CONCEPT 2. The molecules of life

• What is the monomer of carbohydrates?

  Monosaccharide
• What is the function of carbohydrates?

  Store chemical energy and form structural components
• What is the general formula of carbohydrates?

  (CH2O)n
• How are carbohydrates joined together?


  Glycosidic bonds/ether links formed between the hydroxyl group from one carbon atom and the hydroxyl or amine group of another.
• What kind of reaction are glycosidic reactions an example of?

  Condensation reaction, where water is released as a result of the formation of a covalent bond.
• Examples of monosaccharides: glucose and fructose
• Example of disaccharides: lactose and sucrose
• Examples of polysaccharides: starch, glycogen and cellulose
• Features of starch: sugar storage in plants. Made up of alpha glucose, containing α 1-4 and α 1-6 glycosidic links. Capable of forming branches which can be used for energy and is easily digested.
• Features of cellulose. structural polysaccharide in plants. Made up of beta glucose, containing β 1-4 glycosidic bonds. It is a linear molecule and capable of forming fibrils through the hydrogen bonding of hydroxyl groups providing strength for a cell wall.
• Features of glycogen. composed of glucose and used as energy storage in animals, fungi and bacteria. It forms more branches than starch meaning it contains more bonds that store energy.
• What is the monomer of a nucleic acid?

  Nucleotide
• What are the components of a nucleotide?

  A) Phosphate group

  B) pentose sugar

  C) nitrogen containing base

  
• How are nucleic acids joined together?

  Phosphodiester bonds which are formed through a condensation reaction where hydroxyl groups condense between 5' carbon and 3' carbon, releasing water.
• How are complementary base pairs joined together?

  Hydrogen bonds
• DNA.

  • Sugar: Deoxyribose
  • Purines (double ringed): Adenine, Guanine
  • Pyrimidines (single ringed): Cytosine, Thymine
  • Structure: double helix, long and linear chain
• RNA.

  • Sugar: Ribose
  • Purines (double ringed): Adenine, Guanine
  • Pyrimidines (single ringed): Uracil, Cytosine
  • Structure: single stranded, bases are able to fold over themselves
• What types of RNA are there?

  mRNA: used to make copies of DNA

  tRNA (transfer): interact with amino acids during protein synthesis

  rRNA (ribosomal): structural, allows formation of ribosomes
• What is the monomer of proteins?

  Amino acids
• What is the structure of amino acids?

  A) R group side chain

  B) Carboxyl group

  C) Animo Group

  D) Hydrogen

  E) central carbon

  
• What is the significance of the R groups/side chains?

  Determine intermolecular forces the molecule is able to form.

  • Non-polar (hydrophobic) = dispersion force
  • Polar and charged (hydrophilic) = ionic interactions
  • Polar and uncharged (hydrophilic) = dipole-dipole interactions or hydrogen bonds
• How are amino acids joined together?

  Through peptide bonds, formed through a condensation reaction where the carboxyl and amino group are condensed and water is released.
• What is the primary structure of a protein?

  Linear sequence of amino acids of the polypeptide chain. Stabilised by peptide bonds.
• What is the secondary structure of a protein?

  Refers to the local folding of the polypeptide chain, forming alpha helixes and beta pleated sheets through hydrogen bonds.
• What is the tertiary structure of proteins?

  Refers to the overall 3D functional shape of the polypeptide chain, achieved by intermolecular forces including hydrogen bonds, disulphide bonds, hydrophobic interactions and ionic bonds.
• What is the quaternary structure of proteins?

  The overall 3D function shape of two or more polypeptide chains, forming a large protein molecule.
• What are the characteristics of lipids?

  Generally hydrophobic, nonpolar molecules that function as energy storage and assist in cell structure
• What are lipids composed of? Carbon, hydrogen and little oxygen
• What can lipids dissolve in?

  Insoluble in water as it is non-polar but can be dissolved in organic, non-polar solvents.
• What are the three key lipids?

  Triglycerides, phospholipids, steroids
• What is the function of triglycerides?

  Includes fats and oils, triglycerides are high energy molecules used for long term energy storage. They are formed through a condensation reaction between the hydroxyl group of glycerol and a fatty acid chain, releasing water and creating an ether link.
• What is the difference between a saturated and unsaturated triglyceride?

  In a saturated triglyceride, only single covalent bonds are formed with carbon, thus can be more compact than unsaturated fats where there are one or more double bonds with carbon, causing kinks.
• What does it mean to be amphipathic?

  Having both hydrophilic and hydrophobic regions
• Features of phospholipids

  • Amphipathic: polar head and non polar tails
  • Head and tails are attached by ether bonds
  • Tails can be unsaturated or saturated
• How does saturation of lipid tails impact membrane fluidity?

  Saturated fats make membranes more rigid as they can compact in comparison to unsaturated tails which increases the fluidity of the plasma membrane, kinks pushing other tails away.
• How does cholesterol affect membrane fluidity?

  This steroid reduces membrane fluidity, its head anchoring between phosphate heads and its body pulling fatty acids together
• What is hydrolysis?

  Chemical reaction that breaks down a compound by adding water.