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BIOLOGY REVISION > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

1
Q

What is a nucleotide?

A

A phosphate ester of a pentose sugar containing

  • 5 carbon sugar
  • phosphate group
  • nitrogenous base
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2
Q

What is the pentose sugar in DNA and RNA?

A 
DNA= deoxyribose
RNA= ribose
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3
Q

How are the phosphate and the pentose sugar joined?

A

By a phosphoester bond

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4
Q

What are some 3 roles of nucleotides?

A

Roles of nucleotide:

  • monomers of nucleic acids
  • help regulate metabolic pathways
  • components of co enzymes
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5
Q

What are the structures of Adenosine, AMP, ADP and ATP?

A
  • Adenosine = adenine +ribose
  • AMP (mono phosphate) = adenine + ribose +1 phosphate
  • ADP (diphosphate) = adenine +ribose +2 phosphate
  • ATP (triphosphate) = adenine+ribose + 3 phosphate
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6
Q

Discuss the double helix structure of DNA

A

DNA

  • 2 polynucleotide strands that run antiparalell
  • strands run from 5’ to 3’
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7
Q

What are the complimentary base pairs?

A

Complimentary base pairs are Adenine to Thymine and Guanine to Cytosine (always a purine to a pyrimidine)

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8
Q

Which nitrogenous bases are a) pyrimidine b) purine

A 
Pyrimidine = Cytosine and thymine
Purine = guanine and adenine
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9
Q

What bond joins phosphates to pentose to deoxyribose in a DNA strand?

A

Phosphodiester bond (each phosphate has two bonds)

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10
Q

How many hydrogen bonds to each base pairing form?

A 
A---T = 2 hydrogen bonds
C---G = 3 hydrogen bonds
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11
Q

Where is DNA found in comparison to RNA?

A

DNA is found in the nucleus while RNA is found in the nucleus and the cytoplasm

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12
Q

Discuss differences between DNA and RNA

A 
DNA = deoxyribose, thymine, found in nucleus
RNA= ribose, uracil, found in nucleus and cytoplasm and is shorter than DNA
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13
Q

Is DNA a macromolecule or a polymer?

A

DNA is both a MACROMOLECULE and a POLYMER

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14
Q

How is DNA organised in eukaryotic cells?

A

Eukaryotic Cells:

  • DNA molecule wound around a HISTONE PROTEIN. this is a NUCLEOSOME
  • CHROMATIN is the term for DNA packaged with histone proteins
  • naked loop in mitochondria and chloroplasts
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15
Q

How is DNA organised in prokaryotic cells?

A

Prokaryotic cells:

-Loop of naked DNA (no histone proteins)

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16
Q

How do you purify DNA?

A

Purification by precipitation:

  1. Vile of DNA in solution
  2. Add SALT and ETHANOL
  3. CENTRIFUGE forces solid to the bottom
  4. Left with a PELLET of solid containing the DNA
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17
Q

What is a genome?

A

A genome is all the DNA a cell contains

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18
Q

What phase of the cell cycle is DNA replicated?

A

DNA is replicated in the S phase of interphase. The DNA in mitochondria and chloroplasts is replicated in G2 phase of interphase.

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19
Q

Describe the first big step of DNA replication

A

DNA replication:

  1. Double helix is unwound by gyrase
  2. Strands unzipped by DNA helicase
20
Q

Describe the second big step of DNA replication

A

Synthesis of new strand:

  1. free activated nucelotides align and hydrogen bond
  2. DNA polymerase catalyses addition of bases in the 5’ to 3’ direction
  3. Leading strand is synthesised continuously and lagging strand is synthesised discontinuously in fragments
  4. fragements of lagging strand are joined by ligase enzymes
21
Q

Give the role of 4 enzymes involved in DNA replication

A
  • Gyrase- unwinds double helix
  • Helicase- Unzips the strands by breaking H bonds
  • DNA polymerase- catalyses the addition of new bases in 5’ 3’ direction
  • Ligase- joins fragments of the lagging strand
  • Hydrolysis of activated nucleotides supplies the energy to make phosphodiester bonds
22
Q

Why is DNA replication semiconservative?

A

Semi conservative replication because each new DNA molecule consists of one parental strand and one daughter strand

23
Q

How is DNA replication different in prokaryotes? Does this happen at all in eukaryotes?

A

Prokaryotes DNA is a loop so a BUBBLE SPROUTS from the loop and unwind and unzips and thrn complimentary nucleotides join to exposed nucleotides. REPLICATION BUBBLE. This also occursin MITOCHONDRIA and CHLOROPLASTS

24
Q

If in prokaryotes, mitochondria and chloroplasts there is a replication bubble, what is this referred to as in eukaryotes?

A

Eukaryotes = replication fork

25
Q

how often do mutations occur during DNA replication?

A

1 in 10 to the power of 8

26
Q

Are mutations always harmful?

A

Mutations aren’t always harmful, they account for the existent of alleles.

27
Q

What is a proteome?

A

Proteome = all the proteins in a cell

28
Q

What is a codon?

A

Codon = base triplet, each triplet codes for an amino acid on a length of mRNA

29
Q

What are the 3 features of genetic code?

A
  • Near universal = same triplet codes for the same amino acid in most organisms
  • Degenerate = more than one triplet code coding for the same amino acid
  • Non overlapping = sequence is read from a fixed point so any insertion or deletion causes a frame shift
30
Q

How is DNA made into RNA? How then is RNA made into a protein?

A

DNA ——- RNA ———-protein

1) transcription 2) translation

31
Q

Describe the steps of transcription

A

Transcription:

  1. gene unwinds and unzips
  2. RNA Polymerase catalyses temporary bonding betwen RNA nucleotides and DNA bases
  3. template strand + MRNA made (coding strand)
  4. mRNA passes out of nucleus through the nuclear envelope and attaches to a ribosome
32
Q

What bases does mRNA have? Why?

A

A U G C because it attaches to the bases on the template strand which have regular bases

33
Q

What bases does the template strand have?

A

A T C G

34
Q

How are ribosomes made?

A
  • Ribosomes are made in the NUCLEOLUS by EQUAL PARTS rRNA and PROTEIN.
  • two small SUB UNITS pass out of the nucleolus and join together with the help of a MAGNESIUM ION to from a ribosome
35
Q

What is the structure of tRNA?

A

tRNA is made in the NUCLEOLUS and is a SINGLE stranded polynucleotide. They twist into the hairpin shape. one end is an ANTICODON and the other is a TRIO OF UNPAIRED BASES that bind to an amino acid.

36
Q

What are the steps of translation?

A

Translation:

  1. tRNA brings an amino acid and finds where their anti codon can temporarily hydrogen bond to the mRNA codon
  2. ribosome moves along the mRNA, reads, and peptide bonds form whenever two amino acids are adjacent to each other ( ATP needed)
  3. Ribosome stops when it reaches a stop codon
37
Q

What happens to the mRNA after translation?

A

mRNA breaks down (gets degraded). Its components recycled

38
Q

What happens to the new polypeptide after translation?

A

The new polypeptide is helped by CHAPERONE PROTEINS to fold correctly into its 3D shape.

39
Q

What is the structure od ATP?

A

3 phosphate + ribose + adenosine

40
Q

Where is carbon 5 found?

A

Carbon 5 is found embedded in the bond between the phosphate and ribose

41
Q

How does ATP release energy?

A

Hydrolysis of ATP releases energy

42
Q

What charge are the phosphates and what does this mean?

A

The phosphates are negatively charged so they repel each other. This means the bonds are unstable so they have a low activation energy so are easily broken

43
Q

What is the equation for hydrolysis and condensation of ATP?

A 
ATP + H2O ==== ADP + Pi (+energy)
ATP hydrolase (hydrolysis of ATP)
ATP synthase (synthesis of ATP)
44
Q

What kind of turnover does ATP have ans what does this mean?

A

ATP has a high turnover rate meaning it is a short term energy molecule due to unstable bonds

45
Q

Give examples of processes that require ATP

A

ATP is used in muscle contraction, active transport and creation of lysosomes

46
Q

How can ATP activate other molecules?

A

Hydrolyse ATP to release a Pi which binds to the molecule making it less stable, therefore more reactive

47
Q

Where are some processes where ATP is made?

A

ATP is made in photo-phosphorylation, oxidative phosphorylation and substrate level phosphorylation

BIOLOGY REVISION (21 decks)

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