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SACE Biology II > Topic 1 - DNA and Proteins > Flashcards

Topic 1 - DNA and Proteins Flashcards

1
Q

State what is meant by a nucleic acid? (1 mark)

A

A macromolecule made up of repeating units called nucleotides

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2
Q

What shape does a DNA molecule take? (1 mark)

A

Double Helix

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3
Q

What type of secondary interaction holds the DNA molecule together? (1 mark)

A

Hydrogen Bonding

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4
Q

What three subunits make up a nucleotide? (3 marks)

A

Phosphate, Sugar, Base

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5
Q

What are four differences between DNA and RNA (4 marks)

A
  1. DNA is long / RNA is short
  2. DNA is double stranded / RNA is single stranded
  3. DNA uses ATCG / RNA uses AUCG
  4. DNA uses a deoxyribose sugar / RNA uses a ribose sugar
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6
Q

What are three differences between prokaryotic and eukaryotic DNA? (3 marks)

A
  1. Prokaryotic DNA is circular / Eukaryotic is linear
  2. Prokaryotic has one chromosome / Eukaryotic have many
  3. Prokaryotic DNA is unbound / Eukaryotic is bound to globular proteins called histones
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7
Q

Why is DNA replication described as semi-conservative? (2 marks)

A

Both original strands act as a template for the synthesis of a new strand (1)

Resulting molecule(s) contain one original (conserved) and one newly-synthesised strand (1)

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8
Q

What is the role of the helicase enzyme in DNA replication? (2 marks)

A

Breaks the weak hydrogen bonds between bases (1)

Exposes the inward-facing nitrogenous bases (1)

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9
Q

What is a gene? (2 marks)

A

Sequences of nucleotide bases (1) that code for the production of a protein or RNA molecule (1)

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10
Q

What is a protein? (1 mark)

A

A large molecule, made up of smaller molecules called amino acids (1)

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11
Q

How many DNA bases make up a codon? (1 mark)

A

3

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12
Q

Why is the genetic code described as degenerate? (1 mark)

A

Several nucleotide sequences may code for the same amino acid (1)

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13
Q

What are three similarities and three differences between DNA replication and transcription?

A

Similarities:

  1. Both use helicase to break hydrogen bonding (1)
  2. Both use a polymerase enzyme to synthesise a backbone (1)
  3. Both occur in the nucleus (1)

Differences:

  1. Replication copies an entire molecule, transcription copies just one gene (1)
  2. Replication adds DNA nucleotides while transcription adds RNA nucleotides (1)
  3. Replication occurs before cell division while transcription occurs when a protein is needed (1)
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13
Q

What are three similarities and three differences between DNA replication and transcription?

A

Similarities:

  1. Both use helicase to break hydrogen bonding (1)
  2. Both use a polymerase enzyme to synthesise a backbone (1)
  3. Both occur in the nucleus (1)

Differences:

  1. Replication copies an entire molecule, transcription copies just one gene (1)
  2. Replication adds DNA nucleotides while transcription adds RNA nucleotides (1)
  3. Replication occurs before cell division while transcription occurs when a protein is needed (1)
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14
Q

Describe the process of RNA splicing (2 marks)

A

The premature pre-mRNA molecule folds into segments, exposing the introns (1)

An enzyme called spliceosome ‘cuts’ the introns out, leaving only the exons (1)

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15
Q

What is the ribosome made up of?

A

Ribosomal RNA (rRNA) and Protein

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16
Q

What are the respective roles of the two subunits within the ribosome (2 marks)

A

Small ribosomal subunit reads the mRNA codon (1)

Large ribosomal subunit brings the relevant amino acid to join the polypeptide chain (1)

17
Q

Describe the process whereby a polypeptide chain is assembled from an mRNA molecule (4 marks)

A

The mRNA lodges between the two ribosomal subunits and the first codon is completely covered by the ribosome (1)

The small ribosomal subunit reads the codon, and a tRNA molecule uses the anticodon to bring a specific amino acid to the ribosome (1)

The large ribosomal subunit attaches the amino acid in place (1)

The previous steps repeat until a stop codon is reached, whereby the polypeptide chain moves to the endoplasmic reticulum for modification (1)

18
Q

Describe the process by which a mature mRNA molecule is formed (5 marks)

A

The helicase enzyme breaks the weak hydrogen bonding, exposing the inward-facing bases (1)

Free RNA nucleotides join via hydrogen bonding between complementary base pairings (1)

RNA polymerase synthesises a new phosphate-sugar backbone (1)

The RNA strand detaches and exits the nucleus through pores in the nuclear membrane (1)

Non-coding segments of the pre-mRNA are removed via RNA splicing to form a mature mRNA molecule (1)

19
Q

What is the primary structure of a protein? (1 mark)

A

The sequence of amino acids within the polypeptide chain (1)

20
Q

What is the secondary structure of a protein? (1 mark)

A

The interactions between side-chains through peptide bonding, forming structures such as alpha helices and beta pleated sheets (1)

21
Q

What is the tertiary structure of a protein?

A

The unique three-dimensional structure that determines the protein’s biological function

22
Q

What is the quarternary structure of a protein?

A

The arrangement of polypeptide chains into a folded, functional protein

23
Q

Describe enzyme activity using the induced-fit model (4 marks)

A

The enzyme’s active site is complementary to the substrate, allowing the formation of an enzyme-substrate complex (1)

This complex induces a fit of higher specificity between the active site and substrate (1)

This induced fit places pressure on the bonds within the substrate, weakening them (1)

Therefore less thermal energy is required to break the bonds within the substrate, lowering the activation energy of the reaction (1)

24
Q

State five factors that affect the rate of an enzyme-catalysed reaction (5 marks)

A
  1. Temperature (1)
  2. pH (1)
  3. Enzyme concentration (1)
  4. Substrate concentration (1)
  5. Inhibitor Concentration (1)
25
Q

Describe the role of an inorganic ion in enzyme activity (1 mark)

A

Inorganic ions bind to the enzyme, altering its charge and supporting its function (1)

26
Q

Describe the role of a prosthetic group in enzyme function (1 mark)

A

Prosthetic groups bind permanently with the enzyme, supporting its function (1)

27
Q

Describe the role of coenzymes in enzyme function (1 mark)

A

Coenzymes bind temporarily to the enzyme, supporting its function (1)

28
Q

Describe how a competitive inhibitor inhibits enzyme function (3 marks)

A

Competitive inhibitors are complementary in shape to the enzyme’s active site (1)

This allows them to bind to the active site, occupying it (1)

Therefore, an enzyme-substrate complex cannot form and the enzyme cannot catalyse the reaction (1)

29
Q

Describe how a non-competitive inhibitor inhibits enzyme function (3 marks)

A

A non-competitive inhibitor binds to an allosteric site on the enzyme (1)

This denatures the enzyme’s active site so it is no longer complementary to the substrate (1)

Therefore, an enzyme-substrate complex cannot form and the enzyme is inhibited (1)

30
Q

Describe what is meant by silencing and activating genes (2 marks)

A

Silencing a gene describes preventing it from being transcribed (1), while activating a gene allows it to be transcribed (1)

30
Q

Describe how DNA Methylation prevents gene expression (3 marks)

A

A methyl group is added to a cytosine base within the gene (1)

This prevents RNA polymerase from accessing the gene during transcription (1)

Therefore, the gene cannot be transcribed, silencing it (1)

31
Q

State the DNA nucleotide that is most often methylated (1 mark)

A

Cytosine (1)

32
Q

State what is meant by an epigenetic factor (1 mark)

A

Epigenetic factors are factors that affect gene expression without changing the DNA nucleotide sequence (1)

33
Q

State what is meant by the term mutation (1 mark)

A

A change in the DNA nucleotide sequence (1)

34
Q

State what is meant by a missense mutation (1 mark)

A

A mutation that results in the production of a different amino acid (1)

35
Q

State what is meant by a samesense mutation (1 mark)

A

A mutation that results in the production of the same amino acid (1)

36
Q

State what is meant by a frameshift mutation (1 mark)

A

A mutation that results in a shift in all subsequent nucleotide bases (1)

37
Q

State what is meant by a nonsense mutation (1 mark)

A

A mutation that results in the production of a stop codon (1 mark)

38
Q

State four factors (mutagens) that affect the rate of mutation (4 marks)

A
  1. Mutagenic Chemicals (1)
  2. Virus (1)
  3. Ionising Radiation (1)
  4. Non-ionising Radiation (1)
39
Q

What is a DNA profile?

A

A series of DNA bands that comprise a unique personal DNA fingerprint

SACE Biology II (4 decks)

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