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Biology🧬 > Nucleic Acids & DNA replication🧬 > Flashcards

Nucleic Acids & DNA replication🧬 Flashcards

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1
Q

What is the structure of a nucleotide?

A
  • Pentose sugar
  • Nitrogenous base
  • Phosphate group
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2
Q

Structure of DNA

A 
•Deoxyribose sugar
•Phosphates bonded to pentoses by covalent bonds (condensation)
•Nitrogenous base 
•Double stranded
•Sugar phosphate backbones are anti-parallel 
-form a double helix
•Contains pyrimidines: C and T
•Contains purines: A and G
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3
Q

Structure of RNA

A
  • Ribose sugar
  • Phosphates groups
  • Single stranded
  • Contains pyrimidines: C and U
  • Contains purines: A and G
  • Tend to be short lived
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4
Q

What is a pyrimidine?

A
  • A base with a single ring structure
  • Cytosine
  • Thymine
  • Uracil
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5
Q

What is a purine?

A
  • A base with a double ring structure
  • Adenine
  • Guanine
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6
Q

How are polynucleotides formed?

A
  • One nucleotide can join to another by a condensation reaction
  • Takes place between the sugar and phosphate groups
  • Many nucleotides joining up this way form a polynucleotide chain
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7
Q

What is a nucleoside?

A
  • Organic base + pentose sugar but no phosphate
  • Nucleoside monophosphate (1p)
  • Nucleoside diphosphate (2p)
  • Nucleoside triphosphate (3p)
  • Phosphorylated nucleoside (2/3p)
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8
Q

What is the structure of ATP?

A
  • Adenine nitrogenous base
  • Ribose
  • 3 phosphate groups
  • Forms a phosphorylated nucleotide
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9
Q

What are the similarities and differences between ATP, RNA & DNA?

A

•All made of a pentose sugar
-containing a phosphate group
•Made of different pentose sugars
•Contain different number of phosphate groups

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10
Q

Hydrolysis of ATP

A

ATP + water
(Hydrolysis)—>
(Condensation)

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11
Q

What is an exergonic reaction?

A

A reaction that releases energy

E.g. ATP hydrolysis

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12
Q

What are the advantages of ATP as a supplier of energy?

A

•Hydrolysis involves a single reaction that releases energy immediately - glucose takes longer
•Only one enzyme is needed to release energy from ATP compared to many in glucose
•ATP releases energy in small amounts, when & where it is needed, so no energy is wasted
-glucose releases large amounts of energy all at once
•ATP is a universal source of energy
•Readily available as the phosphate group is transferred on demand

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13
Q

What is ATP synthase?

A
  • Catalyses condensation reaction to produce ATP

* During respiration or photosynthesis

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14
Q

What are the roles of ATP?

A 
•Metabolic processes
-building large, complex molecules 
•Active transport
-change shape of carrier proteins and allow molecules/ions to move against a conc gradient
•Movement 
-for muscle contraction
•Nerve transmissions
-sodium-potassium pumps
•Secretions
-packaging into vesicles
•Homeostasis
-energy lost as heat from ATP hydrolysis 
•Adding phosphate groups to proteins
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15
Q

What is the complimentary base pairing rule?

A
  • Adenine must always pair with Thymine (or Uracil in RNA)

* Cytosine must always pair with Guanine

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16
Q

What are the two main functions of DNA?

A
  • DNA replication

* Protein synthesis

17
Q

What is the process of DNA replication?

A
  • Helicase enzyme breaks hydrogen bonds between complementary strands
  • Both strands are used as templates
  • Free nucleotides pair with complementary bases now exposed
  • Hydrogen bonds form between the bases
  • DNA polymerase joins adjacent nucleotides by condensation reactions, forming phosphodiester bonds
  • 2 identical DNA molecules are produced
18
Q

What is the semi-conservative idea?

A

Each new DNA molecule contains one original strand and one newly formed strand

19
Q

Describe Meselson and Stahl’s experiment

A
  • Grew E.coli in a medium containing amino acids with the isotope 15N (heavy nitrogen)
  • Bacterium’s DNA contains 15N
  • Centrifuged DNA in caesium chloride solution
  • DNA settles depending on mass
  • 15N bacteria transferred to a growth medium containing 14N (light)
  • Bactria divided
  • 1st gen 50% 15N (og), 50% 14N (new)
  • 2nd gen 25% 15N, 75% 14N
20
Q

Explain Meselson and Stahl’s experiment

A
  • At succeeding generation times, the DNA extracts were found to have a lower proportion of 15N
  • More 14N was incorporated into the bacterial DNA
  • Due to semi-conservative theory
21
Q

What is a nucleic acid?

A

A polymer of nucleotides

22
Q

What is a sugar-phosphate backbone?

A

The deoxyribose of one nucleotide forms a bond with the phosphate of another nucleotide to form a sugar-phosphate backbone

23
Q

What bonds hold the two strands of double helix together?

A

Hydrogen bonds between a pair of nitrogenous bases

24
Q

What does the complementary base pairing rule ensure?

A
  • DNA replicates correctly

* Same proportion of A/T and C/G

25
Q

What does anti parallel mean?

A
  • 5’ end to 3’ end

* 3’ end to 5’ end

26
Q

What is genetic code?

A

The way in which information about the sequence of amino acids in a protein is coded by the bases on a molecule of DNA

27
Q

What does genetic stability rely on?

A

The genetic code being passed on to daughter cells without changes or errors

28
Q

What is conservative replication?

A
  • Original double stranded DNA molecule remained

* Totally new double stranded molecule was produced

29
Q

What is dispersive replication?

A

Both strands consist of sections of new and old DNA

30
Q

Why might testing a DNA enzyme on synthetic DNA not provide a valid conclusion in using it for humans? OWTTE (could be on exam)

A
  • Enzyme may be less effective against human DNA
  • The synthetic DNA may be single stranded whereas human is double
  • May not have been tested on a live sample
  • Could damage healthy cells
  • Could have side effects
31
Q

What is the function of DNA helicase?

A

Unwinds and unzips DNA molecule for replication

32
Q

What is the function of DNA polymerase?

A

Forms phosphodiester bonds between adjacent nucleotides during replication

Biology🧬 (24 decks)

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