Biological Molecules Flashcards
What are the 4 important functions of proteins in the body?
Protection, structure, signals and reactions.
What does an alpha amino acid mean?
The amino group (NH2) is joined to the first carbon next to the carboxyl group. Almost all amino acids in living systems are alpha.
What are the 2 functional groups in amino acids?
Carboxyl and amine/amino.
What is a zwitterion?
A species that contains both positive and negative charges but has no overall charge. Many amino acids are zwitterions meaning they can act as both acids and bases (amphoteric).
What is the isoelectric point (pl)?
The pH at which the amino acid is balanced between anionic and cationic forms and is primary in the zwitterionic (neutral) form.
Are all natural amino acids L or D? Does this mean they are all S or R chirality?
L. They are all S chirality except glycine which is chiral and cysteine which is R.
What is the hydrophobic effect?
Causes the hydrophobic side chains to be clustered in the interior of the protein. Major driving force for protein folding.
Are glycine, alanine, serine and threonine small, medium or large? Hydrophobic or hydrophilic?
Small. Hydrophilic.
Are cysteine, valine, isoleucine, lecucine, proline, phenylalanine, tyrosine, methionine and tryptophan small, medium or large? Hydrophobic or hydrophilic?
Medium/large. Hydrophobic.
What are the 3 polar amino acids?
Asparagine, glutamine and histidine.
What are the 2 acidic amino acids?
Aspartic acid and glutamine acid (both hydrophilic).
What are the 2 basic amino acids?
Lysine and arginine (hydrophilic).
What is umami?
A common amino acid with a savoury taste also called monosodium glutamate. Important for cells osmotic balance.
How are proteins formed from amino acids?
In a dehydration/condensation reaction where the amino group of one amino acids forms a peptide bond to the carboxyl group of another amino acid. They are then referred to as amino acid residues.
What dipeptide does phenylalanine make?
Aspartame. People who cannot synthesis this reaction have phenylketonuria. A build up of The causes mental retardation if not discovered early.
How do we write the primary structure of a protein?
From the N terminus to C terminus, either as single letters or in 3 letters.
What role do hydrogen bonds play in protein structure?
They stabilise secondary structure by forming between the negatively charged O in C=O and the positively charged H in N-H.
What are salt bridges?
Strong interactions between charged amino acid side chains that can stabilise peptide and protein structures. Not common.
What are disulphide bridges?
Covalent bonds/bridges between the S-H groups of cysteine. Prialt (pain killer) has 3.
Why do proteins fold?
Because they are more stable in their folded/native state. They only remain folded in a narrow range of conditions of pH, salt concentration and temperature. Misfolding can lead to diseases such as Alzheimers.
What can the folding pattern of a protein be described by?
The angles of rotation around the bonds in the main chain.
What must protein structures achieve in the secondary structure?
- Low energy conformations of individual residues.
- Hydrogen bonding
- Formation of compact and well packed structures.
What is the alpha helix?
The pattern of hydrogen bonding is NH to C=O. Phi is -57 and psi is -47. Peptide bond is trans. 3.6 residues per turn(n). Displacement (d) between successive residues along the helix axis is 1.5 A. Distance along the helix axis per turn (pitch, p) is 5.5A. P=n x d.
What is the antiparallel B-sheet?
Has phi of -139 and psi +35. Peptide bond is trans. 2 residues per turn (n). Displacement (d) between successive residues along the helix axis is 3.4 A. Distance along the helix axis per turn (pitch, p)is 6.8 A.
