Chapter 2- Nucleic Acids

Question 1

What are the 3 components of a DNA nucleotide?

Answer 1

Pentose sugar (deoxyribose), phosphate group, nitrogen-containing base

Question 2

How are the components of a DNA nucleotide formed?

Answer 2

Through condensation reactions

Question 3

What bonds join the nucleotides together?

Answer 3

Phosphodiester bonds

Question 4

Structure of RNA

Answer 4

-single polypeptide chain
-short
-ribose is the pentose sugar
Bases are adenine, guanine, cytosine, uracil

Question 5

Structure of DNA

Answer 5

-pentose sugar = deoxyribose
-2 strands in double helix structure
-extremely long
-bases - adenine, guanine, cytosine, thymine
-H bonds between bases
-complementary base pairing = A + T, C+G

Question 6

How does the structure of DNA relate to its function?

Answer 6

-stable structure = passes through generations without change (rarely mutates)
-H bonds can separate during DNA replication
-extremely large - stores generic info
-bases pairs are within mbackbone - genetic info protected
-base pairing means DNA can replicate

Question 7

Process of DNA replication (semi-conservative replication)

Answer 7

1. DNA helicaxe breaks H bonds between base pairs -> double helix becomes 2 separate strands
2. One strand becomes a template
3. Free nucleotides bind via complementary base pairing
4. Nucleotides are joined together by condensation reactions using DNA polymerase, creating a new polynucleotide strand -> each new DNA strand has 1 original strand + 1 new strand - ‘semi-conservative replication’

Question 8

What are the 3 components of ATP?

Answer 8

Adenine, pentose sugar (ribose), 3 phosphate groups

Question 9

Adenosine triphosphate + water -> ? + ?

Answer 9

Adenosine diphosphate + Inorganic phosphate

Question 10

What type of reaction is: adenosine triphosphate + water -> adenosine diphosphate + Inorganic phosphate? And is it reversible?

Answer 10

Hydrolysis reaction catalysed by ATP hydrolase
Yes it is reversible (other way = condensation reaction catalysed by ATP synthase)

Question 11

What are the roles of ATP?

Answer 11

-Immediate energy source -> release less than glucose + cells can’t store large quantities of ATP
-ATP energy is released in smaller, manageable quantities
-Hydrolysis of ATP -> ADP = single reaction -> immediate energy

Question 12

How is ATP used in energy-requiring processes?

Answer 12

-Metabolic processes
-Movement e..g muscle contraction
-Active transport = energy to change shape of carrier proteins
-Secretion
-Activation of molecules -> inorganic phosphate used to phosphorylate other compounds (makes them > reactive)

Question 13

How is water a polar molecule?

Answer 13

H has slight + charge
O has slight - charge

Question 14

Features of water

Answer 14

-High SHC - buffer against temp. Variations
-Latent heat of vaporisation - H bonds take lot of energy to evaporate -> effective means of cooling
-cohesion - H bonds have large cohesive forces -> pulled in tube
-surface tension - water pulled back when meeting air - surface acts like a skin

Question 15

Importance of water in organisms?

Answer 15

-Metabolism - used in reactions in aqueous mediums
-Solvent - dissolves other substances e.g. urea
-Evaporation - cools organisms -> temp control
-X easily compressed - provides support
-Transparent - so aquatic plants can photosynthesise