3.3.13.2 Proteins
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What are the properties of polypeptides?
Strong and flexible
What does a peptide bond form between?
One of the hydrogen atoms of the amino group of one amino acid The OH group of the carboxylic acid of another amino acid
How do you hydrolyse proteins?
Boiling it in acid
Where do hydrophobic amino acid residues point?
Into the middle of the helix so that hydrophobic molecules can protect themselves
Where do hydrophilic amino acid residues point?
Out of the helix
What is the position of the residues in a beta pleated sheet?
They can point in any direction
Where are ionic bonds found in a DNA molecule?
Between charged residues
Where can van der Waals forces be found in a DNA molecule?
Between hydrophobic interactions
What is the process of thin layer chromatography?
The protein is hydrolysed by adding it to hydrochloric acid A small spot of amino acids is placed on a line 1cm above the bottom of the silica plate The plate is placed in a solvent where the solvent does not reach the line The solvent is called the mobile phase The solvent rises up the plate, carrying the amino acids with it The amino acids which lag behind have a lower affinity for the solvent due to the decreased intermolecular forces The solvent front is the line reached by the solvent When the solvent has reached far up the plate, the plate is removed and the points reached by the amino acids is marked The plate is marked by spraying it with ninhydrin then shining ultra-violet light on it Rf = distance moved by spot / distance moved by solvent The Rf value is the same for every amino acid
What are proteins?
Sequences of amino acids joined by peptide bonds
How is a polypeptide formed?
OH of the carboxylic acid H of the amine group Forms a CONH group
How do you work out the monomer of a condensation polymer?
Find the linkage group
Why are polyethene and polypropene bad for the environment?
They’re long chain alkene molecules so are unreactive and are not biodegradable
What functional groups does an amino acid have?
Amine and carboxylic acid
How many naturally occuring amino acids are there?
20
What are the properties of an amino acid?
Chiral: four different functional groups Ionic: dissolve in water
Functional group of an amide?
-CONH2
What type of polymer is a polypeptide?
Condensation polymers because water is formed when the amino acid acids join
How do you hydrolyse proteins?
Boil in HCl which hydrolyses the peptide linkages
What are the types of bonds that hold a protein together?
Hydrogen bonding Ionic attractions Disulfide bridges: -CH2S - SCH2-
How can amino acids be seperated?
Thin layer chromatography Plate consisting of a thin, flexible layer of silica The white powder is the stationary phase A small spot is placed at the bottom of the paper The end of the plate is placed in a solvent The solvent rises up the plate, carrying the amino acids The stronger the intermolecular forces between the amino acid and the solvent, the closer the amino acid is to the solvent front