nucleic acids

Question 1

describe the structure of DNA

Answer 1

-polymer of nucleotides
-each nucleotide formed from deoxyribose, a phosphate group and an nitrogenous base
-phosphodiester bonds between adjacent nucleotides
-2 strands held by hydrogens bonds
-hydrogen bonds between adenine, thymine and cytosine, guanine

Question 1

describe how the structure of DNA relates to its function

Answer 1

1.Sugar-phosphate backbone so provides strength
2. large molecule so can store lots of information
3. Helix so compact
4. base sequence codes for amino acids
5. Double stranded so strands can act as templates
6. Complementary base pairing (Adenine to thymine and guanine to cytosine) so accurate replication
7. Weak hydrogen bonds for so strands easily separated
8. Many weak hydrogen bonds so stable/strong molecule

Question 2

describe semi-conservative replication of DNA

Answer 2

1.DNA helicase breaks H bonds between the strands
2.Each stand acts as a template
3.Free DNA nucleotides attach by complementary base pairing (thymine and adenine or guanine and cytosine) with template by H bonds reforming
4.DNA polymerase joins up free adjacent nucleotides with
phosphodiester bonds in a condensation reaction.
5.New DNA molecule contains one old strand and one new
strand.

Question 3

Describe the reaction to hydrolyse ATP and the products of this reaction.

Answer 3

Hydrolysis of ATP to Adenosine diphosphate (ADP) and inorganic phosphate group (PI) catalysed by ATP hydrolase.

Question 4

Describe the reaction to synthesise an ATP molecule

Answer 4

Condensation of ADP and Pi catalysed by ATP synthase during respiration/photosynthesis
ATP is made up of Adenine, ribose and three phosphate

Question 5

describe why ATP is useful in biological processes

Answer 5

-releases energy in small amounts
-break single bond down in one step to release energy rapidly
-phosphorylates substances to make them more reactive
-can easily be reformed in one step

Question 6

describe two uses of ATP

Answer 6

-hydrolysis of ATP provides energy for active transport/protein synthesis/DNA replication
-hydrolysis of ATP provides an inorganic phosphate to phosphorylate a substance to make them more reactive

Question 7

explain the properties that make water important for organisms

Answer 7

1. a metabolite in condensation/hydrolysis reactions.
2. a solvent so allowing transport of substances
3. high specific heat capacity so buffers changes intemperature (takes a lot of heat energy to change temperature) .
4. large latent heat of vaporisation so provides cooling effect
5. cohesion (hydrogen bonding) so supports columns of water
6. cohesion (hydrogen bonding) so produces surface tension supporting small organisms.