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AS Biology > Nucleic Acids and Their Functions > Flashcards

Nucleic Acids and Their Functions Flashcards

1
Q

What is a polynucleotide?

A

A molecule containing nucleotides, can comtain thousands

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2
Q

What are the two groups of organic bases?

A

Purine- double ring structure.

Pyramidine- single ring structure

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3
Q

What are the 2 purine cases?

A

Adenine

Guanine

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4
Q

What are the 3 pyramidine bases?

A

Cytosine
Thymine
Uracil

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5
Q

What replaces thymine in RNA?

A

Uracil

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6
Q

How is DNA structured?

A

Two polynucleotide strands wound into a double helix
Pentose sugar = deoxyribose
Sugar + phosphate groups on outside, form sugar-phosphate backbone.
Bases of the 2 strand face inwards and form complimentary base pairs.

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7
Q

How is the double helix maintained?

A

Hydrogen bonds form between the complementary base pairs
A-T = 2
C-G = 3

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8
Q

What are the carbon atom units at each end of a strand?

A

C3 at one

C5 at the other

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9
Q

The two strands are antiparallel, what does this mean?

A

The nucleotides are arranged in the opposite direction to those in the other strand

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10
Q

What are the 4 ways in which DNA’s structure helps its function?

A
  • very stable so genetic info passes unchanged to each gen
  • very large molecule so can carry large genetic info amount
  • 2 strands can separate as only held by hydrogen bonds
  • genetic info protected by sugar-phosphate backbone
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11
Q

What is RNA’s structure?

A

1 polynucleotide stran

Pentose sugar is ribose

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12
Q

What does mRNA do and where is it made?

A

Carries genetic code from DNA to ribosomes

Synthesised in nucleus

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13
Q

What is the function rRNA and where is it found?

A

Combines with protein to make ribosomes

Found in cytoplasm

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14
Q

How is tRNA (transfer) structured?

A

Each molecule has 3 base sequence called anticodon- Complementary to codons on mRNA.
Has amino acid attachment site. Each molecule is specific to an amino acid.

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15
Q

What are the 2 major functions of DNA?

A

Replication for cell division

Carryjng genetic code for protein synthesis in all cells.

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16
Q

How does replication occur?

A

Chromosomes make copies of themselves so that when cells divide, each daughter cell receives exact copy of genetic info.

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17
Q

When/where does replication take place?

A

Cell’s nucleus during interphase (s phase) of cell cycle.

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18
Q

What is transcription?

A

The mechanism by which the base sequence of a gene on a DNA strand is converted into the complimentary base sequence of mRNA.

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19
Q

Hoe does transcription occur?

A

DNA helicase breaks bases’ hydrogen bonds, separating 2 strands and exposing bases.
RNA polymerase binds to template strand. Free RNA nucleotides align oposite complementary bases. Polymerase moves along DNA, forming bonds that add nucleotides to RNA strand 1 at a tine.
mRNA molecule synthesised. Helix rewound behind polymerase.
Polymerase separates when it reaches a stop codon.

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20
Q

What is a nucleotide and what is it made up of?

A

A monomer of nucleoc acid comprising of a pentose sugar, a nitrogenous base and a phosphate group attached to the fifth carbon of the sugar

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21
Q

What is translation?

A

The process of translating the codons in mRNA into a specific sequence of amino acids, forming a polypeptide chain at the ribosome.

22
Q

What are the 3 stages of translation?

A

Initiation
Elongation
Termination

23
Q

How does initiation occur?

A

Ribosome attaches to start codon at 1 end of mRNA molecule.
First tRNA, with an anticodon complimentary to first codon on mRNA,
attaches to ribosome.
The 3 bases of mRNA’s codon and tRNA’s anticodon bond with hydrogen bonds.
A 2nd tRNA with anticodon comp to 2nd codon on mRNA attaches to other attachment site and codon-ac bind

24
Q

How does elongation occur?

A

Ribosomal enzhme catalyses peptide bond formation between the 2 amino acids. First tRNA leaves ribosome, leaving attachment site vacant.
Ribosome moves along 1 codon on the mRNA strand.
The next tRNA binds.

25
Q

How does termination occur?

A

The sequence repeats until a stop codon is reached.

Ribosome-mRNA-polypeptide complex separates

26
Q

What is added to a protein to form a glycoprotein?

A

Carbohydrate

27
Q

What does ATP do and what is it known as?

A

Transports chemical energy from where it is made to where it is needed.
Universal energy currency- involved in energy changes in all living organisms

28
Q

What is ATP made up of?

A

Nitrogenous base-adenine
Ribose sugar
3 phosphate groups

29
Q

What happens when energy is needed?

A

Enzyme ATPase hydrolyses bond between 3rd and 2nd phosphate group, forming ADP and and inorganic phosphate ion (Pi). Chemical energy is released.

30
Q

What is an exergonic reaction?

A

Reaction in which emergy is released

31
Q

How many kJ of enegy are released per ATP mole hydrolysed?

A

30.6kj

32
Q

How is ATP hydrolysis reversible?

A

ADP and Pi can combine in condensation reaction, forming ATP and water.

33
Q

What is the addition of phosphate to ADP called and what is it catalysed by?

A

Phosphorylation.

Catalysed by ATP Synthase.

34
Q

What is an endergonic reaction?

A

Reaction using energy

35
Q

What are the 4 advs of ATP to provide energy instead of direct glucose use?

A
  • single reaction that releases energy immediately
  • only 1 enzyme needed
  • releases in small amounts, when and where needed
  • provides common energy sources for many reactions, increasing cell’s efficiency and control
36
Q

What is gene (which DNA is divided into thousands of)?

A

A sequence of DNA bases that codes for one polypeptide.

37
Q

How many bases encode an amino acid and what is it named?

A

3- triplet code.

38
Q

How many possible codes are there?

A

64

39
Q

What codon always starts the amino acid chain?

A

Methionine (AUG)

40
Q

What are the 3 stop codon codes?

A

UAA, UAG, UGA

41
Q

What is pre-mRNA?

A

The mRNA directly after being formed , needs to be processed before synthesing proteins.

42
Q

How is pre-mRNA processed?

A

Introns are removed by endonuclease enzymes. The remaining base sequences, the exons are joined together by ligase enzymes.

43
Q

What are inteons?

A

Sequences of bases in pre-mRNA that aren’t needed for protein production.

44
Q

What are the 3 DNA replication theories?

A

Conservative replication theory
Semi-conservative replication theory
Dispersive replication theory

45
Q

What is the conservative replication theory?

A

Parental DNA double helix remains intact and. Whole new double helix is made from 2 strands of entirely new material.

46
Q

What is the semi-conservative replication theory?

A

Parental double helix separates into 2 strands, each acting as a template for sythesis of a new strand.
Each new DNA molecule will contain 1 new strand and 1 parental strand.

47
Q

What is the dispersive replication theory?

A

2 copies of the DNA double helix are formed.

Each new molecule will contain distinct regions of DNA composed from the parental strands.

48
Q

Part of Meselson and Stahl’s experiments need to know:-

A

DNA from first gen culture was extracted and centrifuged, settling at a mid point in the tube.
=ruled out conservative the entirely heavy 15n parental band would’ve been produced.

49
Q

Proven DNA replication method:-

A

Semi-conservative

50
Q

Proven DNA replication method:-

A

Semi-conservative

AS Biology (14 decks)

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