Proteins Flashcards
Functions of proteins
Enzymes Transport molecules Structural Hormones Storage Contraction Defence against infection Membrane Plasma proteins
Draw an amino acid
Amino group consisting of N with two h
R group carbon with r group and hydrogen
Carboxyl
Carbon with a double bonded oxygen and a OH group
Structure of protein
Polymers made up of many subunits called amino acids
Amino acids are joined together by peptide bonds
Primary structure
The sequence of amino acids found in a polypeptide chain
Secondary structure
The polypeptide chain can fold to form a Alpha-Helix or a beta pleated sheet
Tertiary structure
The overall 3D shape of the polypeptide chain. Folding superimposed on top of the secondary structure held together by bonds between the R groups
Bonds of the tertiary structure?
Weak hydrogen bonds
Ionic bonds
Hydrophobic interactions
Strong covalent disulphide bonds
Explain how the sequence of amino acids in a polypeptide determines the 3D shape of a functional protein (3)
The sequence of the amino acids determines the sequence of the r groups in the polypeptide
Different bonds form between different r groups e.g ionic between two charged r groups
Hence the order of the amino acids determines the position of the tertiary bonds and hence how the polypeptide chain folds into its 3D shape
Quaternary structure
Some proteins have a quaternary structure because they are made up of more than 1 polypeptide chain
Conjugated proteins
The non protein part called the prosthetic group eg haem group of haemoglobin
Two types of protein
Globular
Fibrous
Biuret test for proteins
Add 2cm3 of your sample to a test tube and add an equal volume of sodium hydroxide solution
Holding test tube at 45o use a pipettes to add a small volume of copper sulfate
Negative result stays blue
Positive goes purple
Rf value equation
Distance moves by sample/ distance moves by solvent front
