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nucleic acids and DNA replication Flashcards

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Organic Chemistry 101 flashcards
1
Q

DNA replication

A

DNA helicase unwinds the double helix by breaking H-bonds

makes it single stranded - both used as template

DNA nucleotides form hydrogen bonds with complimentary bases on DNA strand
AT 2, GC 3

DNA polymerase forms phosphodiester bonds between new DNA nucleotides

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2
Q

nucleic acids

A

2 types - deoxyribonucleic acid and ribonucleic acid

elements - C, H, O, N, P

monomer - nucleotide

  • phosphate group, pentose sugar, nitrogenous base

carry the genetic code for the production of proteins
- common to all living organisms and viruses providing evidence for evolution

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3
Q

nitrogenous bases

A

purines - 9 membered ring
A, G

pyrimidines - 6 membered ring
T, C, U

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4
Q

condensation of nucleotides

A

phosphodiester bond between the OH of C3 of the 1st nucleotide and phosphate group of the 2nd

  • every polynucleotide chain has unbonded P at beginning (5 prime end) (5C)
  • finished with unbonded OH - 3 prime end
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5
Q

polynucleotide chains

A

RNA - only one - single stranded

DNA - two - double stranded
double helix - 2 strands twist around eachother
- are anti-parallel
- held together by H-bonds between complimentary nucleotides

the molecule is more stable, ie if bases mutated/ damaged one strand - can be copied correctly from other strand

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6
Q

nucleotide bonding

A

A + T - 2 bonds
C + G - 3 bonds

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7
Q

similarities

A

P group
OH group
phosphodiester bonding
A, C, G

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8
Q

functions of DNA

A
  1. DNA Replication = passing on genetic information from one generation to the next.
    1. Protein Synthesis = DNA base sequence carries the code for the primary structure / aa sequence of proteins.

DNA - transcription - tRNA, mRNA, rRNA
- translation - polypeptide

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9
Q

functions of RNA

A

mRNA - messenger RNA - carries the code for the amino acid sequence from the DNA to the ribosome - complementary sequence to 1 gene from DNA with introns sliced out - codons can be translated into a polypeptide by ribosomes

rRNA - ribosomal RNA - component of a ribosome

tRNA - transfer RNA - carries a specific amino acid to mRNA codons during translation

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10
Q

ATP synthesis

A

by a kind of condensation reaction known as PHOSPHORYLATION (addiction of a P group)

ATP synthase
ATP hydrolase

endothermic reaction - occurs during anaerobic and aerobic respiration and photosynthesis

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11
Q

ATP

A

adenosine triphosphate - energy currency of the cell - energy storage

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12
Q

where does energy come from

A

energy to phosphorylate ADP comes from glucose in respiration and light in photosynthesis

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13
Q

functions of ATP

A

hydrolysis - 30-31Kj

  • active transport
  • muscle contraction

add to

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14
Q

3 possible replication models

A

conservative replication - original + new

semi conservative - each daughter DNA molecule has one old strand and one new strand

dispersive - each daughter DNA molecule has a random mixture of old and new

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15
Q

evidence of semi conservative bias

A

Semi-Conservative DNA Replication is defined as:
- both DNA strands are used as templates for replication.
- each new daughter DNA molecule has one old / original strand and one new strand.

  • growth medium with 15 nitrogen - grown for many generations so all DNA contain 15 N
  • growth medium with 14 N grown for one generation (repeated with other molecules so many different generations)
  • from each flask, a few cells removed and DNA extracted from them - centrifuged
  • first (15N) last (14N) middle (mixture)
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16
Q

spec notes on replication

A

The process of semi-conservative replication of DNA in terms of:

unwinding of the double helix
breakage of hydrogen bonds between complementary bases in the polynucleotide strands
the role of DNA helicase in unwinding DNA and breaking its hydrogen bonds
attraction of new DNA nucleotides to exposed bases on template strands and base pairing
the role of DNA polymerase in the condensation reaction that joins adjacent nucleotides.

17
Q

function of semi conservative replication

A

ensures genetic continuity between generations of cells.

18
Q

spec notes nucleotides

A

DNA holds genetic information
RNA transfers genetic information from DNA to the ribosomes

Both DNA and RNA are polymers of nucleotides. Each nucleotide is formed from a pentose, a nitrogen-containing organic base and a phosphate group

19
Q

spec notes ATP

A

A single molecule of adenosine triphosphate (ATP) is a nucleotide derivative and is formed from a molecule of ribose, a molecule of adenine and three phosphate groups.

Hydrolysis of ATP to adenosine diphosphate (ADP) and an inorganic phosphate group (Pi) is catalysed by the enzyme ATP hydrolase.

The hydrolysis of ATP can be coupled to energy-requiring reactions within cells.

The inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds, often making them more reactive.

ATP is resynthesised by the condensation of ADP and Pi. This reaction is catalysed by the enzyme ATP synthase during photosynthesis, or during respiration.

20
Q

role of DNA in living cells

A

base sequence of genes codes for functional RNA and amino acid sequence of polypeptides

genetic information determines inherited characteristics = influences structure and function of organisms

21
Q

relate the structure of DNA to its functions

A

sugar-phosphate backbone and many H-bonds provide stability

long molecule stores lots of information

helix is compact for storage in nucleus

base sequence of triplets codes for amino acids

double-stranded for semi-conservative replication

complementary base pairings for accurate replication

weak H-bonds break so strands separate for replication

22
Q

structure and function of mRNA

A

long ribose polynucleotide (shorter than DNA)
uracil instead of thymine
single stranded and linear
codon sequence is complementary to exons of 1 gene from 1 DNA strand

breaks down quickly so no excess polypeptide forms
ribosomes can move along strand and tRNA can bind to exposed bases
can be translated into a specific polypeptide by ribosomes

23
Q

structure of tRNA

A

single strand of about 80 nucleotides

folded into clover shape (some base pairings)

anticodon on one end, amino acid binding site on other

anticodon binds to complimentary mRNA codon
amino acid corresponds to anticodon

24
Q

role of ATP in cells

A

ATP hydrolase catalyses ATP -> ADP + Pi

energy released is coupled to metabolic reactions

phosphate group phosphorylates compounds to make them more reactive

25
Q

why ATP is suitable as the energy currency

A

high energy bonds between phosphate groups

small amounts of energy released at a term = less energy wasted as heat

single-step hydrolysis = energy available quickly

readily resynthesised

? biological molecules (8 decks)

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