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A-level Biology Year 1 > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

DNA, RNA & ATP

1
Q

What is a nucleotide?

A

The monomer of nucleic acids, made up of a phosphate group, organic nitrogenous base and a pentose sugar.

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2
Q

What is the structure of a DNA nucleotide?

A
  • A phosphate
  • A deoxyribose sugar
  • A base (ATCG)
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3
Q

Why are phosphate ions important in DNA?

A

They help create strong sugar phosphate backbones along with the deoxyribose sugar

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4
Q

How are polynucleotides formed?

A

A condensation reaction between the phosphate of one nucleotide and the pentose sugar of another. This forms phosphodiester bonds between the two nucleotides.

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5
Q

What are the 4 bases in DNA?

A
  • Thymine
  • Adenine
  • Cytosine
  • Guanine
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6
Q

Which bases bind together in DNA?

A

Cytosine to Guanine
Thymine to Adenine

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7
Q

What bond is between two complimentary bases?

A

Hydrogen bonds

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8
Q

How does DNA’s double helix structure relate to its function?

A
  • Provides strength and stability for passing through generations
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9
Q

How does DNA’s large structure relate to its function?

A

Can store lots of information

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10
Q

How does DNA’s coiled structure relate to its function?

A

Compact so can store a lot of info in a small space

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11
Q

How does DNA’s base sequence structure relate to its function?

A

Gives triplets that code for amino acids

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12
Q

How does DNA’s double stranded structure relate to its function?

A

Allows for semiconservative replication where both strands act as a template

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13
Q

How does DNA’s hydrogen bonds between bases structure relate to its function?

A

Many hydrogen bonds so stable

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14
Q

What is the structure of an RNA nucelotide?

A
  • A phosphate
  • A ribose sugar
  • A base (AUGC)
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15
Q

What are the three types of RNA?

A

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

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16
Q

Is RNA polynucleotides single or double stranded?

A

Single

17
Q

What is the general role of RNA?

A

Responsible for the copying of DNA inside and outside the nucleus so that DNA soes not have to leave the nucleus, protecting it from damages

18
Q

How is DNA replicated?

A

Semi-conservatively

19
Q

What is semi-conservative replication?

A

Before a cell divides, it needs to copy the DNA so that identical cells are made.
When a new cell in made, one of the DNA strands is from the mother cell and one is new.

20
Q

Why is semi-conservative replication important?

A

To ensure there is genetic continuity between generations and to make sure we can replace cells regularly

21
Q

What enzymes are involved in the semi-conservative replication of DNA?

A
  • DNA helicase
  • DNA polymerase
  • DNA ligase
22
Q

I belive in you

A

Youll get better

23
Q

What are the stages in the process of DNA replication?

A
  1. DNA helicase breaks hydrogen bonds so DNA unwinds
  2. Each strand used as a template which free floating nucleotides attach to (via complimentary base pairs)
  3. DNA polymerase catalyses the formation of phosphodiester bonds between nucleotides
  4. Two new daughter DNA strands have one parental DNA strand and one new
24
Q

What is the leading strand in DNA?

A

As DNA is unzipped from the 3’ end to the 5’ end, DNA polymerase will attach to the 3’ end and move towards the replication fork.
DNA polymerase synthesises the leading strand continuously.

25
Q

What is the lagging strand?

A

When DNA polymerase moves away from the replication form, so can only synthesise the lagging strand in segments.
DNA ligase is then used to join the segments together.

26
Q

True or false:
Complimentary bases have the same frequency as each other.

A

True
So if 13% of bases in a DNA sample are thymine, 13% of them will be adenine

27
Q

What is the Meselson and Stahl model?
How was it done?

A

The model that proved DNA replicated semi-conservatively (theorised by Watson and Crick).

  1. Bacteria with heavy nitrogen DNA is centrifuged to show DNA is at the bottom of tube
  2. Bacteria is allowed to use lighter nitrogen in replication

If semi-conservative:
DNA now containing one of each type of nitrogen sits in the middle of centrifuge

If conservative:
Two lines in centrifuge as two different weights present

28
Q

What is the structure of ATP?

A

A ribose sugar
Three phosphates
An adenine base

29
Q

What are the features of ATP?

A
  • Small but useful amount of energy prevents wastage
  • Stable so doesn’t breakdown without enzyme, prevents wastage
  • Recyclable so can be reused
  • Quick hydrolysis so allows cell to respond to sudden changes
  • Soluble so can be transported to where energy is needed
30
Q

What is the use of ATP?

A

The primary carrier of energy in cells, produced in aerobic respiration.
‘‘The universal energy currency’’

31
Q

ATP is useful in many biological processes. Explain why. (4)

A
  1. Releases energy in small /manageable amounts; (there is very little energy lost as heat - so there is little danger of thermal death of cells)
  2. Releases energy instantaneously
    because it is broken down in a one-step reaction (a single bond is broken)
  3. Phosphorylates other compounds, making them more reactive;
  4. Can be rapidly reformed/resynthesized;
  5. Cannot leave cells, so is not lost
32
Q

Describe how DNA is replicated. (6)

A
  1. Strands separate / H-bonds break;
  2. DNA helicase (involved);
  3. Both strands/each strand act(s) as (a) template(s);
  4. (Free) nucleotides attach;
  5. Complementary/specific base pairing / AT and GC;
  6. DNA polymerase joins nucleotides (on new strand);
  7. H-bonds reform;
  8. Semi-conservative replication / new DNA molecules contain one old strand and one new strand;
33
Q

Explain why new nucleotides can only be added in a 5’ to 3’ direction. (4)

A
  1. Reference to DNA polymerase;
  2. (Which is) specific;
  3. Only complementary with / binds to 5’ end (of strand);
    Reject hydrogen bonds / base pairing
  4. Shapes of 5’ end and 3’ end are different / description of how different;
34
Q

Explain how the structure of DNA is related to its functions. (6)

A
  1. sugar-phosphate backbone gives strength;
    (coiling gives) compact shape;
  2. sequence of bases allows information to be stored;
  3. long molecule stores large amount of information;
  4. information can be replicated / complementary base pairing;
  5. (double helix protects) weak hydrogen bonds / double helix makes
    molecule stable prevents code being corrupted;
  6. chains held together by weak hydrogen bonds;
    chains can split for replication / transcription

A-level Biology Year 1 (19 decks)

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