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biological molecules > Nucleic Acids And ATP > Flashcards

Nucleic Acids And ATP Flashcards

1
Q

What is the structure of a nucleotide

A

Phosphate group, Pentose sugar, nitrogen containing base

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2
Q

Function of DNA

A

Holds genetic information which codes for polypeptides

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3
Q

What is DNA Pentose sugar

A

Deoxyribose

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4
Q

What is the function of RNA

A

Transfer genetic info from DNA to ribosomes

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5
Q

How are polynucleotides formed

A

● Condensation reactions, removing water molecules
● Between phosphate group of one nucleotide and deoxyribose / ribose
● Forming phosphodiester bond

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6
Q

When nucleotides join together what type of bond does it form

A

Phosphodiester bond

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7
Q

In a polynucleotide what are the chain of sugars known as

A

Sugar phosphate backbone

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8
Q

Compare the structure of DNA and RNA

A

DNA- double helix- 2 polynucleotide strands
Pentose sugar= deoxyribose
Nitrogen contains base= thymine
Longer

RNA- single helix
Nitrogen containing base is uracil
Pentose sugar= ribose
Shorter

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9
Q

What are the complementary base pairs of DNA

A

2 hydrogen Bonds with adenine and thymine
3 hydrogen bonds between guanine and cytosine

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10
Q

What are the complementary base pairs of RNA

A

2 hydrogen bonds between adenine and uracil
3 hydrogen bonds between guanine and cytosine

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11
Q

How does the structure of DNA relate to its function

A

● Two strands → both can act as templates for semi-conservative replication
● Hydrogen bonds between bases are weak → strands can be separated for replication
● Complementary base pairing → accurate replication
● Many hydrogen bonds between bases → stable / strong molecule
● Double helix with sugar phosphate backbone → protects bases / hydrogen bonds
● Long molecule → store lots of genetic information (that codes for polypeptides)
● Double helix (coiled) → compact

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12
Q

Describe the structure of (messenger) RNA

A

● Polymer of nucleotides (polynucleotide)
● Each nucleotide formed from ribose, a phosphate
group and a nitrogen-containing organic base
● Bases - uracil, adenine, cytosine, guanine
● Phosphodiester bonds join adjacent nucleotides
● Single helix

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13
Q

Why is semi conservative replication important

A

Ensures genetic continuity between generations of cells

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14
Q

Why is semi conservative replication described as semi conservative

A

-strands from DNA acts as a template
-new DNA molecule contains one old and one new strand

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15
Q

What is the semi conservative process breifly review

A
  1. DNA helicase breaks hydrogen bonds between complementary bases, unwinding the double helix
  2. Both strands act as templates
  3. Free DNA nucleotides attracted to exposed bases and join by specific complementary base pairing
  4. Hydrogen bonds form between adenine-thymine and guanine-cytosine
  5. DNA polymerase joins adjacent nucleotides on new strand by condensation reactions
  6. Forming phosphodiester bonds
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16
Q

What is a phosphodiester bond

A

2 ester bonds in a polynucleotide

17
Q

Which scientist validated Watson and Crick of the structure of DNA and the theory of semi conservative replication

A

Meleson and stahl

18
Q

Describe the work of Meselson and Stahl in validating the Watson-Crick model of semi-conservative DNA replication

A
  1. Bacteria grown in medium containing heavy nitrogen so nitrogen is incorporated into DNA bases
    ○ DNA extracted & centrifuged → settles near bottom, as all DNA molecules contain 2 ‘heavy’ strands
  2. Bacteria transferred to medium containing light nitrogen and allowed to divide once
    ○ DNA extracted & centrifuged → settles in middle, as all DNA molecules contain 1 original ‘heavy’ and 1 new ‘light’ strand
  3. Bacteria in light nitrogen allowed to divide again
    ○ DNA extracted & centrifuged → half settles in middle, as
    contains 1 original ‘heavy’ and 1 new ‘light’ strand; half settles near top, as contains 2 ‘light’ strands
19
Q

What is the nucleotide ATP deprived from

A

A molecule of ribose, adenine and 3 phosphate groups

20
Q

What is ATP known as

A

Adenosine triphosphate

21
Q

Describe how ATP is broken down

A

● ATP (+ water) → ADP (adenosine diphosphate) + Pi (inorganic phosphate)
● Hydrolysis reaction, using a water molecule
● Catalysed by ATP hydrolase

22
Q

Give two ways in which the hydrolysis of ATP is used in cells

A

● Coupled to energy requiring reactions within cells (releases energy) ○ eg. active transport, protein synthesis
● Inorganic phosphate released can be used to phosphorylate
(add phosphate to) other compounds, making them more reactive

23
Q

Describe how ATP is resynthesised in cells

A

● ADP + Pi → ATP (+ water)
● Condensation reaction, removing a water molecule
● Catalysed by ATP synthase (enzyme)
● During respiration and photosynthesis

24
Q

what are 2 similarities of RNA and DNA

A

Both important information carrying molecules
both are polymers of nucleotides

25
Q

how is the sugar phosphate backbone made in a polynucleotide

A

series of condensation reactions between the deoxyribose sugar and the phosphate group making a polynucleotide and a phosphodiester bond

26
Q

the DNA polymer occurs in pairs and is joined by what

A

hydrogen bonds between bases leading to the double helix

27
Q

Use your knowledge of enzyme action to suggest why DNA polymerase moves in opposite directions along DNA strands

A

● DNA has antiparallel strands
● So shapes / arrangements of nucleotides on two ends are different
● DNA polymerase is an enzyme with a specific shaped active site
● So can only bind to substrate with complementary shape

28
Q

Name the two scientists who proposed models of the chemical structure of DNA and of DNA replication

A

Watson and Crick

29
Q

what is the last step of semi conservative replication

A

DNA polymerase in the condensation reaction that joins adjacent nucleotides.

30
Q

Describe the work of Meselson and Stahl in validating the Watson-Crick
model of semi-conservative DNA replication

A
  1. Bacteria grown in medium containing heavy nitrogen (15N) so
    nitrogen is incorporated into DNA bases
    ○ DNA extracted & centrifuged → settles near bottom, as all
    DNA molecules contain 2 ‘heavy’ strands
  2. Bacteria transferred to medium containing light nitrogen (14N)
    and allowed to divide once
    ○ DNA extracted & centrifuged → settles in middle, as all DNA
    molecules contain 1 original ‘heavy’ and 1 new ‘light’ strand
  3. Bacteria in light nitrogen (14N) allowed to divide again
    ○ DNA extracted & centrifuged → half settles in middle, as
    contains 1 original ‘heavy’ and 1 new ‘light’ strand; half settles
    near top, as contains 2 ‘light’ strands
31
Q

Why did many scientists initially doubt that DNA carried the genetic code?

A

The relative simplicity of DNA - chemically simple molecule with few components

32
Q

Suggest how the properties of ATP make it a suitable immediate source of
energy for cells

A

● Releases energy in (relatively) small amounts / little energy lost as heat
● Single reaction / one bond hydrolysed to release energy (so immediate release)
● Cannot pass out of cell

biological molecules (5 decks)

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