Deck 5: Membranes and an Introduction to Signal Transduction

Question 1

The major lipid component of cell membranes is _____.

A) triacylglycerol
B) cholesterol
C) glycerophospholipid
D) plasmologen
E) ganglioside

Answer 1

glycerophospholipid

Question 2

Which of the following terms describes all glycerophospholipid?

A) zwitterionic
B) amphipathic
C) nonpolar
D) amphoteric
E) none of the above

Answer 2

amphipathic

Question 3

The most notable difference between _____ and other membrane lipids is its planar nature.

A) cholesterol
B) arachidonic acid
C) ganglioside
D) plasmologen
E) triacylglycerol

Answer 3

cholesterol

Question 4

In a mixed bilayer at lower temperatures, cholesterol restricts the movement of nearby acyl chains, resulting in a more _____ membrane. As the percentage of cholesterol in the membrane increases past a certain point, the membrane becomes more _____.
Dropdown 1: solid, fluid
Dropdown 2: solid, fluid

Question 5

In an $\alpha$ helical protein that spans a cell membrane, _____ would likely be in the center of the membrane, _____ would likely be associated with the polar head groups, and _____ would likely be associated with the aqueous environment.

A) Trp; Asn; Ala
B) Leu; Gln; Asp
C) Tyr; Glu; Gly
D) Ile; Arg; Gln
E) Val; Ser; Thr

Question 6

Which of the following statements describes integral membrane proteins?

A) They never completely span the lipid bilayer.
B) They are easily removed by changes in pH or high salt.
C) Amino acids that contact the core of the membrane are hydrophobic.
D) They tend to be water soluble.
E) Their association with the membrane is through an attached fatty acyl or prenyl group.

Question 7

The movement of glucose into a cell when blood sugar is high is accomplished by _____. The movement of K⁺ against its concentration gradient is accomplished by _____.

A) simple diffusion; active transport
B) passive transport; passive transport
C) active transport; membrane potential
D) simple diffusion; passive transport
E) passive transport; active transport

Question 8

What type of transporter is responsible for moving water across membranes?

A) aquachannel
B) aquaporin
C) aquaphore
D) aquaporter
E) aquapermease

Question 9

What is a transporter that moves two different molecules or ions in the same direction?

A) uniporter
B) diporter
C) symporter
D) antiporter
E) none of the above

Question 10

Integrins and aquaporins are examples of _____.

A) uniporters
B) peripheral membrane proteins
C) integral membrane proteins
D) signal transduction receptors
E) none of the above is correct

Question 11

______ are amphipathic molecules that constitute the major lipid components of the cell membrane.

Question 12

With respect to polarity, membrane lipids can be described as ______.

Question 13

An example of nonmediated transport is ______.

Question 14

A transporter that moves two substances simultaneously in the same direction is an example of a(n) ______.

Question 15

Regions of a membrane that contain tightly packed cholesterol and sphingolipids are called _____ and are thought to be important to _____.

Question 16

A lipid raft is a(n) _____ in the lipid bilayer of a cell membrane.

A) transmembrane protein
B) integral membrane protein oriented to the intracellular side
C) integral membrane protein oriented to the extracellular side
D) region of high cholesterol and sphingolipid content
E) none of the above

Question 17

Which of the following is true regarding membrane asymmetry?

A) Transverse diffusion occurs very quickly.
B) Lateral diffusion occurs very slowly.
C) A flippase causes lateral diffusion to occur very rapidly.
D) Carbohydrates attached to membrane lipids are usually found on the cytosolic side of the membrane.
E) None of the above

Question 18

Use the diagram below to answer the following question. The enzyme flippase would catalyze which of the following types of reactions?

A) exchange of a phospholipid in position A for a cholesterol in position A
B) exchange for a lipid in position A for a lipid in position B
C) exchange for a phospholipid in position A with a phospholipid in position C
D) exchange of a lipid in position B for a lipid in position D
E) exchange of a glycerolphospholipid in position A for a sphingolipid in position C

Question 19

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

Question 20

Proteins that bind molecules and elicit a cellular response are called _____.

Question 21

Activation of a G protein in response to hormone binding requires binding of _____ to the _____ subunit.

A) GDP; $\beta$
B) GTP; $\alpha$
C) GDP; $\beta$ .
D) GTP; $\gamma$
E) GDP; $\alpha$ .

Question 22

What enzyme is activated by association with an active G protein?

A) adenylate cyclase
B) cAMP phosphodiesterase
C) protein kinase A
D) protein kinase G
E) all of the above

Question 23

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

Question 24

For cAMP to _____ protein kinase A, cAMP binds to the _____ subunits.
Dropdown 1: inhibit, activate
Dropdown 2: regulatory, catalytic, allosteric

Question 25

cAMP binds to the _____ subunits of protein kinase A, allowing the tetramer to dissociate and release _____.

A) active subunits; an active catalytic dimer
B) active subunits; two active catalytic monomers
C) regulatory subunits; an active catalytic dimer
D) regulatory subunits; two active catalytic monomers
E) regulatory subunits; two active regulatory monomers

Question 26

A molecule that often functions as a second messenger is ______.

Question 27

The activity of protein kinase A is affected by which of the following?
I. activated adenylate cyclase
II. levels of cAMP
III. phosphodiesterases
IV. cholera toxin

A) I only
B) II only
C) I, IV
D) I, II, III
E) I, II, III, IV

Question 28

Which of the following correctly ranks the steps in the secretory pathway?
1) Ligand (hormone) binds to receptor.
2) Activated adenylate cyclase produces cAMP from ATP.
3) G protein ? subunit exchanges bound GDP for GTP.
4) cAMP binds to the regulatory subunits of PKA, activating it.
5) G? subunit dissociates from complex and activates adenylate cyclase.
6) Active PKA subunits phosphorylate targets in the cell, regulating function.
7) The catalytic subunits of PKA dissociate.

A) 1, 2, 5, 4, 6, 7, 3
B) 1, 3, 5, 2, 4, 7, 6
C) 2, 4, 1, 3, 5, 6, 7
D) 2, 4, 3, 5, 4, 6, 7
E) 1, 3, 4, 2, 5, 7, 6

Question 29

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

Question 30

The _____ receptor is a receptor tyrosine kinase.

A) $\alpha$ ₁- adrenergic
B) $\beta$ ₂-adrenergic
C) calmodulin
D) insulin
E) cortisol

Question 31

Two molecules of insulin must bind to the insulin receptor for activation to occur.

Question 32

The _____ signaling pathway undergoes autophosphorylation, resulting in kinase activation.

Question 33

Which of the following is (are) the result of insulin binding to its receptor?
I. MAPK activation via Erk, which regulates gene expression
II. PI3K activation, leading to an increase in glucose transport
III. PI3K activation, leading to increased protein synthesis
IV. Autophosphorylation

A) II, III, IV
B) I, II, III, IV
C) II, III
D) I, II
E) III only