2.1 - 2.4 Nucleic acids

Question 1

What are the 2 types of nucleic acid?

Answer 1

Deoxyribonucleic Acid (DNA)
Ribonucleic Acid (RNA)

Question 2

Describe the structure of a DNA nucleotide

Answer 2

• Phosphate
• Deoxyribose sugar
• Nitrogenous base

Question 3

Name the 4 DNA bases

Answer 3

Adenine
Thymine
Guanine
Cytosine

Question 4

Describe the structure of an RNA nucleotide

Answer 4

• Phosphate
• Ribose sugar
• Nitrogenous base

Question 5

Name the 4 RNA bases

Answer 5

Adenine
Uracil
Guanine
Cytosine

Question 6

What is the structure of DNA?

Answer 6

• Double helix
• Anti-parallel nucleotide strands
• Complementary base pairing
• Phosphodiester bond between the 5’ carbon of one nucleotide and the 3’ carbon of another
• Hydrogen bonding holding DNA strands together

Question 7

Name the complimentary base pairs

Answer 7

Adenine - Thymine
Cytosine - Guanine

Question 8

What is the function of DNA?

Answer 8

• Store genetic information
• Allow protein synthesis
• Allows genetic info to pass from cell to cell and generation to generation

Question 9

Describe the process of DNA replication

Answer 9

1. DNA Helicase unszips the two strands by breaking the hydrogen bonds between the complementary base pairs. This allows each strand to act as a template.
2. Free DNA nucleotides align with their complementary base pair on the exposed strands. They attach via hydrogen bonds (A with T, C with G)
3. DNA Polymerase joins adjacent nucleoides together in a condensation reaction. This forms a phosphodiester bond between nucleotides.
4. Each DNA molecule now has one new strand and one original strand. Therefore this process is called semi-conservative replication.

Question 10

Describe how DNA’s sugar-phosphate backbone contributes to its function

Answer 10

Provides strength/stability to molecule

Question 11

Describe how DNA’s length contributes to its function

Answer 11

Long so can store lots of information

Question 12

Describe how DNA’s helical structure contributes to its function

Answer 12

Compact

Question 13

Describe how DNA having a sequence of bases contributes to its function

Answer 13

Allows for very accurate replication

Question 14

Describe how DNA’s double stranded structure contributes to its function

Answer 14

Both strands can act as templates during DNA replication

Question 15

Describe how DNA’s relatively weak hydrogen bonds contribute to its function

Answer 15

Allows strands to be easily separated for replication or protein synthesis

Question 16

Describe the structure of ATP

Answer 16

• 3 phosphate groups
• Ribose sugar
• Adenine base

Question 17

Give the word and symbol equation illustrating how ATP stores energy

Answer 17

ATP + H₂O ⇌ ADP + Pi + E

ATP + water ⇌ ADP + inorganic phosphate + energy

Question 18

Name the enzyme which converts:
ATP + H₂O → ADP + Pi + E

Answer 18

ATP hydrolase

Question 19

Name the enzyme which converts:
ATP + H₂O ← ADP + Pi + E

Answer 19

ATP synthase

Question 20

What are the two main roles of ATP?

Answer 20

• Providing energy for energy-requiring reactions
• Phosphorylation of molecules (inorganic phosphate can be transferred to other molecules)

Question 21

Give examples of ATP providing energy for energy-requiring reactions

Answer 21

• Muscle contraction
• Active transport
• Metabolic processes
• Endo/exocytosis

Question 22

Why is energy stored as ATP?

Answer 22

• Only one hydrolysis reaction required so energy can be released quickly
• Releases small, manageable amounts of energy

Question 23

Why can cells not store ATP?

Answer 23

• It is too reactive
• Instead, energy-demanding cells have more mitochondria

Question 24

Explain why water is a solvent

Answer 24

Partially + and - charges of water attract the charges on other molecules, causing them to separate (dissolve)

Question 25

Explain why water being a solvent is of biological significance

Answer 25

Metabolic reactions inside living organisms can only happen when the reactants are dissolved in water

Question 26

Explain why water has a high specific heat capacity

Answer 26

Can absorb large amounts of heat before it changes temp, due to h-bonds

Question 27

Explain why water having a high specific heat capacity is of biological importance

Answer 27

Large bodies of water have a stable temperature (important for habitats)

Question 28

Explain why water has a relatively large latent heat of vaporisation

Answer 28

Some molecules of water have enough kinetic energy to evaporate. These molecules take energy with them so the water cools down.

Question 29

Explain why water having a relatively large latent heat of vaporisation is of biological importance

Answer 29

Provides a cooling effect via evaporation i.e sweating

Question 30

Explain why water has strong cohesion between molecules

Answer 30

Due to their polarity, water molecules attract each other and form hydrogen bonds

Question 31

Explain why water having strong cohesion between molecules is of biological importance

Answer 31

Supports column of water moving up the xylem in transpiration stream. Surface tension can support small organisms on top of the water.

Question 32

Describe the function of hydrogen ions (H+)

Answer 32

Control pH

Question 33

Describe the function of iron ions (Fe2+)

Answer 33

A component of haemaglobin

Question 34

Describe the function of sodium ions (Na+)

Answer 34

Transport of glucose and amino acids

Question 35

Describe the function of phosphate ions

Answer 35

Component of DNA and ATP