what are proteins made from?
Long chains of amino aicds
what are the monomer of proteins?
Amino aicds
when is a dipeptide formed?
When 2 amino acids join together
whens a polypeptide formed?
when more than 2 amino acids join together
what are proteins made up of?
One or more polypeptides
Do different amino acids have different variable groups?
Yes
general structure of amino acids
CH(3)
/
h(2)N-C-COOH
/
H- Carboxyl group (-COOH)
- amine or amino group (-NH2)
- and a carbon containing R group (variable group)
how many amino acids are there?
20
- the only difference between them is what makes up their carbon-containing R group
what reaction forms polypeptides?
condensation reactions
- amino acids linked together by condensation reactions
what are the bonds formed between the amino acids called?
Peptide bonds
how many structural levels do proteins have?
four
primary structure of proteins?
the sequence of amino acids in the polypeptide chain
Secondary structure of amino acids?
- hydrogen bonds form between the amino acids in chain
- causes it to coil into an alpha (a) helix or into a beta (b) pleated sheet
tertiary structure of amino acids?
- coiled and folded further
- more bonds form between different parts of the polypeptide chain (hydrogen bonds and ionic bonds)
- disulfide bridges also form
- for proteins made from a single polypeptide chain this forms their final 3D structure
what are ionic bonds?
attractions between negative and positive charges on different parts of a molecule
how are disulfide bridges formed?
whenever two molecules of the amino acid cysteine come close together - sulfur atom in one cysteine bond to the other sulfur atom in the other
Quaternary structure of proteins?
- some proteins made of several different polypeptide chains held together by bonds
- Quaternary structure is the way these chains are assembled together
- for proteins made form more than one polypeptide chain this forms their final 3D structure
examples of proteins?
- enzymes
- antibodies
- transport proteins
- structural proteins
about enzymes?
- spherical shaped due to tight folding of polypeptide chains
- they’re soluble + often have roles in metabolism
about antibodies?
- involved in immune response
- made up of 2 short polypeptide chains and two long polypeptide chains bonded together
- antibodies have variable regions, amino acid sequences in these regions vary greatly
about transport proteins?
(example channel proteins - present in cell membranes)
- channel proteins contain hydrophobic and hydrophilic amino acids, cause protein to fold and form a channel
- these proteins transport molecules and ions across membranes
about structural proteins?
- they’re physically strong
- consist of long polypeptide chains lying parallel to each other with cross links between them
- structural proteins include keratin ( hair and nails) and collagen (connective tissue)
which test do you use to test for proteins?
Biuret test
how to perform the biuret test?
2 stages
1 - test solution needs to be alkaline, so add a few droplets of sodium hydroxide solution
2 - then add some copper(II) sulfate solution
