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Genetics > ch 9 proteins and their synthesis > Flashcards

ch 9 proteins and their synthesis Flashcards

1
Q

r group properties

A
  • charged
  • hydrophilic
  • hydrophobic
  • aromatic
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2
Q

primary structure

A

linear sequence of amino acids

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3
Q

secondary structure

A

arises from interaction btw neighboring amino acids
- alpha helix or pleated sheet

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4
Q

tertiary structure

A

interactions btw more distant amino acids or cofactors
- 3d

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5
Q

quaternary structure

A

interactions btw multiple polypeptides
- dimer, trimer, tetramer
- homo - identical polypeptides
- hetero - different polypeptides

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6
Q

polypeptide

A

chain of amino acids linked by peptide bonds

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7
Q

3d structure of tertiary structure stabilized by

A
  • hydrophobic interactions
  • ionic interactions
  • h-bonding
  • van de waals forces
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8
Q

2 major protein classes

A
  • structural (myosin, actin, collagen)
  • active (PEP carboxylase, endonuclease)
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9
Q

sanger sequencing

A

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

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10
Q

unambigous

A

1 codon, 1 amino acid

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11
Q

degernate

A

1 amino acid, >1 codon

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12
Q

3 features of the genetic code

A
  1. each amino acid is specified by a group of three nucleotides, a codon, in the mRNA
  2. the genetic code is non-overlapping
  3. of the 64 possible codons, 61 encode individual amino acids. therefore most amino acids are specified by more than one codon
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13
Q

5 components required for translation

A

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

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14
Q

tRNA

A
  • 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
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15
Q

aminoacyl-tRNA synthetase

A

charging accuracy is crucial for translation
- binds only one amino acid
- binds only the appropriate tRNA

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16
Q

how does the cellular tRNA set relate to degeneracy

A
  1. more than one tRNA species can be charged with the same amino acid — isoacceptors - most organisms contain at least 3 different tRNAs that are charged with serine
  2. a single tRNA species can recognize more than one codon — wobble
17
Q

wobble

A

the ability of the 3rd nucleotide of the anticodon (5’ end) to pair imprecisely, allowing the anticodon to align with different codons
G-C or G-U pair
U-A pr U-G pair

18
Q

ribosome function

A

brings all components together
catalyzes peptide bond formation

19
Q

two subunits of ribosomes

A

small subunit - binds mRNA, decoding site
large subunit - catalyzes peptide bond formation

20
Q

APE

A

key site of interaction on the ribosome
A - amino acyl site - incoming tRNA binds
P - peptidyl site - tRNA temporarily carrying the elongating pp chain
E - exit site - empty tRNA leaves

21
Q

3 steps of translation

A
  1. initiation
  2. elongation
  3. termination
22
Q

initiation (prokaryotes)

A

SSU binds to mRNA - start codon is positioned at P site
fMet-tRNA binds to the start codon - IF1 and IF2 ensure correct positioning
16S aligns with shine-dalgarno sequence to position the start codon at the P site
the large subunit recognizes the 30S initiation complex and binds - IF1 and IF2 are released

23
Q

shine-dalgarno sequence

A

ribosome binding site (RBS)
base-paring btw the shine-dalgarno sequence and the 16S rRNA aligns the start codon in the P site

24
Q

initiation (eukaryotes)

A

small subunit recognizes the 5’ cap and binds - i-tRNA and IF associated
mRNA is scanned processively for the 1st AUG (start codon)
large subunit binds - IF release, i-tRNA in P site

25
Q

elongation

A

continuing cycle of peptide bond catalysis

26
Q

termination

A

stop codon recognized by a RF
RF binds in the A site
hydrolysis breaks the bond btw the tRNA (P site and the PP chain
ribosome subunits dissociated from each other and mRNA

27
Q

nonsense mutation

A

introduction of a stop codon leading to premature termination of translation
- generally biologically inactive
- may be toxic

28
Q

3 types of post-translational processing

A

protein folding
covalent additions of chemical groups or peptides to defined positions/sequences
protein sorting and trageting

29
Q

post-translational processing

A

chaperonin complexes aid protein folding

30
Q

chemical modifications

A
  • addition of chemical groups
  • addition of polypeptides
  • addition of complex molecules
  • cleavage
  • amino acid modification
31
Q

phosphorylation regulates:

A

enzyme activity
protein-protein interactions
protein-nucleic acid interactions
cellular localization

32
Q

protein degradation

A

tagging a protein with ubiquitin targets a protein for destruction
- small peptide attached to lysine side chains

33
Q

signal sequence

A

the amino-terminal sequence of a secreted protein which is required for the export of the protein from the cell

34
Q

nuclear localization sequence (nls)

A

the sequence of a protein required for its transport from the cytoplasm to the nucleus

Genetics (9 decks)

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