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Biochem > Protein synthesis and protein function > Flashcards

Protein synthesis and protein function Flashcards

1
Q

describe the makeup of a ribosome

A

multimeric structure consisting of >50 proteins and one copy of each of the 4 rRNAs (18s, 5.8S, 28s and 5S)

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2
Q

what do snoRNAs do

A

serve as a guide RNAs to direct specific modifications of the rRNAs. modifications include 100 methylations and 100 isomerizations

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3
Q

what are free ribosomes

A

move anywhere in the cytosol but not found in the nucleus and other organelles

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4
Q

what are membrane bound ribosomes

A

on ER

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5
Q

where does translation start

A

at the 5’ end of the mRNA

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6
Q

what are tRNAs charged with

A

addition of specific amino acid that corresponds to that codon

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7
Q

what creates the aminoacyl tRNA

A

aminoacyl tRNA synthetases

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8
Q

what region does the tRNA contain that is complemetary to the codon

A

the anticodon

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9
Q

what are the steps of translation

A

-activation
- initiation
- elongation
- termination

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10
Q

what happens in activation of translation

A

formation of aminoacyl- tRNAs

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11
Q

what happens in the initiation of translation

A

binding of small ribosomes to 5’ end of mRNA and subsequent binding of initiatory Met-tRNA

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12
Q

what happens in the elongation of translation

A

synthesis of peptide chain

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13
Q

what happens in the terminaiton of translation

A

synthesis stops and peptide is released from the ribosome

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14
Q

what does wobble mean

A

if the third base is a U it can pair with A, G or Inosine and if it is a C it can pair with G or I

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15
Q

summarize translation

A
  • a small ribosomal unit attaches to the 5’ end of the mRNA
  • the subunit moves along the mRNA until it encounters AUG, then the Met-tRNA and large ribosomal subunit bind. aminoacyl tRNAs bind the A site
  • the ribosome moves 5’ to 3’ along the mRNA. as the ribosome moves the Met-tRNA shifts to the P site. the A site then opens for the next aminoacyl tRNA corresponding to the next codon to bind
  • a peptide bond is formed between the met -tRNA and the new aminoacyl tRNA in the A site leaving the dipeptide in the A site and an empty tRNA in the P site. the ribosome moves discharging empty tRNA and shifting the peptide into the P site until it reaches a stop codon
  • termination of polypeptide chain involved hydrolysis of the ester bond which releases the protein
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16
Q

what is primary structure

A

amino acid sequence

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17
Q

what is secondary structure

A

stretches of the polypeptide chain that forms alpha helices or beta sheets

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18
Q

what is the teritary structure

A

3D strucutre of protein ( how it folds)

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19
Q

what is quaternary structure

A

proteins with multiple polypeptide chains

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20
Q

what are protein motifs

A

shared sequences of amino acids that can be used to identify potential members of a protein family

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21
Q

what are protein domains

A

strucutral entities that function independently within a protein and can be built from a specific motif or set of motifs

22
Q

what are examples of protein sequence motifs

A
  • proteolytic enzyme cleavage sites
  • phosphorylation sites
    -binding motifs
    -transmembrane spanning sequences
  • protein secretion leader sequences
23
Q

what are supersecondary structures

A

formed by the 3D arrangement of amino acids and do not neccessarily predict a biological function

24
Q

where can sequence motifs be found

A

proteins and DNA

25
Q

what are helix-loop helix motifs and where are they found

A

common in transcription factors and consists of alpha helices bound by a looping stretch of amino acids

26
Q

what are helix turn helix motifs

A

DNA binding motifs consisting of 2 alpha helices joined by a short stretch of amino acids

27
Q

what are zinc finger motifs

A

DNA binding motif consisting of two B strands

28
Q

what are DNA sequence motifs

A

-DNA promotor and transcription factor binding sites
-DNA sequence repeat elements

29
Q

what does the periodontal membrane do

A

acts as shock absorber for jaw

30
Q

what do ameloblasts form

A

enamel

31
Q

what do odontoblasts form

A

dentin

32
Q

what do undifferentiated mesenchymal cells and fibroblasts form

A

pulp

33
Q

what do cementoblasts form

A

cementum

34
Q

what forms the periodontal ligament

A

fibroblasts from the dental follicle

35
Q

what forms alveolar bone

A

osteoblasts

36
Q

what is enamel made of

A

90% amelogenin and 10% enamelin

37
Q

what happens in enamel as apatite crystals grow

A

amelogenin is removed

38
Q

what does amelogenin contain

A

proline, leucine, histadine, and glutamine, but no hydroxyproline or cystine

39
Q

where are the genes for amelogenin located

A

one of the X (AMELX) and one of the Y (AMELY) chromosome

40
Q

what are the stages of ameloblast differentiation during dental enamel formation

A

-inductive stage
-pre-secretory stage
- maturation stage

41
Q

what is the self assembly of amelogenin dependent on

A

hydroophilic C terminus

42
Q

what occurs before formation of enamel

A

dentin

43
Q

what do odontoblasts that form dentin differentiate from

A

cells in dental papilla

44
Q

where do odontoblasts secrete their organic matrix

A

around the area that is directly adjacent to the inner enamel epithelium

45
Q

where do odontoblasts move toward

A

center of tooth to form the odontoblast process

46
Q

what do odontoblasts secrete

A

hydroxyapatite crystals and mineralizes matric forming the mantle dentin

47
Q

what is the major component found in dental

A

type 1 collagen

48
Q

what forms first in the cementum

A

acellular cementum

49
Q

what does the acellular cementum form froom

A

cementoblasts from the dental follicle

50
Q

what does the cellular cementum form from

A

cementoblasts from the adjacent area of bone

51
Q

what is in cementum

A

collagen, osteopontin, osteocalcin, osteonectin

52
Q

what do cells in the periodontal ligament secrete

A

collagen which interacts with fibers on surface of adjacent bone and cementum

Biochem (34 decks)

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