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Biology > Nucleic Acids and ATP > Flashcards

Nucleic Acids and ATP Flashcards

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1
Q

Name the pentose sugars in DNA & RNA.

A

DNA: deoxyribose
RNA: ribose

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2
Q

State the role of DNA living in cells.

A

Base sequences of gene codes for functional RNA & amino acid sequence of polypeptides.
Genetic information determines inherited characteristics = influences structure & function of organisms.

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3
Q

State the role of RNA in living cells.

A
  • mRNA: complementary sequence to 1 gene from DNA with introns (non-coding regions) spliced out. Codons can be translated into a polypeptide by ribosomes.
    -rRNA: component of ribosomes (along with proteins).
  • tRNA: supplies complementary amino acid to mRNA codons during translation.
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4
Q

How do polynucleotides form?

A

Condensation reactions between nucleotides form stronger phosphodiester bonds (sugar-phosphate backbone).

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5
Q

Describe the structure of DNA.

A

Double helix of 2 polynucleotide strands (deoxyribose).
H-bonds between complementary purine & pyrimidine base pairs on opposite strands:
adenine (A) + thymine (T)
guanine (G) + cytosine (C)

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6
Q

Which bases are purine and which are pyrimidine?

A

A & G = 2-ring purine bases
T & C & U = 1-ring pyrimidine bases

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7
Q

Name the complementary base pairs in DNA.

A

2 H-bonds between adenine (A) + thymine (T)
3 H-bonds between guanine (G) + cytosine (C)

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8
Q

Name the complementary base pairs in RNA.

A

2 H-bonds between adenine (A) + uracil (U)
3 H-bonds between guanine (G) + cytosine (C)

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9
Q

Relate the structure of DNA to its functions.

A
  • sugar phosphate backbone & many H-bonds provide stability
  • long molecule stores lots of information
  • helix is compact for storage in nucleus
  • base sequence of triplets codes for amino acids
  • double-stranded for semi-conservative replication
  • complementary base pairing for accurate replication
    -weak H-bonds break so strands separate for replication
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10
Q

Describe the structure of mRNA.

A
  • long ribose polynucleotide (shorter than DNA)
  • contains uracil instead of thymine
  • single-stranded and linear (no complementary base pairing)
  • codon sequence is complementary to exons of 1 gene from 1 DNA strand
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11
Q

Relate the structure of mRNA to its functions.

A
  • breaks down quickly so no excess polypeptide forms
  • ribosome can move along strand & tRNA can bind to exposed bases
  • can be translated into a specific polypeptide by ribosomes
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12
Q

Describe the structure of tRNA.

A
  • single strand of around 80 nucleotides
  • folded into clover shape
  • anticodon on one end, amino acid binding site on the other:
    a) anticodon binds to complementary mRNA codon
    b) amino acid corresponds to anticodon
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13
Q

Order DNA, mRNA and tRNA according to increasing length.

A

tRNA
mRNA
DNA

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14
Q

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

A

Chemically simple molecule with few components.

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15
Q

Why is DNA replication described as semi-conservative?

A
  • strands from original DNA molecule act as a template
  • new DNA molecule contains 1 old strand & 1 new strand
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16
Q

Outline the process of semiconservative DNA replication.

A
  1. DNA helicase breaks H-bonds between base pairs
  2. Each strand acts as a template
  3. Free nucleotides from nuclear sap attach to exposed bases by complementary base pairing
  4. DNA polymers catalyses condensation reactions that join adjacent nucleotides on new strand and phosphodiester bonds form
  5. H-bonds reform between complementary base pairs
17
Q

Describe the structure of ATP.

A

Nucleotide derivative of adenine with 3 phosphate groups.

18
Q

Explain the role of ATP in cells.

A

ATP hydrolase catalyses ATP –> ADP + Pi
- energy released is coupled to metabolic reactions
- phosphate group phosphorylates compounds to make them more reactive

19
Q

How is ATP resynthesised in cells?

A
  • ATP synthase catalyses condensation reaction between ADP + Pi
  • during photosynthesis & respiration
20
Q

Explain why ATP is suitable as the ‘energy currency’ of cells.

A
  • high energy bonds between phosphate groups
  • small amounts of energy released at a time = less energy wasted as heat
  • single-step hydrolysis = energy available quickly
    -readily resynthesised

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