1
Q
polypeptides
A
- precursor to proteins
- amino acids assembled on and released from ribosomes as polypeptides
- amino acid polymer
2
Q
proteins
A
polypeptides folded up into a functional three-dimensional conformation
3
Q
amino acids
A
20 naturally occurring
- carboxyl group
- amino group
- R (Radical) group bound to central carbon atom
- nomenclature N-(alpha carbon)-Co
4
Q
R group (side chain) of amino acid…
A
- determines type of amino acid
- non-polar, polar, polar positive and polar negatively charged
5
Q
peptide bond
A
- dehydration (condensation) reaction facilitates bond between carboxyl group of one amino acid and amino group of another
- two amino acids linked together constitute a dipeptide, three a tripeptide, etc
6
Q
primary structure
A
sequence of amino acids
7
Q
secondary structure
A
alpha helix and beta pleated sheets
8
Q
tertiary structure
A
3-D conformation
9
Q
quaternary structure
A
composed of more than one polypeptide chains
10
Q
post-translational modification (PTM)
A
- polypeptide chains modified once they have been synthesized (occurs after translation)
- modifications are crucial to functional capability of final protein product (can aid in function or distinguish between two common proteins)
- 20,000 proteins encoded within human genome; however, PMT increased the number >10ˆ6
11
Q
PTM examples
A
- N-terminus amino acid removed or modified (removal of methionine)
- individual amino acid residues modified
-carbohydrate side chains are sometimes attached - polypeptide chains may be trimmed (truncation)
- signal sequences are removed
- poylpeptide chains often complexed with metals (hemoglobin/myoglobin)
12
Q
proteins folding
A
- not spontaneous
- dependent on chaperones: proteins that mediate folding process
- added by chaperones
13
Q
diseases of protein folding
A
- Creutzfeldt-Jakob disease
- transmittable brain disorder in mammals
- presence of prions (misfolded proteins) in brain
14
Q
proteins…
A
- most abundant macromolecules in cells
- play diverse roles in body
- this is why proteins were thought to be the genetic material
15
Q
histones
A
bind to DNA in eukaryotes
16
Q
transcription factors
A
regulate gene expression
17
Q
enzymes
A
- most diverse and extensive group of proteins
- specialize in catalyzing chemical reactions
- increase rate of chemical reaction reaching equilibrium (are no used in the reaction
- involved in biological catalysis: process whereby enzymes lower energy of activation for given reaction
Genetics Unit 2
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