biological molecules

• what is a monomer?


  small, single molecule, many of which can be joined together to form a polymer
• 2 glucose molecules join to form a disaccharide, what are the products of this reaction

  maltose + water
• 1 glucose molecule and 1 galactose molecule join to form a disaccharide, what are the products of this reaction

  lactose + water
• 1 glucose molecule and 1 fructose molecule join to form a disaccharide, what are the products of this reaction


  sucrose + water
• define a condensation reaction

  a condensation reaction joins monomers together and forms a chemical bond and released water
• define hydrolysis


  a hydrolysis reaction breaks a chemical bond between monomers and uses water
• describe a biochemical test to identify non-reducing sugars

  1. heat with acid (HCl) and neutralise (NaOH)

  2. heat with benedict's solution

  3. red precipitate
• A student carried out the Benedict's test. Suggest a method, other than using a colorimeter, that this student could use to measure the quantity of reducing sugar in a solution.

  1. filter + dry precipitate

  2. find mass/weight
• describe two differences between the structure of a cellulose molecule and a glycogen molecule

  1. cellulose is made up of beta-glucose and glycogen is made up of alpha glucose

  2. cellulose molecule has a straight chain and glycogen is branched
• describe and explain 2 features of starch that make it a good storage molecule

  1. insoluble so doesn't affect water potential

  2. branched/coiled - compact
• what is the test used to identify presence of starch

  iodine/potassium test
• describe the structure of glycogen

  1. polymer of α-glucose;

  2. (Joined by) glycosidic bonds

  3. Branched structure;
• how does glycogen act as a source of energy?

  1. hydrolysed (to glucose)

  2. glucose used in respiration
• what is the chemical bond that joins two monomers together called?

  glycosidic bond
• explain one way in which starch molecules are adapted for their function in plant cells

  1. insoluble

  2. doesn't affect water potential
• explain one way in which cellulose molecules are adapted for their function in plant cells

  1. long and straight chains

  2. become linked together by many hydrogen bonds to form fibrils

  3. provide strength (to cell wall)
• name the group represented by COOH in a lipid

  carboxyl
• describe the test for lipids

  1. add ethanol THEN add water AND shake

  2. white/milky emulsion
• describe how a triglyceride molecule is formed

  1. One glycerol and three fatty acids;

  2. Condensation (reactions) and removal of three molecules of water;

  3. Ester bond(s) (formed);
• describe how an ester bond is formed in a phospholipid molecule

  1. condensation (reaction)

  2. between glycerol and fatty acid
• name the type of bond between a glycerol and fatty acids in a triglyceride

  ester bond
• name the type of peptidase that will hydrolyse a peptide bond

  endo (peptidase)
• describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst

  1. substrate binds to active site (forming ESC)

  2. active site changes slightly to become complimentary to substrate

  3. reduces activation energy
• explain how a competitive inhibitor decreases the rate of an enzyme controlled reaction

  1. inhibitor is a similar shape to the substrate

  2. fits/binds to active site

  3. prevents/reduces enzyme-substrate complex forming
• describe how the structure of a protein depends on the amino acid it contains

  1. structure determined by position of amino acid

  2. primary structure is sequence of amino acid

  3. secondary structure formed by H bonding

  4. Tertiary structure formed by interactions between R groups

  5. creates active site in enzymes
• Explain how the active site of an enzyme causes a high rate of reaction.

  1. lowers Ea

  2. induced fit causes active site of enzyme to change shape

  3. enzyme-substrate complex causes bonds to form/break
• describe the test to check the presence of protein in a sample

  1. add biuret reagent

  2. positive result = purple/lilac/violet
• describe 2 ways in which all dipeptides are similar and 1 way in which they are different

  similarities:

  1. amine group at end

  2. all contain C,H,N and O

  
  

  differences:

  1. different R groups
• Describe how a non-competitive inhibitor can reduce the rate of an enzyme-controlled reaction.

  1. attaches to allosteric site

  2. changes shape of active site

  3. so active site +substrate are no longer complementary so no/less ESC formed
• describe how a peptide bond is formed between two amino acids to form a dipeptide

  1. condensation reaction

  2. between amine and carboxyl
• what is an unsaturated fatty acid?

  a fatty acid with at least one double bond between carbon atoms
• 2 glucose molecules join to form a disaccharide, what are the products of this reaction

  maltose + water
• what is a monomer?
• describe the structure of a monosaccharide

  • carbon backbone (3-6 carbons long)
  • one C double bonds with oxygen
  • other carbons bonded to one H and one OH
• How does alpha glucose differ from beta glucose?

  in alpha, OH is below C1, in beta OH is above C1

  (ABBA)
• what is meant by semi-quantitative testing 


  gives an indication on the concentration of sugar

  used for diagnostic testing in medicine
• describe the structure of amylose and amylopectin

  amylose - tightly coiled, unbranched chain of alpha glucose

  amylopectin - branched chain
• how are side branches beneficial to polysaccharides
• how are side branches beneficial to polysaccharides

  increased SA for enzymes to react so energy is released quicker
• how does the structure of a triglyceride relate to its properties

  • LONG HYDROCARBON TAILS - contain lots of energy which is released when broken down
  • INSOLUBLE - doesn't affect water potential so no osmosis
  • INSULATION - lipid around nerve cells = electrical insulator
  • BUOYANCY - less dense than water
  • PROTECTION - fat around organs = shock absorber