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Block 1 > Cell Biology Week 2 > Flashcards

Cell Biology Week 2 Flashcards

1
Q

What is the D domain of the tRNA important for?

A

The D domain is important for ribosome recognition

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2
Q

DNA->protein in eukaryotes

A

DNA is transcribed to mRNA, which include introns and exons. The mRNA is processed: 5’capped, spliced, and 3’ Poly A tail added.
The processed mRNA is exported out of the nucleus and translated to protein via ribosomes

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3
Q

DNA->protein in prokaryotes

A

DNA is transcribed to mRNA which is directly translated to protein via ribosome

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4
Q

How is the genetic code translated?

A

The amino acid is added to tRNA via a tRNA synthases (there are 20) via ATP hydrolysis. The tRNA+amino acid then binds to the mRNA codon in ribosome and added to growing polypeptide chain

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5
Q

Prokaryotic Ribosomes

A

70S which are made of 50s and 30s subunits

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6
Q

Eukaryotic ribosome

A

80s which are made of 60s and 40s subunits

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7
Q

What is the final phase of protein synthesis?

A

The peptide is hydrolyzed when Release factor is bound to the A-site

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8
Q

Actinomycin D

A

drug that binds to DNA and blocks the movement of RNA polymerase (prevents RNA synthesis)

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9
Q

Drugs that only affect bacteria

A

Tetracycline, Streptomycin, Chloramphenicol, Erythromycin, Rifamycin

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10
Q

Drugs that affect both baccteria and eukaryotes

A

Puromycin, Actinomycin D

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11
Q

Drugs that only affect eukaryotes

A

Cyclohexamide, Anisomycin alpha-amanitin

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12
Q

alpha-amanitin

A

blocks mRNA synthesis by binding preferentially to RNA pol II

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13
Q

Upf proteins

A

Triggers mRNA degradation of mRNA that have been abnormally spliced

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14
Q

Post-translational modifications

A

chemical modifications of a protein by adding of biochemical functional groups, changing the chemical nature of the protein or making structural changes

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15
Q

molecular chaperones

A

help guide the folding of most proteins

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16
Q

Hsp60 family

A

a family of chaperones, uses GroES as cap and ATP hydrolysis to correctly fold protein

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17
Q

mono-ubiquitylation

A

protein targeted for histone regulation

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18
Q

multi-ubiquitylation

A

protein targeted for endocytosis

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19
Q

polyubiquitylation

A

protein targeted for proteasomal degradation or DNA repair

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20
Q

What do protein aggregation cause?

A

human disease

Sometimes proteins undergo rare conformational change and cannot undergo proteasomal degradation

Ex. prions

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21
Q

What types of proteins have what types of sorting signal?

A

Cytosol proteins do not have sorting signal

Nucleus proteins have nuclear localization signal

Mitochondrial proteins have sorting signal

Proteins cotranslated in ER have signal sequence

Lysosomal proteins are tagged w/ mannose-6-phosphate

Resident ER proteins have the KDEL sequence

22
Q

When do ribosomes attach to ER membranes?

A

If they are synthesizing polypeptides destined for the endomembrane system or for export from the cell

Transported via cotranslational import

23
Q

When do ribosomes remain free in cytosol?

A

If they are synthesizing polypeptide destined for cytosol or for import into the nucleus, mitochondria, chloroplasts or peroxisome

Transported via post-translational import

24
Q

Function of miRNA

A

translational repression or mRNA degradation

25
Q

Hypomethylation

A

leads to gene amplification

26
Q

Hypermethylation

A

leads to gene deletion

27
Q

miRNA based treatment

A

Two methods: miRNA that target native miRNA and miRNA that target mRNA

28
Q

Miravirsen

A

inhibits the biogenesis of miR-122; treats hepatitis c infection

29
Q

Why are euk cells organized into a complex set of organelles?

A

Because once the cells got bigger they ran into the surface to volume problem

30
Q

signal sequence

A

specific sequence on a protein that is recognized by a specific receptor for delivery of that protein

Signal sequence can be placed at the end of the protein, or can be inside the protein at various regions that contribute to forming the signal patch

31
Q

Nuclear envelope

A

double lipid bilayer and is continuous with the ER.

Proteins are transported through the nuclear pores, they do not cross through the membranes

32
Q

How do proteins enter the nucleus?

A

Via gated transport through nuclear pores, need nuclear localization signal

Proteins 60kDa enter the nucleus by active transport

33
Q

Nuclear localization signal (NLS)

A

signal that allows for the import of proteins into the nucleus

Most nuclear imports are signalled with a chain of positively charged amino acids

34
Q

Describe active transport through nuclear pores?

A

Nuclear import receptors bind to the NLS on their cargo proteins and to the nucleoporins of the nuclear pore complex

GTP-Ran binding to the loaded nuclear import receptor occurs in the nucleus to release the protein into the nucleus

35
Q

How is nuclear transport during T-cell activation controlled?

A

via phosphorylation/dephosphorylation

Calcineurin dephosphorylates the NF-AT therefore allowing for the import signal to be recognized thereby driving the protein into the nucleus

36
Q

What does IL-2 do?

A

Clonal expansion of memory T-cells

37
Q

cyclosporine

A

inhibits calcineurin -> inhibits T-cell activation

38
Q

Collagen

A

secreted by smooth muscle cells via default (constitutive secretory) pathway
16 types - primarily types I, II, III
main component of connective tissue

39
Q

co-translational translocation

A

as the peptide is being created, the peptide enters through the ER lumen

40
Q

Pre-pro-peptide formation

A

once the final mRNA exits from the cell nucleus and enters into the cytoplasm, it links with the ribosomal subunits and the process of translation

41
Q

signal recognition particle (SRP)

A

the SRP recognizes the signal sequence, and then directs the pre-pro-peptide into the ER

42
Q

The new signal hypothesis

A

the binding of SRP to signal peptide causes a pause in translation -> SRP bound ribosome attaches to SRP receptor in ER membrane -> translation continues and translocation begins -> SRP and SRP receptor displaced and recycled

43
Q

stop transfer sequence

A

used in single pass or multipass transmembrane proteins

Typically hydrophobic

44
Q

How multipass transmembrane protein with internal ER signal sequence is inserted into the ER membrane

A

via many start and stop transfer sequences

45
Q

Hydroxylation of prolines and lysines

A

is needed to aid crosslinking of alpha peptides; enzymatic step that required Vit. C as cofactor

In scurvy, lack of vit. C leads to lack to hydroxylation of prolines and lysines which cause looser triple helix of collagen

46
Q

propeptide vs. procollagen

A

propetide is when the signal peptide on the n-terminal is dissolved in the ER

procollagen is composed of a twisted portion (center) and two loose ends on either end. Where the hydroxylated (both pro and lys) and glycosylated (only lys) propeptide twists towards the left tightly and then the 3 propeptides form a triple helix

47
Q

How proteins exit the ER and enter Golgi

A

so from cytosol, ER is contranslational translocation thru the protein pore in the ER membrance. Once protein is in ER, all subsequent transport occurs via vesicle transport and lipid bilayer fusion

48
Q

COPI

A

mediates transport forward through the Golgi in the default pathway for delivery to the plasma membrane or extracellular matrix and also back through the golgi to deliver ER proteins back to the ER where they belong.
KDEL signal sequence triggers this reverse transport back to ER

49
Q

COPII

A

Only mediates the transport of vesicles forward from ER to golgi

50
Q

clathrin

A

Clathrin coats regulate receptor mediated vesicle transport

In the transgolgi, clathrin coats sort lysosomal protein for transport to lysosomes, and also sort substances for storage in secretory vesicles
At the plasma membrane, clathrin coats are used for the uptake of extracellular material via receptor mediated endocytosis

51
Q

unfolded protein response (UPR)

A

upregulate the expression and function of chaperones and foldases

activate ERAD

reduce the translation of mRNA to decrease the processing demand for newly synthesized proteins

52
Q

ERAD

A

quality control system to rid the cell of misfolded and unfolded proteins that are toxic to cell

Block 1 (9 decks)

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