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Biology > Nucleic acids > Flashcards

Nucleic acids Flashcards

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1
Q

Name the four nitrogenous bases in DNA

A
  • adenine
  • thymine
  • cytosine
  • guanine
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2
Q

Name the four nitrogenous bases in RNA

A
  • adenine
  • cytosine
  • uracil
  • guanine
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3
Q

List 3 properties of DNA and explain how they are related to its function

A
  • DNA is very stable so it passes from generation to generation without changing (only rarely does it mutate)
  • The two polynucleotide strands are linked only by hydrogen bonds which means that it is easy for the strands to seperate during DNA replication and protein synthesis
  • DNA is a huge molecule so can store vast amounts of information
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4
Q

How many hydrogen bonds form between base pairs?

A

A-T: two
C-G: three

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5
Q

What type of protein is found in chromosomes?

A

Histone

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6
Q

What molecules are DNA and RNA made up from?

A
  • phosphate group
  • nitrogenous bases
  • pentose sugar (deoxyribose in DNA and ribose in RNA)
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7
Q

What are the monomers of DNA and RNA called?

A

Nucleotides

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8
Q

How many chromosomes are usually found in a human cell?

A

46

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9
Q

Why is there variability in the stability of different sections of DNA?

A
  • The base pairings account for this as there are 3 hydrogen bonds between cytosine and guanine but only 2 between adenine and thymine
  • So the higher the proportion of of C-G pairings, the more stable the DNA molecule
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10
Q

How are the two polynucleotide chains that make up a DNA molecule held together?

A

Hydrogen bonds between the complementary bases of the nucleotides

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11
Q

What bond is formed between nucleotides?

A

Phosphodiester bonds

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12
Q

What conditions need to be met in order for DNA replication to occur?

A
  • The enzymes, DNA helicase and DNA polymerase must be present
  • ATP is required to drive the process
  • A ‘pool’ of the four nucleotides (free nucleotides)
  • Both strands of DNA need to be present so they can be copied
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13
Q

What are the two main stages of cell division?

A
  • Nuclear division (mitosis and meiosis)
  • Cell division
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14
Q

Explain why DNA replication is described as semi-conservative

A

Because the two daughter DNA molecules formed are genetically identical to the parent DNA molecule and each daughter DNA molecule contains one old and one new polynucleotide strand

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15
Q

Explain the process of DNA replication

A
  • DNA helicase unwinds the parent DNA molecule and breaks the hydrogen bonds between the complementary base pairs, exposing the nitrogenous bases on the two polynucleotide strands
  • Hydrolysis of ATP activates the free nucleotides that are free and abundant in the nucleus
  • The activated nucleotides attach themselves to the bases on the parent polynucleotide strands by complementary base pairing, forming hydrogen bonds
  • DNA polymerase catalyses the condensation reaction that joins adjacent nucleotides, forming the sugar-phosphate backbone
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16
Q

What is an ATP molecule made up of?

A
  • three phosphates
  • ribose sugar
  • adenine
17
Q

List 3 of the main biological functions of ATP

A
  • Metabolic processes such as the building of macromolecules (e.g. starch and polypeptides)
  • Active transport. The ATP changes the shape of carrier proteins which allows the movement of molecules against their concentration gradient
  • Movement, muscles need ATP so they have energy to contract
18
Q

Explain why ATP is an immediate source of energy

A
  • ATP releases its energy very rapidly
  • The energy is released in a single step and is transferred directly to the reaction requiring it
  • The energy containing phosphate bond is easily broken down to release the energy it holds
  • ATP is too unstable to be a long term energy store
19
Q

Explain how surface tension in water occurs

A
  • Where water molecules meet air, they tend to be pulled back into the body of water rather than escaping it (this force is surface tension)
  • Means that water surface acts like a skin and is strong enough to support small organisms
20
Q

Give 5 reasons water is important to living organisms

A
  • Has a relatively high specific heat capacity and so acts as a buffer against sudden temperature variations which makes the aquatic environment a temperature stable one
  • Is a metabolite in many metabolic reactions, including condensation and hydrolysis reactions
  • Is an important solvent in which metabolic reactions occur
  • Has a relatively large latent heat of vaporisation, providing a cooling effect with little loss of water through evaporation
  • Has strong cohesion between water molecules; this supports columns of water in the tube-like transport cells of plants and produces surface tension where water meets air

Biology (17 decks)

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