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Cell Bio > Test 2 > Flashcards

Test 2 Flashcards

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Biology 101 flashcards
1
Q

What does trafficking depend on?

A

vesicle coat proteins and cargo-receptor interactions

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2
Q

What allows for selective trafficking through the cell?

A

Coat proteins and cargo-specific receptors

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3
Q

What marks the flow of traffic between compartments?

A

Coat Proteins

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4
Q

Name the three families of coat proteins and what they do

A

COPI - Retrograde
COPII - Anterograde
Clathrin – trans-golgi and beyond

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5
Q

What is the difference between retrograde and anterograde?

A

Retrograde – against normal flow of secretion
Anterograde – with normal flow of secretion

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6
Q

True or False: Receptors in the ER/Golgi bind specific cargo

A

True

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7
Q

What does an ERD2 (KDEL) receptor do?

A

Going to move something back to ER. Retrograde.

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8
Q

What does a mutation in the ERD2 (KDEL) receptor lead to?

A

Mutation in many of these proteins results in aggregation of cargo in the wrong location.

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9
Q

What does protein coat formation depend on?

A

Small G-proteins (small GTPases)

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10
Q

Describe Arf’s role in vesicle formation.

A

Arf –small g-protein involved in coat formation and vesicle budding

Arf-GDP – inactive
Arf-GTP – active

Arf-GTP binds adaptor protein that recruits cargo/receptor complex and initiates coat assembly

COPI and Clathrin – Arf
COPII - Sar

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11
Q

What is dynamin and what does it do?

A

Dynamin is a protein that constricts the vesicle as it forms, and promotes vesicle fission and budding.

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12
Q

How do clathrin coated vesicles form?

A

Many three subunit trimers fit together, it forms spherical shape.
Triskelions link together to build coat.
As we recruit more and more coat proteins, the shape becomes more formed.

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13
Q

What happens to the protein coat when the vesicle reaches the plasma membrane?

A

The coat is removed.

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14
Q

What does a clathrin coat mean for a vesicles final location?

A

It is going to the cell surface for secretion.

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15
Q

True or False: The Cell is able to create different size and structure clathrin depending on needs

A

True

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16
Q

How is vesicle fusion accomplished?

A

Through snare complexes (AKA Snare pairs)

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17
Q

Describe how a cell knows a vesicle is in the right spot.

A

If v-snare and t-snare match, they coil together and pull the vesicle membrane into the target membrane, which leads to a fusion event and the generation of a pore. This incorporates the vesicle into the target membrane.

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18
Q

What does a snare complex do?

A

Mediate the fusion of vesicle and target membrane – requires energy – provided by pairing of SNARE complexes through coiled-coil domains

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19
Q

what are v-snares and t-snares?

A

v-snare- Vesicle SNAREs
t-SNARE – Target SNAREs

20
Q

What is a Rab?

A

A small g-protein on the surface of vesicle - binds to tethering factor on target membrane

21
Q

What is the pancreas?

A

A specialized organ for secretion

22
Q

Describe the insulin glucagon relationship

A

Insulin lowers blood sugar by facilitating glucose uptake into cells, while glucagon raises blood sugar by stimulating the liver to release stored glucose; when blood sugar is high, insulin is secreted by pancreatic beta cells, and when it drops too low, pancreatic alpha cells release glucagon to compensate.

23
Q

What is a secretory cell of the pancreas called?

A

A beta cell

24
Q

What is a lysosome?

A

Special digestive organelles that create a low pH via a proton pump

25
Q

Describe how the pH of the lysosome is maintained.

A

By proton pumps that selectively move protons (H+) into the interior of the lysosome

26
Q

Give two benefits of the acidic environment of the lysosome.

A
  1. Acid hydrolases are optimally active at pH 5, but not at pH 7.
  2. Acidic environment of lysosome also facilitates denaturation of lysosomal contents
27
Q

What would happen if a lysosome ruptured?

A

Rupture could cause autolysis AKA eating yourself.

28
Q

What is autophagy?

A

“self eating”
The breakdown of the cell’s own components, including organelles

This is a way to recover energy and materials.

29
Q

What percent of cellular proteins are broken down per hour through autophagy?

A

1%

30
Q

True or False: Autophagy can also be induced as a response to stress/starvation

A

True

31
Q

How does autophagy work?

A

The Autophagosome fuses with the lysosome which creates a phagolysosome and breaks down materials.

32
Q

Describe the roles of Atg9 and Atg2 in autophagy.

A

Atg9 – scramblase necessary for membrane expansion of autophagosome

Atg2 – lipid transfer protein – supplies phospholipids for autophagosome formation

33
Q

If autophagy in neurons is disrupted, what occurs?

A

Harmful aggregate formation.

34
Q

What do endosomes do?

A

Endosomes represent an intersection between secretion and endocytosis

Involved in recycling cell surface receptors and other molecules

Can also target molecules for degradation in lysosome

35
Q

What is the The ubiquitin-Proteasome pathway?

A

A cytosolic recycling system

Ubiquitin-proteasome pathway – major pathway for regulated protein degradation

36
Q

What are two things protein levels in the cell depend on?

A
  1. rate of protein synthesis
  2. rate of protein degradation
37
Q

What does the proteasome recognize? What does it use energy to do?

A

The proteasome recognizes ubiquitinated proteins and uses energy to break peptide bonds.

38
Q

What does the E3 ligase system do? Describe the steps.

A

The E3 ligase system marks protein for degradation by adding ubiquitin to them

  1. Ubiquitin added to ubiquitin-activating enzyme, E1 (requires ATP hydrolysis)
  2. Ubiquitin transferred to ubiquitin conjugating enzyme, E2
  3. E2 then interacts with ubiquitin ligase (E3), which selectively targets proteins. Ubiquitin is then transferred to target protein.
39
Q

What does Polyubiquitination of a protein do?

A

Targets it for proteasomal degradation

40
Q

What is a proteasome made of?

A

A complex of proteases – cleaves peptide bonds between amino acids

This requires energy (ATP hydrolysis)

41
Q

What are the three main parts of Cell signaling?

A
  1. Signal perception
  2. Intracellular signal transduction
  3. Cellular response
42
Q

What is paracrine signaling?

A

signaling to neighboring target cells

43
Q

What is autocrine signaling?

A

“self” signaling

44
Q

Describe direct cell-cell signaling.

A

Within an individual tissue cells linked by gap junctions, which provide direct connections between
the cytoplasms of adjacent cells, allow ions and small
molecules to diffuse between neighboring cells.

Gap junctions also allow the passage of some intracellular signaling mol-
ecules, such as cAMP and Ca2+, between adjacent cells, potentially coordinating the responses of cells in tissues.

45
Q

Describe Endocrine Signaling

A

Long distance signaling through secreted molecules in circulatory system.

46
Q
A

Cell Bio (3 decks)

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