Biochemistry - Amino Acids Flashcards
Alpha Amino Acids
These are AA with primary amino grup(NH2)
What does pK value measure?
Availability of protons, the lower the less tightly they are held.
What are features of Amino Acids?
R Group
Dipolar due to Amino and Carboxylic functional groups readily ionising.
Conjugate
This is a substance formed when an acid loses a hydrogen ion
Zwitterions
Neutral molecules that intramolecularly have both a positve and negative charge
Why is all AA being zwitterions important?
More soluble in polar solvents than nonpolar
Where are peptide bonds found?
Between CO and NH by condensation reactions
Condensation Reactions
These are reactions between two reactangs yielding one large product and a smaller product such as water.
What is the primary structure of protein?
Linear peptide with NTD and CTD with variable electrostatic charges
What are the three categories of electrostatic charge of amino side chains?
Polar, Charged or Non Polar
Non Polar AA
Nine, like glycine with H and Ala, Val, Leu being aliphatic
Aliphatic
These are organic compounds where the carbon atoms form open chains.
What is the side chain of methionine?
Thioether side chain
Uncharged Polar Side Chains
These have either Hydroxyl, Amide or Thiol groups
Serine
This has a thiol group with capacity of disulphide bond formation
Amide
This is a functional group containg a carbonyl group and a nitrogen atom
Thiol(Sulfhydryl)
These consist of a S with two lone pairs bound to a H
Charged Polar Side Chaines
These are either anionic or cationinc, being 5
How is histidine unique?
Carrying an imidazole group ionizing readily at physiological pH so can be both neutral or cationic
What do polypeptide chains depend on?
Hydration tendency of polar and ionic side chains and non-polar side chains with each other.
Hydrophobic Effect
THis is the tendency of non-polar molecules and molecular segments in an aqueous solution to avoid contact with water molecules
Which amino acids are optically active?
All except glycine
Optically Active
This is the ability of a substance to rotate the plane of polarization of a bean that passes through it.
Why are AA optically active?
Chiral Centre
Chiral Centre
This is an atom in a molecule bounded to four different chemical species.
Enantiomer
Two isomers that cannot be superimposed on one another.
Why is chirality important?
It derives enantiomer forms.
Superimposition
This is where you may lay two things over one another where you cant tell them apart
What are the two Enantiomers of amino acids?
Can exist in L and D forms being mirror images.
Plane-polarized light
This is the light form in which the electric field oscillates in a single plane.
How does Plane-Polarised Light relate to AA?
Light passing through chiral molecules results in CW or CCW optical rotation
Why does AA rotate under plane-polarised light?
Asymmetric arrangement of atoms, where EM radiation interact with electrons, inducing oscillations creating polarized EM field rotation in direction of light propogation
What is an example of different biological functions in AA enantiomers?
Thalidomide L forms for sedation whilst D forms birth defects
Fischer Projection
This is a 2D representation of a 3D organic molecule
Racemic Mixture
This means equal amounts of each enantiomer
How is equilibrium favoured in one direction in racemic mixtures?
Chiral processes like enzyme.
