Nucleic Acids Flashcards

1
Q

What is a nucleotide

A

Monomers of nucleic acids (DNA and RNA)

Made up of:
- phosphate group (always the same)
- pentose sugar (deoxyribose in DNA , ribose in RNA)
- nitrogenous base (DNA= A T C G. RNA= A U C G )

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2
Q

How many hydrogen bonds hold base pairs together

A

G-C has 3 hydrogen bonds
A-T has 2 hydrogen bonds

  • purines and pyrimidines always pair together (complementary base pairs)
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3
Q

How are nucleotides joined in condensation reactions

A

Covalent bonds

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4
Q

What are purines

A

Adenine and Guanine
- purines are larger than Pyrimidines

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5
Q

What are Pyrimidines

A

Cytosine, Thymine and uracil (RNA)
- Pyrimidines are smaller than purines

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6
Q

Why do purines always bond with pyrimidines

A
  • their structure
  • where they can form hydrogen bonds
  • to remain parallel (never have 2 large molecules and 2 small molecules)
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7
Q

DNA helicase, DNA polymerase, DNA ligase

A

DNA helicase- unzips DNA helix
DNA polymerase- catalyses the joining of nucleotides
DNA ligase- sticks DNA fragments together

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8
Q

DNA replication

A
  1. DNA helicase unwinds the DNA and forms a replication fork
    - helicase unwinds and unzips
    - breaks hydrogen bonds
  2. Each strand acts as a template
    - free nucleotides pair with the complementary exposed nucleotides
  3. DNA polymerase catalyses the joining together of nucleotides
    - hydrogen bonds reform
  4. Hydrogen bonds form down the middle
    - this is semi conserved DNA (one old strand, one new strand)
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9
Q

3 parts of the genetic code

A

Triplet- the bases on DNA form triplet codons consisting of 3 nucleotide bases

Non overlapping- each base will only code for one amino acid in one triplet codon

Degenerate- each amino acid can be coded for by multiple codons

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10
Q

Nucleotide vs Nucleoside

A

Nucleotide- has a nitrogenous base, deoxyribose sugar and phosphate

Nucleoside- does not have a phosphate

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11
Q

Phosphorylation

A

The addition of a phosphate group

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12
Q

Energy uses

A
  • muscle contraction
  • memory formation
  • transmission of nerve impulses
  • cell division
  • active transport
  • translocation
  • photosynthesis
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13
Q

Structure of ATP

A

Adenine — Ribose |
|
3 phosphates

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14
Q

Translation

A
  1. mRNA attaches to a ribosome
  2. The first mRNA codon binds to a tRNA molecule with a complementary anticodon
  3. The tRNA is bound to an amino acid specific to its anticodon
  4. A second tRNA (carrying another amino acid) binds the tk adjacent mRNA codon
  5. A peptide bind forms between the amino acids
  6. The ribosome continues along the mRNA molecule, from codon to codon
  7. Amino acids are bonded together in a polypeptide chain until a stop codon is reached
  8. The polypeptide is released
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15
Q

Transcription

A
  1. DNA helicase unwinds and unzips DNA
  2. RNA nucleotides bind to complementary DNA bases in the template strand (antisense)
  3. RNA polymerase joins rna nucleotides together with phosphodiester bonds
  4. A stop codon causes rna polymerase to detach
  5. The mRNA molecule detaches from the DNA and leaves the nucleus
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