Nucleic acids

Question 1

Describe a nucleotide

Answer 1

phosphate group, pentose sugar, nitrogen containing base

Question 2

difference between DNA and RNA

Answer 2

nucleotides: dna bases are ATCG and rna bases are AUCG. DNA has a deoxyribose sugar and RNA has a ribose sugar
Moleules : DNA forms double helix with hydrogen bonds between two polynucleotide strands (complementary base pairing), molecules of RNA form single polynucleotide strands and are shorter in length

Question 3

why does DNA need to replicate

Answer 3

DNA replication allows stem cells to divide to produce new cells, meaning that there is genetic continuity between generations of cells

Question 4

How did Meselson and Stahl provide evidence for semi-conservative replication?

Answer 4

They supplied heavy nitrogen (N15) to dividing bacteria so that all DNA made during replication contained (N15). They then switched to light nitrogen (N14) so that any new DNA made contained (N14). The result showed that new molecules produced during replication contained one strand containing (N15) and one containing (N14).

Question 5

What happens to an ATP molecule when energy is required by a cell?

Answer 5

A hydrolysis reaction catalysed by the enzyme ATP hydrolase breaks a phosphate bond to release energy. The products are ADP and Pi.

Question 6

State 5 important properties of water.

Answer 6

matabolite, good solvent, large latent heat of vapourisation (allows heat loss through evaporation)
high SHC, cohesive (important in plants)

Question 7

role of iron ions

Answer 7

prosthetic gorups in heamoglobin which bind to oxygen

Question 8

role of hydrogen ions

Answer 8

lower pH: ensures optimum pH for enzymes

Question 9

role of sodium ions

Answer 9

co transport of glucose in ileum

Question 10

role of phosphate ions

Answer 10

phosphate groups in DNA and RNA

Question 11

How are nucleotides joined together to form a polymer?

Answer 11

Phosphodiester bonds form between the phosphate group of one nucleotide and the pentose sugar of the next nucleotide as a result of condensation reactions.

Question 12

How does the process of semi-conservative replication take place?

Answer 12

Hydrogen bonds between the bases on polynucleotide strands are broken by DNA helicase, free DNA nucleotides are attracted to their complementary exposed bases, and the nucleotides are joined together by DNA polymerase to form a DNA molecule with one new strand and one original strand

Question 13

describe a molecule of ATP

Answer 13

adenine - ribose - three phosphate groups