Protein synthesis and protein function Flashcards
describe the makeup of a ribosome
multimeric structure consisting of >50 proteins and one copy of each of the 4 rRNAs (18s, 5.8S, 28s and 5S)
what do snoRNAs do
serve as a guide RNAs to direct specific modifications of the rRNAs. modifications include 100 methylations and 100 isomerizations
what are free ribosomes
move anywhere in the cytosol but not found in the nucleus and other organelles
what are membrane bound ribosomes
on ER
where does translation start
at the 5’ end of the mRNA
what are tRNAs charged with
addition of specific amino acid that corresponds to that codon
what creates the aminoacyl tRNA
aminoacyl tRNA synthetases
what region does the tRNA contain that is complemetary to the codon
the anticodon
what are the steps of translation
-activation
- initiation
- elongation
- termination
what happens in activation of translation
formation of aminoacyl- tRNAs
what happens in the initiation of translation
binding of small ribosomes to 5’ end of mRNA and subsequent binding of initiatory Met-tRNA
what happens in the elongation of translation
synthesis of peptide chain
what happens in the terminaiton of translation
synthesis stops and peptide is released from the ribosome
what does wobble mean
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
summarize translation
- 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
what is primary structure
amino acid sequence
what is secondary structure
stretches of the polypeptide chain that forms alpha helices or beta sheets
what is the teritary structure
3D strucutre of protein ( how it folds)
what is quaternary structure
proteins with multiple polypeptide chains
what are protein motifs
shared sequences of amino acids that can be used to identify potential members of a protein family
what are protein domains
strucutral entities that function independently within a protein and can be built from a specific motif or set of motifs
what are examples of protein sequence motifs
- proteolytic enzyme cleavage sites
- phosphorylation sites
-binding motifs
-transmembrane spanning sequences - protein secretion leader sequences
what are supersecondary structures
formed by the 3D arrangement of amino acids and do not neccessarily predict a biological function
where can sequence motifs be found
proteins and DNA
what are helix-loop helix motifs and where are they found
common in transcription factors and consists of alpha helices bound by a looping stretch of amino acids
what are helix turn helix motifs
DNA binding motifs consisting of 2 alpha helices joined by a short stretch of amino acids
what are zinc finger motifs
DNA binding motif consisting of two B strands
what are DNA sequence motifs
-DNA promotor and transcription factor binding sites
-DNA sequence repeat elements
what does the periodontal membrane do
acts as shock absorber for jaw
what do ameloblasts form
enamel
what do odontoblasts form
dentin
what do undifferentiated mesenchymal cells and fibroblasts form
pulp
what do cementoblasts form
cementum
what forms the periodontal ligament
fibroblasts from the dental follicle
what forms alveolar bone
osteoblasts
what is enamel made of
90% amelogenin and 10% enamelin
what happens in enamel as apatite crystals grow
amelogenin is removed
what does amelogenin contain
proline, leucine, histadine, and glutamine, but no hydroxyproline or cystine
where are the genes for amelogenin located
one of the X (AMELX) and one of the Y (AMELY) chromosome
what are the stages of ameloblast differentiation during dental enamel formation
-inductive stage
-pre-secretory stage
- maturation stage
what is the self assembly of amelogenin dependent on
hydroophilic C terminus
what occurs before formation of enamel
dentin
what do odontoblasts that form dentin differentiate from
cells in dental papilla
where do odontoblasts secrete their organic matrix
around the area that is directly adjacent to the inner enamel epithelium
where do odontoblasts move toward
center of tooth to form the odontoblast process
what do odontoblasts secrete
hydroxyapatite crystals and mineralizes matric forming the mantle dentin
what is the major component found in dental
type 1 collagen
what forms first in the cementum
acellular cementum
what does the acellular cementum form froom
cementoblasts from the dental follicle
what does the cellular cementum form from
cementoblasts from the adjacent area of bone
what is in cementum
collagen, osteopontin, osteocalcin, osteonectin
what do cells in the periodontal ligament secrete
collagen which interacts with fibers on surface of adjacent bone and cementum
