2- amino acids and peptides Flashcards
(32 cards)
What are amino acids
Building blocks of peptides ( which make proteins )
Number of amino acids in the body that make up proteins
20
Components of an amino acid
Amine group ( NH2) Carboxyl group COOH Side chain (R) H Central C
Stereoisomers of amino acids
Can form L or D stereoisomers
Groups can be arranged in 2 ways
Only the L isomer is found in amino acids that make up proteins
How can amino acid side chains affect their properties
Some amino acid chains are negative, positive or uncharged polar making the amino acid polar and hydrophilic ( OXYGEN, POLAR OR NITROGEN ATOMS )
Some side chains are non polar = amino acid is non polar and hydrophobic ( water hating )
Naming amino acids
Often have a full name, one letter name and 3 letter
1 letter may be first letter OR another letter
Peptide bonds
AA join together into chains via peptide bonds
Carboxylic and amino group
COVALENT BOND between carbon of carboxyl group and nitrogen of the amine group of second AA
Loose one oxygen and hydrogen from carboxyl and 1 hydrogen from amino group ; h20
Condensation reaction
FORMING product 2—1
Making bonds
Loosing water
Hydrolysis reaction
BREAKING DOWN 1—2
Breaking bonds
Using water
Peptide
Many AA joining via peptide bonds
Polypeptide
many amino acids
Dipeptide
2 amino acids
Tripeptide
3 amino acids
Some peptides are directional
DIfferent ends
Insulin peptide
2 different peptide chains - a chain and b chain
2 chains attached by disulphide bonds ( covalent ) on side chain of cysteine amino acids
As pH increases, charge on peptide
DECREASES
As pH decreases, charge on peptide
INCREASES
Protein folding
whats it based on
how ?
Proteins must fold into their correct 3d shape to function
Protein folding is based on : hyrogen bonds, electrostatic (ionic) bonds, van der waals forces, hydrophobic and hydrophilic interactions
Hydrophobic /non polar regions of the protein fold in on themselves so they’re protected from the water
Fold into most stable conformation
Determined by sequence of AA present
Protein structure ?
To suit the proteins function
Collagen
Rigid and strong
3d shape
rope like
3 strands twisted
Elastin
Stretchy
Helps to make skin stretchy and retain form
Elastin made up of short pieces of polypeptide which are cross linked, individual protein molecules stretch but cross links keep everything in ordered form
Enzymes
Specific active site that fits their substrate
Primary level of protein structure
Sequence of amino acids
Determined by sequence of nucleotides in the gene that codes for that protein
Each 3 nucleotides in the gene ( codon) codes for a particular amino acid
Gives them their unique function
Secondary level of protein structure
Regular repeating structure like alpha helix and B sheet
Way that polypeptides are coiled
Stabilized by H bonds between C=O and N-H, non covalent