BMSC 220 > Topic 7 > Flashcards

Topic 7 Flashcards

(58 cards)

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1
Q

translation is carried out on…

A

ribosomes

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2
Q

mRNA read ….

A

5’ to 3’

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3
Q

tRNA

A

allow for change in “language” (between mRNA and amino acids)

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4
Q

how many possible amino acid encoding codons?

A

61 (+3 STOP)

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5
Q

tRNA read….

A

3’ to 5’ (anticodon)

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6
Q

aminoacyl tRNA

A

special tRNA with a specific amino acid covalently bound at 3’ end

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7
Q

rRNA

A

serves both a structural and functional role; RNA components of ribosomal subunit

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8
Q

anticodon is located on…

A

the tRNA

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9
Q

______ ribosomes are more complex than_________ ribosomes.

A

eukaryotic, prokaryotic

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10
Q

prokaryotic ribosomes

A

70S; 50S large, 30S small

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11
Q

eukaryotic ribosomes

A

80S; 60S large, 40S small

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12
Q

what makes up ribosomes?

A

protein and rRNA

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13
Q

ribosomes are assembled where

A

nucleolus of nucleus

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14
Q

describe ribosome assemble

A
  • ribosomal proteins are imported to nucleolus
  • they attach to pre-rRNA
  • pre-rRNA splits to two (large and small subunit)
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15
Q

tRNAs are synthesized by…

A

RNA pol III

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16
Q

__-shaped structure is critical for proper anticodon function

A

L

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17
Q

3 steps of tRNA processing

A

produced through RNA processing

  • RNA cleavage
  • covalent addition of CCA
  • base modification (RNA editing)
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18
Q

There are _____ different aminoacyl tRNA synthetase

A

20

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19
Q

Each aminoacyl tRNA synthetase recognizes

A
  • correct amino acid

- correct codon on mRNA

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20
Q

Three steps to “charge” a tRNA

A
  • activation of amino acid
  • addition of amino acid to tRNA
  • proper folding of tRNA which can bring amino acid to the ribosome
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21
Q

What are the first 2 controls for specificity of amino acid incorporation into a protein?

A
  • matching correct amino acid to correct tRNA (specificity of enzyme)
  • correct base-pairing of codon and anticodon (specificity of base pairing)
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22
Q

wobble hypothesis

A

some tRNAs can recognize more than one mRNA codon

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23
Q

monocistronic

A
  • one gene codes for one protein

- eukaryotic genome

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24
Q

plycistronic

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A
  • one gene codes for more than one protein

- prokaryotic genome

25
3 stages of translation
- initiation - elongation - termination
26
signals for translation initiation in prokaryotes
-Shine-Dalgarno sequence
27
signals for translation initiation in eukaryotes
small ribosomal unit binds to 5' cap of mRNA and slide along until it finds start codon
28
initiation of translation in euk. part 1
40S ribosomal subunit + eIFs (eukaryote Initiation Factors) + charged tRNAmet assemble
29
initiation of translation in euk. part 2
- assembly from Step 1 meets up with a mature mRNA (poly AA tail + PABP and 5' cap) - and binds to its 5’m7G cap
30
initiation of translation in euk. part 3
Step 2 assembly starts at 5’m7G cap and scans mRNA for AUG start codon
31
initiation of translation in euk. part 4
- Entire complex dissociates from start site (except the 40S subunit and tRNAmet ), - 60S ribosomal subunit attaches
32
elongation stage involves which 3 tRNA binding sites?
- A (aminoacyl) site - P (peptidyl) site - E (exit) site
33
A (aminoacyl) site
arrival
34
P (peptidyl) site
pause
35
decoding centre
within small subunit; ensures proper aminoacyl tRNA pairs with codon
36
third step in specificity
decoding centre
37
elongation of translation step 1
tRNAmet is at start site from the cap
38
elongation of translation step 2
the next tRNA comes to A site
39
elongation of translation step 3
a peptide bond forms between the first two amino acids
40
elongation of translation step 4
ribosome moves downstream (A site to P site); translocation
41
elongation of translation step 5
repeat steps 2-4
42
termination of translation step 1
stop codon ends up in A site
43
termination of translation step 2
a releasing factor moves into A site
44
termination of translation step 3
poly-peptide chain released
45
termination of translation step 4
release factor causes ribosome to disassemble from mRNA
46
post-translational modification
chemical modification of a polypeptide chain after translation
47
chaperones
protein that keeps protein unfolded until completely synthesized and facilitates folding, but does not incorporate into complex
48
proteolysis or cleavage
important for maturation of several proteins
49
signal sequences
mature proteins that target proteins to specific cellular compartments
50
some enzymes and hormones require....... to create a functionally active protein
cleavage
51
types of post-translational modification
- phosphorylation - glycosylation - lipid addition - ubiquitylation
52
phosphorylation
small molecules such as phosphate added to regulate protein activity
53
glycosylation
carbohydrate addition to form glycoproteins
54
lipid addition
lipid addition to form lipoproteins
55
ubiquitylation
addition of ubiquitin polypeptide to target proteins for degradation
56
unlike protein cleavage, PTMs are....
reversible
57
What processes can ultimately regulate the level of a protein in the cell?
regulation of degradation
58
autpophagy
protein degradation by lysosomes
BMSC 220
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