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A level biology > Nucleic acids > Flashcards

Nucleic acids Flashcards

1
Q

Nucleic acids

A
  • MONOMER= Nucleotides
  • Nitrogen-containing organic substances
  • Form DNA and RNA
  • important information-carrying molecules
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2
Q

Nucleotide structure

A

Made up of 3 components:
1. Pentose sugar
2. Phosphate group
3. Nitrogeonous base (cytosine, guanine, uracil, adenine, thymine)
* These join in condensation reactions to form mononucleotides
* Dinucleotide is formed when 2 mononucleotides are joined together
* Polynucleotides are formed through the continued linking of mononucleotides

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3
Q

Phosphodiester bond

A

formed in condensation reactions between a pentose sugar of one mononucleotide and a phosphate group of another

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4
Q

RNA structure

A

Ribonucleic acid
* Polymer made up of nucleotides
* Single, short polynucleotide strand
* Ribose (pentose) sugar
* BASES: adenine, gunaine, cytosine and uracil
* Held together by phosphodiester bonds
* Different types e.g tRNA, mRNA and rRNA

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5
Q

DNA structure

A

Deoxyribonucleic acid
* Deoxyribose (pentose) sugar
* BASES: adenine, thymine, cytosine and guanine
* Made up of 2 polynucleotide strands
* Long molecule joined by H-bonds between bases
* Anti-parallel because chains run in opposite directions
* Double-helix- polynucleotide chains are twisted to form a structural backbone of DNA

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6
Q

Complementary base pairings

A
  • Adenine (A) pairs with Thymine (T) in DNA to form 2 hydrogen bonds
  • Cytosine (C) pairs with Guanine (G) to form 3 hydrogen bonds
  • But in RNA Uracil (U) pairs with Adenine instead of thymine
  • The quantitities of A and T are always the same
  • The quantities for C and G are always the same
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7
Q

Double helix

A
  • Uprights of phosphate and deoxyribose wind around one another
  • The form the structural backbone of DNA
  • 2 antiparallel poltnucleotide strands twist around in opposite dirctions
  • Each strand can act as a template in DNA replication
  • DNA fibres are wound around histone proteins
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8
Q

Stability of DNA

A
  • Phosphate backbone protects the more chemically reactive bases in the double helix
  • H-bonds link base pairs forming bridges between the phosphodiester uprights
  • The higher the proportion of C-G pairings, the more stable the DNA molecule
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9
Q

Function of DNA

A
  • hereditary material responsible for passing genetic information from cell to cell and generation to generation
  • variety of DNA base pairs provides genetic diversity
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10
Q

How is the structure of DNA related to its function?

A
  1. Stable structure due to sugar phosphate backbone (covalent bonds) and the double helix
  2. Double stranded = replication can occur using 1 strand as template
  3. Weak h-bonds= easy unravelling of 2 strands in helix for replication
  4. Large molecule= carries a lot of genetic information
  5. Complementary base pairing allows identical copies to be made
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11
Q

mRNA

A
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12
Q

tRNA

A
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13
Q

r

rRNA

A
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14
Q

Compare DNA to RNA

A
  1. DNA contains base thymine, RNA contains base Uracil
  2. DNA contains pentose sugar deoxyribose, RNA contains the pentose sugar ribose
  3. DNA is double stranded, RNA is single strandes
  4. DNA is a much larger molecule because it contains and entire genome but RNA is much shorther because its only 1 gene
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15
Q

Prime groups

A
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16
Q

DNA replication

A
  • Before a nucleus divises its DNA must be replicated to ensure all daughter cells have the genetic information to produce enzymes and other proteins
  • Precise process because all new cells are genetically identical to the original
17
Q

Process of semi-conservative replication

A
  1. Enzyme DNA helicase breaks the H-bonds linking DNA base pairs
  2. Double helix seperates into 2 strands and unwinds
  3. Exposed polynucleotide strand acts as a template to which complementary free nucleotides bind by specific base pairings
  4. Condensation reaction joins nucleotides together using the enzyme DNA polymerase to form the ,issing polynuclotide pair
  5. Each new DNA molecule contains an original DNA strand, so half of the original DNA has been saved and built into each of the new DNA molecules
18
Q

Semi-conservative replication

A
19
Q

Conservative replication

A
20
Q

Dispersive

Dispersive replocation

A
21
Q

Meselson and Stahl experiment

A

A level biology (18 decks)

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