Protein

Question 1

Primary structure

Answer 1

specific linear sequence of amino acids

Question 2

Secondary structure

Answer 2

• folds and coils at various locations of polypeptide due to hydrogen bonding in the polypeptide backbone.
  Common structures:
• β-pleated sheet
• α-helix

Question 3

Tertiary structure

Answer 3

3D structure is determined by intermolecular reactions between R-groups in the polypeptide chain.

Question 4

Quaternary structure

Answer 4

some proteins consist of 2 or more polypeptide chains aggregated into one functional macromolecule

E.g., Hemoglobin consists of 2 types of polypeptide chains (2 α, 2 β);

Question 5

What is the basic structure of an amino acid? How many amino acids are there? How many are essential?

Answer 5

• Amino Acids contain:
  1. a central carbon
  2. an amino group (-NH2 or NH3+)
  3. a carboxyl group (-COOH or COO-)
  4. an H atom
  5. a side chain (R)
• There are 20 amino acids, 8 of which are essential (must obtain from diet) (**Note: some sources cite 9
  essential amino acids)

Question 6

What type of reaction occurs in the synthesis of peptides? What type of bond is formed?

Answer 6

During the synthesis of peptides (multiple amino acids) a dehydration synthesis reaction occurs bonding the amino acids creating a peptide joined by a peptide bond.

Question 7

polypeptide

Answer 7

a peptide with more than 50 amino acids linked together

Question 8

Define protein. How is a polypeptide different from a protein?

Answer 8

What is a Protein?
A protein is a large molecule made of amino acids, essential for many functions in the body, like enzymes, hormones, and structural support.

Difference Between Polypeptide and Protein:
- A polypeptide is a single chain of amino acids.
- A protein is one or more polypeptides folded into a functional shape.

Question 9

Define denaturation. What factors cause a protein to denture? What are some practical examples?

Answer 9

Denaturation
Denaturation is when a protein loses its shape due to changes in pH, salt, or temperature, causing it to stop working.

Causes:
- pH changes
- Salt levels
- Heat

Example:
- Heat styling hair temporarily changes its structure.

Question 10

Is denaturation irreversible, reversible or both? Explain.

Answer 10

Denaturation can be both reversible or irreversible, depending on the conditions and the protein involved.

• Reversible: If mild changes occur (e.g., slight temperature or pH shifts), proteins may regain their original shape and function when normal conditions are restored.
• Irreversible: If extreme changes happen (e.g., very high heat or strong acids), the protein structure is permanently altered, and it cannot return to its original form.

Example:
- Reversible: Some proteins may refold after a small temperature increase.
- Irreversible: Cooking an egg denatures its proteins permanently.