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Cell Biology > Intermembrane Transport > Flashcards

Intermembrane Transport Flashcards

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1
Q

What is the function of the smooth ER?

A

synthesize lipids and steroids

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2
Q

On the ER, what is the name of the closed fattened membrane sacs?

A

cisternae

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3
Q

What two structural features do the ER and Golgi apparatus have in common

A

cisternae

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4
Q

What is the function of the rough ER?

A

produce cell membrane proteins and secretory proteins

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5
Q

What is meant by “co-translational translocation”? What organelle is this relevant to?

A

translation and translocation happen at same time; ER

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6
Q

What is meant by “protein sorting”?

A

transporting proteins from where they are created (e.g. cytosol) to where they are used (e.g. organelle)

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7
Q

Vesicles pinch off of one compartment, move through the cytosol, and fuse with another compartment. This process is knwon as what?

A

vesicular transport

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8
Q

T or F: Vesicular transport occurrs intracellularly and intercellularly

A

True

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9
Q

The nucleus is surrounded by a double membrane known as the _____

A

nuclear envelope

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10
Q

What is the name for the perforating structural features of the nucleus that allows it to communicated with the cytosol?

A

nuclear pores

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11
Q

The synthesis for the majority of membrane content occurs in which organelle?

A

ER

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12
Q

In what organelle are many hormones synthesized?

A

smooth ER

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13
Q

Liver is able to detoxify the body of alcohol. What organelle in liver cells allow it to do this?

A

smooth ER

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14
Q

In many eukaryotes, cells are able to sequester calcium from the cytosol. What organelle might allow it to do this?

A

smooth ER

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15
Q

Which would you NOT expect to find in the cytosol?

a) metabolic pathways
b) protein synthesis
c) ATP synthesis by oxidative phosphorylation
d) the cytoskeleton

A

c

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16
Q

Which is the primary function of the lysosome?

A

intracellular degradation

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17
Q

On the way to a lysosome, material that has been ingested must first pass through a series of compartments. What are these compartments?

A

endosomes

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18
Q

What do the endosomes do?

A

sort endocytosed material and recycle some of them back to the plasma membrane

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19
Q

Which organelles break down lipids and toxic molecules?

A

peroxisomes

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20
Q

The movements of vesicles along the cytoskeleton is driven by cellular component?

A

motor proteins

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21
Q

What are the 4 defining characteristics of membrane enclosed organelles?

A

1) specific function depends on compartmentalization
2) usually similar in function and location across cell types
3) can differ in number across cell type
4) dynamic

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22
Q

What is the origin and destiny of cytosolic proteins?

A

Origin: free ribosomes;
Destiny: cytosol

“Created within and stays within”

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23
Q

What is the destiny and origin of organellar proteins?

A

Destiny: the given organelle
Origin: free ribosome

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24
Q

What is the origin and destiny of secreted proteins?

A

Origin: ribosomes on ER
Destiny: secretion from the cell

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25
Q

What is the origin and destiny of membrane proteins?

A

Origin: ribosomes on ER
Destiny: cell membrane

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26
Q

What are the 3 mechanisms by which proteins are imported into the cell?

A

1) gated transport
2) trans membrane
3) vesicular

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27
Q

What is required of nuclear proteins greater than 5000daltons?

A

Nuclear localization signals (NLSs)

28
Q

What sort of amino acids would you expect to find on nuclear localization signals?

A

Positive (basic)

29
Q

Which of the following is false regarding trans membrane transport into the mitochondria?

A) a group of specialized membrane proteins called transporters is required
B) multiple signal sequences on the transported protein
C) the protein must be prefolded before entering the organelle
D) the protein to be imported is called a preprotein

A

(C); the protein must be kept unfolded, which is accomplished by chaperons

30
Q

Translocators are required for which type of protein transport:

A) gated transport 
B) translocation
C) vesicular transport 
D) endocytosis
E) transmembrane transport
A

(E)

31
Q

What are the 4 steps by which proteins are imported into the matrix of the mitochondria?

A

1) signal recognized by receptor protein
2) complex moves to contact site
3) protein moves to matrix; signal peptide cleaved
4) protein folds

32
Q

If a mitochondria lacked protease, which stage would be affected of transmembrane transport?

A) the import of the protein into the cell
B) recognition of the preprotein the mitochondria
C) the protein would not be folded into a functional protein
D) the protein could not be transferred to the contact site

A

(C)

33
Q

The signal sequence at the end of a protein being transported into the mitochondria or chloroplast is usually at which end?

A

N-terminus

34
Q

What is different between a protein being transported into the mitochondrial matrix vs inner membrane?

A

For inner membrane, the protein has a stop sequence that anchors it to the inner membrane.

35
Q

What is the difference between smooth ER and rough ER in terms of the things they produce?

A

smooth: lipids, steroids
rough: proteins

36
Q

Where is the site of lipid and steroid synthesis?

A

smooth ER

37
Q

What does the term co-translational translocation mean? What type of transport does it apply to?

A

translation and translocation occur at same time; transmembrane transport (ER)

38
Q

Which of the following is false regarding ER protein transport?

A) protein transport into the ER is co-translational
B) after translocation into the ER, the proteins are modified and sent to different locations
C) the protein signal sequence is a short, hydrophilic sequence at the N terminus
D) the signal sequence is cleaved while the protein is still growing on the ribosome

A

(C); the sequence is hydrophobic

39
Q

What is the function of a signal recognition protein? What type of protein transport is this associated with?

A

an SRP recognizes the ER signal sequence and guides the protein into the ER membrane; transmembrane transport

40
Q

What is the function of an SRP receptor?

A

interacts with the SRP and mediates the binding of ribosomes to the ER membrane translocation channel

41
Q

How does the signal sequence get removed during translocation to the ER?

A

an integral protein, signal peptidase

42
Q

What are the two types of exocytosis? What’s the difference?

A

1) constitutive secretory pathway, 2) regulated secretory pathway. (1) is continuous, (2) noncontinuous releases only in response to signals (“regulated”)

43
Q

What are the three regions of the Golgi apparatus and where are they in relation to the ER

A

cis, medial, trans; cis=closest to the ER, medial and trans farthest from ER

44
Q

What is the term for the internalization of small droplets of liquid materials?

A

pinocytosis (a type of endocytosis)

45
Q

What is the term for the internalization of bacteria, damaged cells, such as macrophages and neutrophils.

A

phagocytosis

46
Q

What is receptor mediated endocytosis? What is an example?

A

the internalization of extraellualar materials mediated by specific membrane receptors; receptor mediated endocytosis of LDL particles

47
Q

What is LDL? What is its structure?

A

LDL=low density lipoprotein– a carrier of blood cholesterol; an LDL particle is composed of phospholipid protein shell and cholesterol core.

48
Q

What is the function of the Golgi apparatus?

A

modifies and sort secreted proteins and membrane proteins

49
Q

What are transport vesicles?

A

The vehicle by which a protein is transported to another organelle.

50
Q

What are the three steps of vesicular traffic?

A

1) vesicle buds from donor membrane

2) vesicle travels to and 3) fuses with target membrane

51
Q

True or False: SNARE complex assembly leads to membrane fusion

A

True

52
Q

What is the primary funtion of SNARE proteins?

A

to mediate vesicle fusion (fusion of vesicles with target membrane)

53
Q

Membrane fusion requires what complex of proteins?

A

SNARE proteins

54
Q

What specific protein complexes are the targets of the bacterial neurotoxins responsible for botulism and tetanus?

A

SNARE proteins

55
Q

The snare complex with each individual SNAREs anchored in the same membrane is defined as the

A

cis-SNARE complex

56
Q

The SNARE complex with SNAREs emanated from apposing membranes are defined as the

A

trans-SNARE complex.

57
Q

What is the difference between trans and cis SNAREs?

A

cis- each SNARE is anchored in the same membrane (after membranes merge)
trans- SNAREs emanate from apposing membranes (before membranes merge)

58
Q

What leads to a liberation of the individual SNAREs allowing for further fusion to take place?

A

ATP hydrolysis by ATPase

59
Q

A SNARE complex is composed of what protein structure?

A

alpha helices (4 of them) in a coiled coil motif

60
Q

What is the “central layer” of a SNARE protein?

A

side chains of amino acid residues (3 Gln, 1 Arg)

61
Q

The trans-SNARE complex is sometimes called

A

SNAREpin

62
Q

What is the SNAREpin?

A

ANother name for the trans SNARE complex

63
Q

What is the hemifusion stalk?

A

a hemifusion intermediate; during membrane fusion, this is when the leaflets of the membrane come into contact

64
Q

What helps to ensure the fidelity of membrane traffic ?

A

unique SNAREs for each trafficking event

65
Q

Where are the signal sequences for nuclear proteins, mito/chloro proteins, and ER proteins respectively?

A

anywhere, N terminus, N terminus

Cell Biology (9 decks)

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