ch 9 proteins and their synthesis Flashcards
r group properties
- charged
- hydrophilic
- hydrophobic
- aromatic
primary structure
linear sequence of amino acids
secondary structure
arises from interaction btw neighboring amino acids
- alpha helix or pleated sheet
tertiary structure
interactions btw more distant amino acids or cofactors
- 3d
quaternary structure
interactions btw multiple polypeptides
- dimer, trimer, tetramer
- homo - identical polypeptides
- hetero - different polypeptides
polypeptide
chain of amino acids linked by peptide bonds
3d structure of tertiary structure stabilized by
- hydrophobic interactions
- ionic interactions
- h-bonding
- van de waals forces
2 major protein classes
- structural (myosin, actin, collagen)
- active (PEP carboxylase, endonuclease)
sanger sequencing
determining amino acid sequence
- proteolytic enzymes cut btw specific amino acids to produce specific fragments
- movement through electrophoretic field depends on size and charge of fragments
unambigous
1 codon, 1 amino acid
degernate
1 amino acid, >1 codon
3 features of the genetic code
- each amino acid is specified by a group of three nucleotides, a codon, in the mRNA
- the genetic code is non-overlapping
- of the 64 possible codons, 61 encode individual amino acids. therefore most amino acids are specified by more than one codon
5 components required for translation
mRNA - template for protein synthesis
amino acids - protein building blocks
tRNAs - carry aa to the ribosome, decode mRNA info
ribosome - RNP complex, catalyzes peptide bond formation
protein factors - IF, EF, RF
tRNA
- adapter molecule for protein synthesis
- base-pairing btw tRNA and an mRNA codon specifies the aa to be inserted
- a cell must contain at least 20 different tRNA (one for each aa)
- aa are covalently attached to tRNA = charging
aminoacyl-tRNA synthetase
charging accuracy is crucial for translation
- binds only one amino acid
- binds only the appropriate tRNA