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Chapter 4: Translation and Protein Structure ((Hydrophobic Amino Acids,…
Chapter 4: Translation and Protein Structure
Hydrophobic Amino Acids
Alanine (Ala, A)
Valine (Val, V)
Leucine (Leu, L)
Isoleucine (Ile, I)
Tyrosine (Tyr, Y)
Methionine (Met, M)
Tryptophan (Trp, W)
Phenylalanine (Phe, F)
Special Amino Acids
Proline (Pro, P)
#
R Group linked back to amino group
Creates kink in chain, restricts rotation of C-N bonds
Hydrophobic
Glycine (Gly, G)
#
R Group is H, so symmetrical and Nonpolar
Increases flexibility of Polypeptide Backbone
Hydrophobic
Cysteine (Cys, C)
#
Hydrophilic
--SH group - when two come into contact with each other form S-S disulfide bond. This bond forms cross-bridges that affects structure
Hydrophilic Amino Acids
Basic
Arginine (Arg, R)
Lysine (Lys, K)
Histidine (His, H)
Acidic
Aspartic acid (Asp, D)
Glutamic acid (Glu, E)
Polar
Glutamine (Gln, Q)
Serine (Ser, S)
Asparagine (Asn, N)
Threonine (Thr, T)
Protein Structure
Residues: Amino acids incorporated into proteins
Secondary Structure: Interactions between stretches of amino acids in a protein
Results from hydrogen bonding in polypep backbone
Alpha helix: Tight right-handed coil
Beta sheet: Folds back on itself, forming pleated sheet-carbonyl and amide group across strands
Primary Structure: Sequence of amino acids in a protein
Tertiary Structure: Longer-range interactions between secondary structures- overall 3D shape of polypeptide
Made up of several secondary structure combinations
Determines Function
Quaternary Structure: Individual polypeptides that interact with each other
Proteins can be Denatured (unfolded) by chemical or temperature changes
Chaperones: Proteins that protect slow-folding or denatured proteins until they attain their structure
Amino acids are ionic at physiological pH (Zwitterion); tetrahedral
Water is needed to break peptide bond
Peptide chains are synthesized starting at amino-terminal end, ending at carboxyl-terminal end