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Biology AS level section 1 > Chapter 2 - Nucleic acids > Flashcards

Chapter 2 - Nucleic acids Flashcards

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1
Q

What is the structure of a nucleotide

A

A nucleotide contains:

  • A phosphate group (PO43-)
  • A pentose sugar
  • A nitrogen containing base
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2
Q

How are the components of a nucleotide joined

A

They are joined by a condensation reaction
The nitrogen containing base joins to the carbon one on the pentose sugar
The phosphate group attaches to the carbon 5 on the pentose sugar

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3
Q

What are nucleic acids with examples

A
  • polymers, made up of monomers called nucleotides
  • information carrying molecules
  • examples of nucleic acids:
    DNA - deoxyribonucleic acid
    RNA - ribonucleic acid
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4
Q

How are nucleotides joined

A

They are joined by condensation reactions between the phosphate group and the carbon 3 on the pentose sugar.
They form phosphodiester bonds
This forms a polynucleotide.

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5
Q

DNA vs RNA

A
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6
Q

What is complementary base pairing

A
  • Base pairs are bonded by hydrogen bonds, holding the two polynucleotide strands together.
  • Adenine (A) pairs with Thymine (T) (2 H bonds)
  • Guanine (G) pairs with Cytosine (C) (3 H bonds)
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7
Q

What is the structure of DNA

A
  • Two sugar-phosphate backbones held together by H bonds between complementary N-containing bases
  • The 2 antiparallel polynucleotide chains wrap round each other
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8
Q

How does the structure of DNA relate to its function

A
  • Double stranded – both strands can act as templates
  • Hydrogen bonds between complementary base pairs
    easy separation of strands during replication
  • hold the structure together
  • Complementary base pairing – allows for accurate replication
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9
Q

What is DNA replication

A

DNA replication occurs during interphase and is when the DNA forms exact replicas of itself
This is binary fission in prokaryotes and mitosis and meiosis in eukaryotic cells

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10
Q

What is semiconservative DNA replication and who came up with this model

A
  • Proposed by Watson and Crick
  • States that two strands in a DNA helix acts as templates to form two new helices, from free DNA nucleotides.
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11
Q

Process of semi conservative DNA replication

A
  • DNA helicase breaks H bonds between complementary bases, unwinding the helix and separating the DNA strands
  • Both strands act as templates
  • Free DNA nucleotides line up by complementary base pairing (A-T, C-G) and H bonds form between complementary base pairs
  • DNA polymerase joins adjacent DNA nucleotides (condensation reaction), forming phosphodiester bonds
  • Each new DNA molecule made up of one old strand and one new

Key points: unwinding the helix, each new DNA molecule is made up of one old strand and one new

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12
Q

Diagram of semiconservative DNA replication

A
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13
Q

Who provided evidence for semi conservative DNA replication

A

Meselson and Stahl

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14
Q

What was the process of the experiment to prove semi-conservative DNA repliaction

A
  • Grew bacteria in growth medium containing 15N (Generation 0)
  • Centrifuged bacterial DNA
  • Grew bacteria in 14N and centrifuged (Generation 1)
  • Continued to grow in 14N for 2 more generations and centrifuged (Generation 2 and 3)
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15
Q

Diagram showing the results of Meselson and Stahl’s experiment

A
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16
Q

What is ATP and what are its uses

A

ATP is Adenosine Triphosphate – a nucleotide derivative
All living organisms require energy
ATP is the main source of energy used in cell processes
ATP is able to release energy rapidly

17
Q

Structure of ATP

A
18
Q

How does ATP release energy

A
  • ATP is hydrolysed into ADP (adenosine diphosphate)
  • This breaks the bond between the 2nd and 3rd phosphate group
  • This is catalysed by the enzyme ATP hydrolase
19
Q

diagram showing the interconversion between ATP and ADP + Pi

A
20
Q

What are the three methods in which ATP is synthesised

A
  • Photophosphorylation - during photosynthesis using energy from light
  • Oxidative phosphorylation - during aerobic respiration
  • Substrate level phosphorylation - using a phosphorus molecule from a donor molecule (the substrate)
21
Q

Why is ATP a good intermediate energy source

A
  • It releases relatively small amounts of energy so little energy is lost as heat
  • It releases energy instantaneously, so energy is readily available
  • It can phosphorylate other compounds, making them more reactive
  • It can be rapidly re-synthesised for re-use
  • It is not lost from cells
22
Q

What are the uses of ATP

A

Metabolic reactions
Muscle contraction for movement
Active transport across membranes
Formation of lysosomes for secretion
Activation of molecules by phosphorylation – glycolysis in respiration

23
Q

What is the structure and function of water

A
  • dipolar - has positive and negative areas
  • able to easily form hydrogen bonds
24
Q

What are the main properties of water

A
25
Q

Other important features of water

A

Ice floats - maintaining an aquatic earth habitat
Not easily compressed - provides support
Transparent - allows light through for photosynthesis

26
Q

Role of the 4 inorganic ions

A

Biology AS level section 1 (2 decks)

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