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Bio > Nucleic acids > Flashcards

Nucleic acids Flashcards

1
Q

What is DNA?

A

Deoxyribonucleic acid that holds genetic information.

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2
Q

What is RNA?

A

Ribonucleic acid that transfers genetic information from the DNA to the ribosomes.

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3
Q

How are ribosomes formed?

A

In the nucleolus by rRNA and proteins.

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4
Q

What does a nucleotide look like?

A

Formed by a pentose sugar, a nitrogenous base and a phosphate group.

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5
Q

What is the difference between the nucleotide in DNA and RNA?

A

In DNA, the pentose sugar is deoxyribose and the bases can be adenine, thymine, cytosine and guanine. In RNA, the pentose sugar is ribose and the thymine is replaced by uracil.

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6
Q

Describe structure of DNA

A

Double helix with two antiparallel polynucleotide chains held together by hydrogen bonds between specific complementary base pairs (A-T, C-G). Sugar phosphate backbone joined to sugar of next nucleotide by phosphodiester bond.

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7
Q

Describe structure of RNA

A

Single stranded, short polynucleotide chain.

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8
Q

Why is DNA adapted to carry out its function?

A

Sugar phosphate backbone / double stranded helix provides stability and strength.
Weak hydrogen bonds allow strands to be separated by DNA helicase during replication.
Extremely large to store lots of information.
Coiled into helix - compact.
Complementary base pairs - replicate accurately.
Many hydrogen bonds - stable.
Base sequence allows info to be stored and transcribed into correct order of amino acids.
Double-stranded - each strand acts as template during replication.

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9
Q

What is a chromosome?

A

Long coiled, linear strands of DNA and histones.

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10
Q

T and C are ____ which means…

A

Pyrimidines which means they have one ring.

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11
Q

A and G are ____ which means…

A

Purines which means they have two rings.

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12
Q

Why is DNA 3 rings wide always?

A

To avoid kinking.

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13
Q

Why is ribose sugar in DNA called deoxyribose?

A

It has one fewer oxygen. No oxygen on carbon 3.

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14
Q

What bond is formed between two nucleotides in a condensation reaction?

A

A phosphodiester bond.

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15
Q

Describe the structure of ATP (adenosine triphosphate)

A

A molecule of ribose, a molecule of adenine and 3 phosphate groups.

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16
Q

How does the hydrolysis of ATP release energy?

A

High energy, unstable phosphoanhydride bond with low activation energy between 2 phosphate group breaks via hydrolysis and releases energy to create ADP. ATP + H2O -> ADP + Pi + energy.

17
Q

How is ATP formed?

A

The energy released by respiration is used to add a phosphate to ADP in a condensation reaction with ATP synthase.

18
Q

Which enzyme catalyses the hydrolysis of ATP to ADP and an inorganic phosphate group?

A

ATP hydrolase.

19
Q

What enzyme catalyses the synthesis of ATP?

A

ATP synthase.

20
Q

How does the synthesis of ATP happen in plant cells that have chlorophyll?

A

During photosynthesis (photophosphorylation).

21
Q

When does the synthesis of ATP happen in animal and plant cells?

A

During respiration (oxidative phosphorylation).

22
Q

What is the role of ATP?

A

Immediate energy source for a cell.

23
Q

Why is ATP a better energy source than glucose?

A

Each ATP molecule releases less energy than each glucose molecule therefore the energy for reactions is released in smaller, more manageable quantities.
Hydrolysis of ATP is a single step reaction that releases energy immediately opposed to the long series of reactions that the breakdown of glucose is.

24
Q

What can the inorganic phosphate group released in the hydrolysis of ATP be used for?

A

It can phosphorylate other compounds, making them more reactive.

25
Q

When is DNA replicated?

A

During S phase of interphase in mitosis and meiosis and during binary fission in bacteria.

26
Q

What is semi-conservative model of DNA replication?

A

The original DNA molecule split into two separate strands each of which then replicated its missing half. One strand of new material each.

27
Q

What is conservative model of DNA replication?

A

Original DNA molecule remained intact and separate copy was built from new nucleotides. 1 made of entirely new material and 1 original.

28
Q

Describe DNA replication with correct enzymes

A
  • DNA helicase separates strands by breaking hydrogen bonds, leaving two template strands.
  • Free complementary nucleotides bind to exposed base pairs to copy DNA molecule faithfully.
  • DNA polymerase joins the nucleotides together, forming phosphodiester bonds between them by condensation reaction.
  • Two identical strands of DNA formed.
29
Q

Meselson and Stahl experiment in OneNote

A

In OneNote

30
Q

How many hydrogen bonds between C and G; and A and T

A

3; 2

31
Q

How did scientists figure out that DNA was the genetic material

A

Swapping foot of algae (where nucleus was located) and the structure being dictated by nucleus.
Transformation in bacteria only occurred when DNA was present.

32
Q

Why does can nucleotides only be added in 5’ to 3’ direction

A

DNA polymerase is specific. Complementary only to 5’ end of strand which has different shape to 3’ end.

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