Biological Macromolecules: Proteins Overview

Enzymes

• Specialized proteins that catalyze biological reactions in living cells.
• Regulate nearly all biological reactions critical for life.

Transport Proteins

• Assist in the transport of essential chemicals, gases, and nutrients within the body.
• Examples include hemoglobin and blood plasma proteins.

Storage Proteins

• Store nutrients within cells or tissues, serving as a reserve food supply.
• Can be mobilized to provide energy when necessary, e.g., casein and ferritin.

Contractile/Motile Proteins

• Responsible for muscle movement and contraction.
• Change shape to facilitate movement; key examples include actin and myosin.

Structural Proteins

• Provide support and structure to various tissues.
• Include collagen in tendons, elastin in ligaments, keratin in hair/nails, and fibroin in silk.

Regulatory Proteins

• Control cellular activities and physiological functions.
• Includes insulin for blood sugar regulation, growth hormones affecting mineral transport, and repressors influencing enzyme biosynthesis.

Monelin

• A protein derived from an African plant, known for its intensely sweet taste.
• Used as a non-toxic sweetener for human consumption.

Antifreeze Proteins

• Found in the blood plasma of Antarctic fish.
• Protects blood from freezing in sub-zero temperatures.

Resilin

• A protein found in the wing hinges of certain insects.
• Known for its exceptional elastic properties.

Fibrous Proteins

• Characterized by a rod-like structure; insoluble in water.
• Composed of polypeptide chains aligned parallel to the axis, reinforced by strong hydrogen and disulfide bonds; examples include collagen and keratin.

Globular Proteins

• Spherical in shape and highly soluble in water due to their amino acid composition.
• Includes myoglobin, albumin, globulin, casein, hemoglobin, various enzymes, and protein hormones.

Membrane Proteins

• Associated with lipid membranes, often embedded in the lipid bilayer.
• Features amino acids that interact with the non-polar environment; typically insoluble in water.

Simple Proteins

• Upon hydrolysis, yield only amino acids, without other major by-products.
• Examples include albumin from egg whites, globulins from serum, glutelin from wheat, and coryzenin from rice.

Conjugated Proteins

• Release both amino acids and additional organic or inorganic components when hydrolyzed.
• The non-amino acid part is known as the prosthetic group; classification depends on the nature of prosthetic groups.