Homework Questions: Final Exam Flashcards
When secreted in the human body, the hormone glucagon causes rapid degeneration of glycogen in liver cells. This mobilization of glycogen is accomplished through a signaling pathway. What is the proper temporal sequence of the following steps in this reaction cascade?
A - displacement of GDP with GTPon the a-subunit of the G-proteins
B - phosphorylation of glycogen
C - dissociation of the regulatory subunits activates protein kinaseA
D - phosphorylation of glycogen phosphorylase
E - glucagons binds to a specific, transmembrane receptor
F - formation of cyclic-AMP by adenylyl cyclase
E-A-F-C-D-B
Which of the following statements concerning receptors is CORRECT?
a) they have a ligand binding site on the extracellular side of the membrane
b) they have an active site on the extracellular side of the membrane
c) they contain an enzyme activity for which the signal molecule is a substrate
d) they bind signal molecules in a non-specific manner
a) they have a ligand binding site on the extracellular side of the membrane
insulin binds to a receptor that ______.
I. is coupled to a G protein
II. possesses tyrosine kinase activity
III. possesses serine/threonine phosphatase activity
IV. interacts with proteins such as IRS-1
II, IV
which of the following would diminish a hormone signal mediated via a G protein signal transduction system?
a) addition of a substance which inhibits adenylate cyclase
b) greater than normal expression of the receptor in the cell membrane
c) addition of a substance which inhibits the GTPase activity of the G protein
d) addition of a substance such as caffeine, which inhibits phosphodiesterase
a) addition of a substance which inhibits adenylate cyclase
the second messenger ________ is produced by the enzyme __________.
a) nitric oxide; arginase
b) cGMP; GTP cyclase
c) cAMP; adenylate cyclase
d) triacylglycerol; phospholipase C
e) inositol diphosphate; phospholipase C
c) cAMP; adenylate cyclase
the _______ receptor is a receptor kinase.
a) a1-adrenergic
b) B2-adrenergic
c) calmodulin
d) insulin
e) cortisol
d) insulin
which one of the following statements about the glucagon signaling pathway is TRUE?
a) the G protein is a second messenger
b) activated adenylate cyclase decreases the concentration of cAMP
c) protein kinase A is the target protein (enzyme)
d) the glucagon receptor protein interacts with adenylate cyclase
e) the activity of protein kinase A is dependent on the concentration of cAMP
e) the activity of protein kinase A is dependent on the concentration of cAMP
which of the following does NOT occur in biological signaling systems?
a) protein-protein interactions
b) ligand-protein interactions
c) opening or closing of ion channels
d) autophosphorylation
e) all of the above processes may occur
e) all of the above processes may occur
In a G protein signal-transduction system, what role does the G protein play?
a) it activates a target protein (enzyme)
b) it produces the second messenger molecule
c) it reverses the activation of the receptor caused by ligand binding
d) it transmits the signal from the receptor to other components of the signaling system
d) it transmits the signal from the receptor to other components of the signaling system
ligand binding to a receptor tyrosine kinase causes _______ of the receptor which then ________ the next protein in the signaling pathway.
a) methylation; hydrolyzes
b) hydrolysis; inhibits
c) phosphorylation; phosphorylates
d) acylation; activates
e) none of the above
c) phosphorylation; phosphorylates
which of the following is a ligand of the B2-adrenergic receptor?
a) tyrosine
b) serotonin
c) norepinephrine
d) caffeine
e) adenosine
c) norepinephrine
a small molecule produced inside a cell in response to a hormone binding to its receptor is called a(n) ___________.
a) inside messenger
b) agonist
c) antagonist
d) second messenger
e) G protein
d) second messenger
what group is attached to the pyrimidine ring in thymine and is not present in uracil?
a) ribose
b) -CH3
c) -NH2
d) deoxyribose
e) none of the above
b) -CH3
the coenzymes known as NAD+, FAD and coenzyme A all contain a derivative of ______.
a) uridine
b) thymidine
c) adenosine
d) guanosine
e) cytidine
c) adenosine
nucleoside triphosphate are useful for energy transfer because the pisphoanhydride bonds are relatively ________.
a) stable
b) biocompatible
c) high energy
d) large
e) low energy
c) high energy
which of the following is correctly paired with its nucleoside?
a) cytosine: cytidine diphosphate
b) adenine: adenylate
c) uridine: uridine triphosphate
d) guanine: guanosine
e) thymine: thymidylate
d) guanine: guanosine
which of the following is TRUE about the about the oligonucleotide that is represented below?
AUCCGAUC
a) it has an A at its 3’ terminus
b) it is a DNA oligonucleotide
c) it contains 3 pyrimidine bases
d) it has a purine at its 5’ terminus
d) it has a purine at its 5’ terminus
identify the purine nucleoside.
a) cytosine
b) guanosine
c) uridine
d) adenylic acid
b) guanosine
the 5 end of a polynucleotide contains ______ while the 3’ end contains ______.
a) a hydroxyl group; a phosphate group
b) a phosphate group: a hydroxyl group
c) a phosphate group: a phosphate group
d) a hydroxyl group: a hydroxyl group
e) none of the above
b) a phosphate group: a hydroxyl group
an A-T base pair consists of ________ H-bond(s); a C-G base pair consists of _______ H-bond(s)
a) 3;2
b) 2;3
c) 2;2
d) 1;2
e) 2;1
b) 2;3
which of the following statements is TRUE regarding phosphodiester bonds that link adjacent nucleotides in both RNA and DNA?
a) phosphodiester bonds join the 3’ hydroxyl of one nucleotide to the hydroxyl of the next
b) phosphodiester bonds are unchanged at pH 7.0
c) phosphodiester bonds always link G with C and A with either T or U
d) phosphodiester bonds are positively charged
a) phosphodiester bonds join the 3’ hydroxyl of one nucleotide to the hydroxyl of the next
Which of the following statements about the structure of the double-stranded DNA is FALSE?
a) some groups of the bases exposed in the grooves of double-stranded DNA
b) the phosphodiester backbone interacts with Mg2+ in the cell
c) DNA is stabilized primarily by H-bonding between the bases
d) only non-covalent forces stabilize the helix so that the DNA can unwind during replication and transcription
c) DNA is stabilized primarily by H-bonding between the bases
which of the following statements is NOT true about base Watson-Crick complementary pairing:
a) each base is hydrogen bonded to a base in the opposite strand to form planar base pair
b) each A pairs with T and each G pairs with C
c) an A:T base pair is stronger that a G:C pair
d) each DNA strand can act as a template for the synthesis of its complementary strand
c) an A:T base pair is stronger that a G:C pair
differences in structure between a DNA helix and an RNA helix can predominantly be attributed to the presence of _____ in RNA
a) uracil
b) 2’ hydroxyl group
c) 3’ hydroxyl group
d) smaller sizes of RNA molecules
e) none of the above
b) 2’ hydroxyl group
the replication of DNA is made possible by the presence of ______ strands in the double helix of DNA
a) antiparallel
b) hydrogen bonded
c) complementary
d) genomic
e) none of the above
c) complementary
DNA encodes proteins undergoes the process of ______ to produce _______.
a) translation; proteins
b) transcription; proteins
c) transcription; tRNA
d) transcription; mRNA
e) translation; rRNA
d) transcription; mRNA
the DNA strand that serves as the template for the synthesis of RNA is often called the ________.
a) transfer strand
b) messenger strand
c) coding strand
d) noncoding strand
e) transcription strand
d) noncoding strand
