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PL1003 > Topic 1 Biomolecules - Nucleotides and Nucleic Acids > Flashcards

Topic 1 Biomolecules - Nucleotides and Nucleic Acids Flashcards

1
Q

What are the 3 components of a nucleotide?

A

A phosphate group, a pentose sugar and a nitrogenous base

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2
Q

What are the 2 components of a nucleosides?

A

pentose sugar and a nitrogenous base

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3
Q

What is DNA a carrier of and what is it divided into?

A

carrier of genetic information and is divided into specific sequences called genes

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4
Q

What are genes packed into?

A

packed into separate chromosomes of distinctive structures found in nearly every cell of every higher organism

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5
Q

What is DNA and RNA composed of?

A

4 monomers known as nucleotides

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6
Q

What is the difference between the pentose sugars Ribose and Deoxyribose?

A

Ribose has a hydroxyl group on carbon 2 whereas deoxyribose has a hydrogen on carbons 2

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7
Q

What bases are derivatives of purine?

A

Adenine and Guanine

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8
Q

What bases are derivatives of pyrimdines?

A

Uracil, Thymine and Cytosine

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9
Q

what are heterocycles?

A

Organic rings systems that contain an element other than carbon as part of that ring

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10
Q

What does a pyrimidine contain?

A

a single six-membered ring

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11
Q

What does purine contain?

A

has a bicyclic structure with a six-membered ring fused to a five-membered ring

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12
Q

In nucleosides how are sugars and bases linked?

A

Linked via a condensation reaction to form a nucleoside

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13
Q

What does the addition of a phosphate group to the sugar via a condensation reaction result in?

A

results in either a ribonucleotide or a deoxynucleotide (phosphate esters of the corresponding nucleoside)

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14
Q

What do DNA/RNA exist as?

A

exist as macromolecular polymers and allow hereditary characteristic to be passed on from one generation to another

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15
Q

What is the function of DNA?

A

Serves as the master copy for most information in the cell

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16
Q

What is the function of RNA?

A

several types but overall acts to transfer information from DNA to the rest of the cell through protein synthesis

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17
Q

What 4 bases does DNA contain?

A

Adenine, Thymine, Guanine and Cytosine

18
Q

What 4 bases does RNA contain?

A

Adenine, Uracil, Guanine and Cytosine

19
Q

Describe the primary structure of DNA?

A

sugar/phosphate backbone

Base groups protruding from the chain at regular intervals

primary structure is the sequence of bases

20
Q

How is the primary structure formed in DNA?

A

Formed by the 3’-5’ phosphodiester bonds between nucleotides

21
Q

What does the 5’ end of DNA end with?

A

a phosphate

22
Q

What does the 3’ end of DNA end with?

A

an OH

23
Q

How many hydrogen bonds are there between Guanine and Cytosine?

A

3 hydrogen bonds

24
Q

How many hydrogen bonds are there between Adenine and Thymine?

A

2 hydrogen bonds

25
Q

What percent of each DNA base does human DNA contain?

A

30% adenine, 30% thymine, 20% guanine, 20% cytosine

26
Q

What can DNA be described as (structurally)?

A

Double Helix

27
Q

Describe DNA’s Double helix model?

A

The bases on one strand hydrogen bond to the complementary bases on the other strand of DNA

The two strands run antiparallel

The location of the sugar-phosphate backbones on the outside of the molecule, coupled with the twist, produces grooves on the surface of the double helix

These grooves may provide binding sites for molecules which interact with DNA

28
Q

What forces stabilise the Double helix?

A

Hydrogen bonding – large number of relatively weak H bonds contribute greatly to preventing the strands from separating under normal physiological conditions

Hydrophobic affects - produced by hydrophobic purines/ pyrimidine rings moving away from the aqueous solvent into the interior of the double helix

Electrostatic interactions - involves the phospho-diester group of the DNA backbone and a cation especially Mg2+

Stacking interaction - stacked base pairs form weak Van der Waals attractions. These forces are additive. Therefore the greater the number of base pairs the more stable will be the helix.

29
Q

What does Ribosomal RNA (rRNA) do?

A

Combines with a series of proteins to form complex structures called ribosomes that serve as the physical sites for protein synthesis (translation)

30
Q

What does Messenger RNA (mRNA) do?

A

Carries genetic instructions for protein synthesis from DNA to the ribosomes

31
Q

What does Transfer RNA (tRNA) do?

A

Delivers specific individual amino acids to the ribosomes for protein synthesis

32
Q

How do DNA and RNA differ?

A

RNA is single stranded whereas DNA is double stranded

RNA contains a ribose sugar whereas DNA contains a deoxyribose sugar

DNA contains the base pairs Adenine, thymine, guanine and cytosine, whereas RNA contains the base pairs Adenine, uracil, guanine and cytosine

RNA is smaller than DNA

33
Q

What happens during the polymerisation step of DNA replication?

A

Involves addition of free nucleoside triphosphates (high energy compounds)

  1. the strands unwind and separate
  2. Each then acts as a template for a complementary strand to be built
34
Q

What happens during the control step of DNA replication?

A

DNA polymerase builds new double helices and repairs slightly damaged ones by lining up nucleotides in the right order

  1. A section of double stranded DNA Polymerase binds to the double helix by wrapping around it
  2. The enzyme pulls the helix apart
  3. The nucleotides are brought in to build a new strand of DNA
35
Q

What does PCR do?

A

Mimics nature for the rapid production of multiple copies of a DNA nucleotide sequence in the laboratory

36
Q

In PCR what is required for the reaction mixture?

A

target DNA

The two primers

all four deoxyribose triphosphates

a thermostable DNA polymerase

37
Q

What are some applications of PCR?

A

Detection of infectious organisms, including the viruses that cause AIDS and hepatitis

Detection of genetic variations, including mutations, in human genes

Amplification of DNA collected at a crime scene and comparison with the samples taken from suspects (forensics)

38
Q

What happens when a cell divides?

A

Its DNA unwinds before being copied and distributed to new daughter cells.

39
Q

Describe DNA as a drug target in cancer?

A

Cancer is a disease characterised by excessive cell division

many anticancer drugs work by inhibiting cell division which can be directly targeting DNA

40
Q

What is Doxorubicin?

A

Doxorubicin is an example of an intercalating drug (a flat (planar) molecule capable of interacting with DNA by insertion between the base-pairs of the DNA ladder)

41
Q

Describe the chemistry of doxorubicin?

A

A planar aromatic ring slides between two adjacent base pairs in the DNA ladder

Binding is stabilised by hydrophobic interactions

prevents unwinding of DNA and so blocks cell division which ultimately leads to death of the cancer cell.

42
Q

What are ziduvudine (AZT) and aciclovir used for?

A

They are nucleoside derivative drugs used to treat HIV and Herpes Simplex/Herpes Zoster virus

Are an example of DNA as a drug target

PL1003 (8 decks)

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