chemistry of life

• Molecules are very important in biology
• Key biological molecules


  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic acids
  • Water
• Water makes up 55-60% of an adult human's body weight, and up to 90% in some organisms
• Muscles and kidneys are about 79% water, and even bones are 31% water
• If all the water was removed from the human body, what would be left are proteins, lipids, carbohydrates and nucleic acids
• Carbohydrates and lipids


  Made of carbon, hydrogen and oxygen
• Proteins


  Made of carbon, hydrogen, oxygen, nitrogen and sometimes sulfur
• Types of carbohydrates


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Monosaccharides


  Simple sugars like glucose and fructose
• Disaccharides


  Made up of two simple sugars joined together, like sucrose
• Polysaccharides


  Polymers made up of many sugars joined together, like starch, glycogen and cellulose
• Starch


  • Storage unit for surplus glucose made in photosynthesis
  • Tested for using iodine solution which turns blue-black in its presence
• Glycogen


  • Storage unit for surplus glucose used by animals
  • Found in liver and muscle tissues
• Cellulose


  • Found in plant cell walls
• Proteins


  • Polymers made up of amino acids
  • Fold into complex 3D shapes held together by weak bonds
• Enzymes


  • Proteins that catalyse chemical reactions
  • Denature and lose their structure above certain temperatures
• There are 20 different amino acids that make up proteins
• It is estimated there are about 50,000 different proteins in the human body
• Functions of proteins


  • In cell membranes controlling substance movement
  • As enzymes in photosynthesis, respiration, DNA copying, digestion
  • As hormones like insulin, estrogen, testosterone
  • As antibodies fighting infection
• Lipids


  Many are triglycerides with a glycerol molecule and three fatty acid tails
• Triglycerides are a form of dietary fat found in meats, dairy and cooking oils, and also made by the liver
• Cells and tissues use triglycerides for energy or store them as fat
• Water has unique properties due to its polar nature, including high surface tension, cohesion, adhesion, and solubility.
• Water has unique properties due to its polar nature, including high surface tension, cohesion, adhesion, and viscosity.
• Hydrophobic interactions are non-specific attractions between nonpolar molecules or regions of molecules that exclude water from their vicinity.
• Hydrophobic interactions are non-specific attractions between nonpolar molecules or parts of molecules that exclude water from their surfaces.
• The polarity of water allows it to dissolve many substances that cannot be dissolved in nonpolar liquids such as oil.
• Polar covalent bonds between atoms can lead to hydrogen bonding, which plays an important role in biological systems.
• The hydrogen bond is an electrostatic interaction between a positively charged hydrogen atom and a negatively charged oxygen or nitrogen atom.
• Water plays an important role in maintaining homeostasis within cells and organisms.
• Water is essential for all living organisms because it serves as a medium for chemical reactions, helps regulate body temperature, acts as a lubricant, and provides structural support.
• Hydrophobic interactions occur when nonpolar groups repel one another, leading to clustering of these groups together.
• Ionic bonds occur when there is a complete transfer of electrons from one atom to another, resulting in oppositely charged ions.
• Ionic bonds occur when there is a complete transfer of electrons from one atom to another, resulting in oppositely charged ions held together by strong electrostatic forces.
• Ionic compounds have strong electrostatic forces of attraction between oppositely charged ions.
• The hydrogen bond is an electrostatic attraction between a partially positive hydrogen atom on one molecule and a partially negative oxygen or nitrogen atom on another molecule.
• Polar covalent bonds form when electrons are shared unequally between atoms, resulting in partial positive (+) and negative (-) charges on the bonded atoms.
• Metals form positive ions by losing electrons, while nonmetals form negative ions by gaining electrons.
• Ionic compounds consist of positively charged metal ions (cations) and negatively charged nonmetal ions (anions), held together by electrostatic forces.