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• Polysaccharides

  • Starch
  • Glycogen
  • Cellulose
• Organic compounds make up about 95% of the dry weight of the protoplasm
• Excess glucose is often stored as starch
• Disaccharides

  • Lactose
  • Maltose
  • Sucrose
• Monosaccharides

  • Glucose
  • Galactose
  • Fructose
• Organic compounds


  Chemical compounds containing the element carbon
• Subtypes of carbohydrates

  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Polysaccharides


  A long chain of monosaccharides linked by glycosidic bonds
• Disaccharides

  • Form when two monosaccharides undergo a dehydration reaction
  • Hydrolysis breaks them down into monomers
• Carbohydrates


  • Supply energy for cell processes
  • A means of storing energy
  • Give structural support to cell walls
• Monosaccharides


  • Simple sugars, most common of which is Glucose
  • Number of carbons usually ranges from 3-7
  • Most monosaccharides end with the suffix -ose
• Organic compounds in the cell

  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic Acids
• Lipids


  Naturally occurring, nonpolar substances mostly insoluble in water
• Glucose is an important source of energy for humans
• Chemical components of the cell

  • Organic compounds
  • Inorganic compounds
• Glycogenolysis


  Process of breaking down glycogen
• Lipids


  • From the Greek word lipos, meaning "fat"
  • Naturally occurring, nonpolar substances mostly insoluble in water, yet soluble in nonpolar solvents
  • Store large amounts of energy over long periods of time
  • Act as an energy source
  • Play a major role in the structure of cell membranes
  • Act as a source of metabolic water
  • Reduce the loss of water by evaporation
  • Serve as membrane components, storage forms of energy, precursors to other biomolecules, insulation barriers, protective coatings, vitamins, and hormones
  • Major classes include saturated and unsaturated fatty acids, triglycerides, lipoproteins, phospholipids, glycolipids, steroids, and eicosanoids
  • All lipids can be synthesized from acetyl-CoA, which can be generated from various sources
  • Simple lipids include esters of fatty acids and an alcohol
  • Compound lipids include materials containing substances in addition to an alcohol and fatty acid
  • Derived lipids include those that cannot be neatly classified into the above categories
• Cellulose


  • Most abundant natural biopolymer
  • Cell wall of plants is mostly made up of cellulose; provides structural support to the cell
• Glycogen breakdown


  Release glucose
• Proteins


  • Act as building blocks of many structural components of the cell; required for growth
  • Form enzymes which catalyse chemical reactions
  • Form hormones which control growth and metabolism
  • Amino acid polymers responsible for implementing instructions contained within the genetic code
  • Twenty different amino acids are used to synthesize proteins, about half are formed as metabolic intermediates, while the remainder must be provided through the diet
  • Each protein formed in the body, unique in its own structure and function, participates in processes that characterize the individuality of cells, tissues, organs, and organ systems
  • A typical cell contains thousands of different proteins, each with a different function, and many serve as enzymes that catalyze reactions
  • Other proteins transport different compounds either outside or inside cells
  • Some act as storage proteins
• Nucleic Acids


  • Play a vital role in protein synthesis
  • Are nucleotide polymers that store and transmit genetic information
  • Genetic information contained in nucleic acids is stored and replicated in chromosomes
  • A chromosome is a DNA molecule, and genes are segments of intact DNA
  • The flow of information from nucleic acids to protein
• Proteins as enzymes


  • clotting proteins and immunoglobulins
• Proteins as storage proteins

  • myoglobin
• Water

  An inorganic compound composed of hydrogen and oxygen
• Proteins as contractile proteins

  • actin, myosin, troponin
• Hydrogen, oxygen, nitrogen, carbon, sulfur, and phosphorus normally makeup more than 99% of the mass of living cells
• Cells generally contain many more protein molecules than DNA molecules, yet DNA is typically the largest biomolecule in the cell
• Proteins as structural proteins


  • collagen, elastin
• Proteins as transport proteins

  • lipoproteins, transferrin, bilirubin-binding proteins
• Proteins as defense proteins

  • clotting proteins, immunoglobulins
• Proteins

  • Many serve as enzymes that catalyze reactions
  • Some transport different compounds either outside or inside cells
  • Some act as storage proteins
  • Some act as defense proteins
  • Some act as contractile proteins
  • Some are merely structural in nature
• Importance of Water in the Cell

  • Water sustains life due to its chemical and physical properties
  • Water is a polar molecule and the solvent of life
  • Water is the transport medium in the blood
  • Water acts as a medium for biochemical reactions
  • Water helps in maintaining a stable internal environment within a living organism
  • Water helps in lubrication
  • Water molecules have very high cohesion
  • Water molecules tend to stick to each other and move in long unbroken columns through the vascular tissues in plants
• Ninety-nine percent of the molecules inside living cells are water molecules
• Flow of information from nucleic acids to protein

  1. DNA —> mRNA —> tRNA —> rRNA —> protein

  2. The nucleotide sequence in a gene of DNA specifies the assembly of a nucleotide sequence in an mRNA molecule, which in turn directs the assembly of the amino acid sequence in protein through a tRNA and rRNA molecule
• Types of Biomolecules

  • Digestive
  • Transport
  • Structural
  • Hormones
  • Defense
  • Contractile
  • Storage
• Transport Proteins


  • Hemoglobin
  • Albumin
• Hormones


  • Insulin
  • Thyroxine
• Contractile Proteins


  • Actin
  • Myosin
• Function of Digestive Enzymes

  Help in digestion of food by catabolizing nutrients into monomeric units
• Function of Defense Proteins

  Protect the body from foreign pathogens