Proteins

Question 1

What are proteins made from?

Answer 1

One or more polypeptide chains

Question 2

What is the general structure of amino acids?

Answer 2

A carboxyl group (-COOH), an amine group (-NH2) and an R group attached to a carbon atom

Question 3

What is the exception to the rule that R groups contain carbon?

Answer 3

Glycine (its R group consists of just one hydrogen atom)

Question 4

All living things share a bank of how many amino acids?

Answer 4

20 (the only difference between them is what makes up their R group)

Question 5

How are dipeptides and polypeptides formed?

Answer 5

Condensation reactions - peptide bonds form between amino acids

Question 6

Primary structure

Answer 6

Sequence of amino acids in the polypeptide chain

Question 7

Secondary structure

Answer 7

Folding of chain due to hydrogen bonds forming between amino acids, into an alpha helix (intramolecular) or a beta pleated sheet (intermolecular)

Question 8

Tertiary structure

Answer 8

Folding into a precise 3D shape, formed by interactions between R groups (hydrogen, ionic, disulphide bonds). This creates the active site in enzymes

Question 9

Quaternary structure

Answer 9

The protein’s final 3D structure for proteins made from more than one polypeptide chain, held together by bonds between polypeptides

Question 10

What do transport proteins do?

Answer 10

Transport molecules / ions across membranes

Question 11

What do structural proteins do?

Answer 11

Act as supportive tissue (eg. Collagen which has three polypeptide chains tightly coiled together, making it strong)

Question 12

The biuret test for proteins

Answer 12

• Add sodium hydroxide solution (test solution needs to be alkaline)
• Add copper(II) sulfate solution
• If protein is present, solution turns purple

Question 13

How do disulfide bridges form?

Answer 13

When two molecules of the amino acid cysteine come close together (the sulfur atoms bond)