BIOCHEM FINAL

C

Carbohydrate residues attached to the membrane lipids are A) always positioned on the intracellular side of the membrane. B) always positioned on the inside center of the bilayer. C) always positioned on the extracellular side of the membrane. D) always positioned equally on both sides of the membrane. E) also covalently attached to membrane proteins.

Na/K ATPase pump

Cardiac steroids such as digitoxigenin inhibit the _______________________.

connexin

Cell-to-cell junctions are composed of 12 molecules of this protein.

voltage-gated

Channels that open in response to membrane depolarization are called __________ channels.

dimerize

Cross-phosphorylation is possible when two receptor proteins

E

Ion channels A) can be selective. B) exist in open and closed states. C) in the open state often spontaneously convert into an inactivated state. D) a and b. E) a, b, and c.

micelles

Ionized fatty acids readily form ______________ in aqueous solutions.

C

Why is bound GTP considered a "clock"? A) It behaves in specific time intervals. B) It is regulated by energy. C) The Galpha receptors have intrinsic GTPase activity, hydrolyzing GTP to GDP and Pi. D) All of the above. E) None of the above.

Adenylate cyclase

____________ is the membrane protein that catalyzes the conversion of ATP to cAMP.

protein kinase inhibitors

______________ may be effective anti-cancer drugs.

Cerebroside

________________ is a membrane lipid composed of sphingosine, fatty acid, and a simple sugar.

omega-3 fatty acids

__________________ contain a double bond three carbons from the distal end of the fatty acid.

aquaporins

___________________ are an important class of channels that increase the rate at which water flows through membranes.

lipid vesicles (or liposomes)

___________________ are aqueous compartments enclosed by a lipid bilayer.

Peripheral

___________________ membrane proteins are bound primarily by electrostatic and hydrogen bond interactions with the head groups of lipids.

epinephrine, adrenaline

_______________________ binds to β-andrenergic receptors.

Inositol 1,4,5-triphosphate

_______________________ is a secondary messenger and is abbreviated IP3.

D

1. Which of the following statements is consistent with the structure of biological membranes? A) All membrane proteins are integral and associate with the hydrophobic region of the membrane. B) Both proteins and lipids readily undergo transverse ("flip-flop") diffusion from the inside to the outside of the membrane. C) Membranes are symmetric. D) The membrane lipids self-assemble to form the lipid bilayer. E) A biological membrane consists of proteins sandwiched between two layers of lipids, which are referred to as a lipid bilayer.

seven-transmembrane-helix

7TM is an abbreviation for _______________________ receptors.

multi-drug resistance

A P-glycoprotein transporter is also referred to as MDR protein which is an acronym for _________________________.

ligand-gated

A channel that opens in response to binding a particular molecule is called a ________ channel.

oncogene

A gene that leads to the transformation of susceptible cell types into cell types with cancerlike characteristics.

digitalis

A plant extract of steroids used to treat heart failure.

clathrin

A protein that polymerizes into a lattice network around a budding membrane.

D

Advantages of second messengers include: A) the signal can be amplified by making many second messengers. B) second messengers can freely diffuse to other sites within the cell. C) a few common second messengers can be used in multiple signaling pathways. D) All of the above. E) None of the above.

are shed

As potassium moves through the ion channel, the associated water molecules ________.

GTP

EGR signaling is terminated by the action of phosphatases and the hydrolysis of _____________ by Ras.

C

Example(s) of a mechanism by which a signaling processes might be terminated: A) change in temperature B) aggregation of all protein subunits C) protein dephosphorylation by phosphatases D) All of the above. E) None of the above.

whooping cough and cholera

Example(s) of disease(s) caused by altered G-protein activity:

cAMP, calcium ion, and diacyl glycerol

Examples of second messengers include:

E

How do the membranes of archaea differ from bacteria and eukaryotes? A) The lipids do not contain a carboxylic acid ester, but instead have an ether link to the glycerol. B) The alkyl chains are branched. C) The stereochemistry of the central carbon of glycerol is inverted. D) A and C are correct. E) A, B, and C are correct.

It causes an exchange of GTP for bound GDP.

How does the binding of hormone to receptor set a response in action?

C

How does the potassium channel maintain selectivity for potassium versus sodium ions? A) The ion size is the determining factor. B) The size of the ion and associated waters relative to the pore size is the determining factor in channel selectivity. C) Dehydration of the potassium ion is compensated energetically by interactions with oxygen atoms in the selectivity filter, which is not possible with sodium ions. D) All of the above. E) None of the above.

B

How is calmodulin activated? A) by binding of both calcium and potassium B) by binding Ca2+ when the cytosolic concentration is greater than 500 nM C) by binding to a positively charged helix on another protein D) All of the above. E) None of the above.

two

How many molecules thick are membranes?

D

Hydrophobic molecules can be covalently attached to proteins to increase membrane association. Type(s) of group(s) include A) palmitoyl groups attached via cys residues. B) glycolipid structures attached to the carboxy terminus. C) farnesyl groups attached via cys residues. D) All of the above. E) None of the above.

P-type ATPases

In _________________ a phosphoryl group is transferred from ATP to a specific aspartate residue.

cholesterol

In addition to phospholipids and glycolipids, this is a major type of membrane lipid.

cholesterol

In animals, ________________ is the key regulator of membrane fluidity.

ester

In phosphoglycerides, the fatty acids are linked to the glycerol backbone by the ______________ linkages.

C

In the potassium ion channel, which of the following is critical in the function of the selectivity filter? A) The K+ binds to a critical Glu residue. B) The K+ binds to the amide groups of three residues in the selectivity filter. C) The K+ binds to the carbonyl groups of the backbone of a conserved pentapeptide sequence. D) An ATP molecule must be bound for the selectivity filter to operate. E) None of the above

transducers

Membrane pumps are energy ____________________.

antiporters

Membrane transporters that couple downhill flow of one species to the uphill flow of another species in the opposite direction are called ______.

lipids and proteins

Membranes are primarily comprised of ___.

B

Most signal molecules A) easily diffuse through the membrane and bind to a receptor in the cytoplasm. B) bind to membrane receptors and transmit information across a membrane without traversing the membrane. C) carry out functions in the nucleus after binding to a receptor in the cell membrane. D) a and c. E) a, b, and c.

D

Multidrug resistance in tumor cells is A) due to the action of a membrane pump which transports small molecules out of the cells. B) the development of resistance to several drugs following an initial resistance to a single drug. C) caused by a mutation in the cystic fibrosis gene. D) a and b. E) All of the above.

aspartic acid

P-type ATPases transfer a phosphor group to this amino acid residue side chain.

threonine

Protein kinase A phosphorylates serine and ___________ residues.

small G proteins

Ras is a member of this family of proteins.

palmitoyl

Some proteins are anchored to the membrane by being covalently attached to a _______________ group by a thioester linkage to a specific cysteine residue.

sodium (Na+)

Tetrodotoxin, isolated from puffer fish, binds tightly and specifically to ___________ channels in nerve cells.

Her2

The ________ receptor is approximately 50% identical in amino acid sequence with the EGF receptor and has similar domain structure, but it does not bind any known ligand.

ligand

The acetylcholine receptor is an example of a ____________-gated channel.

fatty acids

The alpha and gamma subunits of heterotrimeric G proteins are anchored to the cell membrane by being covalently linked to this type of molecule.

calcium ion

The binding of IP3 to the IP3 receptor results in the release of __________ from the endoplasmic reticulum.

tyrosine

The catalytically active form of the insulin receptor is a result of phosphorylation of specific ____________ residues in the activation loop.

tyrosine

The cytosolic side, or β subunit, of the insulin receptor is a ________________ kinase.

the percentage of unsaturated fatty acids

The degree of membrane fluidity depends on ____.

phospholipase C

The enzyme responsible for induction of the phosphoinositide cascade is

eversion

The interconversion between two conformations of a transporter is sometimes referred to as __________________.

proton (H+)

The lactose permease transports lactose into the cell along with a ______________.

membrane asymmetry

The low incidence of protein or lipid flip-flop in a membrane preserves ___.

alpha helices of nonpolar amino acids that pass through the membrane.

The most common motif found in membrane spanning proteins is ____.

one second

The rate of diffusion is such that a phospholipid molecule can travel from one end of a bacterium to the other in _______________ of time.

diaglycerol and inositol 1,4,5-triphosphate

What are the two messenger products formed by cleavage of PIP2?

passive transport (facilitated diffusion)

The specific transport of a species down its concentration gradient is referred to as _______________________.

Tm (or melting temperature)

The temperature at which a phospholipid membrane transitions from a rigid to a fluid state is referred to as _______________.

viral and cellular

The v and c in v-src and c-src refer to

gap junctions

These are passages that exist between adjacent cells that allow passage of ions and small molecules.

glycolipids

These membrane components contain carbohydrates.

antiporter

These membrane proteins transport two species in opposite directions across the membrane.

cotransporters

These membrane transporters couple the transport of one species to the downhill flow of another ion species.

protein kinase C (PKC)

This enzyme becomes active when bound to Ca2+ and diacylglycerol.

phospholipase C

This enzyme catalyzes the cleavage of PIP2.

ABC proteins

This family of transport proteins possesses a separate domain or cassette that specifically binds ATP.

lipid raft

This is a complex between cholesterol and membrane phospholipids.

epinephrine

This is a primary messenger that is released by the adrenal gland.

patch-clamp

This is a technique used to measure conductance across a membrane.

amphipathic

This is a term applied to molecules that have both hydrophilic and hydrophobic moieties.

action potential

This is another name for a nerve impulse.

serpentine receptors

This is another name for the seven-transmembrane helix receptors.

R2C2

This is the inactive form of protein kinase A.

16 or 18

This is the number of carbons in most common fatty acids.

lateral diffusion

This is the process by which lipids and proteins move in the membrane bilayer.

cAMP

This molecule is considered as a secondary messenger.

hydropathy

This procedure is used to determine the probability that a segment of a protein will be found embedded in a membrane.

calmodulin

This protein binds to calcium ions and serves as a Ca2+ sensor in eukaryotic cells.

acetylsalicylic acid (aspirin)

This substance inhibits prostaglandin H2 synthase-1 by blocking the channel through which the substrate, arachidonate, travels.

lipophilic

This type of molecule can diffuse across a membrane without the aid of a transporter protein.

selective permeability

Transport systems confer this important property on membranes.

B

What are the similarities between sodium, potassium, and calcium ion channels? A) All allow passage of various ions. B) They contain homologous domains in the membrane spanning regions. C) They all contain five peptides that combine to form the channel. D) All of the above. E) None of the above.

E

What clues provided evidence of the mechanism of channel inactivation? A) Trypsin digestion of the cytoplasmic side caused the channel to stay open. B) Splice variants have different inactivation kinetics. C) Inactivation could be restored by the addition of part of a missing peptide. D) a and b. E) All of the above.

E

What force(s) stabilize(s) the lipid bilayers? A) van der Waals interactions B) Electrostatic and hydrogen bonding between the polar heads and surrounding water C) Covalent bonds between the lipid tails D) Covalent bonds between the lipids and membrane proteins E) A and B

B

What is the function of selectivity filter amino acids in an ion channel? A) They close the channel pore after ion passage. B) They determine the preference for a particular ion. C) They limit the number of ions passing through the channel. D) All of the above. E) None of the above.

input of energy required

When a molecule moves from a concentration of 10^-4 M to 10^-2 M, is the process spontaneous, at equilibrium, or does it require an input of energy?

plasma membrane of apposed cells

Where are gap junctions found?

tyr, ser, thr

Which amino acids can be phosphorylated?

GDP

Which form of the guanyl nucleotide is bound in the unactivated state?

mitochondria

Which membrane-bound organelle is thought to have evolved from bacteria by endosymbosis?

D

Which of the following are true about gap-junctions? A) They are important for intercellular communication. B) Polar molecules smaller then 1 kd can pass through them. C) The channels stay open seconds to minutes. D) All of the above. E) None of the above.

B

Which of the following helps regulate membrane fluidity in animals? A) Protein B) Cholesterol C) ATP D) Magnesium ion E) None of the above

D

Which of the following is NOT correct concerning the ABC proteins? A) They undergo conformational changes upon ATP binding. B) All are also members of the P-loop NTPase superfamily. C) The ATP-binding domains are referred to as ATP-binding cassettes. D) The substrate only binds after the ATP is bound. E) None of the above; they are all true statements.

C

Which of the following is correct concerning the sarcoplasmic reticulum Ca2+ ATPase? A) It is an example of an ABC transporter. B) It transports Ca2+ from the sarcoplasmic reticulum into the cytoplasm. C) This P-type ATPase maintains a calcium ion concentration of approximately 0.1 M in the cytosol and 1.5 M in the sarcoplasmic reticulum. D) One Ca2+ is transported for each ATP hydrolyzed. E) None of the above.

E

Which of the following is the smallest ion? A) Cs+ B) Na+ C) K+ D) Rb+ E) Li+

D

Which of the following is true? A) Membranes are lipid bilayers. B) Membrane lipids have both hydrophobic and hydrophilic properties. C) Many membranes are electrically polarized. D) All of the above. E) None of the above.

D

Which of the following membranes would be the most fluid? A) A bilayer made of lipids with polyunsaturated 18 carbon-fatty acids B) A bilayer made of lipids with saturated 18 carbon-fatty acids C) A bilayer made of lipids with saturated 16 carbon-fatty acids D) A bilayer made of lipids with polyunsaturated 16 carbon-fatty acids E) All of the above are equivalent in fluidity.