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Biology summary flashcards component 1 > nucleic acids > Flashcards

nucleic acids Flashcards

1
Q

What are nucleotides

A
  • RNA and DNA are made up of monomers called nucleotides
  • each nucleotide contain a phosphate froup, nitrogenous organic base and a pentose sugar: ribose in RNA and deoxyribose (DNA)
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2
Q

What are the four types of bases

A
  • there are two groups of organic bases pyrimidines (single rings) and purines (double ringed)
  • guanines (purine)
  • thymine (pyrimidine)
  • Cytosode (pyrimidine
  • adenind (purine)
  • in RNA uracil replaces thymine
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3
Q

What is ATP

A
  • adenosine triphosphate is also a nucleotide with a ribose sugar joined to adnine and three phosphate groups
  • high energu bond between second and third phosphate group broken by hydrolysis via enzyme ATPase 30.6KJ energy released for use in cell
  • adenossine diphosphale is formed and inorganic phsophate
  • reaction is reversible requiring energy from respiration from respiration of glucose to form bond
  • ATP-> ADP + Pi +30.6KJ
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4
Q

What are the advantages of ATP

A
  • energy released quickly from one step reaction involve one enzyme (hydrolysis of glucose takes many steps)
  • energy released in small amouns 30.6KJ where it’s needed one molecule of glucose contains 1880KJ cannot be released all at once
  • universal energy currency common source of energy for all reactions in living things
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5
Q

What are the roles of ATP

A
  • used in may anabolic reactions eg DNA and protein synthesis
  • active transport
  • muscle contraction
  • nerve impulse transmission
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6
Q

What is the structure of DNA

A
  • DNA consists of two polynucleotide strands arranges in a double helix
  • condensation reactions occur between nucleotides
  • the 5Th carbon atom on the deoxyribose sugar is oined to the 3rd carbpm atom or nucleotide above via phosphate
  • continues building single strand of 5’ - 3’
  • the two strands run in opposite directions - antiparallel
  • hydrogen bonds form between complementary base pairs 3 between C and G and 2 between A and T
  • hydrogen bonding is weak byt collectivley they are very strong
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7
Q

Describe the extracting of DNA

A
  • easily extracted by grinding up sample in a solution of ice cold salt washing up liquid
  • detergent dissole the lipids in phospholipid membranes allowing DNA to be released
  • cold temp protects DNA from celullar DNAases addition of proteases digest remaining cellular enzymes and histones DNA is wound around
  • finally adding ethanol to salt cause DNA to precipitate out of solution
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8
Q

What is RNA

A
  • shorter than DNA
  • single stranded
  • ribose sugar
  • thymine replaces with uracil
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9
Q

What is mRNA

A
  • messenger RNA
  • single stranded
  • produced in the nucleus using one DNA strands as a template during transciption
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10
Q

What is rRNA

A
  • ribosomal RNA
  • forms ribosomes with addition of protein
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11
Q

What is tRNA

A
  • transfer RNA
  • winds itself up into a cloverleaf shape
  • has an anticodon at one end and amino acid on another
  • transfer correct amino acid to polypeptide during translation
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12
Q

What is the function of DNA

A
  • protein synthesis - sequences of bases on one strand called template strand determines order of amino acids in a polypeptide
  • replication - cells divide have complete copy of DNA in cell
  • both DNA strands seperate and each strand acts as a template to synthesise a complementary strand
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13
Q

Describe conservative replication

A
  • original parent double stranded molecule is conserved and a new double stranded DNA molecules is synthesised from it
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14
Q

How does DNA replicate

A

by semi conservative replication

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15
Q

Describe semi conservative replication

A
  • parental strands seperate each act as a template to synthesise a new strand
  • new molecule contains one original parental strand and a newly synthesised strand
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16
Q

Describe dispersive replication

A
  • newly synthesised molecule contain fragments from original parent strand and newly synthesised DNA
17
Q

Describe the process of semi conservative replication

A
  • requires ATP, free nucleotides and enzymes
  • DNA helicase breaks hhydrogen bonds between bases causing double helix to unwind and seperate into two strands
  • exposed bases bind to free floating nucleotides in the nucleoplasm
  • DNA polymerase bind to complementady nucleotides forming phosphodiester bonds
  • one strand act as a template for new molecules so newly synthesised DNA contains one parent strand and complementary newly synthesised one
18
Q

Describe meselsohn and stahl experiment

A
  • grow bacteria in an N15 medium N15 is a heavy isotope of nitrogen so all DNA would be heavier. DNa extrated by centrifuging band and appeared lower down the tube
  • bacteria grown on N14 medium normal weight after one generation DNA extracted fromed an inermediate band halfway up the tibe as DNA contain one strand of heavy parent and one strand newly synthesised light rules out conservative replication
  • bacteria grown in N14 Dna extracted formed intermediate band halfway up tube and lighter band twoards the top as half DNA was intermediate rules out dispersive replication
  • DNA therefore replicates semi conservativley
  • if grown for further generations N14 proportion of light DNA would increase
19
Q

What is the genetic code

A
  • sequence of nucleotide baes form a code
  • each code has three letters mcalled the triplet code or codon which codes for a specific amino acid
  • 20 amino acids need bu 43=64 as combination of A,C,G,T so code is degenerate as multiple codes can code for one amino acid
  • code is universal so it is the same in all living things
  • one codon is the start codon where transcription begins AUG
  • each gene found on DNA will code for a different polypeptide
  • one gene one polypeptide
20
Q

What is protein synthesis

A
  • transciption occurs in the nucleus
  • translation occurs at riosomes
  • post translational modification occurs in the golgi body prior to packaging proteins into vesicles
21
Q

Describe transcription

A
  • DNA acts as a template for production of mRNA
  • DNA helicase acts as a specific region on on DNA molecule called the cistron breaking hydrogen bonds between both strands to causing strands to seperate and unwind exposing nucleotide bases
  • free RNA nucleotides pair to exposed bases on the DNA template strand and RNA polymerase joines them by forming the phosphodiester bonds between phosphate group and one nucleotide and the ribose sugar on the next
  • continues until RNA polymerase reaches a stop codon when RNA polymeraase detatched production on mRNA is complete
  • mRNA strand leaves nucleus via the nuclear pores and moves to the ribosomes
22
Q

What are introns and exons

A
  • in eukaryotes introns are present within many genes so are transcribed producing pre mRNA
  • coding regions are exons
  • pre mRNA is splices removing introns non coding regions before passing to ribosomes
  • prokaryotes DNA not contain introns so mRNA produced directly from DNA template
23
Q

What is translation

A
  • involves another pecific RNA molecule transfer RNA tRNA
  • one end of tRNA molecule three exposed bases called the anitocon complementary to the mRNA codon
  • at opposite end of tRNA is the amiino acid where relevant amino acid is found
  • attatchment of relevant amino acid to attatchment site is called amino acid acitvation and requires ATP
  • involved converting codons on mRNA into a sequence of amino acids called the polypeptide
  • each ribosome is made of two subunits made from rRNA and protein
  • mRNA binds smaller sub units where tRNA binds to one of two attatchment sites of larger subunit
24
Q

What is the process if translation

A
  • initiation ; ribosome attatches to the start codon
  • tRNA molecule with a complementary anticodon stop first codon binds to first attatment site on the ribosome
  • second tRNA molecules joined to second attatchment sites and ribosomal enzyme catalyses formation of a peptide bond between two amino acids - elongation
  • firsst tRNA molecule is released and ribosomes now move one codon along mRNA exposes free attatchment site another tRNA molecule joins and process is repeated
  • repeats until stop codon is reached when polypeptide is released - terination
  • usually several ribosomes bind to a single mRNA - polysome
25
Q

Describe post translational modification

A
  • translation produces a polypeptide further modification needed to produce secondary,tertiary and quantenary structure
  • modification occurs in the golgi body
  • modification occurs to produce glycoproteins, lipoproteins and complex quantenary haemoglobin
26
Q

Describe haemoglobin

A
  • form haemoglobin is two alpha chains and two betw chains (coded by 2 genes) assembled together with iron as a prosthetic group
27
Q

Introns

A
  • non coding nucleotide sequence in DNA and pre mRNA that is removed from pre MRNA to produce mature mRNA
28
Q

Exons

A
  • nucleotide sequence on one strand of the DNA molecule and the corresponding mRNA that codes for the production of a specific polypeptide
29
Q

Codon

A
  • the triplet of bases in mRNA that codes for a particular amino acid or a punctuation signal

Biology summary flashcards component 1 (11 decks)

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