Chapter 11 Questions

1
Chapter 11 Questions

• BC368, Spring 2009

2
You are conducting a FRAP experiment and have
bleached a specific membrane lipid. You observe
that there is a negligent recovery of the
bleached portion. Which of the following is the
most likely explanation for this?

• The lipid you chose is very large and diffuses
  slowly.
• The cell has a mutated, defective form of
  flippase.
• The temperature is below the melting point of the
  membrane, so it has entered the gel phase.
• The phospholipids fatty acid tails have a high
  degree of unsaturation, causing the membrane to
  enter the paracrystalline phase.
• The lipid has restricted motion because it is
  associated with the spectrin meshwork within the
  cell.

3
Which of the following is NOT true of cotransport
proteins?

• Transport of two solutes across a membrane is
  coupled.
• One type of cotransport protein increases the
  CO2-carrying capacity of the blood.
• They mediate passive transport processes only.
• They are removable from the membrane only by
  agents that interfere with hydrophobic
  interactions, such as detergents.
• They can create a net separation of charge across
  a membrane.

4
Which of the following is NOT true of the NaK
ATPase?

• It creates a transmembrane potential essential
  for conduction of action potentials in neurons.
• It facilitates Na-driven secondary active
  transport.
• It is a universal means to synthesize ATP.
• It accounts for a significant portion of our
  resting energy demands.
• It helps animal cells maintain osmotic balance.

5
The gills of marine fish have cells that can
remove salt from the body by pumping it into the
environment. Which of the following is TRUE of
this process?

• It must involve ion channels.
• It must involve passive transport.
• It must involve active transport.
• It must involve the NaK pump.
• It must be common to all types of fish.

6
Which of the following compounds do NOT directly
inhibit the P-type ATPase transport systems?

• Ouabain
• Valinomycin
• Vanadate
• Palytoxin
• Digitalis

7
Which characteristic is NOT true about GLUT1?

• GLUT1 is specific for D-glucose.
• GLUT1 is primarily made up of B-sheets.
• GLUT1 contains 12 transmembrane segments.
• The rate equation for GLUT1-catalyzed reactions
  yields an expression analogous to the
  Michaelis-Menten equation.
• There is a possibility for competitive inhibition
  by D-glucose analogues.

8
Chapter 12 questions
Chapter 12 Questions

• BC368, Spring 2009

9
Which of the following is/are true of signal
transduction?

• Amplification allows a small amount of signal to
  cause a cascade that affects the activity of
  hundreds of thousands of proteins.
• The binding of the Grb2 is the first step in the
  signal transduction pathway of RTK receptor
  enzymes.
• Ras phosphorylates MEK, a MAP Kinase Kinase, by
  GDP-GTP exchange.
• Serpentine receptors exert their effects via
  G-proteins.

A. I only B. I and II only C. II and III
only D. I and IV only E. None of these
10
Which of the following is NOT true of cAMP?

• 5-AMP, the product of cAMP degradation, is not
  an active second messenger.
• The diverse protein targets of PKA share a
  consensus sequence that marks them for PKA
  regulation.
• cAMP concentrations are lowered by cholera toxin,
  which inhibits adenylyl cyclase.
• cAMP binds to four regulatory sites on PKA,
  leading to PKA activation.
• Compounds like caffeine that inhibit cyclic
  nucleotide phosphodiesterase increase cAMPs half
  life.

11
Which of the following is NOT true of the insulin
receptor?

• The receptor is a dimer of dimers.
• The receptor is ATP-dependent.
• The receptor must undergo autophosphorylation in
  order to become active.
• Upon activation, the receptor recruits Grb2.
• The receptor partially exerts its effects through
  a MAPK kinase cascade.

12
Glucose uptake by muscle and fat cells is
dependent upon activation of GLUT4 by insulin.
This system fails when insulin secretion no
longer affects blood glucose levels. Which of the
following is LEAST likely to cause diabetes (i.e,
hyperglycemia)?

• IRS-1 is not phosphorylated by the insulin
  receptor.
• Activated IRS-1 does not bind to PI-3K.
• Activated PKB does not recruit GLUT4 to the
  plasma membrane.
• Activated PKB does not phosphorylate glycogen
  synthase kinase 3.
• All of the answers would cause diabetes.

13
Which of the following is NOT an example of
signal amplification?

• The activation of PKA by cAMP in adipose cells.
• The phosphorylation of IRS-1 by the insulin
  receptor in liver cells.
• The conversion of cGMP to 5'-GMP in rod cells.
• The activation of MEK by Raf in liver cells.

A. I only B. II only C. III only D. IV only E.
More than one of these
14
G PROTEIN QUESTIONS

• BC 368, Spring 2009

15
WHICH OF THE FOLLOWING IS NOT TRUE OF G
PROTEIN-COUPLED SIGNAL TRANSDUCTION?

• The GS? subunit dissociates from the ? and ?
  subunits when a stimulant binds to the receptor,
  inducing a conformational change that promotes
  nucleotide exchange.
• The ? subunit is a GTPase that deactivates itself
  by GTP hydrolysis.
• Adenylyl cyclase is activated when all three
  subunits of the GS protein are associated with
  it.
• GI and GS proteins can both bind to adenylyl
  cyclase, creating opposing effects that
  effectively cancel each other out.
• The activation of cAMP-dependent protein kinase,
  PKA, requires binding of two regulatory molecules
  to each of two regulatory subunits, which then
  releases two catalytically active subunits.

16
WHICH OF THE FOLLOWING WOULD LOWER CYTOSOLIC
CAMP?

• Activation of Gs by epinephrine
• A mutation in the gene that codes for the
  Gq-binding portion of phospholipase C
• The activation of GI by prostaglandin E1 in
  adipose tissue
• Getting infected with the bacteria Bordetella
  pertussis
• Increased levels of theophylline in the cell

17
YOU ARE DOING A DRUG STUDY ON SQUIRRELS IN THE
WOODS WHEN AN ANGRY GRIZZLY BEAR BURSTS INTO YOUR
CAMPSITE. UNFORTUNATELY FOR YOU, THE OTHER
MEMBERS OF YOUR GROUP ARE ALL ON THE TRACK TEAM
AND CAN RUN FASTER THAN YOU. ALSO, YOU HAVE NO
NATURAL FIGHT-OR-FLIGHT RESPONSE. UNFORTUNATELY
FOR THE TRACK TEAM, YOU HAVE PACKED SEVERAL ITEMS
THAT MIGHT BE OF USE TO YOU. IN YOUR BACKPACK
YOU HAVE A PACK OF CHEWING TOBACCO (YOU ARE AN
AVID CHEWER), AN EPI-PEN (FOR YOUR BEE ALLERGY),
A VIAL OF MORPHINE (FOR THE SQUIRRELS), AND A
THERMOS OF COFFEE. ASSUMING THAT THESE ALL ACT
IN THE SAME TIME-COURSE, WHAT SHOULD YOU TAKE?

• Morphine
• Coffee
• Epi-pen
• Chew

A) I and III B) II and IV C) I and IV
D) II and III E) II, III, IV
18
Jared and Matt are both trying to impress their
hockey coach in order to get more playing time.
They read in lehninger that prostaglandin e1
(pge1) operates via GI in adipose tissue and that
cAMP triggers mobilization of lipid reserves.
Jared states that aspirin, a prostaglandin
inhibitor, would therefore be good to take before
a big game. Matt disagrees, stating that
adrenaline, known to operate via GS in adipose
tissue, would swamp out pge1s effects. Who gets
more playing time?

• Jared turning off GI would promote lipid
  mobilization.
• Matt only sissies take aspirin.
• Both they have an excellent grasp of signal
  transduction.
• Neither they are clearly spending too much time
  on their studies and are benched.
• Who cares? Hockey, like baseball, is a game, not
  a sport.

19
Glycolysis Questions

• BC368, Spring 2009

20
Which of the following statements concerning
glycolysis is false?

• All reactions of glycolysis occur in the cytosol.
• Glycolysis is a catabolic reaction.
• Four molecules of ATP are made during glycolysis.
• PFK-1 is regulated by allosteric inhibition.
• During aerobic respiration, the rate of glucose
  breakdown is higher than under anaerobic
  conditions.

21
Hexokinase has a ? specificity for glucose and
a ? Km compared to glucokinase.

• higher similar
• lower lower
• similar lower
• lower higher
• higher higher

22
You are hiking in the mountains of Idaho
following an elk herd when you run into a pack of
hungry wolves. You start running as fast as
possible, but you soon become fatigued and your
muscles feel heavy. Why?

• a decreased rate of pyruvate oxidation
• an increased rate of pyruvate reduction
• increased levels of acetyl CoA
• decreased activity of lactate dehydrogenase
• an increased rate of CO2 and H2O formation

A) I and II B) I and IV C) I, II and IV
D) I, III and IV E) All are true
23
In an attempt to get the most out of your
outrageously expensive education in microbiology
and biochemistry youve been brewing your own
beer in lab. Your latest batch is alcoholic but
has no carbonation. What is the best explanation
for this flat, gross beer ?

• The production of pyruvate was inhibited.
• The production of lactate was inhibited.
• There was not enough oxygen.
• There was too much oxygen.
• All your yeast died.

24
Which of the following do you hope will not occur
while you are out on a 14-mile run?

• Decreased glucokinase activity
• Inhibition of PFK-1 by increasing citrate
• Decreased respiratory quotient (volume of carbon
  dioxide exhaled to the volume of oxygen consumed)
• Inhibition of PFK-1 by increasing H
• Inhibition of pyruvate kinase by increasing
  acetyl-CoA

25
Reaction 7 of glycolysis, in which ATP is made
from substrate-level phosphorylation by 1,3-BPG
to form 3-phosphoglycerate (3PG), has ?Gº
18.5kJ/mol but ?G 1.3kJ/mol. This is one of
the few reactions of glycolysis where the
reaction is less favorable under actual
conditions than standard conditions. Which
statements best describe why this is so?
26

• Reaction 6, in which G3P is oxidized to 1,3 BPG,
  is endergonic causing a low concentration of
  reactants for reaction 7.
• The phosphorylation of ATP by the high energy
  1,3 BPG is irreversible, causing buildup of 3PG.
• The actual cytosolic concentration of ATP in
  cells performing glycolysis is higher than what
  is assumed under standard conditions.
• Reaction 8, in which 3PG is converted to 2PG, is
  unfavorable, causing high concentrations of
  reaction 7 products (3PG).

A) I and II B) I and IV C) I, II and IV
D) I, III and IV E) All are true