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Biology > Chapter 15: Intracellular Compartment and Protein Transport > Flashcards

Chapter 15: Intracellular Compartment and Protein Transport Flashcards

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1
Q

What is compartmentalization in cells?

A

Organelles working in separate areas within the cell to perform their function efficiently

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2
Q

Why is cell compartmentalization so efficient?

A

It allows for simultaneous reaction and prevents the disruption of organelle function

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3
Q

How is cell compartmentalization achieved?

A

By many different membrane enclosed organelle

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4
Q

What is the fate of each protein after synthesis?

A
  1. Protein can stay in the cytosol
  2. Protein can be directly transported through the membrane into its target cells
  3. Protein can be imported into the ER and then transported by a vesicle to its target cells
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5
Q

What are the three mechanism that transport protein across the membrane

A
  1. Nuclear Pore
  2. Protein translocator
  3. Transport Vesicle
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6
Q

Describe transport protein via vesicle transport

A

Transported protein are ferried by vesicle which pinch off from one membrane of one compartment and fuse with the membrane of another compartment

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7
Q

How do proteins know where to go?

A

By Signal Sequences

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8
Q

What are signal sequences?

A

sequences located on the N-terminus of some proteins that enable those proteins to find their correct location outside the cell membrane.

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9
Q

What is the consequences of removing a signal peptide from a protein?

A

The protein will stay in the cytosol (default) and will not go to the ER

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10
Q

What must protein need to pass through the nuclear pore?

A

Nuclear localization signal (signal sequence): short stretches of lysine/arginines

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11
Q

How does protein get transported via nuclear pore?

A

Nuclear transport receptor binds to the signal sequence on the protein and transport it through the meshwork of the nuclear fibrils, without disrupting the conformation

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12
Q

What supplies energy for protein transport via nuclear pore?

A

GTP hydrolysis

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13
Q

Describe GTP hydrolysis for nuclear pore transport

A
  1. Receptor delivers cargo Binds with Ran GTP
  2. Nuclear Import receptor with Ran GTP will exit the nucleus
  3. GTP will hydrolyzed to Ran GDP and dissociate with the receptor
  4. Cargo Protein will bind to receptor
  5. Receptor will enter the nuclear pore where it will bind with Ran GTP
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14
Q

Describe transport across mitochondrial and chloroplast membrane

A
  1. Protein unfolds
  2. Signal sequence binds to protein
  3. Translocator will move the protein
  4. Signal Sequence tag is cleaved
  5. Chaperone protein helps refold the protein to be functional
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15
Q

What is the most extensive membrane system in the cell?

A

ER

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16
Q

What are the two types of protein that are transferred from cytosol to ER?

A
  1. Soluble protein
  2. Transmembrane protein
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17
Q

What is the difference between soluble protein and transmembrane protein?

A

Soluble protein are completely translocated across the ER membrane and are released into the ER lumen, while transmembrane are only partially translocated and become embedded to the ER.

Therefore, soluble protein are destined to secrete out of the ER while transmembrane are destined to reside in ER or in plasma membrane.

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18
Q

Describe the process of how soluble protein enter the ER

A

Soluble protein enter the ER as they are being synthesized

  1. Signal recognizing protein (SRP) binds to ER signal sequence on the protein and ribosome.
  2. SRP-Ribosome complex binds to SRP receptor.
  3. SRP is released
  4. Ribosome pass from SRP receptor to protein translocator
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19
Q

Describe the process of how transmembrane protein enter the ER

A

Transmembrane protein is integrated into the ER

The signal peptide remains bound to the translocation channel while the rest of the protein is threaded through as a loop. The translocation will stop once it reaches the hydrophobic stop sequence. Only part of the protein will be integrated

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20
Q

Which sides of the transmembrane protein face when embeded into the ER?

A

C terminus will face cytosol

N terminus will face the ER lumen

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21
Q

How does the protein translocator know when to stop moving the protein down the ER lumen?

A

Protein have a hydrophobic stop transfer sequence

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22
Q

How are cargos transported in the ER?

A

Via vesicle

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23
Q

What are coated vesicles?

A

Vesicles that have a specialized protein coat to help it bud and capture molecule

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24
Q

Describe the process of clathrin vesicular transport?

A
  1. Cargo receptor binds to the plasma membrane, forming a basket like structure to capture molecule
  2. Adaptin binds to cargo receptor
  3. Clathrin binds to the adaptins on the cargo receptors
  4. Dynamin protein assemble around the neck
  5. The vesicle is pinched off form the plasma membrane and clathrin coated vesicle sheds off
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25
Q

What are adaptins?

A

Protein that bind and anchor clathrin to the cargo receptor.

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26
Q

What are dynamin?

A

Protein that wrap around the neck of a vesicle to pinch off the vesicle from the plasma membrane

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27
Q

How does a loaded vesicle know which specific membrane it’s to bind to

A

`RAB protein and SNARE

28
Q

Describe the process of how a vesicle fuse with their target membrane

A
  1. Rab proteins are recognized by tethering protein
  2. SNARE provide additional recognition as the vesicle is attached to the tethering protein
  3. SNARE catalyze membrane fusion
29
Q

What are RAB proteins?

A

Protein on the surface of a vesicle that binds to the target membrane’s tethering protein

30
Q

How does RAB protein ensure that the vesicle fuse to its correct destination?

A

Unique combination of RAB that binds to the tethering protein

31
Q

What are SNARE

A

protein that provide additional recognition after RAB has been captured by the tethering protein and catalyze the fusion of docked vesicle

32
Q

How does SNARE protein catalyze the fusion of vesicle?

A

V snare wraps around the t SNARE, causing the vesicle to dock, coalesce, and fuse.

33
Q

What are the two ways protein can be modified in the ER

A
  1. Disulfide bond formation
  2. Glycosylation
34
Q

What happens to protein when they are in the ER?

A

They are chemically modified

35
Q

Why are proteins modified via disulfide bond formation?

A

The disulfide bond stabilizes the structure of protein that faces the extracellular environment

36
Q

What is glycosylation?

A

Protein converting to glycoprotein in the ER by the covalent attachment of oligosaccharide

37
Q

Describe the process of glycosylation?

A
  1. Oligosaccharide is bound to dolichol
  2. Glycoslylation site (asparagine) is exposed to the ER lumen
  3. Oligosaccharyl transferase catalyzes the transfer of oligosaccharide from dolichol to NH2 site of asparagine
38
Q

Why may be the reason why a protein cannot exit the ER?

A

They are misfolded and not properly assembled. Therefore, they are held by chaperone protein until they are properly folded

39
Q

What happens when there is an accumulation of misfolded protein in the ER?

A

Unfolded protein response (UPR) is triggered

40
Q

What does UPR do when there is an accumulation of misfolded protein in the ER?

A
  • Allow cell to adjust the size of the ER
  • make more chaperone protein

Direct the cell to self-destruct by undergoing apoptosis if the ER reaches full capacity

41
Q

Where do proteins move to after emerging from the ER?

A

Golgi Apparatus

42
Q

What are cisternae?

A

collection of flattened, membrane-enclosed sacs in the golgi

43
Q

What are the two faces of cisternae?

A

Cis Face: Face towards ER
Trans Face: Face towards plasma membrane

44
Q

Why are cisternae important?

A

Important for protein sorting and further glycoslyation and modification of sugar group

Protein can be sorted to different destination: plasma membrane, back to the ER, lysosome

45
Q

What is exocytosis?

A

Outward movement of proteins from the ER to the plasma membrane

46
Q

What is the general pathway of protein from the ER to the plasma membrane

A

1.Protein modification in ER

  1. Controlled exit in ER
  2. Protein modification and sorting in the Golgi Apparatus
  3. Release of protein from the cell
47
Q

What are the two exocytosis pathway

A
  1. Constitutive
  2. Regulated
48
Q

What is constitutive exocytosis pathway?

A

A continuous operation that supplies new lipid and protein to the plasma membrane via secretion of protein to outside of the cell.

49
Q

What are the two main type of endocytosis?

A
  1. Pinocytosis
  2. Phagocytosis
50
Q

What must secretory vesicle need in order to fuse with the plasma membrane?

A

extracellular signal

51
Q

What is regulated exocytosis pathway>

A

secretory cell produces large quantities of a particular product which is stored in secretory vesicles for later release

this only Operates only in specialized secretion cells

52
Q

What is pinocytosis?

A

Cells ingesting fluid and molecule via small vesicles

53
Q

What is phagocytosis?

A

Cells ingesting fluid and molecule via large vesicles

54
Q

What type of cells used pinocytosis/phagocytosis

A

All eukaryotic cells used pinocytosis while certain specialized cell perform phagocytosis

55
Q

Why are phagocytosis significant to eukaryotes?

A

Defense (neutrophils)

Recycling Dead/Damaged Cells

56
Q

Describe the process of defensive phagocytosis

A
  1. Antibodies recognizes and bind target cells
  2. Surface receptors on phagocytic cell are activated by antibody binding
  3. Phagocytic cell extends its pseudopod and engulf the target cells
  4. Engulfed compartment fuses with the lysosome and degrade the target cell
57
Q

What are the two types of pinocytosis?

A
  1. Indiscriminate pinocytosis
  2. Receptor-mediated endocytosis
58
Q

What is indiscriminate pinocytosis?

A

Vesicle trap any molecules that happen to be present in the extracellular fluid and carry them to the cell

59
Q

What is receptor mediated endocytosis?

A

Uptake of specific molecules that bind to complementary receptors on the cell surface

60
Q

Why is receptor mediated endocytosis so efficient?

A

It allow a huge quantity of macromolecules to be transported without minor components in the extracellular being taken up

61
Q

Describe receptor mediated endocytosis with cholesterol uptake

A
  1. Cholesterol binds to LDL
  2. LDL binds to receptors on cell surfaces
  3. Receptor-LDL complexes are
    ingested by receptor-mediated endocytosis
  4. Delivered to endosome
62
Q

What does the endosome do to the molecule that arrived?

A

They are sorted into compartments

63
Q

What are the possible fates of an endocytosed molecule?

A
  1. Be recycled back to the membrane
  2. Degrade in lysosome
  3. Proceed to a different domain in the plasma membrane with cargo-transcytosis
64
Q

What are lysosome?

A

Sac of enzymes capable of breaking down all biological polymer; trash can of the cell

65
Q

Why might a H+ pump be important for the lysosome?

A

It maintains the acidic environment in the lysosome, which enzymes are only active in.

66
Q

What is cystic fibrosis?

A

mutation in chloride transporter channel causes slight misfolding, which causes protein retention in the
ER and degradation.

Biology (20 decks)

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