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A Level Biology - OCR Biology A > 2.1.3 Nucleotides > Flashcards

2.1.3 Nucleotides Flashcards

1
Q

DNA and RNA are both examples of…

A

Nucleic acids

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2
Q

Name the monomer that makes up nucleic acids.

A

Nucleotides

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3
Q

Name the three parts of a nucleotide.

A
  • Phosphate group
  • Pentose sugar
  • Nitrogenous base
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4
Q

Which type of pentose sugar is found in RNA?

A

Ribose

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5
Q

What is the difference between ribose and deoxyribose?

A

Ribose has an extra oxygen atom

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6
Q

Which type of pentose sugar is found in DNA?

A

Deoxyribose

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7
Q

Name the four nitrogenous bases in DNA.

A

Adenine, cytosine, guanine, thymine

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8
Q

Name the four nitrogenous bases in RNA.

A

Adenine, cytosine, guanine, uracil

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9
Q

Does this structure show a purine or a pyrimidine?

A

Purine

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10
Q

Does this structure show a purine or a pyrimidine?

A

Pyrimidine

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11
Q

Which bases are purines?

A

Adenine and guanine

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12
Q

Which bases are pyrimidines?

A

Cytosine, thymine and uracil

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13
Q

Which type of bond links together two or more nucleotides in a chain?

A

Phosphodiester bond

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14
Q

Which type of reaction occurs when a phosphodiester bond is formed?

A

Condensation reaction

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15
Q

How many phosphate groups are in ATP?

A

Three

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16
Q

Which type of pentose sugar is found in ATP and ADP?

A

Ribose

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17
Q

Which type of nitrogenous base is found in ATP and ADP?

A

Adenine (a purine)

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18
Q

How many phosphate groups are in ADP?

A

Two

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19
Q

What is the main difference between the structure of ATP and ADP?

A
  • ATP contains three phosphate groups
  • ADP contains two phosphate groups
20
Q

Describe how ADP is formed.

A
  • A high energy phosphate bond breaks in ATP
  • 7.6 kCal is released
  • ATP is converted into ADP
21
Q

In a DNA strand, is the 5’ (prime) end the phosphate end or the deoxyribose end?

A

Phosphate end

22
Q

Which type of bond occurs between base pairs in DNA?

A

Hydrogen bonds

23
Q

Describe the shape of a DNA molecule.

A

Double helix

24
Q

Which base forms a complementary base pair with adenine?

A

Thymine in DNA

Uracil in RNA

25
Q

Which base forms a complementary base pair with cytosine?

A

Guanine

26
Q

Name the enzyme that ‘unzips’ the DNA double helix during DNA replication.

A

DNA helicase

27
Q

How does DNA helicase ‘unzip’ the DNA double helix during DNA replication?

A

Breaking hydrogen bonds between the base pairs

28
Q

Name the enzyme that catalyses condensation reactions between adjacent nucleotides during DNA replication.

A

DNA polymerase

29
Q

In which direction can nucleotides be synthesised?

A

5’ to 3’ (5 prime to 3 prime)

(From the phosphate end to the deoxyribose end)

30
Q

Why is DNA replication described as semi-conservative?

A

The new DNA molecule is made up of:
- One strand that is conserved from the original DNA molecule
- One strand that is formed from free nucleotides

31
Q

Why is the genetic code described as being universal?

A

In almost all living organisms, the same triplet code codes for the same amino acid

32
Q

The base sequence is read in groups of…

A

3

33
Q

How many different DNA triplets (or RNA codons) are there in the genetic code?

A

64

34
Q

The genetic code is described as ‘degenerate’. Why is this?

A

Most amino acids are coded for by more than one codon (triplet code)

35
Q

A base deletion is an example of which type of mutation?

A

A frameshift mutation

36
Q

Name the molecule that is made during transcription.

A

mRNA

37
Q

Why doesn’t DNA travel from the nucleus to the ribosome for protein synthesis?

A

DNA is too large to leave the nucleus

38
Q

What happens during transcription?

A

DNA is transcribed (copied) and a molecule of mRNA is produced

39
Q

Where does transcription occur?

A

In the nucleus

40
Q

Describe the process of transcription in protein synthesis.

A
  • Free activated RNA nucleotides pair up via hydrogen bonds with their complementary base pairs on the exposed DNA strand
  • Sugar phosphate groups are bonded together with phosphodiester bonds by the enzyme RNA polymerase
  • When the gene has been transcribed, hydrogen bonds between DNA and RNA break
  • mRNA leaves the nucleus through pores in the nuclear envelope
41
Q

What happens during translation?

A

mRNA is translated and an amino acid sequence is produced.

42
Q

What is tRNA?

A

Free nucleotides in the cytoplasm that contain a region where an amino acid can attach

43
Q

What is an anticodon on tRNA?

A

A triplet of unpaired bases

44
Q

Describe the process of translation in protein synthesis.

A
  1. mRNA attaches to the ribosomes
  2. Free tRNA molecules bind with specific amino acids
  3. Anticodons (on the tRNA) bind with complementary codons (on the mRNA)
  4. A peptide bond is formed between the amino acids
  5. This continues until a stop codon is reached
45
Q

Which type of bond occurs between amino acids in a polypeptide chain?

A

Peptide bond

46
Q

Which amino acid is always carried by the first tRNA?

A

Methionine

47
Q

What is the triplet code of the ‘start codon’?

A

AUG

A Level Biology - OCR Biology A (13 decks)

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