2.1.3 Nucleotides and nucleic acids

Question 1

What makes up a nucleotide?

Answer 1

• Pentose sugar
• Nitrogenous base
• Phosphate group

Question 2

What bond forms between nucleotides?

Answer 2

Phosphodiester bonds

Question 3

How many hydrogen bonds between T and A base pairs?

Answer 3

Two

Question 4

How many hydrogen bonds between C and G base pairs

Answer 4

Three

Question 5

What does a deoxyribose sugar (DNA) have on carbon 2’?

Answer 5

Hydrogen

Question 6

Which nitrogenous bases are found on DNA?

Answer 6

Adenine
Cytosine
Guanine
Thymine

Question 7

What shape is DNA?

Answer 7

Double stranded (double helix)

Question 8

What does a ribose sugar (RNA) have on carbon 2’?

Answer 8

Hydroxyl group (OH)

Question 9

Which nitrogenous bases are found on RNA?

Answer 9

Adenine
Cytosine
Guanine
Uracil

Question 10

What shape is RNA?

Answer 10

Single stranded

Question 11

What property does the OH group on RNA give?

Answer 11

More susceptible to hydrolysis so is a transport molecule whereas DNA is a storage molecule

Question 12

What are the pyrimidines?

Answer 12

Smaller bases which contain single carbon ring structures
- Thymine
- Cytosine
- Uracil

Question 13

What are the purines?

Answer 13

Larger bases which contain double carbon ring structures
- Adenine
- Guanine

Question 14

P_____ pair with P_______

Answer 14

Purines
Pyrimidines

Question 15

What is energy needed for?

Answer 15

• Anabolic reactions
• Movement
• Muscle contraction
• Conduction of nerve impulse

Question 16

What makes up adenosine monophosphate (AMP)?

Answer 16

• Adenine base
• Ribose
• One phosphate group

Question 17

What makes up adenosine diphosphate (ADP)?

Answer 17

• Adenine base
• Ribose
• Two phosphate groups

Question 18

What makes up adenosine triphosphate (ATP)?

Answer 18

• Adenine base
• Ribose
• Three phosphate groups

Question 19

How does ATP release energy?

Answer 19

• Releasing a phosphate group through hydrolysis reaction
• Hydrolysed to ADP + phosphate ion

Question 20

What enzyme hydrolyses ATP?

Answer 20

ATPase

Question 21

Why is ATP not a good long term store of energy?

Answer 21

Instability of phosphate bonds as the negative phosphate ions repel each other

Question 22

Why is ATP a good immediate energy store?

Answer 22

Cellular respiration forming ATP is constantly occurring in living cells

Question 23

How is ATP reformed?

Answer 23

By reattaching phosphate group to ADP through a condensation reaction

Question 24

Outline the steps for DNA purification

Answer 24

1) Grind sample
2) Add detergent
3) Add salt
4) Add protease enzyme
5) Add ice cold ethanol

Question 25

What is the purpose of grinding the sample in DNA purification?

Answer 25

Breaks down cell walls

Question 26

What is the purpose of adding detergent to the sample in DNA purification?

Answer 26

Breaks down cell membrane by disrupting the phospholipids, releasing cell contents

Question 27

What is the purpose of adding salt to the sample in DNA purification?

Answer 27

Breaks hydrogen bonds between DNA and water molecules

Question 28

What is the purpose of adding protease enzyme to the sample in DNA purification?

Answer 28

Breaks down histone proteins associated with DNA in the nuclei

Question 29

What is the purpose of adding ice cold ethanol to the sample in DNA purification?

Answer 29

Causes DNA to precipitate out of solution and form as white strands between the layer of sample and layer of ethanol

Question 30

What is semi-conservative replication?

Answer 30

DNA is composed of one original strand and one newly formed one

Question 31

Why is semi-conservative replication important?

Answer 31

Ensures there is genetic continuity so that the cells which are replaced regularly are exactly the same as the old cells

Question 32

Outline the stages of DNA replication?

Answer 32

1) Helicase unwinds DNA helix by breaking hydrogen bonds between base pairs to form single strands (unzipping) 2) Free nucleotides pair up with complementary base pairs on original DNA strand acting as the template 3) DNA polymerase joins nucleotides together on new strand of DNA through condensation recations

Question 33

How is the genetic code universal?

Answer 33

All organisms use the same codons but in different sequences

Question 34

How is the genetic code non overlapping?

Answer 34

Each base is only read once in the codon it is part of

Question 35

How is the genetic code degenerate?

Answer 35

Multiple codons can code for the same amino acid