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Biology AS > 3.8 Nucleic Acids > Flashcards

3.8 Nucleic Acids Flashcards

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1
Q

Where were nucleic acids discovered?

A

Cell nuclei

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2
Q

What are the 2 types of nucleic acids?

A

DNA and RNA

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3
Q

What is the function of nucleic acids?

A

Storage and transfer of genetic material.

Synthesis of polypeptides (proteins).

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4
Q

What elements do nucleic acids contain?

A

C, H, O2, N, P

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5
Q

What are nucleic acids? How are they formed?

A

Large polymers formed from many nucleotides (monomers) linked in a chain

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6
Q

A nucleotide is made up of three components. Name them.

A
  • A pentose monosaccharide, containing 5 carbon atoms
  • A phosphate group, (-PO4)2-, an inorganic molecule that’s acidic and negatively charged
  • A nitrogenous base - complex organic molecule containing 1 or 2 carbon rings and a nitrogen in its structure
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7
Q

How are nucleotides linked together?

A

By condensation reactions to form a polymer called a polynucleotide

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8
Q

Describe the structure of polynucleotides.

A

Phosphate group @ 5th carbon of pentose sugar of one nucleotide forms a covalent bond with hydroxyl group at 3rd carbon of the pentose sugar.

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9
Q

Describe the structure of what’s formed after 2 nucleotides are linked by condensation reactions?

A

Long, strong sugar-phosophate backbone, with a base attached to each sugar

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10
Q

What are phosphodiester bonds broken by?

A

Hydrolysis - reverse of condensation reaction, releasing the nucleotides

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11
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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12
Q

What type of sugar is DNA?

A

Deoxyribose - sugar w/ one less O atoms than ribose

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13
Q

DNA is composed of 4 bases. What 2 groups are these bases broken into?

A

Pyrimadines

Purines

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14
Q

What are pyrimadines?

A

Smaller bases, containing single carbon ring structures.

T and C

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15
Q

What are purines?

A

Larger bases, containing double carbon ring structures.

A and G

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16
Q

What are the 2 strands of a DNA double helix held by?

A

H bonds

17
Q

Describe specifically how 2 strands of DNA double helix are held together.

A

Each strand has a phosphate group, C5, at one end and a hydroxyl group, C3, at the other

18
Q

Why are the 2 strands of a DNA helix said to be antiparallel?

A

The strands are arranged so that they run in opposite directions

19
Q

How many H bonds hold C and G together?

A

3

20
Q

How many H bonds hold A and T together?

A

2

21
Q

Define complementary base pairing.

A

Specific H bonding between nucleic acid bases.

A/U binds to T, C binds to G

22
Q

What do the complementary base pairing rules mean in terms of how DNA bases bond?

A

Small pyrimidine bases always binds to larger purine base.

This arrangement maintains a constant distance between DNA backbones, resulting in parallel polynucleotide chains

23
Q

What else does complementary base pairing ensure?

A

DNA always has equal amounts of A and T, and C and G

24
Q

What carries an organism’s genetic code?

A

Order of sequence of bases along a DNA strand

25
Q

What does RNA play a role in?

A

Transfer of genetic information from DNA -> proteins that make up enzymes and tissues

26
Q

What does DNA store?

A

All the genetic info needed by an organism

27
Q

DNA of eukaryotes is long, compromising hundreds of genes. What is the problem with this?

A

DNA is too big to leave the nucleus to supply info directly to sites of protein synthesis

28
Q

How do eukaryotes get over the problem of DNA being too large to leave the nucleus?

A

A short section of DNA containing 1 gene is transcribed into a short mRNA molecule.
Each mRNA is shorter than the chromosome of DNA.

29
Q

Describe the structure of mRNA

A

Polymer composed of many nucleotide monomers

30
Q

What’s the difference between DNA and mRNA?

A

DNA sugar = deoxyribose
mRNA sugar = ribose

DNA = T + A
mRNA = U + A (Uracil replaces thymine)
31
Q

Is there a difference between Uracil (U) and Adenine (A)?

A

No - U still forms 2 H bonds with A

32
Q

Do nucleotides with U instead of T form in the same way?

A

Yes - by forming phosphodiester bonds through condensation reactions

33
Q

If the problem is that DNA itself is too big to leave the nucleus, how does turning it into RNA polymers help?

A

The RNA polymers are small enough to leave the nucleus - they can travel to ribosomes and trigger protein synthesis

34
Q

What happens to RNA molecules after protein synthesis?

A

RNA is degraded in the cytoplasm - phosphodiester bonds are hydrolysed and RNA nucleotides are released + reused

Biology AS (148 decks)

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