1.5 Flashcards
What are amino acids and what do they make?
Amino acids are the monomers which make up the polymer (called a polypeptide) protein molecule.
What is the basic structure of an amino acid?
The basic structure of an amino acid is:
• Amine/amino group (NH2), a basic group
• Carboxyl group (COOH), an acidic group
• Hydrogen atom (H)
• R group, a variety of different
chemical groups, each amino acid has a different R group
What happened when two amino acids join together? What happens if further condensation reactions take place?
Two amino acid monomers condense together to give a dipeptide. A peptide bond is formed (this is a type of covalent bond) between the OH from one carboxyl group and the H from another amino acid, and water is released. Further condensation reactions form polypeptides.
How can peptide bonds be broken down?
Peptide bonds can be broken down by hydrolysis
What are the four main types of protein structure?
The 4 main types of protein structure are: - Primary
- Secondary
- Tertiary
- Quaternary
What is the primary structure of a protein?
The primary structure of a protein is a chain of amino acids all joined together by several condensation reactions that make up the polypeptide chain. The peptide bond holds each amino acid in place
Secondary structure?
the polypeptide chain gets processed and it either:
1) get twisted to make alpha helix
Or
2) can be bent and folded into a beta pleated sheet
How do the shapes form in the secondary structure?
1)The oxygen bond in the C=O group is slightly negative and the hydrogen in the NH group is slightly positive.
2)This causes a hydrogen bond to form between two amino acids, causing the shape to bend.
3)Although hydrogen bonds are weak, hundreds of them keep the secondary structure stable
Tertiary structure?
1) further folding of secondary structure, forming a unique 3D shape
Bonds in tertiary structure?
- Hydrogen bonds – numerous but easily broken by changes in pH and temp
- Disulfide bonds – not common, fairly strong covalent bond, occurs between the two sulfur-containing R groups
- Ionic bonds - not common, strong bonds (although weaker than disulfide bonds), formed between any carboxyl and amino gp, easily broken by changes in pH
Quaternary structure?
The quaternary structure of a protein is only found in proteins consisting of two or more polypeptide chains. The quaternary structure describes the way these separate polypeptide chains fit together in 3D
Testing for protein?
1)place a sample of the solution to be tested in a test tube
2) add an equal volume of sodium hydroxide solution at room temperature
3)add a few drops of very dilute (0.05%) copper (||) sulfate solution and mix gently
4)a purple coloration indicates the presence of peptide bonds and hence a protein
5) if no protein is present, the solution remains blue
