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genetics > chapter 9 part 1 > Flashcards

chapter 9 part 1 Flashcards

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Biology 101 flashcards
1
Q

how many different amino acids serve as building blocks for peptides

A

20

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2
Q

components of amino acids

A
  • central carbon
  • amino group
  • carboxyl group
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3
Q

what does enzymes of ribosomes catalyze

A

peptide bond between amino acids

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4
Q

where are the peptide bonds formed between amino acids

A

between carboxyl group of one and amino group of next

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5
Q

R-group of amino acids

A

distinct parts - some charged, some polar

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6
Q

ribosome

A

machines that contain multiple rRNAs and proteins

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7
Q

which direction do ribosomes translate mRNA

A

5’ to 3’ direction

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8
Q

ribosome structure

A
  • large ribosomal subunit
  • small ribosomal subunit
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9
Q

how is ribosomal size measured

A

Svedberg units (S) based on size, shape, and hydration state

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10
Q

boundaries of translation

A
  • start codon at N-terminus of protein
  • stop codon at C-terminus
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11
Q

are the 5’ and 3’ UTRs inside or outside of the translated regions

A

outside

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12
Q

4 levels of peptide structure

A
  1. primary
  2. secondary
  3. tertiary
  4. quarternary
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13
Q

primary structure

A

peptide bonds

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14
Q

secondary structures

A

H-bonding between groups along peptide-bonded backbone

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15
Q

tertiary

A

bonds and other interactions between R-groups, or between R-group and peptide-bonded backbone

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16
Q

quaternary structure

A

bonds and other interactions between R-groups and between peptide backbones of dif polypeptdies

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17
Q

small subunit of E. coli ribosomes

A
  • 30S
  • 21 proteins
  • one 16S rRNA molecule
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18
Q

large subunit of E. coli ribosomes

A
  • 50S
  • 31 proteins
  • small 5S rRNA
  • large 23S rRNA
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19
Q

how big is fully assembly ribosome of E. coli

A

70 S

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20
Q

3 important sites on ribosome

A
  1. A-site (aminoacyl)
  2. P-site (peptide)
  3. E-site (exit)
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21
Q

aminoacyl site

A

binds incoming tRNA molecule carrying next amino acid to be added to growing polypeptide chain

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22
Q

peptide site

A

holds tRNA to which the growing polypeptide chain is attached

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23
Q

exit site

A

provides pathway for exit of tRNA after its amino acid has been added to the growing chain

24
Q

what are the most fully characterized of eukaryotic ribosomes

A

Mammalian ribosomes

25
Q

small subunit of eukaryotic ribosome

A
  • 40S
  • 3 proteins
  • one 18S rRNA
26
Q

large subunit of eukaryotic ribosome

A
  • 60S
  • 45-50 proteins
  • three rRNA molecules (5S, 5.8S, and 28S)
27
Q

start codon

A

AUG

28
Q

translation initiation overview

A
  • small ribosomal subunit binds near 5’ end of mRNA and identifies start codon
  • initiator tRNA binds to start codon
  • large subunit joins small subunit to form intact ribosome, translation begins
29
Q

initiator tRNA

A

carries first amino acid of polypeptide and binds to start codon

30
Q

initiation factors

A

proteins that help direct ribosome assembly and binding of initiator tRNA

31
Q

what provides energy for initiation

A

GTP

32
Q

charged tRNAS

A

tRNAS carrying amino acids

33
Q

uncharged tRNAs

A

tRNAs without amino acids

34
Q

bacterial translation initiation

A
  1. small subunit-IF3 complex binds near the 5’ end of mRNA searching for start codon
  2. pre initiation complex
  3. initiator tRNA binds to start codon where P-site will be once the ribosome is fully assembled
  4. 30S initiation complex
  5. 50S subunit joins 30S subunit to form intact ribosome
  6. IF1,2,3 accompanies joining of subunits to create 70S initiation complex
35
Q

what is the bacterial 30S subunit affiliated with

A

initiation factor (IF3), which prevents the 30S subunit from binding the 50S subunit

36
Q

bacterial pre initiation complex

A

forms when 16S rRNA base pairs with Shine-Dalgarno sequence on mRNA

37
Q

Shine-Dalgarno sequence

A

purine-rich (A/G) sequence of about 6 nucleotides 3-9 nucleotides upstream of start codon

38
Q

where is a complementary pyrimidine-rich sequence in bacteria

A

near 3’ end of 16S rRNA (part of small subunit)

39
Q

where does the initiator tRNA bind to in bacteria

A

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

40
Q

amino acid on initiator tRNA

A

modified amino acid
- N-formylmethionine (fMet)

41
Q

charger initiator tRNA name

A

tRNA(fmet)

42
Q

30S initiation complex

A

initiation factor (IF-2) and GTP molecule bound to tRNA(fmet) and IF-1 joins the complex

43
Q

what is the union of the 2 ribosomal subunits in bacterial translation initiation driven by

A

hydrolysis of GTP to GDP

44
Q

70S initiation complex

A

dissociation of IF1, IF2, and IF3 accompanies the joining of subunits

45
Q

eukaryotic translation initiation

A
  1. euk. 40S subunit complexes w/ euk. initiation factor
  2. pre initiation complex
  3. pre initiation complex joins initiation tRNA and eIF5
  4. joins group of at least 4 eIF4 proteins that assemble at 5’ cap of mRNA
  5. small subunit scans along 5’ UTR for start codon
  6. recruitment of 60S subunit to complex
46
Q

preinitiaton complex of eukaryotes

A

eIF1, eIF1A, and eIF3 bind to small subunit

47
Q

initiation complex of eukaryotes

A

pre initiation complex joins group of at least 4 eIF4 proteins that assemble at 5’ cap of mRNA

48
Q

what is required for scanning for start codon in eukaryotes

A

ATP hydrolysis

49
Q

approximately _______ of euk. mRNAs use AUG as start codon

A

90%

50
Q

where is start codon located in eukaryotes

A

Kozak sequence (consensus)

51
Q

what energy does location of start codon use in eukaryotes

A

GTP hydrolysis and dissociation of eIF proteins

52
Q

what is archaeal translation initiation similar to?

A

eukaryotes

53
Q

archaeal translaiton initaition

A
  • met first aa
  • some have Shine-Dalgarno sequences
  • archaeal initiation factor proteins (aIFs) homologous in structure/function to eIFs
54
Q

what carry out elongation in a series of steps?

A

several different elongation factors (EF) and ribosomal proteins

55
Q

bacteria polypeptide elongation

A
  • charged tRNAs affiliated with EF-Tu and GTP try to enter A site
  • tRNA with correct anticodon sequence pairs with codon
  • when tRNA pairs w/ mRNA codon, hydrolysis of GTP releases EF-Tu-GDP from tRNa
  • peptidyl transferase catalyzes peptide bond
  • elongated peptide transferred to the tRNA at the A-site while tRNA from the P-site exits through the E-site
  • using GTP hydrolysis, EF-G translocates the ribosome, moving 3 nucleotides toward the 3’ end of the mRNA
  • tRNa moved from A to P site, opens A site for next charged tRNA carrying anticodon
56
Q

peptidyl transferase

A

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

57
Q

are archaeal/eukaryotic or archaeal/bacteria homologs more alike?

A

archaeal/eukaryotic

genetics (37 decks)

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