Final Exam Review

Question 1

What is meant by a membranes transition temperature?

Answer 1

Membrane lipids go from a liquid crystal to a crystalline gel (or vice versa).

Question 2

How will the transition temperature of a membrane be affected if the amount of unsaturated lipids is increased?

Answer 2

Fluidity will increase and the transition temperature will decrease.

Question 3

What property of integral membrane proteins allow them to remain embedded in a lipid bilayer?

Answer 3

They have a Transmembrane Domain (TMD) made up of hydrophobic amino acids.

Question 4

How many ATPs are required to transport 10 K+ ions into the cell?

Answer 4

It takes 1 ATP to import 2 K+, therefore you will need 5 ATPs.

Question 5

Explain how proton gradients are used in mitochondria in chloroplasts.

Answer 5

Mitochondria: The electrochemical proton gradient across the inner mitochondrial membrane is used to drive ATP synthesis in the critical process of oxidative phosphorylation.
Chloroplasts: The proton gradient functions as an intermediate storage of the harvested light energy and drives ATP synthesis as protons pass across the membrane through the chloroplast ATP synthase.

Question 6

How can Green Fluorescent Protein (GFP) be used to track the movement of membrane proteins?

Answer 6

If you add GFP to N or C terminus of protein of interest; i.e. make a fusion protein.

Question 7

What are the major morphological differences between rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER)?

Answer 7

RER has ribosomes on surface, while the SER do not.

Question 8

What are the major differences in the functions of smooth endoplasmic reticulum (SER) and rough endoplasmic reticulum (RER)?

Answer 8

RER are important for co-translational import, while SER have enzymes which are important for detoxification or storing Ca+.

Question 9

How are proteins selectively moved from one compartment to another?

Answer 9

Vesicular transport!

Question 10

A toxin from toadstools called garafraxin, when added to nervse cells, prevents Na+ ion movement from higher to lower concentrations. A possible explanation for this might be:

a) the toxin enters and blocks Na+ channels.
b) garafraxin binds acetylcholine and changes membrane potential.
c) garafraxin antagonizes the ligand that activates Na+ channels.
d) the toxin deactivates the sodium/potassium ATPase pump.
e) both ‘a’ and ‘c’ could be correct.

Answer 10

e) both ‘a’ and ‘c’ could be correct. (add explanation TBD)

Question 11

Transition of a plasma membrane from a liquid crystal state to a crystalline gel state…?

a) occurs more readily at higher temperatures.
b) requires cholesterol.
c) is aided by phospholipid bilayers embedded with glycoprotein.
d) is favoured when there are more saturated lipids.
e) does not occur in mitochondria inner membranes (IMM)

Answer 11

d) is favoured when there are more saturated lipids. (explanation TBD)

Question 12

Where in chloroplasts and mitochondria are the highest concentration of protons found?

Answer 12

In the thylakoid lumen and intermembrane space, respectively.

Question 13

Where is cytochrome c protein normally found?

Answer 13

Cytochrome C is normally found in the mitochondria’s intermembrane space.

Question 14

What does it mean when cytochrome c is present in the cytoplasm?

Answer 14

When cytochrome c is present, the cell will begin apoptosis.

Question 15

The N-terminus of an integral membrane protein is in the rough endoplasmic reticulum (RER) lumen. If green fluorescent protein (GFP) is fused to the N-terminus of this protein, which is destined for the plasma membrane, which side of the plasma membrane will glow green?

Answer 15

The extracellular side (explanation TBD)

Question 16

Where does all protein synthesis initiate?

Answer 16

ribosomes

Question 17

What are three lines of evidence which support the endosymbiont theory?

Answer 17

Mitochondria and chloroplasts…
1. Have double membranes.
2. Have prokaryotic-type ribosomes.
3. Have their own genomes (circular).

(also, mitochondria inner membrane (IMM) has cardiolipin).
(also, mitochondria & chloroplasts divide by fission, like bacterias).

Question 18

Which of the following statements regarding the intrinsic pathway of apoptosis are not correct?

a) it can be triggered by hypoxia
b) BAX protein binds to the mitochondria inner membrane.
c) cytochrome c leaks out into the cytosol.
d) executioner caspases are activated
e) nuclear lamins break down.

Answer 18

b) BAX protein binds to the mitochondria inner membrane. (explanation TBD)

Question 19

Describe the co-translation process for a protein destined for the endoplasmic reticulum (ER) lumen?

Answer 19

Cotranslational translocation occurs when membrane-bound ribosomes insert growing nascent polypeptide chains directly into an ER translocation pore.(explanation tbd)

Question 20

A mutation in the gene encoding the BiP chaperone protein might:

a) cause the Golgi complex to form incorrectly.
b) produce Transport Vesicles with no ribosomes.
c) cause ER lumen proteins to exit the cytosol.
d) redirect COP II coated vesicles to the ER.
e) result in mis-folded proteins in the ER lumen.

Answer 20

e) result in mis-folded proteins in the ER lumen. (explanation tbd)

Question 21

What is the initial energy source that drives ATP production via photophosphorylation?

Answer 21

Light!

Question 22

Which of the following properties represent a difference between prokaryotic and eukaryotic cells?

a) the presence of a membrane-bound nucleus.
b) the presence of membranes consisting of lipid bilayers.
c) the presence of ribosomes to produce proteins.
d) the presence of DNA
e) susceptibility to viruses

Answer 22

a. the presence of a membrane-bound nucleus (explanation tbd)

Question 23

The synthesis of a plasma membrane receptor protein begins…

a) on free ribosomes in the ER lumen.
b) between the mitochondrial IMM and OMM.
c) on free ribosomes in the cytoplasm.
d) inside the ER translocon.

Answer 23

c) on free ribosomes in the cytoplasm.

Question 24

COP I and COP II proteins…

a) are synthesized in the ER lumen.
b) direct vesicle traffic in opposite directions .
c) move cargo vesicles from ER to the cis-Golgi Network (CGN).
d) are excreted from the cell.
e) integrate into the Extracellular Matrix (ECM).

Answer 24

b) direct vesicle traffic in opposite directions.

Question 25

Alanine (A), valine (V) and proline (P) are hydrophobic amino acids, whereas arginine (R) and lysine (K) are charged amino acids. (M = methionine). Which of the following is most likely a signal sequence?

a) M-K-K-V-R-K-R-M
b) K-V-A-R-A-V-P-K
c) M-V-P-P-A-V-A-P
d) K-K-R-K-M-M-K-K

Answer 25

c) M-V-P-P-A-V-A-P … All start/signal sequences should begin with methionine.

Question 26

What happens to the signal sequence after a protein is synthesized in the ER lumen?

Answer 26

It is cleaved off by signal peptidase.

Question 27

What proteins are critical for vesicle docking at a recipient compartment?

Answer 27

SNAREs (v-SNARE and t-SNARE).

Question 28

Describe how information intrinsic to a protein is required for insertion of that protein into the ER membrane.

Answer 28

Signal sequence: interacts with SRP and targets to translocon in RER. Hydrophobic amino acids of transmembrane domain (TMD) specifies it will insert into membrane.

Question 29

Alanine (A), tryptophan (W) and tyrosine (Y) are hydrophobic amino acids
whereas arginine (R) and lysine (K) are charged amino acids. Which of the following sequences is a likely transmembrane domain found in an integral membrane protein?

a) K-K-W-R-K-R-Y-R-Y-K-W-Y
b) W-W-A-Y-A-W-Y-Y-A-A-W-W
c) K-K-R-K-R-R-K-K-K-R-W-Y
d) K-K-A-A-W-K-Y-Y-W-A-K-R

Answer 29

b) W-W-A-Y-A-W-Y-Y-A-A-W-W

Question 30

The sequence below that best describes the order of co-translational import are:

a) SER -> lysosome -> RER -> vacuole.
b) cytosol -> translocon -> RER lumen.
c) COPII-coated vesicle -> lysosome -> RER lumen.
d) translocon -> cytosol -> chaperone
e) nucleus -> cytosol -> SRP

Answer 30

b) cytosol -> translocon -> RER lumen

Question 31

Which statement about the smooth endoplasmic reticulum (SER) is true?

a) it is continuous with the Golgi complex.
b) it has ribosome on the cytosolic side of membrane.
c) has an important role in detoxification.
d) is the site of co-translational import.
e) it is present at high levels in chondrocytes.

Answer 31

c) has an important role in detoxification.

Question 32

Which of the following statements about the Golgi complex is incorrect:

a) it modifies proteins and lipids by adding carbohydrates.
b) it does not have ribosomes on its membrane surface.
c) it receives and sends off vesicles.
d) it does not send vesicles back to the RER.
e) it is present in eukaryotic cells only.

Answer 32

d) it does not send vesicles back to the RER is the INCORRECT statement.

Question 33

Cellular compartments with the lowest pH are:

a) nucleoplasm and transport vesicles.
b) RER lumen and SER lumen
c) cytosol and endosomes.
d) lysosomes and vacuoles.
e) mitochondria inter-membrane space and Golgi lumen.

Answer 33

d) lysosomes and vacuoles.

Question 34

What type of cytoskeletal structural components are found in the nucleus of animal cells?

a) F-actin
b) microtubules
c) keratin monomer protein
d) intermediate filaments
e) kinesin

Answer 34

d) intermediate filaments

Question 35

Where is the large ribosomal sub-unit assembled?

a) in the nucleolus
b) in the ER lumen
c) in the nucleoplasm
d) at the nuclear pore
e) they are not assembled - they are one protein.

Answer 35

a) in the nucleolus.

Question 36

Which of the following cytoskeletal subunit proteins might have a Nuclear Localization Signal (NLS)?

a) G-actin
b) beta tubulin
c) gamma tubulin
d) keratin monomer
e) lamin

Answer 36

e) lamin