BIOCHEMISTRY AND CLINICAL PATHOLOGY ER20-23T Chapter 1: Introduction to Biochemistry

Chapter 1: Introduction to Biochemistry

Bio : living organisms
Chemistry : chemistry

Introduction to Biochemistry
Biochemistry, also known as the chemistry of life, involves the study of the chemical processes
and transformations in living organisms. This field bridges biology and chemistry by exploring
the complex chemical reactions and structures that give rise to life. The term “biochemistry”
was introduced by Carl Neuberg in 1903.

Definition

• The chemistry of life.
• The science concerned with the chemical basis of life.
• The study of the various molecular processes occurring in living cells and organisms and their chemical reactions.
  
  Scope of Biochemistry in Pharmacy
  Biochemistry plays a crucial role in various aspects of pharmacy, including biochemical tests, drug constitution, drug storage, and drug metabolism.
  
  Biochemical Tests
  These tests determine the specific half-life or expiration date of drugs.
  
  The Half-Life
  This test assesses the stability of biochemical drugs under specific temperatures.
  
  Drug Constitution
  Biochemistry provides insights into the composition of drugs and how modifications in medicinal chemistry can enhance efficacy and minimize side effects.
  
  Drug Storage
  Biochemical tests help establish the optimal storage conditions for drugs, such as enzymes and hormones, which can deteriorate over time due to temperature, oxidation, or contamination.
  
  Drug Metabolism
  Biochemistry helps understand how drugs are metabolized through various biochemical reactions in the presence of enzymes, aiding in the avoidance of drugs with poor metabolism.
  
  Cell and its Biochemical Organization
  A cell is the basic structural and functional unit of life, enclosed by a membrane. Life is composed of various complex, lifeless chemical molecules such as proteins, nucleic acids(DNA & RNA), and polysaccharides.
  
  Cells are primarily composed of water, inorganic ions, and a vast array of organic molecules.
  
• Water: The most abundant molecule in cells, accounting for 70% or more of total cell mass. Its unique properties (polarity, hydrogen bonding) are crucial for cellular processes and act as a solvent for many biochemical reactions.
  
• Inorganic Ions: These include ions like Na+, K+, Mg2+, Ca2+, PO42−​, Cl−, and HCO3−​. They constitute a small percentage of cell mass but play vital roles in various metabolic processes, nerve impulse transmission, muscle contraction, and maintaining osmotic balance.
  
• Organic Molecules (Macromolecules): These are carbon-containing compounds that form the building blocks and machinery of the cell. The four major classes are:
  • Carbohydrates:
    • Composition: Made of carbon, hydrogen, and oxygen, typically in a 1:2:1 ratio (CH2​On​).
    • Monomers: Monosaccharides (simple sugars like glucose, fructose, galactose).
    • Polymers: Disaccharides (sucrose, lactose) and Polysaccharides (starch, glycogen, cellulose).
    • Functions:
      • Primary source of quick energy (glucose).
      • Energy storage (starch in plants, glycogen in animals).
      • Structural components (cellulose in plant cell walls, chitin in fungal cell walls).
  • Lipids:
    • Composition: Primarily carbon and hydrogen, with less oxygen than carbohydrates. They are largely hydrophobic (water-insoluble).
    • Building Blocks: Fatty acids and glycerol.
    • Examples: Fats, oils, phospholipids, steroids.
    • Functions:
      • Long-term energy storage.
      • Major components of cell membranes (phospholipids form the bilayer).
      • Insulation and protection.
      • Hormonal signaling (steroid hormones).
  • Proteins:
    • Composition: Polymers of amino acids, containing carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.
    • Monomers: Amino acids (20 different types).
    • Polymers: Polypeptides, which fold into complex three-dimensional structures to form functional proteins.
    • Functions:
      • Enzymes: Catalyze nearly all biochemical reactions in the cell.
      • Structural support: (e.g., collagen in connective tissues, keratin in hair and nails).
      • Transport: (e.g., hemoglobin transports oxygen, channel proteins facilitate molecule movement across membranes).
      • Defense: (e.g., antibodies).
      • Movement: (e.g., actin and myosin in muscle contraction).
      • Signaling: (e.g., hormones, receptors).
  • Nucleic Acids:
    • Composition: Polymers of nucleotides, containing carbon, hydrogen, oxygen, nitrogen, and phosphorus.
    • Monomers: Nucleotides (composed of a nitrogenous base, a pentose sugar, and a phosphate group).
    • Types:
      • DNA (Deoxyribonucleic Acid): Contains deoxyribose sugar and bases Adenine (A), Guanine (G), Cytosine (C), and Thymine (T).
      • RNA (Ribonucleic Acid): Contains ribose sugar and bases Adenine (A), Guanine (G), Cytosine (C), and Uracil (U).
    • Functions:
      • DNA: Stores and transmits genetic information (hereditary material). It provides the blueprint for all cellular proteins and functions.
      • RNA: Involved in expressing genetic information. Different types of RNA (mRNA, tRNA, rRNA) play crucial roles in protein synthesis.
        
• 
  
  Cellular Structures and Their Biochemical Roles
  The organic molecules are not randomly distributed but are precisely organized into distinct cellular structures, each with specialized biochemical functions.
  
  Cell Membrane (Plasma Membrane):
  Cytoplasm:
  • Biochemical Composition: Consists of the jelly-like cytosol (a watery medium containing dissolved ions, enzymes, and other organic molecules) and various organelles.
  • Biochemical Role: Site of many metabolic pathways (e.g., glycolysis), protein synthesis (by ribosomes), and distribution of nutrients.
• Nucleus (in Eukaryotic Cells):
  • Biochemical Composition: Contains DNA (organized into chromosomes with histone proteins), RNA, and various enzymes (e.g., DNA and RNA polymerases). Enclosed by a double membrane (nuclear envelope) with nuclear pores.
  • Biochemical Role: Houses the cell’s genetic material (DNA), controls gene expression, and is the site of DNA replication and RNA synthesis (transcription). The nucleolus within the nucleus is responsible for ribosome assembly (rRNA synthesis and protein association).
• Mitochondria:
  • Biochemical Composition: Double membrane-bound organelles with their own circular DNA, ribosomes, and numerous enzymes for cellular respiration.
  • Biochemical Role: Known as the “powerhouses” of the cell. They are the primary sites for aerobic respiration, where glucose and other nutrients are broken down to generate ATP (adenosine triphosphate), the main energy currency of the cell.
• Endoplasmic Reticulum (ER):
  • Biochemical Composition: A network of interconnected membranes, studded with ribosomes (Rough ER) or lacking them (Smooth ER). Contains enzymes for protein modification, lipid synthesis, and detoxification.
  • Biochemical Role:
    • Rough ER: Involved in the synthesis, folding, modification, and transport of proteins destined for secretion, insertion into membranes, or delivery to other organelles. Ribosomes on its surface synthesize these proteins.
    • Smooth ER: Involved in lipid and steroid synthesis, detoxification of drugs and poisons, and storage of calcium ions.
• Golgi Apparatus (Golgi Complex):
  • Biochemical Composition: Stacks of flattened membrane-bound sacs (cisternae) containing various enzymes.
  • Biochemical Role: Modifies, sorts, and packages proteins and lipids synthesized in the ER into vesicles for secretion or delivery to other cellular destinations. It’s like the cell’s “post office.”
• Ribosomes:
  • Biochemical Composition: Composed of ribosomal RNA (rRNA) and proteins.
  • Biochemical Role: The sites of protein synthesis (translation), where the genetic code from mRNA is translated into amino acid sequences to form proteins.
• Lysosomes:
  • Biochemical Composition: Membrane-bound sacs containing hydrolytic enzymes.
  • Biochemical Role: Involved in the degradation and recycling of waste materials, cellular debris, and foreign substances (like bacteria).
• Peroxisomes:
  • Biochemical Composition: Membrane-bound organelles containing oxidative enzymes.
  • Biochemical Role: Involved in various metabolic reactions, including the breakdown of fatty acids and detoxification of harmful substances, often producing hydrogen peroxide as a byproduct, which is then broken down into water and oxygen.
• Cytoskeleton:
• Biochemical Composition: A network of protein filaments, including microtubules (tubulin protein), microfilaments (actin protein), and intermediate filaments (various proteins like keratin).
  • Biochemical Role: Provides structural support to the cell, maintains cell shape, facilitates cell movement, and aids in the transport of organelles and vesicles within the cell.
• 
  Complex Molecules
  Complex molecules include small organic compounds like amino acids, nucleotides, and monosaccharides, which serve as monomeric units or building blocks.
  
  Major Complex Biomolecules of Cells

Micromolecules
Micromolecules are small organic molecules present in the cytosol of living cells. There are typically around 100-200 micromolecules in a cell. Common examples include amino acids, nucleotides, sugars, and their phosphorylated derivatives. These molecules are often water soluble, polar, or charged and are present in micromolar to millimolar concentrations.

Macromolecules
Macromolecules have large molecular weights and are formed by the polymerization of
monomer units. Examples include:

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Mrs. Deepika Gupta

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