Biochemistry Flashcards
Structure of an amino acid
Amino group (NH2), alpha carbon, hydrogen, carboxylic acid group (COOH), variable side chain (R)
Functional groups of an amino acid
An amine group (-NH2) and a carboxylic acid acid (COOH)
How do naturally occurring amino acids differ
The R group
Which amino acid isn’t optically active
Glycine
Why are amino acids optically active
They have a chiral carbon
Which which optical isomer naturally occurs and what is the effect on plane polarised light
L-isomer rotates plane polarised light anti-clockwise (the left)
Can amino acid acids act as a base or an acid
Both an acid and a base
Does an amino acid act as an acid or a base in a solution of acid
Base
Does an amino acid act as an acid or a base in a solution of base
Acid
Does an amino acid act as an acid or a base in a solution of isoelectric pH
Zwitterion so both
Which part of an amino acid accepts a proton
The lone pair on the NH2
Which part of the amino acid donates a proton
Carboxylic acid
What is the isoelectric point
pH at which is has no net charge. Midway between two pKa of its two functional groups
Which amino acid has the variable group H
Glycine
Charge on an amino acid in a acidic solution
Positive
Are cations positive or negative
Positive
What binds join amino acids in a protein
Peptide
What sort of polymers are proteins
Condensation polymers
Define fibrous proteins
Long chains of polypeptides found in bundles and insoluble in water
Define globular proteins
Polypeptide chains folded into roughly spherical shapes that are soluble in water
Example of globular protein
Haemoglobin
Example of fibrous protein
Keratin
Define primary structure
The order of alpha-amino acids in a protein
How do you determine the order of amino acids in a protein
Systematically hydrolyse the protein chain and identify each amino acid
How do you separate amino acids
TLC or paper chromatography
What is a proteins secondary structure caused by
Caused by hydrogen bonding between the N-H and the C=O groups of the peptide links along the protein chain causing alpha helix and beta pleated sheets
Define alpha helix
Hydrogen bonds formed every four amino acids forcing the chain into a cylindrical formation. Elastic and flexible.
Define beta pleated sheets
Parallel regions of the protein line up allowing hydrogen bonds to form between them, leading to a flat sheet like structure.
Where do you find beta pleated sheet proteins
In association with Alzheimer’s
Define tertiary structure
The overall 3D shape of a protein. Maintained by hydrogen bonds, ionic interactions and disulphides bonds between R groups of amino acids
What is the tertiary structure necessary for
Biochemical activity
What is broken when a protein is denatured
Tertiary structure
What are disulphides bonds
Between two -SH variable groups. Form strong S-S bonds
How can sulphide bonds be broken
They are destroyed by heat, reduction or reaction with a base
Define enzyme
Proteins that act as biological catalysts, providing an alternative reactions of lower Eact
How do enzymes works
Substrates bond in an active site.
Define lock and key hypothesis
Only molecules that have the right shape can fit into the active site
What determines how a substrate will bind
The size and orientation of an amino acid
How does a substrate bind to the active site
Hydrogen bonding, ionic bonding, and van der waals forces
What does a stereospecific active site cause
An active site which bonds to only one enantiomer of a racemate
Define enzyme inhibitor
A molecule that binds to an enzyme active site and decrease its activity is called an enzyme inhibitor
