1.3 - Protein Structure

Question 1

What are Macromolecules?

Answer 1

• Large molecule made up of smaller subunits
  ○ Polysaccharide - carbohydrates(eg: starch, cellulose)
  ○ Lipids
  ○ Nucleic acids (eg: DNA, RNA)
  ○ Proteins

Question 2

What are Proteins?

Answer 2

• Made from many amino acids which are linked together by peptide bonds
• Protein function is directly linked to protein structure
• The function of a protein nearly always involves binding in a specific complementary manner to another molecule
• Long chains of amino acids.
• Proteins contain C, H, O, N and sometimes S

Question 3

What are Amino Acids?

Answer 3

• Protein plays a crucial role in almost all biological processes and amino acids are the building blocks of it.
• 20 different amino acids can be used in constructing a given protein
• Each amino acid contains an amino group (NH2) at one end and carboxyl group (COOH) at the other end

Question 4

What is a Peptide Bond?

Answer 4

• Bond between two adjacent amino acids.

Question 5

What is the length of Polypeptide Chains?

Answer 5

• The length of each chain varies.

- If greater than 100 amino acids, is called a protein

Question 6

What is the Structure of a Protein?

Answer 6

• The sequence of amino acids determines the way the protein will fold up and hence its shape
• The shape determines how it will function
• Proteins carry out the function by recognising and binding to another specific molecule
• Proteins are globular and have a unique shape that is complementary to the particular molecule they need to bind to

Question 7

What are the four levels of Protein Organisation?

Answer 7

• Primary Structure
• Secondary Structure
• Tertiary Structure
• Quaternary Structure

Question 8

What is the first level of organisation? (structure)

Answer 8

• Sequence of amino acids

- Adjacent amino acids are held together by peptide bonds.

Question 9

What is the second level of organisation? (structure)

Answer 9

• The coiling or folding that contributes to the shape of the protein.
• Weak hydrogen bonds form between hydrogen of 1 amino acid and the oxygen of a different amino acid nearby to form a coil.

Question 10

What is the third level of organisation? (structure)

Answer 10

• Polypeptide chains bend and fold to produce 3-dimenstional shape.
• Formed and stabilized by weak chemical bonds between functional groups.
  - Each type of protein has its own characteristic tertiary structure.

Question 11

What is the fourth level of organisation? (structure)

Answer 11

• Number of polypeptide chains covalently linked together

Question 12

What are functional proteins?

Answer 12

• Structural
  
  • Transport
  • Messenger
  • Receptor
  • Contractile
  • Defensive
    
    • Enzymatic

Question 13

What is the importance of 3D protein structure?

Answer 13

• Some proteins in the cell membrane act as receptors for hormones
• The receptor has a complementary shape to the hormone allowing binding between the molecules
• If the protein is the wrong shape, then the hormone won’t bind

Question 14

How do Antigens and Antibodies bind?

Answer 14

• Antibodies are part of the immune system
  
  • They act by binding to antigens with a complimentary shape
  • Antigens are foreign or non-self molecules
  • The antibody’s job is to recognise and bind to the antigen
    
    • 3D quaternary shape allows this.