Organic Chemistry Chapter on Biochemical Substances

Mass Composition of Human Body

• Proteins are the second most abundant substances in cells, making up ~15% of overall mass and nearly half of dry mass.
• Nitrogen, a key component of proteins, differentiates them from carbohydrates and lipids, which usually lack nitrogen.

Role and Diversity of Proteins

• Proteins serve structural and functional purposes in living organisms, facilitating various biological processes.
• A typical human cell harbors about 9,000 different proteins; the entire human body contains around 100,000 distinct proteins.
• Functional versatility arises from the ability of proteins to bind small molecules, interact with other proteins, and integrate into cell membranes.

Major Categories of Proteins Based on Function

• Catalytic Proteins: Enzymes that accelerate biochemical reactions essential for bodily functions.
• Defense Proteins: Immunoglobulins (antibodies) that are crucial for the immune system's response to pathogens.
• Transport Proteins: Carry biomolecules (e.g., hemoglobin transports oxygen) throughout the body.
• Messenger Proteins: Hormones (e.g., insulin, glucagon, growth hormone) that regulate processes across cells and tissues.
• Contractile Proteins: Facilitate movement; actin and myosin in muscles enable contraction.
• Structural Proteins: Provide support and rigidity; collagen in cartilage and keratin in hair/nails offer strength and protection.
• Transmembrane Proteins: Span cell membranes to control the selective movement of ions and molecules in and out of cells.

Protein Flexibility and Movement

• Muscle contraction is a result of cyclic conformational changes in proteins, highlighted by the interactions between myosin (thick filaments) and actin (thin filaments).
• Myofibrils consist of numerous sarcomeres, the repeat units responsible for the sliding mechanism during muscle contraction.

This quiz focuses on the mass composition data of the human body, specifically emphasizing the major types of biochemical substances. It highlights the significance of proteins in cellular mass and their abundance in nearly all cells. Test your understanding of these foundational concepts in organic chemistry.