ESSENTIAL CELL BIOLOGY EXAM #3
QUESTIONS WITH CORRECT ANSWERS
protein phosphatase - ANSWER-enzyme that catalyzes the removal of a phosphate
group from a protein, often with high specificity for the phosphorylated site
serine/threonine kinase - ANSWER-enzyme that phosphorylates target proteins on
serines or threonines
tyrosine kinase - ANSWER-enzyme that phosphorylates target proteins on tyrosines
GTP-binding protein - ANSWER-intracellular signaling protein whose activity is
determined by its association with either GTP or GDP
ion-channel-coupled receptor - ANSWER-transmembrane receptor protein or protein
complex that opens in response to the binding of a ligand to its external face, allowing
the passage of a specific inorganic ion
G-protein-coupled-receptor (GPCR) - ANSWER-cell-surface receptor that associates
with an intracellular trimeric GTP-binding protein (G protein) after activation by an
extracellular ligand
G protein - ANSWER-a membrane-bound GTP-binding protein involved in intracellular
signaling; composed of three subunits, this intermediary is usually activated by the
binding of a hormone or other ligand to a transmembrane receptor
small intracellular signaling molecule - ANSWER-nucleotide, lipid, ion, or other small
molecule generated or released in response to an extracellular signal
adenylyl cyclase - ANSWER-enzyme that catalyzes the formation of cyclic AMP from
ATP; an important component in some intracellular signaling pathways
cyclic AMP (cAMP) - ANSWER-small intracellular signaling molecule generated from
ATP in response to hormonal stimulation of cell-surface receptors
cyclic-AMP-dependent protein kinase (protein kinase A, PKA) - ANSWER-enzyme that
phosphorylates target proteins in response to a rise in intracellular cyclic AMP
concentration
phospholipase C - ANSWER-enzyme associated with the plasma membrane that
generates two small messenger molecules in response to activation
,inositol phospholipid - ANSWER-minor lipid component of plasma membrane that plays
a part in signal transduction in eukaryotic cells; cleavage yields two small messenger
molecules, IP3 and diacylglycerol
inositol 1,4,5-trisphosphate (IP3) - ANSWER-small intracellular signaling molecule that
triggers the release of Ca2+ from the endooplasmic reticulum into the cytosol; produced
when a signal molecule activates a membrane-bound protein called phospholipase C
diacylglycerol (DAG) - ANSWER-small messenger molecule produced by the cleavage
of membrane inositol phospholipids in response to extracellular signals
protein kinase C (PKC) - ANSWER-enzyme that phosphorylates target proteins in
response to a rise in diacylglycerol and Ca2+ ions
calmodulin (CaM) - ANSWER-small Ca2+-binding protein that modifies the activity of
many target proteins in response to changes in Ca2+ concentration
Ca2+/calmodulin-dependent protein kinase (CaM-kinase) - ANSWER-enzyme that
phosphorylates target proteins in response to an increase in Ca2+ ion concentration
through its interaction with the Ca2+-binding protein calmodulin
adaptation - ANSWER-adjustment of sensitivity following repeated stimulation; allows a
cell or organism to register small changes in a signal despite a high background level of
stimulation
enzyme-coupled receptor - ANSWER-transmembrane protein that, when stimulated by
the binding of a ligand, activates an intracellular enzyme (either a separate enzyme or
part of the receptor itself)
receptor tyrosine kinase (RTK) - ANSWER-enzyme-coupled receptor in which the
intracellular domain has a tyrosine kinase activity, which is activated by ligand binding to
the receptor's extracellular domain
Ras - ANSWER-one of a large family of small GTP-binding proteins (the monomeric
GTPases) that helps relay signals from cell-surface receptors to the nucleus
monomeric GTPase - ANSWER-small, single-subunit GTP-binding protein
MAP-kinase signaling module - ANSWER-set of three functionally interlinked protein
kinases that allows cells to respond to extracellular signal molecules that stmulate
proliferation; includes a mitogen-activated protein kinase (MAP kinase), a MAP kinase
kinase, and a MAP kinase kinase kinase
MAP kinase - ANSWER-mitogen-activated protein kinase
, phosphoinositide 3-kinase (PI 3-kinase) - ANSWER-enzyme that phosphorylates
inositol phospholipids in the plasma membrane, which generates docking sites for
intracellular signaling proteins that promote cell growth and survival
Which of the following phenomena will be observed if a cell's membrane is pierced?
(a) the membrane reseals
(b) the membrane collapses
(c) a tear is formed
(d) the membrane expands - ANSWER-(a) the membrane reseals
The plasma membrane serves many functions, many of which depend on the presence
of specialized membrane proteins. Which of the following roles of the plasma
membrane could still occur if the bilayer were lacking these proteins?
(a) intercellular communication
(b) selective permeability
(c) cellular movement
(d) import/export of molecules - ANSWER-(b) selective permeability
While many prokaryotic cells have a single membrane bilayer, all eukaryotic cells have
a complex system of internal membrane-bound compartments. How might it be
advantageous for the cell to have these additional compartments? - ANSWER-Better
functions more advanced cell
Which type of lipids are the most abundant in the plasma membrane?
(a) phospholipids
(b) glycolipids
(c) sterols
(d) triacylglycerides - ANSWER-(a) phospholipids
Indicate whether the following statements are true or false. If a statement is false,
explain why it is false.
A. Although cholesterol is a hydrophobic molecule, it has a hydrophilic head group like
all other membrane lipids. - ANSWER-True.
Indicate whether the following statements are true or false. If a statement is false,
explain why it is false.
B. Phosphatidylserine is the most abundant type of phospholipid found in cell
membranes. - ANSWER-False. Phosphatidylcholine is the most abundant phospholipid
found in cell membranes.
Indicate whether the following statements are true or false. If a statement is false,
explain why it is false.
QUESTIONS WITH CORRECT ANSWERS
protein phosphatase - ANSWER-enzyme that catalyzes the removal of a phosphate
group from a protein, often with high specificity for the phosphorylated site
serine/threonine kinase - ANSWER-enzyme that phosphorylates target proteins on
serines or threonines
tyrosine kinase - ANSWER-enzyme that phosphorylates target proteins on tyrosines
GTP-binding protein - ANSWER-intracellular signaling protein whose activity is
determined by its association with either GTP or GDP
ion-channel-coupled receptor - ANSWER-transmembrane receptor protein or protein
complex that opens in response to the binding of a ligand to its external face, allowing
the passage of a specific inorganic ion
G-protein-coupled-receptor (GPCR) - ANSWER-cell-surface receptor that associates
with an intracellular trimeric GTP-binding protein (G protein) after activation by an
extracellular ligand
G protein - ANSWER-a membrane-bound GTP-binding protein involved in intracellular
signaling; composed of three subunits, this intermediary is usually activated by the
binding of a hormone or other ligand to a transmembrane receptor
small intracellular signaling molecule - ANSWER-nucleotide, lipid, ion, or other small
molecule generated or released in response to an extracellular signal
adenylyl cyclase - ANSWER-enzyme that catalyzes the formation of cyclic AMP from
ATP; an important component in some intracellular signaling pathways
cyclic AMP (cAMP) - ANSWER-small intracellular signaling molecule generated from
ATP in response to hormonal stimulation of cell-surface receptors
cyclic-AMP-dependent protein kinase (protein kinase A, PKA) - ANSWER-enzyme that
phosphorylates target proteins in response to a rise in intracellular cyclic AMP
concentration
phospholipase C - ANSWER-enzyme associated with the plasma membrane that
generates two small messenger molecules in response to activation
,inositol phospholipid - ANSWER-minor lipid component of plasma membrane that plays
a part in signal transduction in eukaryotic cells; cleavage yields two small messenger
molecules, IP3 and diacylglycerol
inositol 1,4,5-trisphosphate (IP3) - ANSWER-small intracellular signaling molecule that
triggers the release of Ca2+ from the endooplasmic reticulum into the cytosol; produced
when a signal molecule activates a membrane-bound protein called phospholipase C
diacylglycerol (DAG) - ANSWER-small messenger molecule produced by the cleavage
of membrane inositol phospholipids in response to extracellular signals
protein kinase C (PKC) - ANSWER-enzyme that phosphorylates target proteins in
response to a rise in diacylglycerol and Ca2+ ions
calmodulin (CaM) - ANSWER-small Ca2+-binding protein that modifies the activity of
many target proteins in response to changes in Ca2+ concentration
Ca2+/calmodulin-dependent protein kinase (CaM-kinase) - ANSWER-enzyme that
phosphorylates target proteins in response to an increase in Ca2+ ion concentration
through its interaction with the Ca2+-binding protein calmodulin
adaptation - ANSWER-adjustment of sensitivity following repeated stimulation; allows a
cell or organism to register small changes in a signal despite a high background level of
stimulation
enzyme-coupled receptor - ANSWER-transmembrane protein that, when stimulated by
the binding of a ligand, activates an intracellular enzyme (either a separate enzyme or
part of the receptor itself)
receptor tyrosine kinase (RTK) - ANSWER-enzyme-coupled receptor in which the
intracellular domain has a tyrosine kinase activity, which is activated by ligand binding to
the receptor's extracellular domain
Ras - ANSWER-one of a large family of small GTP-binding proteins (the monomeric
GTPases) that helps relay signals from cell-surface receptors to the nucleus
monomeric GTPase - ANSWER-small, single-subunit GTP-binding protein
MAP-kinase signaling module - ANSWER-set of three functionally interlinked protein
kinases that allows cells to respond to extracellular signal molecules that stmulate
proliferation; includes a mitogen-activated protein kinase (MAP kinase), a MAP kinase
kinase, and a MAP kinase kinase kinase
MAP kinase - ANSWER-mitogen-activated protein kinase
, phosphoinositide 3-kinase (PI 3-kinase) - ANSWER-enzyme that phosphorylates
inositol phospholipids in the plasma membrane, which generates docking sites for
intracellular signaling proteins that promote cell growth and survival
Which of the following phenomena will be observed if a cell's membrane is pierced?
(a) the membrane reseals
(b) the membrane collapses
(c) a tear is formed
(d) the membrane expands - ANSWER-(a) the membrane reseals
The plasma membrane serves many functions, many of which depend on the presence
of specialized membrane proteins. Which of the following roles of the plasma
membrane could still occur if the bilayer were lacking these proteins?
(a) intercellular communication
(b) selective permeability
(c) cellular movement
(d) import/export of molecules - ANSWER-(b) selective permeability
While many prokaryotic cells have a single membrane bilayer, all eukaryotic cells have
a complex system of internal membrane-bound compartments. How might it be
advantageous for the cell to have these additional compartments? - ANSWER-Better
functions more advanced cell
Which type of lipids are the most abundant in the plasma membrane?
(a) phospholipids
(b) glycolipids
(c) sterols
(d) triacylglycerides - ANSWER-(a) phospholipids
Indicate whether the following statements are true or false. If a statement is false,
explain why it is false.
A. Although cholesterol is a hydrophobic molecule, it has a hydrophilic head group like
all other membrane lipids. - ANSWER-True.
Indicate whether the following statements are true or false. If a statement is false,
explain why it is false.
B. Phosphatidylserine is the most abundant type of phospholipid found in cell
membranes. - ANSWER-False. Phosphatidylcholine is the most abundant phospholipid
found in cell membranes.
Indicate whether the following statements are true or false. If a statement is false,
explain why it is false.
