Protein Applications and Denaturation

Applications of Proteins

Rubisco

• Catalyzes the CO₂ fixation reaction in the Calvin cycle.
• Full name: ribulose bisphosphate carboxylase.
• One of the most abundant and important enzymes.

Insulin

• Hormone produced by pancreatic beta cells.
• Reduces blood glucose levels by promoting glucose absorption.
• Binds reversibly to cell membrane receptors.

Immunoglobulins (Antibodies)

• Y-shaped proteins produced by plasma B cells.
• Identify and neutralize foreign pathogens.
• Act as markers for pathogen destruction by phagocytes.
• Each antibody is specific to a particular pathogen.

Rhodopsin

• Biological pigment in retinal photoreceptor cells.
• Consists of a retinal molecule surrounded by an opsin polypeptide.
• Light absorption changes its shape, sending a nerve impulse to the brain.
• Essential for low-light vision.

Collagen

• Main structural molecule in connective tissues.
• Fibrous, rope-like protein made of three polypeptides.
• Most abundant protein in the body (about 25%).

Spider Silk

• Various types with different functions (e.g., dragline silk).
• Stronger than steel and tougher than Kevlar.
• Used in web spokes and for suspension.
• Highly extensible and resistant to breaking.

Protein Denaturation

• Tertiary (3D) structure is held by bonds between R groups.
• Heat causes denaturation by breaking intermolecular bonds through vibrations.
• Different proteins have different heat tolerances.
• pH deviation from the optimum can also cause denaturation.
• Alkaline or acidic solutions can break ionic bonds between R groups.
• Example: Pepsin works best at pH 1.5 but denatures at higher pH.