Amino Acids & Polypeptides Flashcards
Amino Acids: the building blocks of proteins
- proteins are polymers of amino acids
- the type and squence of amino acids dictates the structure and function of proteins
How many Common Amino Acids are there?
20
At a physiological pH amino acids are zwitterions meaning
they both contain positive and negative charges, and their net charge is zero
- amino acid group is positive; H+ acceptor (i.e. is basic)
- carboxyl group (COO-) is negative and is a H+ donor (i.e. acidic)
Amino group is an ______ of H+, and it is normally in its protonated form (NH+3). It has a ____ charge
acceptor, positive
Carboxyl group is a H+ _____ and is in the ________ (___)
donor, carboxylate form (COO-)
What does an Amino Acid Look like:
- amino acid group (NH3+)
- carboxyl group (COO-)
- negative charge
- hydrogen ion
- variable side chain (R): unique for each amino acid
- it varies in structure, size, and electric charge. it influence their Solubility in water
Chiral Molecule:
Alpha carbon is attached to four different groups
Amino Acids Mirror Images: Enanitomer
?
Polymerisation of Amino Acids:
- Amino acids polymerise to form peptides & proteins via peptide bonds
- 1 molecule of water is released during the formation of the peptide bond (condensation)
Peptide bonds are covalent bonds that link amino acids together to form peptides, and proteins
Amino Acids are classified based on their chemistry of their R-group, these are:
- Non-poalr/hydrophobic/aliphatic
- Aromtaic
- Hydrophillic polar (uncharged
- Hydrophillic polar (charged)
Non-polar/hydrophobic/aliphatic Amino Acids
- R-group is hydrophobic
- the side chains tend to cluster together in centre of protein
- stablise a protein by inducing a hydrophic effect
Aromatic Amino Acids:
- R-Group has aromatic rings (e.g. benzene rings)
- absorbs UV light
- Contribute to hydrophobic effect
Hydrophilic polar (uncharged) Amino Acids
- side chains are water soluble (causes them to be commonly exposed on protein surface)
- can form intramolecular H bonds
Hydrophilic Polar (charged) Amino Acids
- the most hydrophilic side chains
form ionic bonds between positive and negative ions
Features of Amino Acids (structure & Properties
- An alpha carbon is bound to: primary amino group, caboxyl group, hydrogen, R-group
- at physiological pH amino acids are zwitterions
- have a chiral centre
Features of Amino Acid - An Alpha carbon bound to each of the following:
- a primary amino group (in this case NH3+)
- a carboxyl group (COO-) bonded on the same carbon
- a hydrogen
- a variable functional group (R-group) which dictates its properties inc: electric charge, size, structure, solubility
An Alpha carbon bound to a Function Group (R-Group) in an amino acids dictates what?
properties such as:
- electric charge
- size
- structure
- solubility
Features of Amino Acid - Have a Chiral Centre
- C bonded to 4 different groups & therefore asymetric
- either L-form or D-form (stereoismers)
- mirror images of eachother (when paired referred to as enatiomers)
- have same physical and chemical properties
- L-Form more common
Amino Acids are Amphoteric meaning they
donate and accept H+ and can act as either acid or base
Acid Base proprties of amino acids:
?
Amino Acids polymerise to form:
AA polymerise to form pepides/proteins
Polymerasation of Amino Acids
- peptide bonds are covalent & planar
- Alpha amino group of one AA displaces the hydroxy group pf another AA
- 1 x H2O molecule is released (condensation reaction)
Ionic element to peptide bond of AA
- There is an ionic element as C=O double bond transfers to be C=N double bond, leaving extra elecron from C=O to bond with oxygen = creates oxygen anion and creates a more stable C=N bond
- decreases rotation around this bond
How many AA’s in a peptide
2-50
