Protein Flashcards
(19 cards)
Collagen triple helix
- 3 helical polypeptide chains wrapped around each other
- strong water-insoluble fibres
- repeat sequence of X-Pro-Gly or X-Hyp-Gly
Collagen triple helix strands held together by
H-bonds involving hydroxyproline and hydroxylysine residues
Tertiary structure
Protein folding - Arrangement of helical and pleated sheet sections with respect to each other
Conformations of side chains
= Fibrous proteins
= Globular proteins
Globular proteins
- polar residues face surface and interact with solvent
- non-polar residues face interior and interact with each other
- structure is not static
Fibrous proteins
- mechanically strong, usually play a structural role in nature
Quaternary structure
- Property of proteins that consist of more than one polypeptide chain
- Each chain is a subunit of the oligomer
- Commonly dimers, trimers and tetramers
Haemoglobin
- tetramer
- two α- and two β-chains
- chains are similar to myoglobin
- binds 4 oxygens and exhibits positive cooperativity
proteins
Polymers of α-amino acids (polypeptides)
with α-carbon / Carboxyl group / Amine group / Side chain
Aspartame
- Methyl ester of L-aspartyl-L-phenylalanine
- 200 times sweeter than sugar
- Amino acids have L configuration, substitute D-amino acid for either gives bitter taste
different type of R group
polar, uncharged
non-polar (hydrophobic)
basic
acidic
polar, uncharged R group
hydroxy / amide / phenol (Tyr) / sulphydryl (Cys
non-polar (hydrophobic) R group
alkane /aromatic /methylsulfanyl (Met) / imino acid (Pro)
Basic R group
Histidine / Arginine / Lysine
Acidic R group
Aspartic Acid / Glutamic acid
Non-standard amino acids
- Derived from standard amino acids
- Occur due to post-translational modifications
- extends the range of protein functions by attaching other biochemical functional groups (i.e. phosphate, lipids, carbohydrates), changing the chemical nature of an amino acid or making structural changes (e.g. formation of disulfide bridges).
Interactions occur between side-chains
- Covalent bonds
- Electrostatic interactions/ ion-bridges/ salt-bridges
- Hydrogen-bonds
- Hydrophobic interactions
- van der Waals interactions
> define protein structure; important for functional properties
Covalent bonds between side-chains occurs ….
- Occur due to oxidation of sulfhydryl groups > Disulfide bonds between Cys residues lead to formation of cystine
Hydrogen-bonds between side-chains formed…
Formed between H bonded to an electronegative atom (O or N) and another electronegative atom
Peptide bond has ________ character
partial double bond character
> resonance hybrid of two structures
> peptide bond is therefore planar and stable
> No rotation around the peptide bond.
Free rotation around bonds between α-carbon and its amino nitrogen and carbonyl carbon
