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A Level Biology > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

(50 cards)

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1
Q

What does DNA stand for

A

Deoxyribonucleic acid

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2
Q

What is a nucleotide

A

Biological molecule consisting of a five-carbon sugar, a phosphate group and a nitrogenous base

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3
Q

what is the structure of a nucleotide

A
  • phosphate esters of pentode sugars
  • nitrogenous base is linked to C1 of the sugar
  • phosphate group is linked to C5 of the sugar
  • these are bonded by covalent bonds due to condensation reaction
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4
Q

When do nucleotides become phosphorylated nucleotides

A

When they contain more than one phosphate group
- ADP
- ATP

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5
Q

How are nucleotides able to help with metabolic pathways

A
  • ATP
  • ADP
  • AMP
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6
Q

What is the structure of DNA

A
  • polymer. Many repeated nucleotide units
  • consist two polynucleotide strands
  • two strands run in opposite directions (anti parallel)
  • consist of a phosphate group, five carbon sugar (deoxyribose), one nitrogenous base
  • nitrogenous bases: adenine, guanine, thymine, cytosine
  • covalent bond between the sugar and phosphate group is called a phosphodiester bond
  • phosphodiester bonds broken and formed when polynucleotides are synthesised
  • long so can carry a lot of genetic coding
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7
Q

What is a purine

A

The nucleotide bases containing a double ring structure

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8
Q

what hydrogenous bases are purines

A

Guanine
Adenine

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9
Q

What is a pyramidine

A

Nucleotide base with one ring structure

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10
Q

What hydrogenous bases are pyramidine

A

Cytosine
Thymine
Uracil

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11
Q

What bonds are between hydrogenous pairs

A

Hydrogen bonds

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12
Q

How many hydrogen bonds are between adenine and thymine

A

2

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13
Q

How many hydrogen bonds are between guanine and cytosine

A

3

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14
Q

What gives DNA is helical structure

A

Purine is always paired with a pyrimidine.
- gives DNA ability to twist

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15
Q

What allows the DNA to unzip for transcription and replication

A

Hydrogen bonds
- weak
- easy to break

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16
Q

What part of the DNA is the 5’ end

A

The end of the molecule where the phosphate group is attached to the fifth carbon atom of the deoxyribose sugar

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17
Q

what part of the DNA is the 3’ end

A

Where the phosphate group is attached to the third carbon atom of the deoxyribose sugar

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18
Q

What do the rungs on the DNA ladder contain

A

Complementary base pairs
- joined by hydrogen bonds

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19
Q

What does the antiparallel sugar-phosphate backbone do for the integrity of the DNA

A

Allows the molecule to be very stable
- integrity of the coded information within the base sequences is protected

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20
Q

How is DNA organised in eukaryotic cells

A
  • majority of DNA content is in the nucleus
  • each large molecule of DNA is wound around special histone proteins into chromosomes
  • each chromosome is one molecule of DNA
  • loop of DNA inside mitochondria and chloroplasts
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21
Q

How is DNA organised in prokaryotic cells

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A
  • DNA is in a loop and is within the cytoplasm
  • not wound around histone proteins
  • described as naked
22
Q

What is the structure of RNA

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A
  • pentose sugar (ribose)
  • phosphate group
  • nitrogenous base (uracil instead of thymine)
  • one strand
  • shorter strand
  • either mRNA, tRNA or rRNA
23
Q

What is the structure of ATP

Study These Flashcards
A
  • ribose
  • adenine (nitrogenous base)
  • 3 inorganic phosphates (phosphate group)
24
Q

What is semi-conservative replication

Study These Flashcards
A

How DNA replicated
- results in two new molecules
- each containing one old strand and one new strand
- one old strand is conserved in each new molecule

25
How does a DNA molecule split into two
Unwinds - the double helix untwists, a little at a time, catalysed by a gyrase enzyme Unzips - hydrogen bonds between nucleotide bases are broken. catalysed by DNA HELICASE. This results in two single strands of DNA with exposed nucleotide bases
26
What happens after the DNA has been separated
- free nucleotides, in the nucleoplasm, bond to the exposed bases. Using complementary base pairings - DNA POLYMERASE catalyses the addition of new bases from 5’ to 3’. DNA zips back together - leading strand is synthesised continuously - lagging strand is synthesised in fragments (discontinuous) - these fragments are then joined together by ligase
27
What are the steps of DNA replication
- unwinds - unzips - bases attach - zips back up
28
How can mutations occur in replication
The wrong nucleotide may be inserted - could change the genetic code (point mutation)
29
What is a gene variation
Different variations of a particular gene
30
What are the five main feature of genetic code
- triplet code - non overlapping - degenerate - universal - determines amino acid sequence
31
What is triplet code in genetic code
- three bases (codon) code for an amino acid - the three complementary bases on tRNA form an anticodon - triplet codons for ‘start’ and ‘stop’ signals
32
What does it mean when genetic code is non-overlapping
All of the codons are separate
33
What does it mean when genetic code in degenerate
Most amino acids have more than one code
34
What does it mean that genetic code is universal
All life on earth has the same DNA code for amino acids
35
What does it mean by genetic code can determine amino acid sequences
DNA codes for RNA, this in turn codes for proteins The proteins produced then form and regulate all other processes
36
Examples of the primary structure of a polynucleotide being correct
- shape of the active site must be complementary to the substrate - part of an antibody must have a complementary shape to the antigen on the surface of an invading pathogen - receptor of a cell membrane must have a complementary shape to the cell signalling molecule that it must detect - ion channel protein must have hydrophilic amino acids lining the outside of the channel
37
What is translation
The process of making mRNA from a DNA template
38
What is translation
Formation of a protein, at ribosomes, by assembling amino acids into a particular sequence according to the coded instructions carried from DNA to the ribosomes by mRNA
39
What are the steps of transcription
- gene unwinds and unzips - hydrogen bonds break - RNA POLYMERASE allows nucleotides to bond to their complementary bases - length of RNA that is complementary to the template strand is produced - this forms coding strand - mRNA passes out nucleus and attaches to a ribosome
40
What does the large subunit of ribosomes contain in translation
3 binding site - E - P - A
41
What happens at the A site
Where tRNA enters ribosome - holds tRNA carrying the next amino acid to be added to the polypeptide chain
42
What happens at the P site
Holds tRNA carrying the growing polypeptide chain - where the codon and anticodon bind - condensation reaction forms peptide bonds between amino acids
43
What happens at the E site
Where the tRNA exits the ribosome - site from which tRNA that has lost its amino acid is discharged
44
What are the main steps of translation
- small subunit of ribosome attaches to mRNA - tRNA attaches to mRNA - large subunit of ribosome attached around tRNA on mRNA - tRNA enters A site - polypeptide chain starts to grow - tRNA leaves E site - process continues - release factor enters A site - all elements are released resulting in a polypeptide chain
45
What happens inside the large subunit of ribosome
- anticodon of tRNA attaches to codon of mRNA - polypeptide chain is formed
46
What does the mRNA carry in translation
The nucleotide code for the protein to be made
47
What does tRNA do in translation
Interpret the molecule code - each tRNA carries an amino acid and an anticodon
48
What is the structure of tRNA
Clover structure - D arm - T arm - anti codon - acceptor stem (amino acid)
49
What are the processed of protein synthesis
- DNA unzips: DNA helicase - DNA polymerase bonds adjacent nucleotides - hydrogen bonds form and helix returns - pre mRNA leaves through nuclear pores - turn into mature mRNA with splicing - tRNA brings amino acid into ribosome subunit (A site) - codon and anticodon bind (P site) - polypeptide chain grows - tRNA leaves ribosome (E site) - amino acid binds to tRNA (tRNA activation)
50
What is splicing
The process by which introns, no coding regions of genes, are taken out of the mRNA transcript. Exons, coding regions, are joined together to make mature mRNA

A Level Biology (13 decks)

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