Biological molecules

• Elements found in carbohydrates

  • Carbon
  • Oxygen
  • Hydrogen
• Elements found in lipids

  • Carbon
  • Hydrogen
  • Oxygen
• Elements found in proteins

  • Carbon
  • Sulfur
  • Oxygen
  • Hydrogen
  • Nitrogen
• Elements found in nitric acids

  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
  • Phosphorus
• Water


  One of the most useful molecules for life
• Uses of water in cells

  • Reactant in processes like photosynthesis and hydrolysis
  • Provides structural support
  • Helps maintain optimal body temperature
• Properties of water

  • High heat capacity
  • High heat of vaporization
  • Cohesive properties
  • Good solvent
• Water makes up 60-70% of the human body
• Life evolved in an environment where water was abundant
• Structure of water molecule

  Made from one oxygen atom and two hydrogen atoms
• Polarity of water

  Oxygen atoms are slightly negatively charged, hydrogen atoms are slightly positively charged
• Hydrogen bonding

  Attraction between hydrogen atoms on one water molecule and oxygen atoms on another water molecule
• Water in metabolic reactions

  1. Used in hydrolysis reactions

  2. Released in condensation reactions
• Water has a high heat of vaporization, requiring a lot of energy to evaporate
• Water has a high heat capacity, taking a long time to heat and cool
• Water as a solvent

  Ions and polar molecules can easily dissolve in water
• Cohesive properties of water

  Strong attraction between water molecules due to hydrogen bonding, creating surface tension
• Water provides a stable habitat for many species
• Monomers


  Single subunits, or building blocks of life e.g. amino acids, nucleotides and monosaccharides
• Polymers


  Formed by combining monomers using covalent bonds, complex molecules e.g. protein, DNA, starch
• Condensation reactions

  1. Formation of larger, biological molecules (polymers) from smaller molecules (monomers)

  2. Byproduct is water
• Formation

  1. Smaller, biological molecules (e.g. sugars) in an organism's cells can form larger molecules (e.g. carbohydrates) that can be used around the body

  2. These biological molecules are important to allow the organism to survive
• Condensation


  • Reaction that forms large, biological molecules
  • Releases water and bonds smaller components together into larger molecules
• Products of condensation

  • Condensation of amino acids produces proteins
  • Condensation of two monosaccharides produces disaccharides
  • Many disaccharides form polysaccharides
  • Condensation of fatty acids and monoglycerides produces lipids

  
• Hydrolysis reactions

  • Break down of large, biological molecules into smaller molecules
  • Smaller molecules can then be taken up by cells and used for functions
• Process of hydrolysis

  1. Reaction requires water and splits larger molecules into their smaller components

  2. Smaller molecules like glucose can easily diffuse into cells or be transported using protein channels
• Products of hydrolysis

  • Hydrolysis of protein produces amino acids
  • Hydrolysis of carbohydrates produces disaccharides and monosaccharides
  • Hydrolysis of lipids produces fatty acids and monoglycerides

  
• Carbohydrates


  • Made from carbon, hydrogen and oxygen atoms
  • Made from monosaccharides, which are simple sugars containing three to seven carbon atoms
• Glucose

  • Hexose sugar with chemical formula C6H12O6
  • Important source of energy in humans
  • During cellular respiration, energy released from glucose helps make ATP
• Alpha vs beta glucose


  • Isomers with same molecular formula but different arrangement of atoms in space
  • Carbon atoms numbered 1-6 and OH groups in different orientations around C1

  
• Hexose vs pentose sugars

  • Glucose is a hexose sugar with 6 carbon atoms
  • Pentose sugars have 5 carbon atoms, e.g. ribose which is a component of RNA

  
• Disaccharides

  • Formed when two monosaccharides join via condensation reaction
  • Examples: maltose (glucose + glucose), sucrose (glucose + fructose), lactose (glucose + galactose)
• Polysaccharides


  • Formed when more than two monosaccharides join together
  • Made up of two or more monosaccharides joined by glycosidic bonds
  • Chain may be branched or unbranched, and contain different types of monosaccharides
  • Examples: starch, glycogen, cellulose, chitin
• Glycosidic bonds

  • Formed when -OH groups from neighbouring monosaccharides undergo condensation, releasing water
  • To break glycosidic bond, reverse reaction occurs (hydrolysis) and water is added
• Starch

  • Polysaccharide formed by condensation of alpha-glucose
  • Main energy storage material in plants
  • Broken down into glucose when plants need more energy
  • Can act as food source for humans and animals
  • Doesn't change water potential as insoluble in water
  • Made up of amylopectin and amylose
• Amylopectin


  Highly branched chain of alpha-glucose, allows easy access for enzymes to release glucose
• Amylose


  Linear chain of alpha-glucose with helical structure, good for storage
• Iodine test for starch

  Add iodine to sample, solution turns blue-black if starch is present
• Glycogen

  • Formed by condensation of alpha-glucose, main energy storage material in animals
  • Highly branched structure allows fast release of glucose when needed
  • Compact storage molecule
• Cellulose

  • Main component of plant cell walls
  • Long chain of beta-glucose linked by glycosidic bonds
  • Microfibrils made of many cellulose chains held together by hydrogen bonds
  • Most abundant natural polymer
  • Provides structural support to plant cells
  • Cannot be broken down by human digestive enzymes