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Biology AS > Nucleic Acids, 2.3 > Flashcards

Nucleic Acids, 2.3 Flashcards

1
Q

What is a nucleotide?

A

A monomer

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2
Q

What is nucleic acid?

A

Long polymer made from repeating units

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3
Q

What are nucleotides composed of?

A

Phosphate, Five-Carbon Sugar and a nitrogenous base

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4
Q

What is the bond between the nucleotide bases called?

A

Phosphodiester

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5
Q

Name two purine bases

A

Adenine. Guanine.

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6
Q

Name three pyrimidine bases

A

Thymine. Cytosine. Uracil.

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7
Q

Which bases bind together?

A

A and T. A and U. T and C.

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8
Q

When are they phosphorylated nucleotides?

A

When they contain more than one phosphate group eg ADP

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9
Q

What are the 2 forms of nucleic acids?

A

DNA - deoxyribose nucleic acid. RNA - ribonucleic acid.

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10
Q

Why is DNA important?

A

It makes up the structure of living organisms

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11
Q

What is the structure of DNA?

A

Consists of two strands of polynucleotides that are anti parallel. Arranged in a double helix.

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12
Q

What reaction are nucleotide bonds formed by?

A

Condensation reaction

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13
Q

What is the antiparallel sugar phosphate backbone?

A

The strands run in different directions but are parallel. One runs from 3’ end to 5’ and the other runs from 5’ to 3’

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14
Q

What bonds are the anti parallel strands held together by?

A

Hydrogen

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15
Q

How many hydrogen bonds are between A and T?

A

2

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16
Q

How many hydrogen bonds are between C and G?

17
Q

What is meant by complementary base pairing?

A

Each base can only join with another particular base

18
Q

What is meant by a double helix?

A

When two polynucleotide strands are twisted into a spiral and held together by hydrogen bonds

19
Q

What is DNA wrapped around?

A

Histone proteins`

20
Q

How is DNA arranged in prokaryotes?

A

In a loop not enclose in a nucleus. Described as naked

21
Q

Name the differences between RNA and DNA.

A

RNA has Uracil instead of Thymine. RNA is a single stranded polynucleotide.

22
Q

When does DNA replication occur?

A

During interphase

23
Q

Describe the different stages of DNA replication.

A
  1. Unwind - double helix is untwisted
  2. Unzips - hydrogen bonds broken by DNA Helicase
  3. Free nucleotide bases bond to exposed bases
  4. DNA Polymerase catalyses the addition of new bases, using the DNA strand as a template
  5. Leading strand synthesized continuously
  6. Lagging strand synthesized in fragments
24
Q

What does the hydrolysis of activated nucleotides release?

A

Extra phosphate groups. Supplies energy for the phosphodiester bond

25
Q

Define semi conservative replication

A

DNA replicates and has one new strand and one old strand, the two strands are identical.

26
Q

Why is DNA replication important?

A

Ensures the preservation of genetic information. Structure and functions of proteins relies entirely on the correct sequence being copied,

27
Q

What is the proof for semi conservative replication?

A
  1. Heavy 15N - grown for 14 generations
  2. Mixed with lighter 14N - undergo one replication
  3. Turned out to be a hybrid of both
  4. Allowed to replicate once more
  5. When centrifuged showed two different bands - one hybrid one light
28
Q

What does complementary base pairing allow?

A

Replication. The code to be preserved.

29
Q

Key features of the genetic code.

A

Sequence of 3 bases. Contains thousands of genes each codes for a specific polypeptide. Is universal. Degenerate.

30
Q

What is the triplet code?

A

A sequence of 3 bases which codes for an amino acid

31
Q

What does degenerate mean?

A

Amino acid can be coded for by more than one triplet code

32
Q

Why does a polypeptide need the correct primary structure?

A

So it will fold correctly and will be able to carry out its function

33
Q

What is transcription?

A

Making mRNA from a DNA template

34
Q

What is translation?

A

Formation of proteins at a ribosome using mRNA

35
Q

Which strand of DNA is the mRNA formed from?

A

The template strand - it’s identical to the coding strand

36
Q

Describe the stages of transcription

A
  1. DNA unwinds and unzips- DNA Helicase
  2. RNA polymerase catalyses the formation of a complementary mRNA strand from free RNA nucleotides
  3. As the mRNA strand is formed the DNA recoils behind
  4. mRNA passes out of the nucleus and attaches to a ribosome
37
Q

What are the key features of tRNA?

A

Carry specific amino acids. Have an anticodon that binds to complementary codon on mRNA. Has 3 unpaired bases for amino acid to join.

38
Q

What is the start codon?

39
Q

Describe the stages of translation

A
  1. mRNA attaches to the start codon on a ribosome
  2. tRNA binds to complementary codon on mRNA
  3. tRNA carries an amino acid
  4. Another tRNA attaches and there are now 2 amino acids
  5. The amino acids form a polypeptide bond
  6. This continues until the stop codon is reached

Biology AS (12 decks)

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