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Biology A-level > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

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1
Q

What is the role of DNA?

A

Carries genetic information

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2
Q

What is the role of RNA?

A

Transfers genetic information from DNA to ribosomes

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3
Q

Name the monomer of a nucleic acid

A

nucleotide

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4
Q

State three components of a nucleotide

A

Pentose sugar, nitrogen containing base, and phosphate group

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5
Q

State the five bases of a nucleotide?

A

Adenine, guanine, thymine, cytosine and uracil

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6
Q

What is a pentose sugar?

A

Sugar containing five carbons

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7
Q

What is the pentose sugar in DNA and RNA?

A

DNA- Deoxyribose
RNA- Ribose

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8
Q

What sort of reaction combines two nucleotides?

A

Condensation reaction

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9
Q

What bond is formed when two nucleotides combine?

A

Phosphodiester bond

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10
Q

Describe the structure of DNA

A

Double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs

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11
Q

How is the structure of DNA related to its functions?

A
  • Stable structure which can pass from generation to generation without change
  • Two separate strands (both strands act as template strands) joined by hydrogen bonds for replication
  • Large so carries a lot of genetic info
  • Genetic info protected by sugar phosphate backbone.
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12
Q

Describe the structure of RNA

A

Relatively short polynucleotide chain

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13
Q

What are three differences between RNA and DNA?

A
  • DNA is double stranded RNA single
  • DNA has deoxyribose, RNA ribose
  • DNA has thymine, RNA has uracil
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14
Q

How does complementary base pairing allow us to work out the frequency of relative bases?

A

Knowing the frequency of a base will indicate the frequency of its complementary pair

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15
Q

State the mechanism of DNA replicaiton

A

Semi-conservative

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16
Q

Describe semi-conservative replication?

A

DNA helicase separates the two strands. Free nucleotides bond to their complementary bases. They are joined by DNA polymerase which makes phosphodiester bonds.

17
Q

Why is semi-conservative replication important in the genetic continuity between cells?

A

Half is preserved so there will always be a strand of former DNA so genetic continuity is ensured between generations.

18
Q

State the enzymes involved in DNA replication

A

DNA helicase and DNA polymerase

19
Q

What does DNA helicase do?

A

Unwinds double helix and breaks hydrogen bonds.

20
Q

What does DNA polymerase do?

A

Catalyses the condensation reaction creating phosphodiester bonds between nucleotides. This forms the sugar phosphate backbone.

21
Q

The two strands of the double helix are {} to each other in terms of direction.

A

Antiparallel

22
Q

What are the new strands of DNA formed from?

A

Free nucletides

23
Q

How was semi conservative replication proven true?

A

DNA was marked with a heavy nitrogen isotope. It was then replicated using a light nitrogen isotope. The mass of the DNA was determined by which isotopes it contained.
The results showed that DNA strands were separating and forming a new strand each generation.
Parent DNA- heavy nitrogen isotope
1st generation- half heavy half light
2nd generation- either half and half or entirely light.

24
Q

Why is ATP a suitable energy source for cells?

A

Releases manageable amounts of energy.
Phosphorylates other compounds making them more reactive.
Can be rapidly re-synthesised.

25
Q

Roles of ATP?

A
  • Transport
  • Secretion
  • Activation of molecules
  • Movement
  • Active transport
26
Q

What enzyme is required to make ATP?

A

ATP synthase

27
Q

What reactants are needed to make ATP?

A

ADP and Pi

28
Q

What enzyme is required to hydrolyse ATP?

A

ATP hydrolase

29
Q

What are the properties of water?

A
  • Hydrogen bonds between molecules
  • High specific heat capacity
  • High latent heat of vaporisation
  • Cohesion and surface tension
30
Q

Why is water important to living organisms?

A
  • Used to break down complex molecules
  • Acts as a solvent.
  • Readily dissolves other substances.

Biology A-level (22 decks)

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