Multiple Choice Questions

Peptide hormones and other protein-based ligands act on target cells by binding to _____receptors. a. cell surface b. cystosolic c. nuclear d. both a and b

a. cell surface

The response initiated by protein kinase A is terminated by a. inactivation of the initial receptor b. inactivation of Gs c. degradation of cAMP d. dephosphorylation of phosphoproteins by a protein phosphatase e. all of the above

e. all of the above

The DNA sequence to which a transcription factor binds to affect transcription of a gene is called a(n) a. enhancer b. promoter c. polymerase-binding element d. origin of transcription e. operator

a. enhancer

A proto-oncogene is a gene a. from a normal cell from which an oncogene can arise b. that has been picked up by an oncogenic virus c. that is in the process of evolving into an oncogene d. that is expressed abnormally in a tumor cell e. that has been mutated to alter cell growth control

a. from a normal cell from which an oncogene can arise

Cholera toxin inhibits the ability of the alpha subunit of Gs to hydrolyze GTP. The resulting effect is the ______ of adenylyl cyclase. a. stimulation b. inhibition c. molecular degration d. increased synthesis

a. stimulation

Which of the following is true regarding heterotrimeric G proteins in a resting state? a. The beta subunit it bound to GDP in complex with both the alpha and gamma subunits b. GDP is bound to the alpha subunit in complex with both the beta and gamma subunits c. GTP is bound to the alpha subunit in complex with both the beta and gamma subunits d. G proteins are in complex with G protein coupled receptors

b. GDP is bound to the alpha subunit in complex with both beta and gamma subunits

Lipids covalently attached to a protein usually serve to a. reduce the activity of that protein b. anchor the protein in the plasma membrane c. modify the active site of the protein d. allow the protein to interact with the aqueous cytoplasm

b. anchor the protein in the plasma membrane

Calcium affects proteins in the cell by a. directly inducing gene expression b. binding to target proteins and causing a conformational change c. marking target proteins for degradation d. none of the above

b. binding to target proteins and causing a conformational change

Activation of the Src protein kinase involves the following: a. causing more enzyme to be synthesized b. changing the conformation of the enzyme active site c. phosphorylating the enzyme

b. changing the conformation of the enzyme active site

The IP3 produced by phospholipase C acts to a. open calcium channels in the plasma membrane b. open calcium channels in the endoplasmic reticulum c. activate IP3 dependent kinase d. open channels in mitochondria

b. open calcium channels in the endoplasmic reticulum

Standard chemotherapy drugs have a high incidence of side effects because they: a. target oncogene function b. kill cancer cells specifically c. block or kill all cells undergoing cell division d. target tumor suppressor protein function e. inhibit cell growth of the tumor only

c. block or kill all cells undergoing cell division

Formation of protein 2nd structure involves: a. hydrogen bonding between amino acid side chains b. covalent bonds between amino acid side chains c. hydrogen bonding between atoms in the polypeptide backbone d. bonding between multiple polypeptide chains

c. hydrogen bonding between atoms in the polypeptide backbone

Short-range signaling that involves diffusion of signaling molecules from a source cell is an example of ____ signaling. a. autocrine b. endocrine c. paracrine d. direct cell-to-cell e. electrical

c. paracrine

Amino acids that are identical in evolutionary related proteins are said to be _____.

conserved

The dramatic increase in cancer incidence with age suggests that a. cancer is caused by old age b. genetic factors are not involved c. cancer arises primarily in differentiated, nondividing tissues d. cancer develops due to multiple abnormalities that accumulate over many years

d. cancer develops due multiple abnormalities that accumulate over many years.

SH2 domains are a. protein domains that bind phosphotyrosine-containing peptides b. the domains on receptor protein-tyrosine kinases that contain the phosphorylated tyrosine c. domains that mediate the dimerization of receptor protein-tyrosine kinases d. the domains on receptor protein-tyrosine kinases that possesses the kinase activity

a. protein domains that bind phosphotyrosine-containing peptides

Which of the following statements is true? a. MAP kinase is important for phosphorylating MAP kinase kinase b. Sos acts as a GEF to activate Ras c. Ras becomes activated when an RTK phosphorylates its bound GDP to create GTP d. Raf phosphorlates transcription factors located in the nucleus

b. Sos acts as a GEF to activate Ras

MAPK signaling pathways amplify as well as propagate a signal because: a. downstream kinases are more active than upstream kinases b. each kinases in the cascade can phosphorylate multiple targets c. the cell expresses more copies of downstream kinases d. ligand-receptor binding occurs in the nucleus

b. each kinase in the cascade can phosphorylate multiple targets

Signaling by hormones is an example of ______ signaling. a. autocrine b. endocrine c. paracrine d. direct cell-to-cell e. electrical

b. endocrine

The transcription factor NF-kB is activated by a protein kinase that a. phosphorylates NF-kB directly to activate it b. phosphorylates the inhibitory factor IkB, causing it to be degraded and to release NF-kB c. phosphorylates a MAP kinase to initiate its cascade d. activates a phosphatase that removes an inhibiting phosphate from the NF-kB e. phosphorylates a protease that then degrades IkB, releasing NF-kB

b. phosphorylates the inhibitory factor IkB, causing it to be degraded and to release NF-kB

Diacylglycerol and calcium activate a. protein kinase A b. protein kinase C c. PI 3-kinase d. Ca2+/calmodulin-dependent kinase e. a tyrosine kinase

b. protein kinase C

Loss-of-function mutations can be oncogenic if the mutant gene codes for a(n) a. adaptor protein b. tumor suppressor protein c. gene that regulates the cell cycle d. DNA synthesis enzyme e. growth factor receptor

b. tumor suppressor protein

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

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

The first step in the activation of receptor tyrosine kinase (RTK) signaling pathways is: a. Ras activation b. receptor phosphorylation c. receptor dimerization d. binding of SH2-containing proteins e. release of G proteins

c. receptor dimerization

Which of the following is considered a second messenger? a. cAMP b. IP3 c. DAG d. all of the above

d. all of the above

The majority of oncogene proteins are a. metabolic enzymes b. structural proteins, such as nuclear lamins c. proteins involved in cell adhesion d. components of signaling pathways that regulate cell proliferation

d. components of signaling pathways that regulate cell proliferation

Which of the following is not a commonly observed consequence of the binding of a signaling molecule to its cell surface receptor? a. receptor dimerization b. receptor phosphorylation c. conformational changes in the receptor d. increased synthesis of the receptor

d. increased synthesis of the receptor