Biology 🌺

• Carbon

  All life is based around carbon, which is able to combine with many other elements to form a large number of carbon-based (or organic) molecules
• Forms of pure carbon

  • coal
  • diamond
  • graphite
  • fullerenes
• Carbon bonding

  The four valence electrons allow carbon to form single, double, or triple covalent bonds with other carbon atoms
• Organic Molecules

  • Phospholipid
  • Epinephrine
  • Proline
  • Alanine
  • Creatine
• Water is essential for life. It is the medium in which the reactions of life take place
• Water


  The most important feature of the chemical behaviour of water is its dipole nature
• Water is called the universal solvent as a large range of compounds dissolve in it
• When sodium chloride (NaCl) is added to water

  The negative oxygen is attracted to the sodium ions, while the positive hydrogens are attracted to the negative chloride ions
• Functional Groups

  Have definite chemical properties that they retain no matter where they occur
• Functional groups determine

  The characteristics and chemical reactivity of molecules
• Most chemical reactions that occur in organisms involve the transfer of a functional group as an intact unit from one molecule to another
• Hydrogen Bonds

  Involve at least one hydrogen atom covalently linked to an electronegative atom, attracted to another electronegative atom (often oxygen or nitrogen atoms)
• Formation of a water dimer

  Example of hydrogen bonding where a water molecule has a slight positive charge on the hydrogens and a slight negative charge on the oxygen, resulting in electrical attraction between molecules and formation of a hydrogen bond
• Biological importance of hydrogen bonding

  • Formation of proteins and nucleic acids (e.g. DNA)
• Water dimer formation

  Forms by hydrogen bonding between the positive and negative charges of two water molecules
• Biological Properties of Water

  • Ice is less dense than water
  • High surface tension
  • Low viscosity
  • Liquid at room temperature
  • Colourless with high transmission of visible light
  • Strong cohesive properties and high tensile strength
  • High latent heat of fusion
  • High latent heat of vaporization
  • High specific heat capacity
  • Ability to dissolve many substances (universal solvent)
• Significance of water properties for life

  • Ice floats and insulates underlying water
  • Water forms droplets and runs off surfaces
  • Water flows through small spaces and capillaries
  • Liquid medium for aquatic life and inside cells
  • Light penetrates tissue and aquatic environments
  • Water can be lifted and does not pull apart easily
  • Cell contents are unlikely to freeze
  • Heat is lost by evaporation
  • Thermally stable aquatic environments
  • Medium for chemical reactions and transport in organisms
• Carbohydrates

  Family of organic molecules made up of carbon, hydrogen, and oxygen atoms, with some being small, simple molecules and others forming long polymers
• Simple carbohydrates

  Also known as sugars, with common arrangements being pentose (e.g., ribose and deoxyribose) and hexose (e.g., glucose and fructose), which naturally form rings in solution
• Monosaccharides

  • Primary energy sources for cellular metabolism, including glucose and fructose, generally containing between three and seven carbon atoms in their chains
• Monosaccharides


  Single-sugar molecules containing between three and seven carbon atoms in their carbon chains
• Monosaccharides

  • Glucose (grape sugar and blood sugar)
  • Fructose (honey and fruit juices)
• Monosaccharides


  Reducing sugars that can participate in reduction reactions
• Glucose is a monosaccharide sugar occurring in L- and D- forms. D-glucose can be utilized by cells while the L-form cannot
• Disaccharides

  Double-sugar molecules joined with a glycosidic bond, used as energy sources and building blocks for larger molecules
• Formation of disaccharides

  Depends on the monomers involved and whether they are in their α- or β- form
• Only a few disaccharides, like lactose, are classified as reducing sugars
• Disaccharides provide a convenient way to transport glucose
• Carbohydrate Isomers

  Compounds with the same chemical formula but different arrangement of atoms
• Structural isomers have atoms linked in a different sequence, leading to different properties in resulting polymers like starch and cellulose
• Optical isomers


  Identical in every way but are mirror images of each other
• Condensation & Hydrolysis


  Monosaccharides joined to form disaccharides and polysaccharides, with water released in the process
• Carbohydrate condensation

  Compound sugars broken down into constituent monosaccharides with the help of water and enzymes
• Carbohydrate hydrolysis

  Breaking down compound sugars into constituent monosaccharides with the help of water and enzymes
• Cellulose is a glucose polymer, an important structural material in plants, made up of unbranched chains of β-glucose molecules joined by 1,4 glycosidic links
• Cellulose microfibrils are very strong and form a major structural component of plant cells, like in the cell wall
• Starch is a polymer of glucose, made up of long chains of α-glucose molecules
• Cellulose


  Repeating chains of β-glucose molecules
• Cellulose


  • 1,4 glycosidic bonds create unbranched chains
• Amylopectin


  Starch polymer made up of long chains of α-glucose molecules