biological molecules

• all biological molecules

  • lipids
  • carbohydrates
  • nucleic acids
  • water
  • proteins
• condensation reaction

  when polymers are formed, it results in water being released (monomer to polymer)
• hydrolysis reaction

  when polymers split into shorter chains, they need the addition of water (polymer to monomer)
• metabolism


  the sum of all chemical reactions that take place in the body
• monosaccherides


  sweet tasting, soluble substance with formula (CH2O)n n=(3-7)

  examples:

  glucose

  galactose

  fructose
• isomers


  molecules with same molecular formula, but with atoms connected in a different way

  a glucose

  b glucose
• disaccherides


  glucose + glucose = maltose

  glucose + fructose = sucrose

  glucose + galactose = lactose
• starch

  • a glucose monomers linked by glycosidic bonds, formed by condensation reaction
  • chain of a glucose wound into tight coil
  • found in plants as starch grains, in seeds and storage organs
  • insoluble - doesnt draw in water
  • compact - fits in small spaces
  • easily hydrolysed to a glucose, so can be used in respiration
• glycogen

  • a glucose monomers
  • shorter chains, highly branched
  • easily hydrolysed due to shorter chains
• cellulose

  • b glucose monomers
  • to form glycosidic bonds, each molecule is rotated 180 degrees compared to one next to it
  • straight, unbranched chains that run parallel
  • hydrogen bonds link chains to make it strong
  • good structual material
  • group to form microfibril fibres
  • prevent cells from bursting, so are turgid when full of water. helps support stems
• main lipid groups

  triglycerides

  phospholipids
• roles of lipids

  • phospholipids contribute to flexibility of membranes and transfer of lipid soluble substances across them.
  • source of energy
  • waterproofing
  • insulation
  • protection
• lipids as source of energy


  when oxidised, lipids provide over twice the energy as the same mass of carbohydrate
• lipids for waterproofing


  plants and insects have waxy, lipid cuticles that conserve water.

  mammals produce an oily secretion from the sabaccous glands in the skin
• lipids for insulation


  slow heat conductors. stored beneath bpdy to retain heat. act as electrical inulators in myelin sheath around nerve cells
• lipids for protection


  fat often stored around delicate organs such as the kidney
• properties of triglycerides

  • have 3 fatty acids combined with glycerol
  • each fatty acid forms an ester bond with glycerol in a condensation reaction
  • hydrolysis of triglyceride produces glycerol and 3 fatty acids
  • glycerol molecule in all triglycerides is the same
  • over 70 different fatty acids and all have a carboxyl group with hydrocarbon chain attatched
  • either saturated, monounsaturated or polyunsaturated
• saturated fatty acid chain


  no carbon-carbon double bonds
• monounsaturated fatty acid chain


  single double bond
• polyunsaturated fatty acid chain


  more than one double bond
• structure of triglycerides

  • high ratio of energy storing carbon - hydrogen bonds to carbon atoms - good source of energy
  • low mass to energy ratio - good storage molecule as much energy can be stored in small volume
  • large, non-polar molecules so insolube in water. their storage doesnt affect osmosis in cells or their water potential
  • high ration of hydrogen to oxygen atoms, release water when oxidised
• properties of phospholipids

  • one of fatty acid molecules replaced by phosphate molecule
  • hydrophilic
  • hydrophilic head - repels fat
  • hydrophobic tail - mixes reasily with fat
• structure of phospholipids

  • polar - form bilayer within cell-surface membrane in an aqueous environment. a hydrophobic barrier form between inside and outside of cell
  • heads help to hold at surface of membrane
  • structure allows them to form glycolipids by combining with carbohydrates in membrane. important in cell recognition
• lipids are stored in...

  adipose tissue
• lipids have...

  ester bonds
• properties of proteins

  • large molecules
  • vary in shape
  • enzymes (group of proteins) involved in almost every living process
• structure of amino acid


  basic monomer units. combine to make a polymer, polypeptide. polypeptides combine to form proteins. every amino acid has a central atom to which are attatched 4 chemical groups:

  • amino group (-NH2)
  • carboxyl group (-COOH)
  • hydrogen atom (-H)
  • R group (different in every amino acid)
• amino acid structure

  
• formation of peptide bond

  amino acid monomers combine into dipeptide. bond forms between carboxyl group of one amino acid to the amino group of another in a condensation reaction between OH and H. bond can be broken by hydrolysis
• primary structure of polypeptides

  • amino acid monomers joined through polymerisation (sequence of amino acids). forms chain called a polypeptide. forms primary structure of any protein.
  • sequence determined by DNA. limitless types of primary protein structure
  • structure determines shape, therefore the function
• secondary structure of proteins

  • amino acids that make up polypeptide possess amino groups and carboxyl groups
  • hydrogen of amino group has positive charge, oxygen of carboxyl group has negative charge, so both readily form weak hydrogen bonds.
  • bonds cause the long peptide chain to be twisted into 3D shape (a-helix or b-sheet)


  .
• tertiary structure of proteins


  interaction between R groups

  structure maintained by different bonds, depending on primary structure of protein:

  • disulphide (covalent) bridges - fairly strong, not easily broken
  • ionic bonds - formed between any carboxyl and amino acid groups not involved in forming peptide bonds, easily broken by pH changes
  • hydrogen bonds - numerous, easily broken
• quarternary structure of proteins 


  several polypeptide chains bonded together.
• anabolic reactions 


  reactions that build up molecules
• catabolic reaction


  reactions that break down molecules
• metabolic pathway


  sequence of enzyme controlled reactions
• specificity 


  only able to catalyse specific reaction
• extracellular


  an enzyme that is secreted by a cell and functions outside of that cell
• intracellular 


  an enzyme that functions within the cell it was produced
• enzyme-substrate complex


  substrate joins active site