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BMS 300- Unit 1 > Lecture 7-Protein Transport > Flashcards

Lecture 7-Protein Transport Flashcards

1
Q

What is the difference between the smooth and rough endoplasmic reticulum?

A

Smooth ER- lacks ribosomes
Rough ER- has ribosomes

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2
Q

Where are calcium ions strored?

A

Smooth ER

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3
Q

What organelle is abundant in cells that secrete hormones like the liver?

A

Smooth ER

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4
Q

What is the endoplasmic reticulum mainly responsible for?

A

Proteostasis

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5
Q

What two things does proteostasis ensure?

A
  1. Amount of proteins will be regulated
  2. Quality of proteins will be regulated
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6
Q

What is the first step of cotranslational translocation?

A

SR-SRP complex bring hydrophobic polypeptide to ER

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7
Q

What is the second step of cotranslational translocation?

A

SR-SRP complex leaves. Hydrophobic polypeptide is looped into the translocon/binds to recognition site

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8
Q

What is the third step of cotranslational translocation?

A

Hydrophobic loop pushes open the plug

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9
Q

What is the fourth step of cotranslational translocation?

A

Signal peptide leaves translocon by lateral gate and the signal peptidase degrades it

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10
Q

What is the final step of cotranslational translocation?

A

Polypeptide is released in ER lumen at the end of translation

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11
Q

What are the three regions in the translocation process?

A

Cytosol–>ER Membrane–>ER lumen

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12
Q

What two items are required in order to initiate the translocation of the first transmembrane?

A

Signal recognition particle (SRP) and its receptor (SR)

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13
Q

What is the threading of the subsequent transmembrane domains managed by? (2 concepts)

A
  1. The ribosome-translocation assembly
  2. The hydrophobicity of the translated domain
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14
Q

What do the ‘N’ terminus and ‘C’ terminus represent?

A

N terminus- first amino group has free amino group

C terminus- last amino group has free carboxyl group

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15
Q

Properly folded/modified proteins are packaged into ______ to be shipped to the ____ ______ and other locations in the cell

A

Vesicles

Golgi Apparatus

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16
Q

What do chaperone proteins do?

A

Assist in the folding of proteins/identify improperly folded proteins that need to undergo degradation

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17
Q

What is the function of the ER-associated degradation (ERAD) pathway?

A

Degrades troubled proteins by ubiquitin-proteasome system (UPS)

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18
Q

What are the four main steps of the ERAD pathway?

A
  1. Cell recognizes protein as misfolded
  2. Protein is ubiquitinated
  3. Protein is retrotranslocateted from ER cytosol to cytoplasm (kicked out)
  4. Protein is degraded by proteosome
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19
Q

Which response is activated if the ERAD pathway cannot handle the misfolded proteins?

A

The Unfolded Protein Response (UPR)

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20
Q

What two ways does the UPR assist in misfolded proteins?

A
  1. Inhibits protein translation (stop making more proteins)
  2. Increase chaperon protein levels entering the ER
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21
Q

What is the last resort if the ERAD pathway and UPR homeostasis cannot be restores/ER stress continues

A

Autophagy (cell suicide)

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22
Q

What is the role of the Golgi apparatus?

A

Major sorting and dispatch station for the products of the ER

like the mail room

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23
Q

What face do vesicles enter and exit in the golgi?

A

Enter- cis face (faces ER)

Exits- trans face (faces cell membrane)

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24
Q

What are three protein destinations from the golgi?

A
  1. Lysosomes (degradative proteins)
  2. Plasma membrane (channels)
  3. Extracellular fluid (hormones)
25
Q

What is a vesicle?

A

-Enclosed lipid bilayer (liposome)
-Contains cytoplasm and carries materials

26
Q

What is endocytosis and what are the three types?

A

Endocytosis brings substances into the cell (entering cytoplasm)

Three types: phagocytosis, pinocytosis, and receptor-mediated endocytosis

27
Q

What is exocytosis?

A

Exocytosis moves substances out of the cell or into a membrane (exiting cytoplasm)

28
Q

What is the role of phagocytosis?

A

Means “to eat”
-Engulfs large particles
-Example: macrophages

29
Q

What is the role of pinocytosis?

A

Means “to drink”
-Little sips of extracellular fluid and small particles

30
Q

What are three types of coated vesicles used in receptor mediated endocytosis?

A

COP2, COP1, and Clathrin

31
Q

COP2 goes from ____ to ____

A

ER to Golgi

32
Q

COP1 goes from ____ to ____

A

Golgi to ER membrane

33
Q

Clathrin goes from _____ to _____

A

Plasma membrane to plasma membrane

34
Q

Explain the process of clathrin in receptor mediated endocytosis

A
  1. Cage is made of triskelion proteins
  2. Triskelions bind together to give structure to vesicle
  3. Dynamin separates vesicle from membrane
  4. Coat is shed when vesicles dock at target membrane

Cage, bind, separate, shed

35
Q

What are the 5 steps for exocytosis-SNARE complex?

A
  1. v-SNAREs in the vesicle bind to t-SNAREs in the target membrane
  2. Water is squeezed from between the two membranes
  3. Stalk formation
  4. Hemi-fusion
  5. Fusion/release substance into extracellular membrane

Bind, water, stalk, small fusion, big fusion

36
Q

What are four SNARE proteins?

A

VAMP
Syntaxin
SNAP-25
Synaptotagmin

37
Q

What does calcium bind to in order to activate the SNARE Complex?

A

Synaptotagmin

38
Q

What three SNARE proteins wind together as alpha helices?

A

VAMP, Syntaxin, and SNAP-25

39
Q

When is cargo released in SNARE complex?

A

Vesicle is brought close enough to the target membrane and fuses

40
Q

What part of the cytoskeleton only supports cell structure?

A

Intermediate filaments

41
Q

What part(s) of the cytoskeleton supports cell structure AND transport?

A

Microtubules and Actin

42
Q

What part of the cytoskeleton is responsible for short transport?

A

Actin

43
Q

What part of the cytoskeleton is responsible for long transport?

A

Microtubules

44
Q

What is a dimer? What is the structure/function of a dimer?

A

Two intermediate filament monomers join to form a dimer

Has rope like consistency (flexible but strong!)

45
Q

What is the orientation of microtubules?

Hint: where do the plus/minus ends face

A

Plus end- towards membrane

Minus end- towards nucleus

46
Q

What does actin polymerize into?

A

Double strand filament

47
Q

What are three functions of F-actin?

A
  1. Short distance transport
  2. Muscle contraction
  3. Cell division
48
Q

What are three types of motor proteins?

A

Kinesin
Dynein
Myosin

49
Q

What are motor proteins? What is their function?

A

-ATPases
-Bind and cleave ATP to ADP
-Energy released powers movement alone cytoskeleton

50
Q

Is Kinesin a microtubule or actin?

A

Microtubule

Long transport

51
Q

Explain the kinesin mechanism

A
  1. ATP binding purple foot swings blue foot forward
  2. Blue foot releases ADP when attaching to beta subunit
  3. Purple foot breaks ATP down to ADP+Pi and foot releases
  4. Purple foot swings forward when ATP enters blue foot
52
Q

Is Dynein a microtubule or actin?

A

Microtubule

Long transport

53
Q

Which end does Kinesin move to?

Which end does Dynein move to?

A

Kinesin- plus end

Dynein- minus end

54
Q

Is myosin a microtubule or actin?

A

Actin

55
Q

Which end does Myosin V move to?

Which end does Myosin VI move to?

A

Myosin V- plus end (towards membrane)

Myosin VI- minus end (towards nucleus)

56
Q

The presence of a signal peptide in a protein sequence indicates that it will LEAST likely be processed in the

Rough ER
Golgi apparatus
Cytoplasm
None of the above

A

Cytoplasm

57
Q

What is the last resort for ER stress due to unfolded proteins?

ERAD
UPR
Proteosome
Autophagy

A

Autophagy

58
Q

Which of the following proteins are MOST directly affected by changes in Ca2+ concentration?

VAMP/synaptobrevin
Syntaxin
Synaptotagmin
SNAP-25

A

Synaptotagmin

59
Q

Mutations in which of the following will affect vesicle transport from the Golgi apparatus to the ER?

VAMP
Clathrin
COP I
COP II

A

COP I

BMS 300- Unit 1 (12 decks)

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