of the endoplasmic reticulum b. cytoplasm of the cell c. extracellular side of the cell membrane d. cytoplasmic side of the cell membrane

c. extracellular side of the cell membrane

Predict what happens if each adenylyl cyclase enzyme is able to convert only one molecule of ATP into cAMP, reducing the amount of cAMP produced. a. Phosphatases are activated to reduce the competition for the target protein of protein kinase A. b. Not enough cAMP is generated and the cell undergoes signal termination. c. Additional G protein‑coupled ligands are expressed to compensate for the reduction in cAMP production. d. Not enough molecules of protein kinase A are activated and the cellular response is dampened.

d. Not enough molecules of protein kinase A are activated and the cellular response is dampened.

Ras is most similar to: a. the γ (gamma) subunit of three-subunit G proteins. b. ion channels. c. the β (beta) subunit of three-subunit G proteins. d. the α (alpha) subunit of three-subunit G proteins. e. receptor kinases.

d. the α (alpha) subunit of three-subunit G proteins.

Contraction of muscles is an example of how the motor protein ______ interacts with the cytoskeletal elements called ______ to produce movement. a. actin; dynein b. kinesin; microtubules c. dynein; microtubules d. myosin; dynein e. myosin; actin filaments

e. myosin; actin filaments