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A-level Biology Longridge Towers School > Chapter 2 Nucleic Acids > Flashcards

Chapter 2 Nucleic Acids Flashcards

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1
Q

What are the two types of nucleic acid?

A

RNA - Ribonucleic Acid
DNA - Deoxyribonucleic Acid

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2
Q

What is the role of DNA?

A

It carries genetic information

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3
Q

What is the role of mRNA?

A

It transfers genetic information from DNA to the ribosomes.

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4
Q

Name the monomer of a nucleic acid.

A

Nucleotide

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5
Q

State the three components to a nucleotide.

A

Pentose sugar + Nitrogen containing organic base + Phosphate group

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6
Q

State the five possible bases of a nucleotide.

A

Adenine, guanine, thymine, cytosine, uracil

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7
Q

What is a pentose sugar?

A

A sugar which contains 5 carbons.

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8
Q

What is the pentose sugar present in DNA?

A

Deoxyribose

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9
Q

What is the pentose sugar present in RNA?

A

Ribose

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10
Q

What type of reaction binds nucleotides to form a sugar phosphate backbone?

A

Condensation reaction

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11
Q

What bond is formed when two nucleotides are combined?

A

A phosphodiester bond

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12
Q

What is one nucleotide by itself called?

A

A mononucleotide

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13
Q

What are two bonded nucleotides called?

A

Dinucleotides

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14
Q

What is a long chain of nucleotides called?

A

A polynucleotide.

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15
Q

Describe the structure of DNA.

A

A DNA molecule is a double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs.

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16
Q

Give 5 ways that the structure of DNA is related to its function.

A
  1. It has a very stable structure which can pass from generation to generation without change
  2. It contains two separate strands joined by hydrogen bonds to allow for replication.
  3. It is a large molecule so carries large amount of genetic information.
  4. The genetic information is protected by the sugar-phosphate backbone.
  5. Base pairing leads to DNA being able to replicate and transfer information as mRNA.
17
Q

State the complementary base pairings.

A

A-T/U, C-G

18
Q

State the number of hydrogen bonds formed between adenine and thymine/uracil.

A

2

19
Q

State the number of hydrogen bonds formed between cytosine and guanine.

A

3

20
Q

Describe the structure of RNA

A

An RNA molecule is a relatively short polynucleotide chain/ single strand.

21
Q

What are the three differences between DNA and RNA?

A
  1. DNA is double stranded; RNA is single stranded
  2. DNA has deoxyribose; RNA has ribose
  3. DNA has thymine; RNA has uracil
22
Q

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

A

Knowing the frequency of one base will indicate the frequency of its complementary pair. Knowing the frequency of all bases equal to 1 or 100% will allow the other bases to be calculated.

23
Q

State the mechanism of DNA replication.

A

Semi-conservative replication.

24
Q

Describe semi-conservative replication

A

DNA helicase causes the two strand of DNA to separate, free nucleotides bind to their complementary bases, they are joined together by DNA polymerase which makes phosphodiester bonds

25
Q

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

A

It ensures genetic continuity between generations of cells. It means that there will always be a strand of the former DNA molecule used as a template. Semi-conservative means half is preserved, half is new.

26
Q

What are the main stages in DNA replication?

A
  1. DNA unwinds.
  2. Hydrogen bonds break.
  3. New nucleotides attracted to the template strands.
  4. Condensation reactions bond nucleotides together.
27
Q

State the enzymes involved in DNA replication.

A

DNA helicase + DNA polymerase

28
Q

What does DNA helicase do?

A

It unwinds the DNA and breaks the hydrogen bonds.

29
Q

What does DNA polymerase do?

A

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

30
Q

The two strands of the double helix are …………. to each other, in terms of direction.

A

Antiparallel

31
Q

What are the new strands of DNA formed from?

A

Free nucleotides.

32
Q

How do the free nucleotides get into the right order when they form the new strand of DNA during replication?

A

The original strand acts as a template and the free nucleotides attach to complementary bases by specific base pairing.

33
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.
By centrifuging the solution the DNA was separated by mass.
The results showed that DNA strands were separating and forming a new strand each generation.
Parent DNA was shown to be all heavy nitrogen isotope
The 1st Generation DNA was shown to be half heavy and half light isotope.
The 2nd generation was either half and half or entirely light.

34
Q

Give 4 things that make ATP a suitable energy source for cells.

A
  1. ATP releases manageable amounts of energy.
  2. It releases energy instantaneously
  3. ATP phosphorylates other compounds so they are more reactive.
  4. ATP can be rapidly re-synthesised.
35
Q

Give 5 uses of ATP.

A
  1. Metabolic processes
  2. Movement(muscle contraction)
  3. Active transport
  4. Secretion
  5. Activation of molecules
36
Q

Give 5 properties of water.

A
  1. It is a polar molecule
  2. There are hydrogen bonds between molecules
  3. It has a high specific heat capacity.
  4. It has a high latent heat of evaporation.
  5. There is cohesion and surface tension between molecules.
37
Q

What is the importance of water to living organisms?

A

In metabolism water is used to break down complex molecules(hydrolysis).
It acts as a solvent, water readily dissolves other substances.

A-level Biology Longridge Towers School (37 decks)

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