Nucleic Acids Flashcards

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1
Q

DNA (Deoxyribonucleic Acid)

A
  • Stores genetic information
  • Made up of a deoxyribose sugar, a phosphate group and nitrogenous base
  • Double helix structure - the 2 strands in DNA are antiparallel
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2
Q

RNA (Ribonucleic Acid)

A
  • Transfers genetic information from the nucleus to the ribosomes
  • Made up of a ribose sugar, a phosphate group and a nitrogenous base
  • Short, polynucleotide chain structure
  • RNA is single stranded, unlike DNA
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3
Q

Polynucleotide

A
  • Long chain of nucleotides joined in condensation reactions
  • Held together by phosphodiester bonds
  • Bond formed between the sugar of one nucleotide and the phosphate of the adjacent nucleotide
  • Chain of sugars and phosphates formed is known as a sugar-phosphate backbone
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4
Q

Complementary Base Pairings

A
  • Bases are joined by hydrogen bonds
  • Adenine (A) joins with thymine (T)
  • A and T form 2 hydrogen bonds
  • Guanine (G) joins with cytosine (C)
  • G and C form 3 hydrogen bonds
  • In RNA, Adenine (A) joins with uracil (U)
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5
Q

Why is DNA a stable molecule?

A
  • Sugar phosphate backbone protects nitrogen bases, which are more chemically reactive
  • There are 3 hydrogen bonds between C and G making the molecule more stable when there is a higher proportion of these bonds
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6
Q

Process of DNA Replication

A
  • DNA Helicase breaks the hydrogen bonds between the complementary bases on the 2 strands of DNA, causing them to separate
  • Free nucleotides form hydrogen bonds between their complementary bases on the template strand
  • DNA polymerase forms phosphodiester bonds between the adjacent nucleotides forming the sugar phosphate backbone on the new strand
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7
Q

Antiparallel Strands

A
  • DNA strands run in opposite directions parallel to one another
  • Each strand has a 3’ end and a 5’ end
  • Only the 3’ end can bind with the active site of polymerase
  • The polymerase enzyme travels in opposite directions on each strand
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8
Q

Conservative Theory

A

DNA molecule is copied and a 2nd new DNA molecule is made

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9
Q

Dispersive Theory

A
  • DNA molecule is cut at various sections with each section being copied
  • The new sections reattach to the original sections of DNA to produce 2 DNA molecules
  • Both DNA molecules have a mix of the old and the new DNA
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10
Q

Semi-Conservative Theory

A
  • 2 strands separate and each strand acts as a template strand to copy a new strand
  • The old strands and the new strands would reattach to create 2 new DNA molecules
  • Both DNA molecules have 1 old strand and 1 new strand
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11
Q

Meselson and Stahl E-coli Experiment

A
  • Grew E-coli in a sample of N-15 and then centrifuged it to show it was heavy
  • Left E-coli to divide in a sample of N-14 (less dense than N-15) and then centrifuged the E-coli again
  • After division 1, 100% of the DNA in the E-coli was a mix of N-14 and N-15 (disproves conservative theory)
  • E-coli was left to divide in N-14 again and centrifuged again
  • After division 2, 50% of the DNA was N-14 and 50% was a mix of N-14 and N-15 (disproves dispersive model)
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12
Q

ATP (Adenosine Triphosphate)

A
  • 3 phosphates, a ribose sugar and an adenine base
  • Nucleotide derivative (modified form of a nucleotide)
  • Provides energy for chemical reactions within the cell (energy isn’t directly from glucose)
  • Synthesised from ADP and inorganic phosphate using energy from reactions (e.g. breakdown of glucose)
  • ADP + P(i) –> ATP + H2O (condensation reaction)
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13
Q

ADP (Adenosine Diphosphate)

A
  • Phosphorylated during respiration
  • When energy is needed in a cell, ATP is broken down into ADP and P(i)
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14
Q

Properties of Water

A
  • Metabolite - can be used/formed in condensation and hydrolysis reactions
  • Solvent - can transport substances
  • Large Specific Latent Heat - allows animals to cool down via evaporation (sweating)
  • Cohesive (polar) molecule - creates surface tension to support small organisms
  • High Specific Capacity - acts as a buffer to temperature (lots of energy can be gained/lost without there being a temperature change)
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