BIOMOLECULES - Water

• Water


  The most abundant chemical in the body
• Water


  • Moves fast and can squeeze into tiny crevasses between other molecules
• 1/2 to 3/4 of the human body consists of water
• Functions of water in the body

  • Carries nutrients to cells and carries waste from body
  • Regulates body temperature
  • Dissolves vitamins, minerals, amino acids and other nutrients
  • Lubricates joints
• It is recommended that teens drink 6-8 glasses (8 fl.oz each) of water each day, in addition to around 4 cups of water from food each day
• Water is essential for all living organisms
• Water plays a key role in the distribution of organisms in the biosphere, desert contain less water and therefore have few species while rain forest have numerous species and are full of life
• Water is used in various metabolic reactions
• The amount of water is kept constant through water cycle
• 75% of the earth's surface is water
• Water


  • Acts as a solvent for many types of solutes
  • Creates a slightly negative oxygen and a slightly positive hydrogen
  • Allows formation of hydrogen bonds
• The chemical formula of water is H2O
• Water


  • Can act as either an acid or a base, maintaining a stable pH in our bodies
  • Absorbs and releases heat energy slowly, and can hold a great deal of heat energy, helping organisms maintain their body temperature in the safe range
• Polar molecule


  Molecule in which electrons are shared unevenly between atoms, causing each end of the molecule to have a slight charge
• Water is essential for life
• Two-thirds of our body is made up of water
• Water is the main component of blood, lymph and digestive secretions, as well as all other liquid parts of the body
• Water is made up of hydrogen and oxygen molecules in the ratio 2:1
• Water


  • Colourless, odourless and tasteless liquid
  • Boils at 100°C and freezes at 0°C
  • Neutral pH of 7
  • Excellent solvent capable of dissolving a number of substances
  • Exists in three states: solid (ice), liquid (water), and gas (steam)
  • Able to absorb heat and maintain it
• Sources of water


  • Tap/bottled water
  • Beverages such as tea and coffee
  • Fruit and vegetables
  • All foods contain a certain amount of water
• Functions of water


  • Transporting nutrients, oxygen, enzymes and hormones around the body
  • Removal of waste products from the body, e.g. from the kidneys
  • Quenches thirst
  • Contains the minerals calcium and fluorine
  • Controls body temperature through perspiration
  • Significant in the hydrolysis of nutrients during digestion
  • Essential element of all body fluids and tissues
• The recommended daily amount of water is between 2 and 3 litres per day
• Acid


  A substance which, when dissolved in water, releases protons
• Strength of an acid

  The extent of dissociation, that is, the amount of protons released compared to the total amount of compound
• Acidity


  Measured on a pH scale, the negative logarithm of the hydrogen ion concentration
• Acid


  A substance that releases hydrogen ions (H+ or protons) when added to water
• Hydrogen ion


  Called a proton (H+ ions)
• Acids


  Called proton donors because they produce H+ ions
• Weak acid


  Substances that dissociate poorly in water, releasing protons but only a small fraction of their molecules dissociate (ionize)
• While 1 M HCl is pH = 0, 1 M acetic acid is only pH = 2.4
• Weak acid


  Have only a modest tendency to shed their protons
• Water


  A very weak acid
• At equilibrium, [H+] = [OH-] = 0.0000001 M = 10-7 M = pH 7
• Only two of every 10^9 (1 billion) molecules in pure water are ionized at any instant
• Base


  A substance that releases OH- or hydroxyl ions when added to water OR an ion that combines with H+ ions
• Bases


  Produce negatively charged OH- or hydroxyl ions
• Basic solutions


  Also called alkaline
• Bases


  Called proton acceptors because they take up hydrogen ions
• When this occurs water is formed
• Salt


  A compound produced by a reaction between an acid and a base