1: BIOLOGICAL MOLECULES - PROTEINS Flashcards
What are amino acids made up of?
- carbon atom
- a carboxyl group (-COOH
- an amine/amino group (-NH2)
- R group (varies depending on amino acid)
How many different amino acids are there?
20
What are the bonds that form between amino acids called?
peptide bonds
What are dipeptides?
2 amino acids joined together by a condensation reaction
What are polypeptides?
3+ amino acids joined together by condensation reactions
What is the name of the reaction that breaks down dipeptides and polypeptides?
hydrolysis
What is the primary structure of a protein?
the sequence of amino acids in the polypeptide chain
What bonds are present in the primary structure of a protein?
peptide bonds
What is the secondary structure of a protein?
polypeptide chain coiled into α helix/folded into β pleated sheet
What bonds cause the secondary structure of a protein to form?
hydrogen bonds
What is the tertiary structure of a protein?
coiled/folded more to form 3D structure (final structure for proteins made up of only 1 polypeptide chain)
What bonds cause the tertiary structure of a protein to form?
- hydrogen bonds
- ionic bonds
- disulfide bridges
What is the quarternary structure of a protein?
more than 1 polypeptide chain bonded together
What bonds are present in the quaternary structure of a protein?
- hydrogen bonds
- ionic bonds
- disulfide bridges
Describe the structure of a protein (5 marks)
- polymer of amino acids
- joined by peptide bonds
- formed by condensation
- primary structure - order of amino acids;
- secondary structure - folding of polypeptide chain due to hydrogen bonding (accept alpha helix / pleated sheet
- tertiary structure - 3D folding due to hydrogen bonding and ionic / disulphide bonds
- quaternary structure - two or more polypeptide chains
How are shape and function linked in proteins?
final 3D structure determines function
What are some functions of proteins?
- enzymes
- antibodies
- transport proteins
- structural proteins
How does the structure of enzymes relate to their function?
specific 3D tertiary structure makes active site complementary to a specific substrate molecule
How does the structure of antibodies relate to their function?
specific 3D structure makes antibody specific to antigen
How does the structure of transport proteins (eg: channel proteins) relate to their function?
- contain hydrophilic and hydrophobic amino acids which cause the protein to fold up and form a channel
- this allows it to transport molecules and ions across membranes
How does the structure of structural proteins (eg: keratin in hair and nails/collagen in connective tissue) relate to their function?
- consist of long polypeptide chains parallel to each other with crosslinks between them
- crosslinks make the proteins strong
How do you test for proteins?
- add a few drops of NaOH (to make it alkaline)
- add copper (II) sulfate solution
- if protein is present, solution changes colour to purple if no proteins are present the solution stays blue
