Biological molecules

• How does water being polar relate to its function ?

  Transport ions/other polar substances easily as they can dissolve in solution.

  Solutes can dissolve/ reactions can occur in cytoplasm.
• Why is ice less dense than water ?

  the orientation of hydrogen bonds causes molecules to push farther apart, which lowers the density.
• Name the 5 properties of water

  1. Polar
  2. Adhesive
  3. Cohesive
  4. High specific heat capacity
  5. Hydrogen bonds
• What functions does water have due to cohesion ?

  Habitat - small insects can walk across the surface due to surface tension

  Cohesion - water can travel up the xylem
• What is the difference between alpha and beta glucose ?

  The orientation of the OH group on the carbon 1. (OH is above in beta and below in alpha )
• Name 4 monosaccharides ?

  Glucose, ribose, galactose and fructose
• Name a non-reducing sugar ?

  Sucrose
• What is the bond in a disaccharide?

  Glycosidic
• What type of reaction forms disaccharides/polysaccharides ?

  Condensation
• Glucose + glucose = maltose
• Glucose and galactose = lactose
• Glucose and fructose = sucrose
• Polysaccharides are created by condensation reactions between many glucose monomers
• Which polysaccharides have alpha glucose as their monomer?

  Starch and glycogen
• What are the bonds between monomers in Starch?

  Amylose = 1-4 glycosidic

  Amylopectin = 1-6 glycosidic
• What are the bonds in cellulose ?

  1-4 glycosidic
• What are the bonds between monomers in glycogen ?

  1-4 and 1-6 glycosidic
• What is the function of starch ?

  Store of glucose in plants
• What is the function of cellulose ?

  Structural support in plants
• What is the function of glycogen?

  Store of glucose in animals
• Structures of polysaccharides

  Cellulose =long straight chain, held in parallel by H-bonds

  Amylose = unbranched helix

  Amylopectin = a branched molecule

  Glycogen = highly branched molecule.
• Advantages of 1-4 glycosidic bonds ?

  They are compact (plants can fit a lot of glucose in a small space )

  Many H-bonds which provide collective strength. (good for cell wall)
• Advantages of 1-6 glycosidic bonds ?

  Branching increases surface area, hydrolysis is rapid and it can be easily converted back to glucose if needed.

  (animals are able to run suddenly to protect themselves from predators)
• what are lipids in and why?

  organic solvents, they are non-polar molecules
• Uses of lipids:

  1. energy yield
  2. energy storage
  3. insulation
  4. hormonal communication
  5. Buoyancy
  6. Protection of organs
• What reaction forms lipids and what bond is formed between the fatty acid and glycerol ?

  esterfication reaction (condensation)

  ester bond
• Give an example of a saturated fatty acid ?

  Animal fat
• Give an example of an unsaturated fatty acid ?

  vegetable oils
• How many water molecules are released when triglyceride is formed?

  3 (one for every ester bond formed )
• What is the difference between phospholipids and triglycerides ?

  Triglyceride = 3 fatty acids chains

  Phospholipids = 2 fatty acid chains and phosphate head
• Why are phospholipids amphipathic?

  They have hydrophobic parts and hydrophilic parts.
• what do phospholipids form in presence of water?

  Bilayers
• Link triglycerides structure to their function:

  Energy storage - long carbon-hydrogen chains that release ATP when broken during respiration. - hydrophobic so do not cause osmotic water uptake therefore more can be stored

  Metabolic water source - when oxidised they release water, animals in the desert retain this water when no source is available.
• Which type of fatty acid will make a membrane more fluid?

  unsaturated fatty acid
• What is the function of cholesterol ?

  Controls the fluidity and permeability of membranes
• Why can cholesterol exist in the bilayer ?

  It has hydrophobic and hydrophilic regions.
• What is the structure of cholesterol ?

  4 carbon rings and OH group at one end
• why are triglycerides energy reserves ?

  they store more energy per gram due to their hydrocarbon chains
• protein Primary structure ?

  The order of amino acids in the polypeptide chain.
• What reaction forms polypeptides and what bond is formed?

  Condensation, peptide bond