Chapter 2.3: Proteins

Question 1

State the 5 components of every protein

Answer 1

1. Central carbon atom
2. Amine Group
3. Carboxyl Group
4. R-Group // Side chain
5. Hydrogen atom

Question 2

Define each structure in a protein

Answer 2

1. PRIMARY STRUCTURE: the sequence of amino acids
2. SECONDARY STRUCTURE: long chains of amino acids fold into regions with repeating patterns (alpha-helix & beta-pleated sheets)
3. TERTIARY STRUCTURE: Final 3-D shape of protein is formed from the interactions between R-groups
4. QUARTERNARY STRUCTURE: 2 or more polypeptide chains bonded together

Question 3

State the bonding present in each structure of a protein

Answer 3

1. PRIMARY STRUCTURE: Peptide bonds
2. SECONDARY STRUCTURE: Hydrogen bonds
3. TERTIARY STRUCTURE:
   a) Hydrophobic interactions
   b) Disulfide bridges
   c) Ionic bonding
   d) Hydrogen bonding
4. QUARTERNARY STRUCTURE: Hydrogen bonds

Question 4

Differenciate between Globular Proteins and Fibrous Proteins

Answer 4

1. Globular (4 polypeptide chains); Fibrous (3 polypeptide chains)
2. Globular (Round & spherical); Fibrous (Long & helical i.e. triple helix)
3. Globular (Multitude of functions); Fibrous (structural)
4. Globular (Irregular amino acid sequence); Fibrous (repetitive)
5. Globular (Sensitive to environment); Fibrous (less sensitive to pH, temperature, etc.)
6. Globular (Enzymes, haemoglobin, insulin); Fibrous (Keratin, Collagen, Elastin)
7. Globular (soluble); Fibrous (insoluble)

Question 5

Mnemonic for the differences between Globular and Fibrous Proteins

Answer 5

SPADES:
Shape
Purpose
Amino Acid Sequence
Durability
Examples
Solubility

Question 6

Describe haemoglobin

Answer 6

• Globular protein
• transports oxygen
• contains a hydrophilic and hydrophobic R-Groups
• Has a prostethic group: Haem
• contains iron atoms
• contains 4 polypeptide chains
• can hold 8 oxygen atoms // 4 oxygen molecules at a time

Question 7

Describe collagen

Answer 7

• Fibrous protein
• provides skin and strengthens bones
• 3 polypeptide chains
• Entirely helical; triple helix
• insoluble