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Wjec Biology As Unit 1 > 1.5 > Flashcards

1.5 Flashcards

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1
Q

What is the monomers of DNA and RNA

A

Nucleotides

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2
Q

What does each nucleotide consist of

A

Phosphate group, nitrogenous base and a pentose sugar

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3
Q

What are the 2 possible pentose sugars in a nucleotide

A

Ribose or deoxyribose

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4
Q

What is a pyrimidine

A

Single ring structure

Cytosine and thymine and uracil

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5
Q

What is a purine

A

Double ring structure

Guanine and adenine

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6
Q

What are the 4 nitrogenous bases

A 
Guanine
Cytosine
Adenine
Thymine - DNA
Uracil - RNA
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7
Q

What is ATP

A

Adenosine Triphosphate
Nucleotide
Ribose sugar, adenine base and 3 phosphate groups

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8
Q

How does ATP supply energy

A 
ATP--> P + ADP + 30.6kjmol
• high energy bond between 2 and 3 phosphate group
• broken via hydrolysis by enzyme ATPase
• 30.6kJ of energy released
• endergonic
• adenosine diohosphate is formed
• reversible
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9
Q

Equation for ATP hydrolysis

A

ATP–> ADP + Pi + 30.6kJ energy

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10
Q

Advantages of ATP

A
  • quick energy release - 1 reaction 1 enzyme
  • released in small amounts when needed - safe
  • universal energy currency - common source of energy in all living things
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11
Q

Roles of ATP in cells

A
  • anabolic reactions eg DNA synthesis
  • active transport
  • muscle contraction
  • nerve impulse transmission
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12
Q

How is DNA formed

A

By a condensation reaction between two nucleotides 5’-3’ direction

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13
Q

Structure of DNA

A
  • two polynucleotide strands - double helix
  • strands run in the opposite direction - anti-parallel
  • strands are held by H bonds between complementary bases
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14
Q

How many H bonds between guanine and cytosine

A

3

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15
Q

How many H bonds between adenine and thymine

A

2

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16
Q

What is mRNA

A

Messenger RNA
• singe-stranded molecule - 300-2000 nucleotides long
• produced in the nucleus during transcription

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17
Q

What is rRNA

A

Ribosomal RNA

• forms ribosomes with the addition of protein

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18
Q

What is tRNA

A

Transfer RNA
• small molecule that winds itself into a cloverleaf shape
• has an anticodon at one end
• amino acid at the other
• transfers correct AA to growing polypeptide during translation

19
Q

What are the 2 functions of DNA

A

Protein synthesis

Replication

20
Q
A

Conservative replication

21
Q
A

Semi-conservative replication

22
Q
A

Dispersive replication

23
Q

Theory of conservative replication

A

Original parent double-strand molecule is conserved, and a new double-stranded DNA molecule synthesised from it

24
Q

Theory of semi-conservative replication

A

parental strands separate, and each strand acts as a template to synthesis a new strand. The new molecule consists of one original parent strand and one newly synthesised strand.

25
Q

Theory of dispersive replication

A

the newly synthesised molecules contain fragments from the original parent strand and newly synthesised DNA

26
Q

Process of semi-conservative DNA replication

A
  1. DNA helixase breaks the hydrogen bonds between bases causijg the double helix to unwind and separate into 2 strands
  2. Free nucleotides in the nucleoplasm bind to exposed base on DNA template strand
  3. DNA polymerase binds to the complementary nucleotides forming the phosphodiester bond
  4. One strand acts as the template for the new molecule, so newly synthesised DNA contains one parents strand and a complementary newly synthesised strand
27
Q

What was the name of the experiment that determined the exact mechanism for DNA replication

A

Meselson-Stahl experiment

28
Q

What did the Meselson-Stahl experiment involve doing?

A
  1. Growing bacteria on a 15N medium so the DNA would be a heavier weight so when extracted by centrifuging the CsCl there would be a low band
  2. Growing bacteria on a 14N medium for 1 generation to form a intermediate band - DNA has 1 heavy parent strand and 1 newly synthesised light strand
  3. Growing bacteria again in 14N for another generation to form 1 intermediate band and 1 lighter band
29
Q

Which step in Meselson-Stahl experiment ruled out conservative replication

A

2

Would have 1 heavy and 1 light

30
Q

Which step in Meselson-Stahl experiment rules out dispersive replication

A

3

Half of DNA intermediate and half light

31
Q

What is a codon

A

The triplet of bases in mRNA that codes for a particular amino acid, or a punctuation signal

32
Q

What are the three steps of protein synthesis

A

Transcription - in nucleus
Translation - at ribosomes
Post-translational modification - in Golgi

33
Q

What happens during transcription

Definition

A

DNA acts as a template for the production of mRNA

34
Q

What is an intron

A

non-coding nucleotide sequence in
DNA and pre-mRNA, that is
removed from pre-mRNA, to
produce mature mRNA.

35
Q

What is an exon

A

nucleotide sequence on one strand of the DNA molecule and the corresponding mRNA that codes for the production of a specific polypeptide.

36
Q

Do prokaryotes contain introns

A

No - mRNA directly produced from DNA template

37
Q

Describe structure of tRNA

A
  • at one end there are 3 exposed bases - anticodon

* opposite end - amino acid attachment site

38
Q

What is amino acid activation

A

Attachment of the relevant amino acid to the attachment site

Requires ATP

39
Q

Which subunit of the ribosome binds to mRNA and which to tRNA

A

Smaller - mRNA

Larger - tRNA binds to one of 2 attachment sites on it

40
Q

What does translation involve

A

Converting the codons on the mRNA into a sequence of amino acids

41
Q

Describe the process of translation

A
  1. INITIATION - ribosome attaches to the start codon
    tRNA molecule with complementary anticodon to the first codon binds to the first attachment site on the ribosome
  2. ELONGATION - Second tRNA molecule joins to the second attachment site
    Ribosomal enzyme catalyses the formation of a peptide bond between the 2 amino acids
    The first tRNA molecule is released and the ribosome now moves one codon along the mRNA which exposes a free attachment site and another tRNA molecule joins and the process is repeated
  3. TERMINATION - a stop codon is reached and the polypeptide is released
42
Q

What is a polysome

A

Several ribosomes bind to a single mRNA strand at the same time

43
Q

Why can ATP be called the ‘universal energy currency’

A

Common energy source used in all living organisms

44
Q

Describe the process of transcription

A

•DNA helicase acts on a specific region of the DNA molecule called the
cistron, breaking the hydrogen bonds between both DNA strands, causing
the strands to separate and unwind, exposing nucleotide bases.
• Free RNA nucleotides pair to exposed bases on the DNA template strand and RNA polymerase joins them by forming the phosphodiester bonds between the phosphate group on one nucleotide and the ribose sugar on the next.
• This continues until the RNA polymerase reaches a STOP codon, when the RNA polymerase detaches and production of mRNA is complete.
• The mRNA strand leaves the nucleus via the nuclear pores and moves to the
ribosomes.

Wjec Biology As Unit 1 (7 decks)

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