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chapter 9 Flashcards

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Biology 101 flashcards
1
Q

how many different amino acids?

A

20

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2
Q

what do amino acids do?

A

serve as building blocks for polypeptides

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3
Q

what do all amino acids have?

A

central carbon
-amino group
-carboxyl group

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4
Q

what type of bond is between the carboxyl group of one amino acid and the amino group of the next?

A

peptide bond

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5
Q

what is distinct about each amino acid?

A

r-group

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6
Q

wht direction to ribosomes translate mRNA in?

A

the 5’ to 3’ direction

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7
Q

what are the two subunits of ribosomes?

A

large ribosomal subunit and the small ribosomal subunits

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8
Q

what is ribosomal subunit size measured in?

A

Svedberg units (S)

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9
Q

what dictates the resulting amino acid sequence?

A

the mRNA sequence

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10
Q

what are the boundaries of translation defined by?

A

the start codon at the N-terminus of the protein
the stop codon at the C-terminus

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11
Q

what segments of the mRNA are outside of the translated regions?

A

the 5’ un-translated region (5’ UTR) and the 3’ UTR

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12
Q

what type of polypeptide structure will we be working with most?

A

primary

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13
Q

how big is the small subunit in E.Coli?

A

30s
-21 proteins, on 16S rRNA molecule

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14
Q

how big is the large subunit in E. Coli?

A

50S
-31 proteins, a small 5S rRNA
=a large 23S rRNA

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15
Q

how big is the fully assembled E. Coli Ribosome?

A

70S

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16
Q

what are the three important sites in the ribosome?

A

-A-Site
-P-Site
-E-Site

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17
Q

A-site

A

Aminoacyl Site
-binds the incoming tRNA molecule that is carrying the next amino acid to be added to the growing polypeptide chain

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18
Q

P-Site

A

Peptidyl Site
-holds the tRNA to which the growing polypeptide chain is attached

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19
Q

E-Site

A

Exit Site
Provides a pathway for the exit of the tRNA after its amino acid has been added to the growing chain

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20
Q

what is the most fully characterized eukaryotic ribosome?

A

the mammalian ribosomes

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21
Q

how big is the small subunit is eukaryotes?

A

40S
-three proteins and one 18S rRNA

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22
Q

how big is the large subunit is eukaroytes?

A

60S
-45 to 50 proteins and three rRNA molecules of 5S, 5.8S, and 28S

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23
Q

how big is the fully assembled ribosome in eukaryotes?

A

80S

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24
Q

where does translation initiation begin?

A

where the small ribosomal subunit binds

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25
Q

where does the initiation tRNA bind to and what does it carry?

A

it carries the first amino acid of the polypeptide and it binds to the start codon (AUG)

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26
Q

what joins last in initiation?

A

the large subunit- it joins the small subunit to form the intact ribosome and translation begins

27
Q

what do initiation factors (proteins) do?

A

help direct ribosome assembly and binding of the initiator tRNA

28
Q

what provides the energy for translation?

A

GTP

29
Q

what are charged tRNAs?

A

tRNAs carrying amino acids

30
Q

what are uncharged tRNAS

A

tRNAs without amino acids attached

31
Q

what components come together in E. Coli to initiate translation?

A

-mRNA
-small ribosomal subunit
-large ribosomal subunit
-initiator tRNA
-thee initiation factor proteins
-GTP

32
Q

what is the 30S subunit in bacteria affiliated with for most of initiation and what does that thing do?

A

-an initiation factor - IF3
-IF3 prevents the 30S subunit from binding the 50S subunit

33
Q

what binds near the 5’ end of the mRNA and what does it do in bacteria?

A

small subunit IF3 complex
-searches for the start codon

34
Q

when does the preinitiation complex form in bacteria?

A

when the 16S rRNA base pairs with the Shine-Dalgarno sequence of the mRNA

35
Q

what is the shine-dalgarno sequence?

A

a purine-rich (A/G) sequence of about six nucleotides

36
Q

where is the shine-dalgarno sequence located?

A

3 to 9 nucleotides upstream of the start codon

37
Q

where is the complementary sequence of the shine-dalgarno sequence located?

A

-it is a pyrmidine-rich (U/C) sequence
-found near the 3’ end of the 16S rRNA (part of the small subunit)

38
Q

where does the initiatior tRNA bind?

A

to the start codon where the P-site will be once the ribosome is assembled

39
Q

what is the amino acid on the inititator tRNA?

A

it is a modified amino acid, N-formylmethione (fMet)

40
Q

what is the charged initiator tRNA called?

A

tRNAfMet

41
Q

what forms the 30S initiation complex

A

-initiator factor - IF-2 and a GTP molecule are bound to the tRNA^fMet and IF-1 going the complex

42
Q

what forms the intact ribosome in bacterial initiation?

A

when the 50S subunit joins the 30S subunit

43
Q

what is the union of the two subunits driven by?

A

hydrolysis of GTP to GDP

44
Q

what accompanies the joining of the subunits to create the 70S initation complex?

A

the dissociation of IF-1, IF-2, and IF3

45
Q

the eukaryotic 40S ribosomal subunit complexes with what

A

eukaryotic initiation factor (elF) proteins

46
Q

in eukarotic translation initiation, elf1A, elf2, elf3, binds the small subunit to forms what?

A

the preinitiation complex

47
Q

what forms the preinitiation complex in eukaryotic translation initiation?

A

elf, elf1A, elf3 binding to the small subunit

48
Q

what does the preinitiation complex go on to join in eukaryotic initiation?

A

it joins with the initiator tRNA and elF5
then joins a group of at least four elF4 proteins that assembles at the 5’ cap of the mRNA

49
Q

what comprises the initiation complex in eukaryotes?

A

when the preinitiation complex joins a group of at least four eIF4 proteins that
assembles at the 5’ cap of the mRNA

50
Q

what happens once the initiation complex is formed in eukaryotic initiation?

A

the small subunit scans along the 5’ UTR in search of the start codon

51
Q

what is required for the small subunit to scan along the 5’ UTR in search of the start codon?

A

ATP hydrolysis

52
Q

what percent of eukaryotic mRNAs use the first AUG as the start codon?

A

90%

53
Q

what is AUG in?

A

the kozak sequence

54
Q

after the start codon is located in eukaryotic initiation, what is recruited and how?

A

the 60S subunit, using the energy of GTP hydrolysis & the dissociation of the elF proteins

55
Q

what is archaeal translation initiation like?

A

eukaryote-like

56
Q

what is the common first amino acid in archaeal translation initiation?

A

methionine

57
Q

do some archael mRNAs contain shine-dalgarno sequences?

A

yes

58
Q

T or F: – Archaeal initiation factor proteins (aIFs) are homologous in structure and function to
eIFs

A

TRUE!

59
Q

what tries to enter the A-site in polypeptide elongation in bacteria?

A

charged tRNAs affiliated with Ef-Tu and GTP

60
Q

what happens when a tRNA pairs with the correct anticodon sequence elongation in bacteria?

A

hyrdrolysis fo GTP releases EF-Tu-GDP from tRNA

61
Q

what catalyzes the peptide bond formation between amino acids at the P and A sites?

A

Peptidyl transferase

62
Q

Using _____ hydrolysis, _____ translocates the ribosome, moving it three nucleotides toward the 3’ end of the mRNA

A

GTP
EF-G

63
Q

what moves the tRNA from the A site to the P site and opens the A site for the next charged tRNA carrying the correct anticodon?

A

when the energy of GTP hydrolysis makes EF-G move around the ribosome (3 nucleotides toward the 3’ end of the mRNA)

genetics (23 decks)

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