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Biology A1 > 8a: Nucleic Acids > Flashcards

8a: Nucleic Acids Flashcards

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1
Q

What is the full form of DNA + RNA?
Why are they named “nucleic acids”?

A
  1. DNA: deoxyribonucleic acid
    RNA: ribonucleic acid
  2. nucleic- due to discovery in the nucleus
    acid - due to presence of phosphate group
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2
Q

DNA + RNA are ______ of monomers called _______

A
  1. polymers
  2. nucleotides
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3
Q

What are the 3 components of a Nucleotide?

A
  • pentose sugar
  • phosphate group
  • nitrogenous organic base
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4
Q

Nucleotides are ______ that join together via ______ to form ________ _________

A
  1. monomers
  2. condensation
  3. polynucleotide strand/chain
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5
Q

How is the polynucleotide chain held together?
What is the sugar-phosphate backbone?
Which components alter the polynucleotide chains apart?

A
  1. phosphate group of one nucleotide is linked to the sugar of the next via phosphodiester bonds (strong covalent)
  2. the phosphate group + sugar are identical throughout the chain
  3. sequence of bases in the polynucleotide
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6
Q

What are the components of DNA nucleotides?

A
  • pentose sugar (deoxyribose)
  • nitrogenous bases:
    Adenine (A), Guanine (G), Cytosine (C), Thymine (T)
  • phosphate group
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7
Q

Which bases in DNA nucleotides are Pyrimidines and Purines?
Which are larger?

A

Purines:
- Adenine + Guanine
Pyrimidines:
- Cytosine + Thymine
Purines are larger than Pyrimidines

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8
Q

Describe the Structure of one DNA molecule:

A
  • 2 polynucleotide strands/chains running anti-parallel to each other, twisting to form a double helix
  • bases in each strand are held together by hydrogen bonding
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9
Q

Which bases are always paired with each other?
How many hydrogen bonds are formed between bases?
What term is used to describe the pairing of bases?

A

1.
- Adenine always pairs with Thymine
- Guanine always pairs with Cytosine
2.
- Adenine forms 2 hydrogen bonds with Thymine
- Guanine forms 3 hydrogen bonds with Cytosine
3. complementary base pairing

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10
Q

Some Viruses have single stranded DNA.
How could an analysis of a piece of DNA tell you if it was single stranded?

A
  • in double stranded DNA, there would be equal portions of the different complementary base pairs, but in single strands the proportion of each base would differ
  • there would not be an equal number of purines/pyrimidines in the single stranded DNA
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11
Q

Explain 4 ways how the Structure of DNA relates to Function:

A
  1. It is Stable:
    - molecule has a double helix structure with many hydrogen bonds between complementary base pairs
    - also contains many (strong covalent) phosphodiester bonds between deoxyribose sugar of one nucleotide, to the phosphate group of another
  2. Contains complementary base pairing:
    - allows DNA to replicate itself exactly when cells divide
    - contains weak hydrogen bonds which allow strands to separate in this process
  3. It is Compact:
    - although DNA molecules are long (so will have lots of coded information), the double helix shape allows DNA to fit inside a nucleus of a cell
  4. It has a precise genetic code:
    - precise genetic code is determined by the sequence of bases, which controls protein synthesis
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12
Q

RNA is a _____ _____ polynucleotide

A
  • single stranded
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13
Q

What are the 3 components that make up RNA nucleotides?

A
  • ribose sugar
  • nitrogenous base pairs:
    Adenine (A), Guanine (G), Cytosine (C) and Uracil (U)
  • phosphate group
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14
Q

Which base is not found in RNA?
Is Uracil a Purine or Pyrimidine?

A
  1. Thymine
  2. Pyrimidine
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15
Q

Why do cells have to undergo DNA replication?

A
  • after cell division new cells must have the same genetic code as the parent cells or they would not be able to make the same proteins needed by the cell
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16
Q

What type of DNA Replication occurs?
Describe + Explain this process:

A
  1. Semi-Conservative
    - An enzyme called DNA helicase unwinds the double helix structure, by breaking weak hydrogen bonds between complementary bases in the polynucleotide strands
    - each exposed polynucleotide strand now acts as a template for the formation of a new strand
    - new DNA nucleotides (present in nucleus), would be attracted to the exposed bases on the template strands, and attach by complementary base pairing with new hydrogen bonds forming between bases
    - the enzyme DNA polymerase joins the new nucleotides together to form a new polynucleotide strand, with phosphodiester bonds forming between adjacent nucleotides via condensation reactions
17
Q

How did Evidence for the Semi-Conservative Replication come about?

A
  1. bacteria E.Coli contain circular molecules of DNA
  2. cultures of these cells are first grown in a medium containing the heavy isotope 15N, so all the DNA will be labelled with 15N
  3. however, this will be transferred to a medium containing normal 14N isotope (light)
  4. these samples are left to replicate, and be centrifuged and extracted
18
Q

What is the role of ATP?
What does ATP stand for?

A
  • ATP is the immediate source of energy used by all cells for metabolic reactions
  • Adenosine Triphosphate
19
Q

What are the components of ATP?
ATP molecules are derived from _______

A
  • 3 phosphate groups (ions)
  • ribose sugar
  • Adenine organic base
    2. nucleotides
20
Q

Describe the Synthesis of ATP:

A
  1. ATP is synthesised by the condensation of ADP (adenosine diphosphate) + Pi (inorganic phosphate)
  2. this reaction is catalysed by the enzyme ATP synthase
  3. this reaction requires an input of energy from a metabolic process e.g respiration, or sometimes light energy from photosynthesis
  4. the addition of phosphate is phosphorylation

ADP + Pi —> ATP

21
Q

Describe the Breakdown of ATP:

A
  1. useful energy is mainly stored in the phosphate-phosphate bonds of the ATP molecule, between the 2nd + 3rd group
  2. this is because the covalent bond between the 2 groups is unstable, and easily hydrolysed by the enzyme ATP hydrolase in an hydrolysis reaction
  3. when this occurs an inorganic phosphate group is removed, ENERGY IS RELEASED, and ATP becomes ADP

ATP ——> ADP + Pi

22
Q

Describe 5 different processes where ATP is required:

A
  1. Active Transport:
    - energy is required to move substances against their concentration gradients, using carrier proteins/pumps in their plasma membrane
    - the protein pumps are also ATP hydrolase enzymes, since they catalyse the hydrolysis of ATP —> ADP + Pi
    - this releases energy which is used to change shape + pump the molecule
  2. Exocytosis:
    - energy is required to make vesicles which are membrane bound species produced by the Golgi Body, to package large materials before secretion from cell
    - energy also required for endocytosis, which brings large molecules into the cells
  3. Biosynthesis:
    - energy required to make larger molecules (polymers) from smaller molecules (monomers) e.g syntheses of proteins via condensation of amino acids
  4. Movement (muscle cells):
    - energy required for muscle contraction
  5. activation of other molecules:
    - ATP can transfer its phosphate group to other molecules (phosphorylating them), making them more reactive e.g glucose requires phosphorylating at the start of respiration to ensure the activation energy of the reaction is reduced
23
Q

Why is ATP not a good long-term energy source?
Why is this not a problem?

A

1.
- due to instability of its phosphate bonds
- cells can only maintain few seconds supply
2. ATP can can be rapidly reformed via the condensation of ADP + Pi (with an input of energy from metabolic process)

24
Q

Why is ATP a more useful source of energy than Glucose?

A
  1. the breakdown of ATP is a single reaction, making it a immediate source of energy, however, the breakdown of Glucose is much more complex involving numerous stages
  2. ATP is soluble, so can be transported inside the cell easily (although it cannot pass through cell membranes)
  3. the breakdown of ATP releases a small amount of energy, ideal for fuelling the energy requiring reactions which occur in the cell. the breakdown for glucose releases too much energy than what is required, therefore a lot of energy would be wasted as heat (inefficient)

Biology A1 (15 decks)

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