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Biology - OCR A > 2.3 - Nucleic Acids > Flashcards

2.3 - Nucleic Acids Flashcards

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1
Q

What is a triplet code?

A

A triplet code is where each codon, consists of three nuceoltides that each code for amino acids.

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2
Q

What is a codon?

A

A codon is a DNA or RNA sequence of three nucleotides on a section on mRNA.

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3
Q

What is an anticodon?

A

An anticodon is a trinucleotide sequence located at one end of a tRNA molecule, which is complementary to a corresponding codon in the mRNA.

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4
Q

Why is genetic code universal?

A

Genetic code is universal because nearly every organism uses the same code.

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5
Q

What is the structure of a nucleotide?

A
  • Phosphate
  • Pentose sugar
  • Nitrogenous base (A, C, G and T)
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6
Q

What is the structure of a nucleotide?

A
  • Phosphate
  • Pentose sugar
  • Nitrogenous base (A, C, G and T)
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7
Q

What pentose sugar does a DNA nucleotide have?

A

Deoxyribose sugar

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8
Q

What pentose sugar does a RNA nucleotide have?

A

Ribose sugar

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9
Q

What is the structure of ATP?

A
  • Adenine
  • Ribose sugar
  • 3x phosphates
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10
Q

What is the name of the process when a phosphate group is added?

A

Phosphorylation

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11
Q

What are 2 types of pyrimidines?

A

Cytosine and thymine

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12
Q

What are 2 types of purines?

A

Adenine and guanine

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13
Q

Why is DNA replication necessary?

A

For cells to divide and replicate

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14
Q

What does a DNA helicase do?

A

It breaks the hydrogen bonds that hold the two strands together

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15
Q

What do DNA polymerase do?

A

They add nucleotides to the template strand

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16
Q

How do the DNA polymerase know where to start adding nucleotides?

A

RNA primers are added to the strands

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17
Q

What is a leading strand?

A

The strand that the DNA polymerase progress down the strand

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18
Q

What is a nucleotide?

A

It is a monomer from which nuclei acids, like DNA and RNA, are formed

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19
Q

How can you tell that a nucleotide is a purine?

A

2 carbon ring structure

20
Q

How can you tell that a nucleotide is a pyrimidine?

A

1 carbon ring structure

21
Q

What can be categorised according to their ring structure?

A

Nitrogenous bases

22
Q

What bases are complementary?

A
  • Thymine (or uracil in RNA) and Adenine
  • Guanine and Cytosine
23
Q

What reaction does DNA and RNA undergo to form a phosphodiester bond?

A

A condensation reaction

24
Q

Where does the phosphodieser bonds form?

A

Between 2 nucleotide monomers to create a polymer

25
Q

What is a phosphodiester bond (nucleotides)?

A

It is a strong covalent bond between the pentose sugar and a phosphate of different nucleotides

26
Q

What is ATP used for?

A

Metabolism as it is an immediate source of energy for biological molecules

27
Q

When is ATP made?

A

In respiration (mostly aerobic)

28
Q

How is ATP made?

A

A condensation reaction using the enzyme ATP synthas
ADP + Pi —> ATP +H2O

29
Q

What happens when ATP is hydrolysed?

A

It breaks one of the bonds between the phosphate group which releases a small amount of energy

30
Q

What does DNA do (nucleic acids)?

A

It codes for a sequels of amino acids in the primary structure of a protein which determines the final 3D structure

31
Q

What is the structure of a DNA strand?

A

DNA polymers forms a double helix made of 2 antiparallel starands that are joined together by hydrogen bonds between the bases of the 2 strands

32
Q

How does DNA’s structure relate to its function?

A

Stable structure - due to the sugar-phosphate backbone and the double helix
Double stranded - both strands can be used as templates in replication
Weak hydrogen bonds - easy separation of the 2 strands
A large molecule - can carry lots of information
Complementary base pairings - identical copies can be made

33
Q

What are the 3 types of RNA?

A

mRNA - messenger RNA
tRNA - transfer RNA
rRNA - ribosomal RNA

34
Q

What does rRNA do?

A

It makes up the bulk of ribosomes

35
Q

What is mRNA?

A

A single strand with a copy of every 3 bases from the DNA

36
Q

What does mRNA do?

A

It is created in the nucleus and it leaves via the nuclear pores to carry a copy of the genetic code to a ribosome

37
Q

Where is tRNA found?

A

In the cytoplasm

38
Q

What is the shape of tRNA?

A

Single stranded but folded to create a cloverleaf shape and is held in place by hydrogen bonds

39
Q

What does tRNA do?

A

It brings an amino acid to the ribosome depending on the 3 bases found which are complementary to the codon on the mRNA

40
Q

What is semiconservative DNA replication?

A

One strand is conserved and one new strand is created

41
Q

How do copying errors in DNA replication occur?

A

They happen randomly and spontaneously

42
Q

What happens when a copying error is made in DNA replication?

A

It changes that DNA base sequence resulting in a mutation

43
Q

When does DNA replication occur in the cell cycle?

A

S-phase of interphase

44
Q

What happens in transcription?

A
  1. The target gene on the DNA unwinds because of the DNA helicase
  2. Free RNA nucleotides match up to their complementary bases on the open strand
  3. The RNA nucleotides bond together along the backbone with phosphodiester bonds in a 5’-3’ direction to produce a copy of mRNA
  4. The single strand of mRNA moves out through the nuclear pores to the ribosomes, and the DNA zips back up
45
Q

What happens in translation?

A
  1. Once the mRNA reaches the ribosome it moves through it in codons
  2. For each codon a tRNA with the complementary anticodons temporarily bind
  3. Each tRNA carries a specific amino acid depending on the anticodon sequence
  4. The amino acids bind together with peptide bonds and eventually form a polypeptide chain
  5. The tRNA molecules move away and the newly synthesised polypeptide can be modified by the ribosome
46
Q

What happens in secretion?

A
  1. After translation the protein is then pinched off into vesicles and goes to the golgi body
  2. The vesicle fuses with the golgi body where the protein is processed and packaged
  3. The packaged protein is then put in a vesicle and goes to the plasma membrane
  4. The vesicle fuses with the membrane and it opens up releasing the protein

Biology - OCR A (25 decks)

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