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intracellular trafficking Flashcards

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Biology 101 flashcards
1
Q

Where does the synthesis of all proteins begin?

A

free ribosomes

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2
Q

What determines the outcome of a protein?

A

It’s destination?

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3
Q

Cotranslational translocation

A

WHILE proteins are translated on membrane bound ribosomes, they are translocated into the ER lumen

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4
Q

Posttranslational translocation

A

AFTER proteins are translated on free ribosomes, they are then translocated into the EU lumen (most common in yeast)

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5
Q

define intracellular trafficking

A

the movement of materials, especially proteins, from compartment to compartment within the cell and the external environment via membrane bound vesicles

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6
Q

What does the word “balance” mean in relation to endo/exocytosis?

A

Because these transport processes require using vesicles made from the phosophlipid bilayer, a balance has to be struck in order to maintain the unit cell membrane

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7
Q

Endocytosis: name the kinds

A

Fluid phase and receptor-mediated endocytosis

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8
Q

fluid-phase endocytosis

A

non-selective

forms vesicles containing extracellular fluid + contents

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9
Q

receptor-mediated endocytosis

A

Receptors aggregate in patches on the extracellular surface of the cell membrane

Receptors associated with “coated pits” either before or after the binding with their ligands

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10
Q

“coated pits”

A

protein coating the cytosolic side of the membrane: coats the vesicles

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11
Q

What is the functional role of the coat?

A

Helps the recruitment of molecules for transport

Anchors transmembrane receptors at the site of the forming vesicle

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12
Q

“coated pits” coating = ?

A

clathrin and dynamin

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13
Q

T/F

a receptor MUST associate with a “coating” BEFORE it receives a shipment?

A

F

It can associated before or after.

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14
Q

Clathrin: where and what

A

coats pits involved in SELECTIVE endocytosis

coats secretory vesicles of REGULATED exocytotic pathways

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15
Q

What Is clathrin exactly?

A

Consists of triskelion subunits which interlock to form geometric shapes

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16
Q

Describe the important role of clathrin in transport, the means by which is executes its task, and any relevant material it needs to complete the job (3)

A

1) Anchors transmembrane receptors
2) Adaptins connect the clathrin to the receptor molecules
3) Clathrin coat is removed immediately after the release of the new vesicle into the cytoplasm: this process requires ATP and HSP 70

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17
Q

How does clathrin anchor to receptors?

A

Adaptins connect the clathrin to the receptor molecules

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18
Q

T/F Clathrin activity is present in places other than the cytosolic wall of the cell membrane. If so, where?

A

T, Golgi bodies for instance

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19
Q

A swastika missing a leg. What protein mildly resembles that? why?

A

clathrin: it’s a structure with “triskelion” subunits

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20
Q

Triskelion. What?

A

the subunits composing clathrin

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21
Q

Two molecules involved with clathrin…

A

ATP and hsp 70

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22
Q

hsp 70

A

along with ATP, involved in removing clathrin coat after the release of vesicles into the cytoplasm

keeps cleaved polypeptide (the signal sequence) unfolded so it can enter the channel

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23
Q

Coatamers

A

Coats vesicles being transported between Golgi stacks (COPI)

coats vesicles being transported from to CGN

24
Q

Exocytosis pathway involves the following

A

begins in the ER, followed by the Golgi, and ends on the cell surface

25
Q

The secretory pathway involves what?

A

begins in the ER, followed by the Golgi, and ends on the cell surface

26
Q

The endocytotic pathway involves

A

1) internalization of materials from the extracellular environment by endosomes
2) degradation of materials by lysosomes

27
Q

What must happen before a coated vesicle can fuse with the receptor membrane?

A

the vesicle has to shed its coat, which requires ATP and hsp 70

28
Q

Vesicle fusion is ____ step process

A

2

29
Q

What are the steps in vesicle fusion?

A

1) Recognition of the appropriate membrane SNARE-V and SNATE-t
2) Fusion of the vesicle and the target membrane NSP (N-ethylmaleimide-sensitive fusion), SNAPS (soluble NSP attachment protein)

30
Q

COPI does what?

A

transporter BETWEEN stacks of Golgi

31
Q

COPII does what?

A

transports from the ER to the Golgi

32
Q

COP stand for

A

coat proteins

33
Q

what do COPS form?

A

coatomers on the cytosolic side of a transporting vesicle

34
Q

NSF and SNAPS

A

mediate vesicle fusion: bind to specific membrane receptors SNARES to become v-SNARES

35
Q

SNARES: What and where

A

membrane receptors present on vesicle membranes (v-SNARES) and target membranes (t-SNARES)

also represent “docking proteins”

36
Q

Docking Proteins would include which important molecules?

A

SNARES (v and t) that help SNAPS fuse to membranes

37
Q

Vesicle Fusion (8 steps)

A

1) remove vesicle coat
2) binding of synapsins on spectrin
3) Binding of SNARE-v to SNARE-t
4) SNAPS bind to SNARE
5) NSF (ATPase bind to SNAP)
6) NSF/SNAP complex disassembles SNARES for reuse
7) Release of NSP and SNAP from SNARE
8) Initiation of calcium dependent membrane fusion

38
Q

SNARES are _______ while SNAPS _______

A

docking proteins while SNAPS mediate the fusion of the vesicle with the membrane

39
Q

NSFs and SNAPS differ from SNARES in that

A

SNAPS are the interface molecules that facilitate the fusion of the vesicles containing the docking proteins NSF and SNARES

40
Q

Pathway of proteins destined for export or to be stored in lysosomes—>

A
  1. free ribosomes
  2. rough endoplasmic reticulum (RER)
  3. Golgi apparatus
  4. Secretory vesicles of lysosomes
41
Q

Proteins containing a signal sequence attached to their N-terminal end are (a and b)

A

a. bound for export or to end up in lysosomes

b. have their N-terminal end cleaved off after proteins ender the lumen of the ER

42
Q

All protein synthesis___

A

begins on free ribosomes

43
Q

Signal Hypothesis: the signal is made from __ and synthesized ____

A

amino acids (obviously) and synthesized first.

44
Q

Signal Hypothesis claims a signal sequence contains

A

20 amino acids and hydrophobic residues

45
Q

SRP

A

signal recognition particle. attaches to signal sequence and prevents further elongation

attaches to sequence as it emerges from ribosome

46
Q

SRP: consists of….

A

six proteins, 7S segment of RNA

47
Q

SRP+protein+ribosomes——>binds to

A

a docking protein on the cytoplasmic face of the ER

48
Q

SRP inserts what and where

A

releases protein, inserts self into membrane channel (translocon)

49
Q

translocon….consists of….

A

translocon consists of three transmembrane proteins (Sec61 proteins)

50
Q

sec61 proteins

A

three transmembrane proteins

51
Q

BiP

A

another Hsp70: pulls the polypeptide chain through the channel into the ER lumen

52
Q

a sugar chain is attached to an asparagine residue

A

this is N-linked glycosylation, last part of the signal hypothesis pathway

53
Q

OVERALL idea/steps about signal hypothesis (unfinished because of complexity, but name some events)

A

1) a free ribosome is producing a new peptide
2) the peptide has a “signal sequence” containing about 20 amino acids and some hydrophobic residues
4) SRP binds to the sequence
5) the signal contains a message for the ribosome to connect to the ER
5) the SRP, peptide, and ribosome connect to a docking protein (SRP receptor) on the face of the ER
6) the signal sequence is cleaved

54
Q

the ER consists of

A

a bilipid-layer membrane CISTERNAE/TUBULES/VESICLES

55
Q

Cytoplasm in the ER

A

divided into

luminal (endoplasmic) compartment

cytoplasmic (cytosolic) compartment

56
Q

subdivision of the ER has ___ subcategories which include

A
  1. Smooth ER (without ribsosomes, attached to the cytoplasmic face)
  2. Rough ER with ribosomes attached to the cytoplasmic face
  3. Transitional ER where vesicles exit to the Golgi apparatus

cell bio intracellular trafficking (9 decks)

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