proteins. you need to know that: proteins have a variety of functions within all living organisms....
TRANSCRIPT
Proteins
You need to know that:•Proteins have a variety of functions within
all living organisms.•The general structure of an amino acid •Condensation reactions form peptide bonds•Amino acids link together to form
polypeptides. •The relationship between primary,
secondary, tertiary and quaternary structure, and protein function.
•The biuret test for proteins.
Proteins
•Enzymes, carrier molecules, hormones, antibodies, cell membrane
•Over 50 % of a cells dry weight is Protein
•Basic Unit Molecule▫Amino acids - 20 amino acids found in living systems
Amino acid structure
•AA-AA Dipeptide
•AA-AA-AA-AA-AA Polypeptide
•Bond between Amino acids - Peptide Bond
Amino acid structure
Levels of Structure
•1. Primary •2. Secondary•3. Tertiary•4. Quaternary
Primary Level of Structure
•The linear sequence of Amino acids
•This is determined by the genetic code built into DNA of a gene
How amino acids combine
↓+ H2O
Linking of amino acids
•This is a hydrolysis reaction
•The bond formed is a peptide bond
Secondary Level of Structure
•When the a chain of polypeptides takes on a specific orientation in space
•2 Main Types▫Alpha Helix▫Beta Pleated Sheet
Tertiary Level of Structure
•Final 3 dimensional configuration
•Held together by many different bonds:▫peptide▫ionic▫hydrogen▫Covalent ▫Disulphide -S – S-
Quaternary Level of Structure
•When 2 or more proteins come together to form a functional unit
Biuret test for protein
•Place test solution in a test tube. Add equal volume of sodium hydroxide, (Biuret A) at room temp.
•Add few drops very dilute (0.05%) copper(II) sulphate solution, (Biuret B) and mix gently.
•Purple colouration = peptide bonds and so a protein.
•If it remains blue = no protein.
Questions• What type of bond links amino acids together? • What type of reaction is involved in linking amino acids
together?
• What 4 different components make up an amino acid? • Name the 2 bonds involved in holding together the
primary structure of a protein.
• Name the bonds involved in holding together the
secondary structure of a protein.
Denatured
•Temperature•pH•salt concentrations•heavy metals