Nucleic Acids

Question 1

What is the structure of nucleotides?

Answer 1

• A pentose sugar, phosphate group and an organic base joined by a condensation reaction
• Two nucleotides form a phosphodiester bond between the deoxyribose sugar of one nucleotide and the phosphate group of another

Question 2

What are the organic bases?

Answer 2

• Adenine
• Guanine
• Thymine
• Uracil
• Cytosine

Question 3

What is the structure of RNA?

Answer 3

• A single, short, polynucleotide chain where the pentose sugar is always ribose
• The bases include adenine, uracil, guanine and cytosine

Question 4

What is the structure of DNA?

Answer 4

• Two long polynucleotide strands joined together by hydrogen bonds between certain bases to form a double helix
• The pentose sugar is aways deoxyribose
• The bases include adenine, thymine, guanine and cytosine

Question 5

How is the DNA molecule adapted to carry out its function?

Answer 5

• Very stable so it can be passed down from generation to generation without change
• Two separate strands only held by hydrogen bonds so they can be separated
• Large molecule to carry large amount of genetic information

Question 6

What is the process of semi-conservative replication?

Answer 6

• DNA helicase breaks the hydrogen bonds between the base pairs of DNA
• This causes the double helix to separate into its two strands and unwind
• Each polynucleotide strand then acts as a template for which complementary free nucleotides are joined together by DNA polymerase which forms phosphodiester bonds
• Each of the new DNA strands contain one new strand and one old strand

Question 7

What is the structure of ATP?

Answer 7

• Adenine, which is an organic base
• Ribose, which is a pentose sugar
• A chain of three phosphate groups

Question 8

How does ATP release energy?

Answer 8

• Water is used to convert ATP into ADP in a hydrolysis reaction
• The bonds between the phosphate groups are unstable so there is a low activation energy
• So when the bonds break they release energy

Question 9

What is ATP used for?

Answer 9

• Metabolic processes
• Movement, provides the energy for muscle contraction
• Active transport

Question 10

How are water molecules bonded?

Answer 10

• Oxygen has a slight negative charge, which gives hydrogen a slight positive charge, making the molecule polar
• The negative pole of one water molecule attracts the positive pole of a different water molecule which forms a hydrogen bonds

Question 11

What are the properties of water?

Answer 11

• High specific heat capacity so acts as a buffer against sudden temperature changes
• High latent heat of vaporisation which makes evaporation of water as sweat an effective means of cooling
• Cohesion due to its hydrogen bonding so it can be pulled up through a tube
• Solvent