Macromolecules

• Biological molecules are composed of subunits (monomers) that are linked to each other to from polymers
• Dehydration reaction aka condensation:

  • two monomers are joined through covalent bonds to form a polymer
  • requires energy
  • loss of water during the reaction
• Hydrolysis (the reverse of condensation):

  • digest polymers and produce monomers
  • covalent bonds are broken and energy is released
  • water is required in the process
• Four types of macromolecules:

  • carbohydrates
  • lipids
  • proteins
  • nucleic acids
• Carbohydrates aka sugars:

  • molecules that contain C, H and O
  • present in most food we eat
  • primary role is for energy storage through breaking H-C bonds
• Carbohydrates differ in complexity. The three types are monosaccharides, disaccharides and polysaccharides
• Polysaccharides are large chains of monosaccharides:

  • storage and most complex carbohydrate
  • they are broken down into simpler carbohydrates through food catabolism
• Polysaccharide examples:

  • starch: made by plants by converting excess glucose
  • glycogen: store excess glucose in humans
  • cellulose: structural material for plant cell walls
  • chitin: structural material found in arthropods and and fungi
• Disaccharides are 2 monosaccharides linked together

  • less readily broken down because they are short term storage
  • often in this form when transported in plants
  • must be digested or broken down into simpler carbohydrates before being absorbed by the cell
• Disaccharide examples:

  • glucose and fructose = sucrose
  • glucose and galactose = lactose
  • glucose and glucose = maltose
• Monosaccharides are the simple sugars

  • simplest carbohydrates and monomer of more complex sugars
  • carbohydrate found in fruit
  • absorbable form
• Monosaccharide examples

  • glucose
  • galactose
  • fructose
• Liver cells convert fructose and galactose into glucose before being absorbed by the cell
• Carbohydrates, particularly glucose, are the main energy source for cells through catabolism (carbohydrate metabolism). If there is not enough glucose, proteins and lipids can be used as an energy source