06S7Acers {Midnight Blues}

06 March 2006

QUESTION 1

give the name of one molecule that could be: [3]molecule A - nucleic acid;; (DNA or RNA also accepted)
molecule B - amino acids;; (vitamins or chlorophyll also accepted)
molecule C - cellulose;;
Explain why molecule C is a good structural molecule whereas molecule D is only good for storage. [4]
Note: molecule C is cellulose and molecule D is amylose
Molecule C: each monomer rotated 180˚ wrt its neighbour; to form long straight chains; -OH groups sticking out to hydrogen bond with those of adjacent strand; giving rigid structure, tensile strength;
Molecule D: adjacent monomers form a 120˚ bond angle, causing the amylase molecule to coil up to form a compact structure occupying little space; large polysaccharide of many monoers, insoluble, thus not affecting water potential
State one way in which the structure of collagen differs from the structure of molecule C. [1]
Must give comparative statement!
Monomers being amino acids; in collagen but monomers are β-glucose; in molecule C (i.e. cellulose)
amino acid units joined by peptide bonds in collagen; but β-glucose units joined by glycosidic bonds in molecule C.
extended helix; in collagen but straight chains; of cellulose.

QUESTION 2

1. Name the parts labelled A and B. [2]
  A: glycerol;
  B: fatty acid;;
2. Name this type of lipid. [1]
  triglyceride;
3. Name the chemical reaction used to form the bonds between A and B. [1]
  condensation
1. State one function of this type of lipid in living organisms. [1]
  energy source or store;; insulation;; waterproofing;; protection;;
2. State one feature of the molecules of this type of lipid which makes them suitable for the function you have given. [1]
  High energy value;; insoluble;; poor conductor of heat;; hydrophobic;;

QUESTION 3

List two structural features represented in the diagram that are common to all enzymes. [2]
disulphide bonds formed between residues far apart on the polypeptide chain; ribonuclease is a globular protein.
presence of active site; which is a pocket or groove on the surface of the protein;
Use this information to describe why ribonuclease becomes inactive.
ref. mercaptoethanol breaks down disulphide bonds between as far apart on the polypeptide chain;
e.g. between residues 26 and 84, between residues 40 and 95, between residues 58 and 110, as well as between residues 65 and 72;
ref. loss of 3-dimensional conformation;
active site; no longer complementary; to sbustrate
cannot form enzyme-substrate complex;

QUESTION 1

give the name of one molecule that could be: [3]molecule A - nucleic acid;; (DNA or RNA also accepted)
molecule B - amino acids;; (vitamins or chlorophyll also accepted)
molecule C - cellulose;;
Explain why molecule C is a good structural molecule whereas molecule D is only good for storage. [4]
Note: molecule C is cellulose and molecule D is amylose
Molecule C: each monomer rotated 180˚ wrt its neighbour; to form long straight chains; -OH groups sticking out to hydrogen bond with those of adjacent strand; giving rigid structure, tensile strength;
Molecule D: adjacent monomers form a 120˚ bond angle, causing the amylase molecule to coil up to form a compact structure occupying little space; large polysaccharide of many monoers, insoluble, thus not affecting water potential
State one way in which the structure of collagen differs from the structure of molecule C. [1]
Must give comparative statement!
Monomers being amino acids; in collagen but monomers are β-glucose; in molecule C (i.e. cellulose)
amino acid units joined by peptide bonds in collagen; but β-glucose units joined by glycosidic bonds in molecule C.
extended helix; in collagen but straight chains; of cellulose.

QUESTION 2

1. Name the parts labelled A and B. [2]
  A: glycerol;
  B: fatty acid;;
2. Name this type of lipid. [1]
  triglyceride;
3. Name the chemical reaction used to form the bonds between A and B. [1]
  condensation
1. State one function of this type of lipid in living organisms. [1]
  energy source or store;; insulation;; waterproofing;; protection;;
2. State one feature of the molecules of this type of lipid which makes them suitable for the function you have given. [1]
  High energy value;; insoluble;; poor conductor of heat;; hydrophobic;;

QUESTION 3

List two structural features represented in the diagram that are common to all enzymes. [2]
disulphide bonds formed between residues far apart on the polypeptide chain; ribonuclease is a globular protein.
presence of active site; which is a pocket or groove on the surface of the protein;
Use this information to describe why ribonuclease becomes inactive.
ref. mercaptoethanol breaks down disulphide bonds between as far apart on the polypeptide chain;
e.g. between residues 26 and 84, between residues 40 and 95, between residues 58 and 110, as well as between residues 65 and 72;
ref. loss of 3-dimensional conformation;
active site; no longer complementary; to sbustrate
cannot form enzyme-substrate complex;