Amino Acids And Proteins Flashcards
In cell membranes, what is the fluid mosaic model?
Lipid bilayer with proteins embedded in it.
What is an amphiphatic molecule?
A molecule with both polar and non-polar regions.
What type of protein isomers are found in humans?
L isomers
If the pH of a solution is < than the pK value of an amino acid, then it will be protonated or de-protonated?
Protonated
If the pH of a solution is > than the pK value of an amino acid, then it will be protonated or de-protonated?
De-protonated
What is the pI (isoelectric point) of an amino acid?
The pH at which the amino acid has no overall net charge.
What is the secondary structure of an amino acid?
The local spatial arrangement of the polypeptide backbone.
How many amino acids are there per turn in the alpha helix?
3.6
Is a peptide alpha helix left or right handed?
Right handed
What is a pK value?
How much an acid dissociates
The lower the pK value, the more acidic/basic a substance is
Acidic
Give details about the structure of collagen.
Triple helical arrangement of collagen chains.
Contains Gly - X - Y repeating sequence.
Hydrogen bonds stabilise interactions between the chains.
What is the domain of a protein?
Part of a polypeptide chain that folds into a distinct shape and often has a specific functional role.
Give four forces involved in maintaining the quaternary structure of a protein.
Covalent, ionic, hydrogen, Van der Waals, hydrophobic
How does pH denature a protein?
Alters ionisation states of amino acids.
How does temperature denature a protein?
Increased vibrational energy of bonds.
What do chaperones do?
Assist proteins in folding.
What is the strength of an acid?
The extent to which it dissociates in solution.
What does Ka mean and how is it worked out?
The acid dissociation constant
[H+][A-]/[HA]
Will a strong acid have a large or a small Ka value?
Large
What is a buffer?
A solution that resists changes in pH on the addition of a small amount of acid or alkali.
What is a biological buffer made up of?
An acid and it’s conjugate base
Give some features of the peptide bond (3)
- Planar because the C-N bond has partial double bond characteristics
- Cannot be twisted
- Peptides always form trans (chair) isomers (opposite sides of the C-C bond)
What does the sequence of amino acids in a protein determine?
- The way in which the polypeptide folds
- The physical characteristics of the protein
What charge to acidic proteins mostly carry?
Negatively charged amino acids
What is a conjugated protein?
A protein with a covalently linked chemical component eg lipoproteins (lipids) and glycoproteins (carbohydrates)
What is the quaternary structure of a protein?
The 3-D arrangement of protein sub-units
What is an amyloid fibre?
A mis-folded, insoluble form of a normally soluble protein
Give features of a beta pleated sheet (3)
- Extended conformation
- Parallel or anti-parallel
- Multiple inter-strand H bonds
