The importance of hydrogen bonds

Question 1

Restriction enzymes

Answer 1

Restriction endonucleases found in bacteria that cut DNA at specific base sequences, so can be used to cut out a desired gene from the rest of genome.

Question 2

Polymerase Chain Reaction

Answer 2

1) Strand separation - DNA heated at 95 degrees c for 5 minutes.
2) Mix with primers.
3) Annealing of primers - Mixture cooled to 55 degrees c.
4) Mix with free nucleotides and DNA polymerase.
5) DNA synthesis - Mixture heated to 70 degrees c (optimum for DNA polymerase)
6) Finish with 2 identical DNA molecules.
7) Repeats - With every cycle, the amount of DNA increases by 2x.

Question 3

Enzymes

Answer 3

Substrate that is complementary to enzymes active site attach by forming hydrogen bonds with one another - enzyme-substrate complexes.

High temperatures and acidic pHs will denature most enzymes by breaking the hydrogen bonds.

The hydrogen bonds in the enzymes tertiary structure determine its 3D shape. Otherwise, it’d be a defective, non-functioning enzyme/protein produced.

Question 4

Water transported up the xylem

Answer 4

1) Water evaporates from leaves.
2) Water molecules form hydrogen bonds between one another, stick together via cohesion.
3) Water forms continuous unbroken column.
4) As water evaporates in leaves, water molecules drawn up xylem as result of cohesion.
5) Column of water is therefore pulled up xylem by transpiration - transpiration stream.
6) Places xylem under negative pressure so there is tension within xylem - cohesion-tension theory.