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BMEG 245 > Organelles Protein Sorting, and Vesicular Transport > Flashcards

Organelles Protein Sorting, and Vesicular Transport Flashcards

Ch. 15

1
Q

What is a polyribosome?

A

mRNA strand with multiple ribosomes translating it

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2
Q

What are the two classes of ribosomes in translation?

A

membrane bound, free

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3
Q

Where are membrane bound ribosomes found?

A

rough endoplasmic reticulum

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4
Q

What are the two types of proteins moved from the cytosol to the rer?

A

water soluble - completely cross the membrane and are released into lumen
transmembrane proteins - become imbedded in the membrane

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5
Q

How does ribosome get to the rer?

A

a signal sequence on the end of the protein being synthesized connects to a signal recognition particle, which stops translation until the SRP binds to a SRP receptor on the membrane.

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6
Q

How does a protein become inbedded in a membrane after it binds to the SRP receptor?

A

The ribosome is passed onto a protein translocation channel, and the SRP is released. The signal sequence opens the translocation channel so the rest of the protein can be synthesized into the lumen

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7
Q

What is the role of the SRP and SRP receptor?

A

to bring ribosomes synthesizing proteins to open translocation channels

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8
Q

How is the protein released into the lumen of the rer? (water soluble proteins)

A

The ribosome leaves the translocation channel once its done translation, a signal peptidase cleaves the protein off of the signal protein (the signal protein is released int the membrane and degrades quickly)

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9
Q

What happens when transmembrane proteins are translated into the rer?

A

Same as water soluble, protein is translated into lumen until stop transfer sequence is reached. Signal peptidase cleaves the signal protein and the stop tranfer sequence remains imbedded in the membrane. Sometimes, the signal protein is not located on the end of the protein, in which case - it is not cleaved by signal peptidase

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10
Q

What is the orientation of transmembrane proteins in the rer?

A

COOH in cytosol, NH2 in the lumen

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11
Q

Can a protein have multiple stop sequences / signal sequences?

A

Yes! When a stop region is reached, another translocation channel opens and threads that segment into the membrane - multiple of these makes it seem like the protein is stitched into the membrane

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12
Q

What is the role of chaperone proteins in the er?

A

It fixes proteins and puts them in the correct conformation before they are shipped to another part of the cell

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13
Q

What is the role of Calnexin?

A

Ir recognized terminal glucoses on N-linked glycand (which was added to protein string) and makes sure they are in the corrct conformation

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14
Q

What happens during Unfolded Protein Response?

A

ER Expansion, Gene activation of chaperone proteins,
inhibition of protein synthesis

UPR is a response to misfolded proteins

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15
Q

Describe the structure of a nuclear pore

A

hole in nuclear membrane is coated with gel like meshwork of nuclear fibrils, cytosolic fibrils stretch into cytosol, nuclear basket is inside nucleus, nuclear import receptors float around inside and outside of hole

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16
Q

How are proteins brought into the nucleus?

A

nuclear import receptors bind to proteins, and the receptors interact with the fibrils - protein complex transverses the nuclear pore and releases protein into nucleus

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17
Q

What powers proteins moving into nucleus?

A

GTPase?

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18
Q

How it mitochondrial protein transport different than into the er?

A

Proteins are recognized by protein translocators on outer membrane and inner membrane, a protein has to be identified by both and then is fed inside the matrix

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19
Q

How does a protein end up a the right location?

A

The signal protein can only bind to the receptors on the place it is meant for

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20
Q

What is the secretory pathway for the cell?

A

Lipids and proteins from the er are delivered to the golgi through exocytosis

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21
Q

What is the endocytic pathway for the cell?

A

extracellular materials are brought into the cell by endocytosis, targeted first by endosomes then to lysosomes for degredation

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22
Q

How is transfer between organelles mediated?

A

transport vesicles

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23
Q

What is the main function of the golgi apparatus?

A

protein modification and protein targeting (sorting)

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24
Q

What is the difference between constitutive and regulated exocytosis?

A

Constitutive - unregulated, stuff just leaves

Regulated - extracellular signal (ligand, hormone, neurotransmitter) binds to a receptor which signals exocytosis

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25
Q

What are exocrine secretions from the pancreas?

A

Acinar cells in pancreas secrete digestive enzymes

26
Q

What are endocrine secretions from the pancreas?

A

beta cells secrete insulin into the blood when blood sugar levels increase

27
Q

What is the difference between endocrine and exocrine?

A

exocrine is a secretion outside the body, or to a surface inside the body
endocrine release stuff into the blood stream or tissue

28
Q

In what direction does traffic move in the golgi?

A

bidirectional - cargo moves forward, golgi proteins and enzymes stay in the golgi by backwards movement by COP1 vesicles

29
Q

How do things reach their destination after leaving the golgi apparatus?

A
  • Secretory granules wait for a signal from outside the cell before they are exocytosed
  • Endosomes recieve things that are endocytosed, lysosomes process them?
  • In epithelial cells, golgi can send things to apical (front) or basolateral (all other) sides
30
Q

What is clathrin?

A

molecule which coats vesicles, clathrin +adaptin 1 goes to lysosome (from golgi) clathrin + adaptin 2 goes to endosomes (from plasma membrane)

31
Q

What is COP1?

A

molecule which coats vesicles from er, golgi cisterna, or golgi apparatus to any of those

32
Q

How does clathrin coating work?

A

cargo molecules from extracellular space bond to receptors on the membrane, adaptin bonds to those receptors and clathrin bonds to adaptin after, , vesicles are then formed and dynamin seals off the end of vesicle, then it gets rid of clathrin and adaptin

33
Q

What is membrane tethering?

A

vesicle with cargo protein has Rab protein on the outside which interacts with a tethering protein on the edge of the cell membrane

34
Q

What is membrane docking?

A

mediated by v(esicle)-snare and t(arget)-snare which get all twisty and pull the vesicle into the cell until it fuses with the cell membrane

35
Q

What are the two types of endosomes? Explain homotypic fusion and transformation

A
  1. Early endosomes - carry Rab5 which helps other early endosomes find each other and fuse (homotypic fusion)
  2. Late endosomes - formed from a bunch of early endosomes before they fuse with degradative lysosomes (transform from Rab5 to Rab7)
36
Q

What is pinocytosis?

A

When a cell absorbs small molecules through endocytosis

37
Q

What is phagocytosis?

A

When a cell absorbs macromolecules through endocytosis

38
Q

Describe receptor - mediated endocytosis

A

LDL binds to LDL receptors on the cells surface, this causes adaptin and clathrin to surround receptor on inside of cell until vesicle is formed and endocytosed. Once inside cell, clathrin and adaptin break off and the vesicle merges with an endosome. The receptor is transported back to the cell membrane. endosome delivers LDL to lysosome which digests LDL and releases stuff into cytosol

39
Q

What is the role of endosomes in the endocytic pathway?

A

Sorting station, they send things to be recycled, degraded, or to transport vesicles

40
Q

Why are lysosomes acidic?

A

It alows the lysosome to digest / degrade proteins through hydrolytic enzymes. The pH is maintained by a proton pump

41
Q

How does the lysosome protect itself from digesting itself?

A

Their membrane proteins are highly glycosylated to protect it from digestion by hydrolases

42
Q

What are the products of lysosomal digestion? What are they used for?

A

Amino acids, sugars, nucleotides -> they can be secreted or used in the cell

43
Q

What is autophagy?

A

it “eats” itself, makes membrane around something already inside

44
Q

What pathways bring materials to lysosomes?

A

autophagy, phagocytosis, endocytosis

45
Q

How was the golgi apparatus discovered? Who discovered it?

A

Camillo Golgi discovered it, he was using silver to dye part of the nervous system and found a “internal reticular apparatus”. However, the golgi’s existence was not confirmed until the electron microscope in the 50s (Nobel Prize in 1906)

46
Q

What was the nobel prize of 1974 awarded for?

A

Discovering the endoplasmic reticulum

47
Q

How was the endoplasmic reticulum discovered?

A

sub-cellular fractionation and electron microscopy

48
Q

What was the nobel prize in 1999 awarded for?

A

Discovering the signal peptide on proteins

49
Q

Describe the experiment used to discover the signal peptide?

A

two proteins were used, one had a signal protein and the other did not. When placed together with a isolated organelle, they hypothesized only the protein with the signal sequence entered the organelle. They added proteases, which could only digest proteins outside the organelle, there was no labeled proteins. Then they used a detergent to break the cell and protease, and then found pieces of labelled proteins (from gel electrophoresis with sdspage). They then knew that only the protein with the signal sequence could enter the cell.

50
Q

What is SDS page? How does it work?

A

SDS page is the type of gel used in a type of gel electrophoresis. This is a process where pieces of proteins are injected into a gel, with a current run across. Each molecule experiences the same force but longer ones will move more slowly towards the positive pole in the gel.

51
Q

What was the nobel prize in 1985 awarded for?

A

Discovery of the regulation of cholestrol metabolism, clathrin and adaptin

52
Q

Describe the cause of Homozygous Familial Hypercholesterolaemia

A

LDL cannot bind to the receptor on the outside of the cell, leads to increased levels of LDL on the surface of the cell, but not inside

53
Q

What was the nobel prize in 2013 awarded for?

A

discovering proteins involved in vesicle transport between the er, golgi, and secretory vesicles

54
Q

How were temperature sensitive Sec mutants isolated (in discovering vesicle transport?

A

Yeast colonies were grown on velvet and imprinted on petri dishes so different samples could be grown at different temperatures. Not all of the yeast grew at 37C, some yeast with mutant sec1-1 only grew at 22-23C.

55
Q

What are the different types of sec mutants?

A

mutant A prevents transport between er and golgi, mutant B accumulated protein in golgi, mutant c accumulates proteins in transport vesicles

56
Q

What type of mutant is sec1-1?

A

mutant type c

57
Q

What was the nobel prize in 2008 awarded for?

A

discovery of gfp

58
Q

What are the uses of gfp?

A

Can be used as a marker for gene expression

59
Q

What is the light path for a microscope and gfp?

A

Light is emitted from a source and directed towards an object, the object absorbs the light and releases fluorescent light through the eyepiece. Dichoric mirrors are used to filter out light when light is emitted, and after it is emitted from sample

60
Q

Why is the emission wavelength longer than the excitation wavelength?

A

vibrational energy is lost

BMEG 245 (6 decks)

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