Nucleic Acids

Question 1

Differences between DNA and RNA

Answer 1

DNA has deoxyribose whereas RNA has ribose

DNA has thymine whereas RNA has uracil

DNA holds genetic info whereas RNA transfers genetic info to ribosomes for protein synthesis

DNA is a double helix whereas RNA is a short polynucleotide chain

Question 2

What holds nucleotides together

Answer 2

Phosphodiester bonds

Question 3

Why is DNA a stable molecule

Answer 3

Phosphodiester backbone protects the more chemically reactive nitrogen containing organic bases inside the double helix.

Hydrogen bonds form bridges between the phosphodiester uprights

Question 4

Process of semi-conservative replication

Answer 4

1. DNA helicase unwinds the the two strands of DNA by breaking hydrogen bonds between the complementary bases
2. One strand acts as a template and complementary base pairing occurs between the template strand and free nucleotides

3.DNA polymerase joins together the free nucleotides to the template stand by forming phosphodiester bonds.

Question 5

What is ATP and how does it work

Answer 5

Adenosine triphosphate ( Ribose, adenine and three phosphates). When ATP is hydrolysed to form ADP and P it releases energy. Energy that comes from the bonds between the phosphates.

Question 6

Uses of the products of ATP

Answer 6

The phosphate can be used to phosphorylate other compounds.

Question 7

Properties of ATP

Answer 7

Immediate source of energy

Isn’t stored

Used in metabolic process, active transport, secretion, movement and activation of molecules

Question 8

5 important properties of water and why

Answer 8

1. It is a metabolite so can be used in condensation and hydrolysis reactions to make or break bonds
2. It is a solvent that allows gases to diffuse readily
3. It has a high specific heat capacity. As water sticks together due to hydrogen bonds, a lot of energy is required to break them. It minimises temperature fluctuations, and can act as a buffer
4. Has a high latent heat of vaporisation, evaporation of water provides a cooling effect
5. Strong cohesion and tension between molecules enables effective transport of water in xylem

Question 9

Name and explain some essential ions

Answer 9

H+ which determine pH of substances

Fe3+ which is a component of haemoglobin

Na+ involved in co transport of glucose and amino acids

PO4 3- are component of ATP + DNA

Question 10

Where are inorganic ions found

Answer 10

In the cytoplasm and bodily fluids of organisms