Chapter 3 - proteins Flashcards
what is the structure of an amino acid?
- amine group (H-N-H)
- variable R group (diff R group=diff amino acids)
- carboxyl group (O=C-O-H)
how are peptides synthesised?
1) peptide bond formed between two amino acids by a condensation reaction (carboxyl + amine group)
resulting in a dipeptide
2) many amino acids joined=polypeptide formed (catalysed by peptidyl transferase)
3) R groups interact forming bonds - causes long chains of amino acids folding in proteins
4) diff sequences of amino acids=diff structures=diff shapes
how to separate amino acids using thin layer chromatography?
1) stationary phase
- layer of silica gel applied to rigid surface
- add amino acids to one end of gel
- submerge this end in organic solvent
2) mobile phase
- organic solvent moves through silica gel
what is the primary structure of protein?
- the sequence in which amino acids are joined
- bonds involved=peptide bonds
what is the secondary structure of proteins?
- oxygen, hydrogen, and nitrogen atoms of amino acids interact
- can form alpha helix or beta pleated sheet
- bonds involved=peptide bonds, hydrogen bonds
what is the tertiary structure of proteins?
- the folding of a protein into its final shape
- R groups interact
- bonds involved=peptide bonds, hydrogen bonds, ionic bonds, disulfide bonds
what is the quaternary structure of proteins?
- results from association of two or more individual proteins (subunits)
hydrophilic and hydrophobic interactions?
- the way a protein folds depends on whether R groups are hydrophilic or hydrophobic
- hydrophilic groups=outside, hydrophobic groups=inside
how are peptides broken down?
- proteases (enzymes) catalyse the breakdown
- water molecule used in hydrolysis reaction
what is the Biuret test for proteins?
1) mix equal volume of sample and 10% sodium hydroxide solution
2) add 1% copper sulfate solution until solution turned blue
3) mix solution
positive=purple
what are globular proteins?
- compact, water soluble, spherical shape, soluble
- essential in regulating many of the processes needed for life
what is insulin?
- a globular protein
- a hormone
- involved in the regulation of blood glucose concentration
- soluble
what are conjugated proteins?
- globular proteins that contain a non protein component (prosthetic group)
what is haemoglobin?
- red, oxygen carrying pigment found in red blood cells
- quaternary protein (four polypeptides subunits)
- each subunit contains a prosthetic haem group
- iron in haem groups enable haemoglobin to carry oxygen
what is catalase?
- an enzyme
- quaternary protein (four haem prosthetic groups)
- iron allows catalase to interact with hydrogen peroxide and speed up its reactions