Review (Lecture 24)

Question 1

What is meant by a membrane’s transition temperature?

Answer 1

Membrane lipids go from liquid crystal to 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/transition temperature will decrease

Question 3

What property of Integral Membrane proteins allows them to remain embedded in a lipid bilayer? (Lecture 16)

Answer 3

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

Question 4

How many ATPs are required to transport 10 K⁺ ions into the cell? (Lecture 16)

Answer 4

Takes 1 ATP to import 2 K+, so the answer is 5 ATP

Question 5

A toxin from toadstools called garafraxin, when added to nerve cells, prevents Na+ ion movement from higher to lower concentrations. A possible explanation for this might be: (Lecture 17)

a) the toxin enters and blocks Na+ channels
b) garafraxin binds acetylcholine and changes the 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 5

e)

Question 6

Transition of a plasma membrane from a liquid crystal state to a crystalline gel state… (Lecture 17)

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 6

d)

Question 7

Explain how proton gradients are used in mitochondria and chloroplasts. (Lecture 18)

Answer 7

Review slides on oxidative phosphorylation and photophosphorylation.

Question 8

How can GFP be used to track the movement of membrane proteins?

What are the major morphological differences between RER and SER? What are the major differences in their functions?

How are proteins selectively moved from one compartment to another?

(Lecture 18)

Answer 8

Add GFP to N or C terminus of protein of interest; ie; make a fusion protein.

RER has ribosomes on surface, SER don’t. RER important for co-translational import, SER has enzymes important for detoxification or store Ca++.

Vesicular transport

Question 9

Where in chloroplast and mitochondria are the highest concentrations of protons found?

Where is cytochrome c protein normally found and what does it mean when it is present in the cytoplasm?

(Lecture 19)

Answer 9

Thylakoid lumen and intermembrane space, respectively

Mitochondria intermembrane space, cell will begin apoptosis

Question 10

The N-terminus of an integral membrane protein is in the RER lumen. If GFP is fused to the N-terminus of this protein, which is destined for the plasma membrane, which side of the plasma membrane glows green? (Lecture 18 slide 24)

Answer 10

Extracellular side (Lecture 18, slide 24)

Question 11

What are 3 lines of evidence supporting the endosymbiont

theory? (3 marks) (Lecture 19)

Answer 11

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 bacteria)

Question 12

Which of the following statements regarding the intrinsic pathway of apoptosis are not correct? (Lecture 19)

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 12

b)

Question 13

Describe the cotranslation process for a protein destined for the

ER lumen? (5 marks)

Answer 13

Review (e.g., Lecture 20, slide 5)

Question 14

A mutation in the gene encoding the BiP chaperone protein might: (Lecture 20)

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

Answer 14

e)

Question 15

What is the initial energy source that drives ATP production via photophosphorylation? (1 mark) (Lecture 20)

Answer 15

Light

Question 16

Which of the following properties are different between prokaryotic and eukaryotic cells? (Lecture 20)

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 16

a)

Question 17

The synthesis of a plasma membrane receptor protein begins: (Lecture 20)

a. In the ER lumen
b. Between the mitochondrial IMM and OMM
c. In the cytoplasm
d. Inside the ER translocon
e. In a Transport Vesicle

Answer 17

c)

Question 18

COP I and COP II proteins : (Lecture 20)

a. are synthesized in the ER lumen
b. direct vesicle traffic in opposite directions
c. movecargovesiclesfromERtothecisGolgiNetwork(CGN) d. are excreted from the cell
e. Integrate into the Extracellular Matrix (ECM)

Answer 18

b)

Question 19

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? (Lecture 20)

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 19

c)

Question 20

What happens to the signal sequence after a protein is synthesized in the ER lumen? (1 mark) (Lecture 20)

Answer 20

It is cleaved off by signal peptidase

Question 21

What is the energy source for tethering and docking? (1 mark) (Lecture 20)

Answer 21

GTP

Question 22

Describe how information intrinsic to a protein is required for insertion of that protein into the ER membrane. (3 marks) (Lecture 21)

Answer 22

Signal sequence: interacts with SRP and targets to translocon in RER

Hydrophobic amino acids of transmembrane domain (TMD) specifies it will insert into membrane

Number of TMD determines how many ‘passes’ protein makes through membrane

Question 23

Which of the following statements about the Golgi complex is incorrect: (Lecture 21)

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 23

d)

Question 24

The sequence below that best describes the order of cotranslational import are: (Lecture 21)

a. SER → lysosome → RER → vacuole
b. cytosol → translocon → RER lumen
c. COPII-coated vesicles → lysosome → RER lumen
d. Translocon → cytosol → chaperone
e. Nucleus → cytosol → SRP

Answer 24

b)

Question 25

Which statement about the SER is true? (Lecture 21)

a. It is continuous with the Golgi complex
b. Has ribosomes on the cytosolic side of membrane c. Has an important role in detoxification
d. Is the site of cotranslational import
e. It is present at high levels in chondrocytes

Answer 25

c)

Question 26

Cellular compartments with the lowest pH are: (Lecture 21)

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

Answer 26

d)

Question 27

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? (Lecture 21)

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 27

b)

Question 28

On the phospholipid bilayer below, draw an integral protein with six transmembrane domains and its C-terminus in the ER lumen. (2 marks) (Lecture 21)

Answer 28

Question 29

Where would you find inward-facing proton-ATPase transporters? (Lecture 22)

A) In the RER lumen

B) Embedded in the inner membrane of lysosomes

C) As soluble proteins in clathrin-coated vesicles

D) In the lysosome membrane and tonoplast of vacuoles

E) In the thylakoid membranes of chloroplasts*

Answer 29

D)

*Why not “E”?

Although the thylakoid lumen has a low pH and thus high [H+], which one would expect for a compartment with inward facing proton-ATPase transporters, the reason it has a low pH is because the electron transport chain is pumping in protons, not the ATPase transporter.

Question 30

How are microtubules and microfilaments different (2 ways)? How are they similar (2 ways)? (4 marks) (Lecture 22)

Question 31

Which of the following statements about Intermediate Filaments is correct?

A) They are non-polar
B) Dynein moves from their plus to minus ends
C) They are composed of alpha and beta-actin monomers D) They bind MAP proteins
E) Theyexhibitdynamicinstability

Answer 31

A)

Question 32

Describe 2 ways that lysosomes and plant vacuoles are similar and 1 way they are different. (3 marks) (Lecture 22)

Answer 32

Similar:

• low internal pH
• Acid hydrolases

Different:

• animal vs plants
• vacuoles have high internal [ion]

Question 33

What type of cytoskeletal structural components are found in the nucleus of animal cells? (Lecture 23)

a. F-actin
b. microtubules
c. keratin monomer protein
d. Intermediate Filaments
e. kinesin

Answer 33

d)

Question 34

Where is the large ribosomal subunit assembled? (Lecture 23)

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 34

a)

Question 35

Which of the following cytoskeletal subunit proteins might have a Nuclear Localization Signal (NLS)? (Lecture 23)

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

Answer 35

e)

Question 36

What happens when microtubule disrupting chemical colchicine is added to a cell? (Lecture 23)

a. The nuclear lamina will disintegrate
b. Vesicle transport in plant root hairs would stop.
c. Causes MT catastrophe
d. COPI and COPII coated vesicles will stop moving. e. Ribosome export from the nucleus is disrupted.

Answer 36

d)