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A-Level Biology - Two > 3.8 Nucleotides and nucleic acids > Flashcards

3.8 Nucleotides and nucleic acids Flashcards

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1
Q

What are the five elements in a nucleic acid?

A

oxygen
hydrogen
nitrogen
carbon
phosphorous

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2
Q

What are the two types of nucleic acid and what do they do?

A

DNA and RNA
- they both have roles in the storage and transfer of genetic information and the synthesis of polypeptides ( proteins )
- they are the basis for heredity

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3
Q

What is the the summarised structure of a nucleic acid?

A
  • large polymers formed from many nucleotides ( the monomers ) linked together in a chain
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4
Q

What are the three components that make up an individual nucleotide?

A
  • a pentose monosaccharide ( sugar ) containing five carbon atoms
  • a nitrogenous base is a complex organic molecule containing one or two carbon rings in its structure as well as nitrogen
  • a phosphate group ( PO4 2-) has a negative charge, is inorganic and is acidic
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5
Q

How are nucleotides linked together, what is the reverse reaction of this and what does it create?

A
  • they are linked together by condensation reactions
  • to form a polymer called a polynucleotide
  • hydrolysis, releasing the individual nucleotides
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6
Q

How does the phosphate group and pentose sugar connect and what are the bonds called?

A
  • the phosphate group at the fifth carbon of the pentose sugar of one nucleotide forms a covalent bond with the hydroxyl group at the third carbon of the pentose sugar of an adjacent nucleotide
  • called phosphodiester bonds
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7
Q

What does the nucleotides being joined together create?

A
  • a large, strong sugar phosphate ‘backbone’ with a base attached to each sugar
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8
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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9
Q

What sugar is used in DNA and how is it different to a ribose?

A
  • Deoxyribose
  • it has one fewer oxygen atoms
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10
Q

What is pyrimidines and what are the bases?

A
  • the smaller bases, which contain single carbon ring structures
  • thymine (T) and cytosine (C)
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11
Q

What is purines and what are the bases?

A
  • the larger bases, which contain double carbon ring structures
  • adenine (A) and guanine (G)
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12
Q

What is DNA made out of overall?

A
  • two strands of polynucleotides coiled into a helix, know as the double helix structure
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13
Q

How are the two strands of the double helix held together?

A
  • hydrogen bonds between the bases
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14
Q

What does each strand that makes up the helix have?

A
  • a phosphate group (5) at one end and a hydroxyl group (3) at the other end
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15
Q

How are the two strands of the double helix arranged?

A
  • they run in opposite directions to one another
  • antiparallel
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16
Q

What does the pairing of bases allow and what are the key properties for?

A
  • DNA to be copied and transcribed
  • molecule of heredity
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17
Q

What bases bind together and what do they form?
What is this known as?

A
  • Adenine and thymine to create two hydrogen bonds
  • Cytosine and Guanine to create three hydrogen bonds
  • complementary base pairing
18
Q

What does complementary base pairing arrange further than the bases and what does this make in the DNA structure?

A
  • a small pyrimidine base always binds to a larger purine base
  • arrangement maintains a constant distance between the DNA ‘backbones’ which results in parallel polynucleotide chains being created
19
Q

What was known about the bases in DNA long before Watson and Cricks discovery in 1953?

A
  • that DNA always has equal amounts of adenine and thymine and equal amounts of cytosine and guanine
20
Q

What carries the genetic information of an organism and in what form?

A
  • the sequence of bases along a DNA strand
  • a code
21
Q

What does RNA stand for?

A
  • Ribonucleic acid
22
Q

What essential role does RNA play?

A
  • the transfer of genetic information from DNA to the proteins that make up the enzymes and tissues of the body
23
Q

What is the one issue with DNA?

A
  • the DNA of each eukaryotic chromosome is a very long molecule, comprising many hundreds of genes and is unable to leave the nucleus in order to supply the information directly to the sites of protein synthesis
24
Q

How is the DNA able to be transported out of the nucleus?

A
  • the relatively short section of the the long DNA molecule corresponding to a single gene is transcribed into a similarly short messenger RNA molecule (mRNA)
25
Q

What is the size comparison of mRNA and what is its overall structure?

A
  • each individual mRNA is therefore much shorter than the whole chromosome of DNA
  • it is a polymer composed of many nucleotide monomers
26
Q

How are RNA and DNA nucleotides different to one another?

A
  • the pentose sugar is ribose rather than deoxyribose and the thymine base is replaced with uracil
27
Q

What is uracil?

A
  • the RNA base of thymine
  • a pyrimidine that forms two hydrogen bonds adenine
28
Q

What are the base pairing rules like in RNA?

A
  • the base pairing rules still apply when RNA nucleotides bind to DNA to make copies of particular sections of DNA
29
Q

How are RNA and DNA nucleotides similar?

A
  • the RNA nucleotides form polymers in the same way as DNA nucleotides, by the formation of phosphodiester bonds in condensation reactions
30
Q

How are the RNA polymers formed and what are they like?

A
  • they are small enough to leave the nucleus and travel to the ribosomes, where they are central in the process of protein synthesis
31
Q

What happens after protein synthesis with the RNA molecules?

A
  • they are degraded in the cytoplasm
  • the phosphodiester bonds are hydrolysed and the RNA molecules are released and reused
32
Q

What are ADP and ATP?

A

Phosphorylated nucleotides

33
Q

How do you phosphorylate a nucleotide?

A
  • you add one or more phosphate groups to it
34
Q

What does ADP stand for?

A

Adenosine diphosphate

35
Q

What does ADP contain?

A
  • the base adenine
  • the sugar ribose
  • two phosphate groups
36
Q

What does ATP stand for?

A

Adenosine triphosphate

37
Q

What does ATP contain?

A
  • the base adenine
  • the sugar ribose
  • three phosphate groups
38
Q

How is ATP involved in the respiration of animals and plants?

A
  • plant and animal cells release energy from glucose (respiration)
  • a cell cannot get it’s energy directly from glucose
  • the energy released from glucose is used to make ATP
  • then molecules of ATP provide energy for chemical reactions in the cell
39
Q

What happens when energy is needed?

A
  • energy is stored in the phosphate bond
  • when this energy is needed by a cell, ATP is broken back down into ADP and inorganic phosphate
  • energy is released from the phosphate bond and used by the cell
40
Q

What is ATP synthesised by and how does this work?

A
  • ADP and inorganic phosphate
  • the ADP is phosphorylated to form ATP and a phosphate bond is formed
41
Q

Why and how is DNA purified?

A
  • scientists often need to extract a pure DNA sample from cells in order to analyse it (forensics)
  • DNA can be purified using a precipitation reaction
42
Q

What is the method of purifying DNA?

A
  1. Crush the kiwi fruit with a pestle and mortar to break open cellulose cell wall.
  2. Add detergent to dissolve phospholipid bonds.
  3. Add protease enzyme to break down the histones/ proteins associated with DNA
  4. Put into a water bath at 40’C as this is the optimum for protease activity
  5. Filter to remove any solids.
  6. Add salt to help clump the DNA together and precipitate.
  7. Add cold alcohol/ethanol because DNA is insoluble in alcohol and so will precipitate it

A-Level Biology - Two (14 decks)

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