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BMS 300 > Processing & Transport of Proteins > Flashcards

Processing & Transport of Proteins Flashcards

1
Q

The smooth endoplasmic reticulum lacks ________

A

Ribosomes

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2
Q

What is the purpose of the smooth ER?

A

The location where lipid and steroid synthesis, cellular detoxification, carbohydrate metabolism, storage of calcium ions, secrete hormones, detoxifying cells

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3
Q

How does the smooth ER regulate muscle contraction?

A

A signal reaches a muscle cell to contract, calcium is released from the sarcoplasmic reticulum, enters the cytosol, and binds to the specific proteins leading to contraction

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4
Q

What is the purpose of the rough ER?

A

Responsible for proteostasis (amount and quality of proteins)

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5
Q

Steps of Cotranslation Translocation

A
  1. Ribosome and protein sequence move from the cytoplasm and SR-SPR (signal recognition particle) complex brings hydrophobic polypeptide to ER
  2. SP-SRP complex moves ribosome on top of the translocon
  3. Protein sequence is threaded through translocon channel
  4. SP-SRP complex leaves, the hydrophobic polypeptide is looped into the translocon and it binds at the signal sequence recognition site.
  5. The hydrophobic loop gets longer as tRNA brings in amino acids and forces the lateral gate open which allows for the signal sequence to enter the ER membrane because the signal sequence is hydrophobic so it can move across the lipid bilayer of the ER
  6. Signal peptide leaves translocon by lateral gate where signal peptidase degrades it
  7. Polypeptide is released into the ER lumen at the end of translation for PTM
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6
Q

What is a transmembrane domain?

A

A membrane-spanning protein domain.

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7
Q

What is required to initiate the translocation of the first transmembrane domain?

A

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

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8
Q

What is the threading of subsequent transmembrane domains managed by?

A

The ribosome translocon assembly and hydrophobicity of the translated domain

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9
Q

What does “C” mean in the transmembrane domain?

A

Free carboxylic group, 1st in sequence

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10
Q

What does “N” mean in the transmembrane domain?

A

Free amino group (last in sequence)

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11
Q

What is the purpose of chaperons in the rough ER?

A

Developing proteins fold and undergo other functional modifications
Ex: glycosylation, disulfide bond formation, oligomerization

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12
Q

What happens to properly folded and modified proteins?

A

They are packaged into vesicles to be shipped to the Golgi apparatus and other locations in the cell

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13
Q

What happens if there is an improperly folded protein?

A

Chaperones identify them and facilitate degradation in the cytosol by proteasomes

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14
Q

What can happen in the ER-associated degradation (ERAD) pathway

A

Degrades troubled proteins by ubiquitin-proteasome system (UPS)
protein is ubiquitinated, retrotranslocation from ER cytosol to the cytoplasm, and degraded by the proteasome

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15
Q

What is the unfolded protein response (UPR)?

A

If the ERAD cannot handle misfolded proteins the cell activates the UPR which either,
1. inhibits protein translation
2. Increase the folding capacity of the ER by causing more chaperons to enter the ER

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16
Q

What happens if ER stress continues and homeostasis cannot be restored?

A

Autophagy

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17
Q

What is tje golgi appartus main function?

A

A major starting and dispatch station for products of the ER

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18
Q

Where do vesicles enter and how are they transported?

A

They enter via the cis face and are transported through membrane-enclosed cisternae

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19
Q

What are lysosomes?

A

Contains proteolytic and degradative proteins to destroy proteins

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20
Q

What is the plasma membrane?

A

Receptors, channels, single or multi-pass proteins

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21
Q

What is the extracellular fluid?

A

Hormones and antibodies

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22
Q

What is a vesicle?

A

An enclosed lipid bilayer contains cytoplasm, carries materials, and is formed by budding off an existing membrane

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23
Q

What is endocytosis?

A

Bring substances into the cell through the cytoplasm

24
Q

What is exocytosis?

A

Moving substances out of a cell or into a membrane exiting the cytoplasm

25
Q

What are the types of endocytosis?

A

Phagocytosis, pinocytosis, receptor-mediated endocytosis

26
Q

What is phagocytosis?

A

“To eat”, engulfs large particles usually microbes
macrophages: immune cells will engulf pathogens

27
Q

What is pinocytosis?

A

“To drink”, little sips of extracellular fluid and small particles, primarily absorb fat droplets

28
Q

Receptor-mediated endocytosis COPII

A

From ER to Golgi

29
Q

Receptor-mediated endocytosis COPI

A

From Golgi to ER membrane

30
Q

Receptor-mediated endocytosis Clathrin

A

To and from the plasma membrane

31
Q

What is the structure of Clathrin?

A

Cage made of triskelion proteins to give structure to vesicle

32
Q

What is dynamin in clathrin?

A

Dynamin separates vesicle from the membrane

33
Q

When is the clathrin coat shedded?

A

It is shredded when the vesicle docks to the target membrane

34
Q

What does SNARE mean?

A

Snap Receptor

35
Q

What is a V-Snare and what are the types of V-Snare proteins?

A

Vesicle membrane proteins, VAMP

36
Q

What is a T-Snare and what are the types of T-Snare proteins?

A

Target membrane proteins, Syntaxin and SNAP-25

37
Q

What is Synaptotagim?

A

Calcium binding proteins on vesicles

38
Q

What are the steps of exocytosis?

A
  1. Calcium binds to synaptotagmin activities SNARE complex
  2. VAMP, Syntaxin, and SNAP-25 alpha helices wind together
  3. The vesicle is brought closer to and fuses with the target membrane
  4. Can release its cargo
39
Q

In the trafficking of vesicles, what are the roads and vehicles?

A

Roads are the cytoskeleton, vehicles are the motor proteins

40
Q

What are the types of cytoskeleton?

A

Structure only: Intermediate filaments
Structure and transport: Microtubules and F-actin

41
Q

What are intermediate filaments?

A

Provide only a rope-like structure

42
Q

What is the function of microtubules?

A

Long-distance transport and cell division

43
Q

What are microtubules made of?

A

A monomer called Tubulin, alpha, and beta-tubulin form dimers

44
Q

What is the structure of microtubules?

A

Polymerize into a tube with a diameter of 13 tubulin

45
Q

How are microtubules orientated?

A

Plus end (growing end) towards the membrane away from the nucleus
Minus end (constant/taken away end) towards the nucleus and away from the membrane

46
Q

What is the function of Filamentous Actin (F-actin)?

A

Structure, short distance transport, muscle contraction & cell division

47
Q

What is the monomer of F actin?

A

Globular actin

48
Q

What is the structure of F-actin?

A

Polymerizes into double-strand filaments

49
Q

What is the function of motor proteins?

A

ATPases: Hydrolyzes ATP and produces ADP & Pi
Energy released powers movement along the cytoskeleton

50
Q

What are the types of motor proteins?

A

Kinesin, Dynesin, and Myosin

51
Q

What is Kinesin?

A

Moves along microtubules towards the plus end

52
Q

Steps of Kinesin

A
  1. ATP binding purple foot swings blue foot forward
  2. Blue foot releasees ADP when attaching to the beta subunit
  3. Purple foot cleaves ATP to ADP and Pi and the foot releases
  4. Purple foot swings forward when ATP enters the blue foot
    REPEAT
53
Q

What is Dynein?

A

Moves along microtubules toward the minus end

54
Q

What is Myosin V?

A

Moves along F-actin towards the plus end

55
Q

What is Myosin VI?

A

Moves along F-actin towards the minus end

BMS 300 (8 decks)

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