b1.2 proteins

Question 1

What are the key components of an amino acid?

Answer 1

• Amine group (-NH₂)
• Carboxyl group (-COOH)
• Alpha carbon (Cα) linking the groups
• R group (side chain) defining properties

Question 2

Define dipeptide, oligopeptide, and polypeptide.

Answer 2

• Dipeptide: Two amino acids linked by a peptide bond
• Oligopeptide: Short chain (3-20 amino acids)
• Polypeptide: Long chain (>20 amino acids)

Question 3

How does a condensation reaction form peptide bonds?

Answer 3

• Amine group (-NH₂) of one amino acid reacts with the carboxyl (-COOH) of another.
• Water (H₂O) is released, forming a peptide bond.

Question 4

Where does polypeptide formation occur in the cell?

Answer 4

Ribosomes (during translation in protein synthesis)

Question 5

Why is there limitless diversity in peptide sequences?

Answer 5

• 20 amino acids can arrange in endless combinations.
• DNA sequences encoding proteins allow variation across species.

Question 5

How do plants and animals source amino acids?

Answer 5

• Plants synthesize all amino acids from inorganic compounds.
• Animals obtain amino acids from food.

Question 5

What are essential and non-essential amino acids?

Answer 5

• Essential: Must be consumed in diet.
• Non-essential: Synthesized by the body.

Question 6

Why do vegans need careful food combinations?

Answer 6

Plant proteins often lack all essential amino acids, requiring varied sources (e.g., rice + beans).

Question 6

What is denaturation?

Answer 6

Loss of protein shape & function due to disrupted bonds.

Question 7

How does pH affect protein structure?

Answer 7

Extreme pH alters ionic interactions, changing shape & function.

Question 8

How does temperature affect protein structure?

Answer 8

High temperatures break hydrogen bonds, unfolding the protein.