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Bio 130 > Chapter 22 > Flashcards

Chapter 22 Flashcards

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Biology 101 flashcards
1
Q

what kinds of RNA are involved in translation

A

all three!

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2
Q

how are the different kinds of RNA used in translation

A

mRNA is read; tRNA brings in amino acids; rRNA makes the ribosomes

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3
Q

what serves as the site of translation

A

ribosomses

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4
Q

what does it mean that the genetic code is degenerate or redundant

A

a single amino acid can be specified by more than one triplet

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5
Q

what does it mean for the genetic code to be non-overlapping

A

the reading frame advances 3 bases at a time and the frame does not change

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6
Q

codon on mRNA

A

triplet of nucleotides that serves as a coding unit for amino acids, start signal, or stop signal

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7
Q

nearly universal genetic code

A

except for small exceptions in mitochondria and bacteria

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8
Q

start codon and what does it code for

A

AUG; methionine

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9
Q

Stop codons and what they code for

A

UAA, UAG, UGA; don’t code for anything

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10
Q

aminoacyl-tRNA synthetases

A

attach amino acids to tRNAs

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11
Q

what are ribosomes composed of

A

rRNA and protein

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12
Q

function of rRNA in ribosomes

A

reads the mRNA

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13
Q

function of protein in ribosomes

A

facilitate protein synthesis

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14
Q

3 basic steps of translation

A

initiation, elongation, termination

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15
Q

initiation

A

3 kinds of RNA come together and first amino acid is placed

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16
Q

elongation

A

successive addition of amino acids by a 3 step process. starts as soon as 2nd tRNA binds to 2nd codon

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17
Q

direction of protein synthesis

A

amino acids are added starting at N-terminus and proceeding towards C-terminus

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18
Q

3 differences of prokaryotic ribosomes

A

smaller in size, contain fewer proteins, smaller RNA molecule

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19
Q

characteristics of all ribosomes

A

large and small subunits that bind only on the mRNA

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20
Q

what are the 4 important ribosome binding sites

A

mRNA binding site, A site, P site, E site

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21
Q

mRNA binding site

A

in between large and small subunits; place where mRNA binds

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22
Q

A site

A

(aminoacyl); binds newly arrived tRNA

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23
Q

P site

A

(peptide); site of growing polypeptide chain

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24
Q

E site

A

(exit); site where the empty tRNA is moved prior to release

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25
Q

structure of transfer RNA

A

3 major loops, 4 base paired regions, anticodon triplet, 3’ terminal sequence (CCA)

26
Q

aminocylation

A

attachment of correct amino acid to CCA sequence

27
Q

when is tRNA in charged form

A

when amino acid is activated

28
Q

anticodon triplet

A

recognizes the appropriate codon on the mRNA and base pairs with codon on mRNA

29
Q

wobble hypothesis

A

often the 3rd base on the codon can pair outside the normal rules

30
Q

Inosine

A

tRNA’s unusual base that can pair with U,C, or A; reason for “wobble”

31
Q

wobble hypothesis seen with codons for…

A

proline, serine, phenylaline

32
Q

messenger RNA contains

A

start codon, stop codon, and untranslated areas

33
Q

start codon

A

starting point for protein synthesis; establishes reading frame

34
Q

stop codon

A

instructs ribosome to terminate protein syn

35
Q

untranslated areas

A

5’ UTR and 3’ UTR (everything outside of start and stop codons);
essential in protein syn and seen in euk and prok

36
Q

coding sequence or open reading frame

A

everything in between start and stop codons

37
Q

N-Formylmethionine (tRNA^fMET)

A

modified amino acid that initiates polypeptide syn in proks and establishes directionality

38
Q

how does N-Formylmethionin work

A

formyl group binds to amino group and blocks it from peptide bonding so only carboxyl group can bond; this establishes directionality of protein syn N to C

39
Q

3 steps of initiation of translation in prok

A
  1. initiation factor binds to 30s subunit with GTP
  2. mRNA with 1st tRNA (fMET) binds to 30s subunit
  3. 50s subunit joins 30s initiation complex by hydrolysis of GTP
40
Q

Shinge-Delgarno site on mRNA

A

positions the 30s subunit in prok

41
Q

what is the purpose of these steps in this order

A

makes it easier to get mRNA inside ribosomes

42
Q

what happens after teh 50s and 30s subunits join

A

initiation factors are released and the ribosome is ready

43
Q

initiation of translation in euks

A

a lot more initiation factors and tRNA carries tRNA (not formulated)

44
Q

3 steps of polypeptide chain elongation in proks

A
  1. binding of aminoacyl tRNA to ribosome
  2. peptide bond formation
  3. translocation-mRNA advanced to next codon
45
Q

peptide bond formation caused by

A

peptidyl transferase activity of the 23s rRNA molecule

46
Q

termination of translation

A

stop codon triggers release of the polypeptide; accompanied by GTP hydrolysis, the ribosomal complex comes apart and mRNA and ribosomes are available for reuse

47
Q

how is the stop codon recoginized

A

not recognized by tRNA; recognized by proteins that mimic the appearance of tRNA called release factors

48
Q

Polyribosome (polysomes)

A

cluster of 2 or more ribosomes simultaneously translating a single mRNA

49
Q

Molecular chaperones

A

facilitate protein folding inside cells, rescue or destroy improperly folded proteins, and prevent polypeptide from interacting they’re in proper conformation

50
Q

silent mutation

A

doesn’t change amino acid sequence

51
Q

missense mutation

A

alters single amino acid (worst is to change hydrophilic and hydrophobic ones)

52
Q

frameshift mutation

A

alter the reading frame (insertions or deletions)

53
Q

indels

A

insertions or deletions

54
Q

nonsense mutations

A

premature stop codon (substitutions, insertions, deletions)

55
Q

3 major destinations for proteins

A

cytosol, other organelles, endomembrane system

56
Q

importance of protein targeting and sorting

A

proteins must be in the right spot for their function

57
Q

protein targeting to cytosol

A

protein is synthesized in cytosol and released

58
Q

protein targeting to other organelles

A

protein is syn in cytosol and released then taken in by posttranslational import

59
Q

what is necessary for the protein to have for posttranslational import

A

targeting signal

60
Q

cotranslational import

A

mRNA associates with free ribosomes which then associate with ER; ribosomes attach to ER shortly after protein syn begins and as protein is syn, it crossed the membrane

61
Q

protein targeting to endomembrane systerm

A

cotranslational import

Bio 130 (19 decks)

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