Introduction to Biochemistry

Definition of Biochemistry

• Biochemistry studies the chemical composition of living things and the chemical reactions occurring within them.
• It encompasses multiple disciplines like organic chemistry, analytical chemistry, physical chemistry, cell biology, physiology, and genetics.

Fields of Biochemistry

• Structural Biochemistry: Focuses on the chemical composition of living organisms and the properties of isolated biological molecules.
• Metabolic Biochemistry: Examines the chemical reactions within the organism, including anabolism (biosynthesis) and catabolism (breakdown).
• Functional Biochemistry: Investigates the chemical processes underlying vital activities like cellular respiration, enzyme activity, muscle contraction, and signal transmission.
• Clinical Biochemistry: Interprets laboratory test results for diagnosis and treatment in medical practice.

Major Components of the Human Body

• The human body is comprised of inorganic and organic components.
• The fundamental unit of life is the cell, containing essential components for survival and continuity.
• Organisms are "open systems," requiring energy for metabolic processes, crucial for survival.

Inorganic Components of the Human Body

• Essential Bioelements:
  • Nonmetals: Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N), Phosphorus (P), Sulfur (S)
  • Elements: Sodium (Na), Potassium (K), Calcium (Ca), Magnesium (Mg), Chlorine (Cl), Iron (Fe)
• Distribution of Bioelements:
  • Oxygen, carbon, hydrogen, and nitrogen make up 96% of cell mass.
  • Macroelements: O, C, N, H, Ca, P
  • Oligoelements: Na, K, Cl, S, Mg, Fe
  • Microelements: Zn, Mn, Co, Cu, F, B, I
  • Ultramicroelements: Li, Al, Si, Cd, Cr, Ni
• Functions of Bioelements:
  • Bioelectric: Nerve impulse transmission
  • Osmotic: Maintaining fluid balance
  • Structural: Building tissues and organs
  • Regulatory: Hormonal and enzymatic processes
  • Mechanical: Bone structure and muscle contraction
  • Energy: ATP production

Water

• Water constitutes 60-70% of body mass.
• Percentage varies with age, sex, tissue metabolism, and body composition.
• Daily intake is through external fluids, food, and metabolic processes.
• Body maintains water balance with precise regulation mechanisms.
• Water is excreted through kidneys, lungs, intestines, and skin.
• Biological Roles of Water:
  • Dissolution and stabilization of molecules and ions.
  • Thermal balance control.
  • Transport of nutrients and waste removal.
  • Mechanical function: lubrication and shock absorption.
  • Structural role: cell shape and tissue integrity.
  • Catabolic role: participating in chemical reactions.
  • Maintenance of acid-base balance.

Mineral Salts

• Essential for body function.
• Examples: chlorides, phosphates, sulfates, and carbonates of sodium, potassium, calcium, and magnesium.

Organic Components of the Human Body: Biomolecules

• Biomolecules comprise the organic molecules composing living matter.
• They contribute to the biochemical, structural, and functional organization of organisms.
• Categories of Biomolecules:
  • Energy & Structure: Carbohydrates and lipids.
  • Structural: Proteins.
  • Informational: Nucleic acids (DNA and RNA).
  • Regulatory: Enzymes, vitamins, and hormones.
• Importance of Biomolecules:
  • Carbohydrates and lipids provide energy.
  • Proteins provide structure and facilitate chemical reactions.
  • Nucleic acids control genetic inheritance.
  • Enzymes, vitamins, and hormones regulate and maintain homeostasis.

Intermediary Metabolism

• A complex process involving catabolism (breakdown) and anabolism (synthesis).
• It is a balanced process that ensures energy acquisition and synthesis of new compounds.
• Metabolic Pathways:
  • Central or Common Pathways:
    • Glycolysis
    • Krebs Cycle (Citric Acid Cycle)
    • Pentose Phosphate Pathway
    • Oxidative Phosphorylation
  • Specific Metabolic Pathways: Examples include hemoglobin synthesis, glycogen synthesis/degradation, lipid metabolism
• Metabolic Roles:
  • Energy Production
  • Biomolecule Synthesis and Degradation Synchronization
  • Precursor Production for Macromolecular Synthesis
  • Maintaining Metabolic Homeostasis

Catabolism and Anabolism

• Catabolism: Breakdown of nutrients into simpler molecules (lactic acid, pyruvic acid, acetyl-CoA, CO2, ammonia, urea).
  • Involves carbohydrates, lipids, and proteins.
  • Oxidative reactions, releasing energy in the form of ATP.
• Anabolism: Biosynthesis of complex molecules from simple ones (carbohydrates, lipids, proteins, nucleic acids).

Regulation of metabolism:

• Gentle mechanisms: feedback inhibition
• Allosteric mechanisms: binding of a molecule to a site other than the active site to change enzyme activity.

The Fundamental Role of Food in Human Health

• Nutrition: Provides energy and essential nutrients for biosynthesis, body temperature maintenance, and physical activities.
• Energy needs vary with growth, development, and age.
• Basal metabolism: energy consumption for basic functions at rest (~1000 kcal/day/m2 of body surface).