Proteins

Question 1

What’s the basic monomer which combines to make up a polymer called a polypeptide

Answer 1

Amino acid

Question 2

What’s the structure of an amino acid

Answer 2

Has a central carbon atom

• amino group (-NH2)
• carboxyl group (-COOH)
• hydrogen atom (-H)
• R group - each amino has different R group.

Question 3

How do amino acids from a dipeptide.

What’s lost

Answer 3

Water is removed in a condensation reaction

• OH from the carboxylate group of one amino acid
• H from the amino group of another amino acid

Question 4

What’s the bond between two amino acids and where

Answer 4

Peptide bond

Between the carbon atom of one amino acid and the nitrogen of another

Question 5

What’s the primary structure

Answer 5

This is just the sequence of amino acids in the polypeptide chain but this will determine the rest of the protein structure

Question 6

What’s the secondary structure

Answer 6

the polypeptide chain doesnt remain flat and straight. Hydrogen bonds form between the amino acids in the chain. This makes it automatically coil into an alpha helix or fold into a beta pleated sheet

Question 7

What’s the tertiary structure

Answer 7

Further folding of the secondary structure. The tertiary structure is held together by bonds between the R groups of the amino acids in the protein, and so depends on what the sequence of amino acids is. There are three kinds of bonds involved:
• Hydrogen bonds, which are weak.
• Ionic bonds between R-groups with positive or negative charges, which are quite strong.
• sulphur bridges - covalent S-S bonds between two cysteine amino acids, which are strong.

So the secondary structure is due to backbone interactions and is thus largely independent of primary sequence, while tertiary structure is due to side chain interactions and thus depends on the amino acid sequence. Thus mutations changing the primary structure may not alter the secondary structure, could have a big impact on tertiary

Question 8

What’s the quaternary structure

Answer 8

Association of several polypeptides

such as Haemoglobin, antibodies, actin in muscle

Question 9

What’s the test for proteins

Answer 9

Add solution to be tested, add an equal volume of sodium hydroxide solution at room temp

Add a few drops of dilute copper sulfate solution and mix gently

If positive turns purple ( peptide bonds)