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A-levle Biology > 2.1.3 - Nucleotides and nucleic acids (set A - Nucleic acid + ATP) > Flashcards

2.1.3 - Nucleotides and nucleic acids (set A - Nucleic acid + ATP) Flashcards

1
Q

Describe the two types of nucleic acid?

A

DNA and RNA

  • both have roles in the storage and transfer of genetic information and the synthesis of proteins
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2
Q

Describe the structure of nucleic acid?

A

Large polymers formed from many nucleotides (monomers) linked together in a chain - they contain the elements carbon,hydrogen,oxygen, nitrogen and phosphorus

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3
Q

Describe the structure of a nucleotide?

A
  • A pentose monosaccharide (sugar) - containing 5 carbon atoms
  • a phosphate group - inorganic molecule that is acidic and negatively charged
  • nitrogenous base - complex organic molecule containing 1 or 2 carbon rings as well as nitrogen
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4
Q

Describe the linking of nucleotides during a condensation reaction and the breaking?

A

Nucleotide linked together by condensation reaction forming a polynucleotide

Convalent bonds formed between the phosphate group of the fifth carbon, pentose sugar and the hydroxyl group of the third carbon, of the pentose sugar of an adjacent nucleotide

The bonds are broken by hydrolysis - releasing individual nucleotides - reaction requires water

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5
Q

Explain in depth how phosphodiester bonds are formed between nucleotides?

A

Phosphate group at the fifth carbon of the pentose sugar of one nucleotide, forms a covalent bond with the hydroxyl group at the third carbon of the pentose sugar of an adjacent nucleotide - form a sugar phosphate backbone with a base attached to each sugar

  • happens during a condensation reaction, catalysed by enzymes
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6
Q

Describe the sugar phosphate backbone?

A

Result of the phosphodiester bonds formed between nucleotides during a condensation reaction - leads to a long strong sugar-phosphate backbone with a base attached to each sugar

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7
Q

Explain the two different groups of DNA nucleotides, number of carbon ring structures of four nucleotides?

A
  • pyrimidines - smaller bases (contain single carbon ring structures) Thymine (T) and Cytosine (C)
  • purines - larger bases (contain double carbon ring structures) Adenine (A) and Guanine (G)
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8
Q

Name the purine bases and describe their structure?

A

Two-ring molecules
- adenine C5H5N5
- guanine C5H5N5O

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9
Q

Name the pyrimidine bases and describe their structure?

A

One-ring molecules
- thymine C5H6N2O2
- cytosine C4H5N3O
- uracil C4H4N2O2 (RNA)

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10
Q

Describe the structure of DNA?

A

Molecule twists to form double helix of 2 deoxyribose polynucleotide strands (2 sugar-phosphate backbones)

H-bonds form between complementary base pairs (AT and GC) on strands that run anti parallel

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11
Q

Describe the structure of the double helix?

A

two complementary strands of nucleotides held together by hydrogen bonds between G-C and A-T base pairs

  • each strand has a phosphate group (5’) at one end and a hydroxyl group (3’) at the other ends - the strands are arranged so they run in opposite directions (antiparallel)
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12
Q

Explain the complementary base pairing?

A
  • Adenine and thymine form two hydrogen bonds and always join with each other
  • Cytosine and guanine form three hydrogen bonds and only bind to each other
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13
Q

Significance of complementary base paring?

A

DNA always has equal amounts of adenine and thymine and equal amounts of cytosine and guanine

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14
Q

Describe what RNA is, reference its role?

A

Ribonucleic acid plays an essential role in the transfer of genetic information from DNA to proteins

  • is a polymer made from long chains of 4 different nucleotides linked together by phosphodiester bonds
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15
Q

Explain the need for RNA?

A

DNA of each eukaryotic chromosome is a very long molecule, comprises of hundreds of genes - unable to leave the nucleus and supply the information directly to the sites of protein synthesis

  • DNA is copied to make a complementary strand of RNA (mRNA)
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16
Q

Describe the sugar which DNA contains?

A

Deoxyribose - type of ribose that lacks one oxygen atom

17
Q

describe the type of sugar that RNA contains?

A

Contains the sugars ribose which is a pentose (monosaccharide with 5 carbon atoms)

18
Q

Explain how the structure of RNA differs to DNA?

A

RNA nucleotides are different to DNA - pentose sugar is ribose rather than deoxyribose and the thymine base is replace with the base uracil (U)

Uracil is a pyrimidine which forms 2 hydrogen bonds with adenine

19
Q

Describe the structure and formation of RNA?

A

RNA nucleotides form polymers through the formation of phosphodiester bonds in condensation reactions

  • RNA polymers are small enough to leave the nucleus and travel to the ribosome
20
Q

Explain how RNA can be recycled in the cytoplasm?

A

After protein synthesis the RNA molecule are degraded in the cytoplasm - the phosphodiester bonds are hydrolysed and the RNA nucleotides are released and reused

21
Q

describe the molecules which make up RNA?

A

Has a phosphate, nitrogenous base and a ribose sugar

  • linked together by covalent bonds
22
Q

Explain the three main types of activity’s cells require energy for?

A
  • synthesis - of large molecules such as proteins
  • transport - pumping molecules or ions across cell membranes by active transport
  • movement - protein fibres in muscle cells that cause muscle contraction
23
Q

What is ATP, give its brief structure?

A

Adenosine triphosphate (ATP) is the source of energy for use and storage at the cellular level

  • nucleotide composed of a nitrogenous base, pentose sugar and three phosphate groups
24
Q

Explain how the structure of ATP differs from the nucleotides involved in the structure of DNA and RNA?

A

In the nucleotide ATP the base is always adenine, and there are three phosphate groups instead of one

  • sugar is ribose, same for RNA
25
Q

Explain why ATP is known as the ‘universal energy currency’?

A

ATP is used for energy transfer in all cells of all living things - for activities like synthesis, transport and movement

26
Q

Explain how ATP releases energy, what type of reaction is it?

A

a large amount of energy is released when the liberated phosphate undergoes other reactions involving bond formation (lot more energy released than used)

  • hydrolysis reaction - as water is involved in the removal of the phosphate group
27
Q

Explain how bond breaking and forming is important for energy release - reference this to ATP?

A

Energy is needed to break bonds and energy is released when bonds are formed

With ATP molecules a small amount of energy is needed to break the relatively weak bond holding the last phosphate group - however a large amount of energy is released when the liberated phosphate undergoes other reactions involving bond formation (lot more energy released than used)

28
Q

Give the word equation for the hydrolysis of ATP?

A

Adenosine triphosphate + water - adenosine diphosphate + inorganic phosphate + energy

29
Q

Give the products from the hydrolysis of ATP?

A

Adenosine diphosphate (ADP), a phosphate ion and the release of energy

30
Q

Why is the hydrolysis of ATP described as being ‘coupled’?

A

Hydrolysis of ATP does not happen in isolation but in association with energy-releasing reactions

  • reactions take place simultaneously
31
Q

Explain why ATP is not a good long term energy store, refrence its structure?

A

The instability of the phosphate bonds impacts its storage potential (fats and carbohydrates are better long term storage)

  • cell therefore don’t store much ATP however this is also due to the constant phosphorylation of ADP - meaning ATP is a good immediate energy store
32
Q

Explain the process phosphorylation, give the name of this type of reaction?

A

Energy released from the breakdown of carbohydrates and fats during cellular respiration is used to create ATP by reattaching a phosphate group to an ADP molecule

  • water is removed, so its a condensation reaction
33
Q

Explain some of the properties of ATP that enhance its fucntion?

A
  • small - allows it to easily move in and out of cells, also water soluble so it can happen in aqueous environments where reactions happen
  • releases energy in small quantities - provides enough energy for cellular needs without wasting energy as heat
  • easily regenerated - can be recharged with energy
34
Q

Explain how the bonds in ATP molecules are important for its role in energy release?

A

Contains bonds between phosphates with intermediate energy - large enough to be useful for cellular respiration but not so large that energy is wasted as heat

A-levle Biology (24 decks)

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