Proteins

Question 1

What are amino acids?

Answer 1

The monomers from which proteins are made.

Question 2

What are proteins?

Answer 2

Polymers

Question 3

What is the general structure of an amino acid?

Answer 3

Where NH2 represents an amine group, COOH represents a carboxyl group and R represents a side chain. The twenty amino acids that are common in all organisms differ only in their side group.

Question 4

How is a peptide bond formed?

Answer 4

A condensation reaction between two amino acids.

Question 5

How are dipeptides formed?

Answer 5

Formed by the condensation of two amino acids.

Question 6

How are polypeptides formed?

Answer 6

Formed by the condensation of many amino acids.

Question 7

How are amino acids joined together to form a dipeptide?

Answer 7

• condensation reaction
• water is removed
• peptide bond forms between OH of carboxyl and H of amine group.

Question 8

Does a functional group only contain one polypeptide?

Answer 8

They may contain one or more polypeptides.

Question 9

What are the 4 levels in a protein?

Answer 9

Primary, Secondary, Tertiary, Quaternary

Question 10

What is a primary structure?

Answer 10

The order of the amino acids in a polypeptide chain - this is a polymer
TIP = THE SEQUENCE IS VITAL-YOU CANNOT JUST SAY A CHAIN OF AMINO ACIDS.

Question 11

What is a secondary structure?

Answer 11

1. The structure of amino acids causes parts of a protein molecule to bend into α shape or fold into β pleated sheets.

Question 12

How do hydrogen bonds relate to the secondary structure?

Answer 12

• Hydrogen bonds hold the secondary structure.
• Hydrogen bonds form between the C=O groups of the carboxyl groups of one amino acids and the H in the amine group of another amino acid.

Question 13

What is the tertiary structure?

Answer 13

1. The further folding of the secondary structure.
2. To form a unique 3D shape.
3. Held in place by ionic, disulfide, and hydrogen bonds.
   - The ionic and disulfide bonds form between the R groups of the different amino acids.
   - The disulfide bonds only sometimes occur, as there must be a sulfur in the R groups for this bond to occur.

Question 14

What is the quaternary structure?

Answer 14

• A protein made up of one or more polypeptide chains. e.g. haemoglobin is made up of 4 polypeptide chains.

Question 15

Conditions that denature a protein?

Answer 15

• too high temperature ( too much kinetic energy)
• too high/low a pH.

Question 16

What happens when a protein is denatured?

Answer 16

When a protein is denatured, this means that bonds that hold the tertiary and secondary structure in shape break, and therefore the unique 3D shape is lost ( e.g. enzymes lose their unique active site shape ).

Question 17

What is the importance of the primary structure?

Answer 17

• If even one amino acid in the sequence is different then it will cause the ionic, disulfide, and hydrogen bonds to form in different locations. This results in different 3D shapes.

Question 18

What is the impact of a primary structure?

Answer 18

Enzymes will have a differently shaped active site ( will be non - functioning ).
Carrier proteins will have a different shape binding site (molecules are complementary and cannot be transported across membranes ).