Chapter 3 - Nucleotides and nucleic acids Flashcards
(95 cards)
1
Q
DNA and RNA are..
A
polymers
2
Q
What monomer makes up DNA and RNA
A
Nucleotides
3
Q
What are the three components of a nucleotide
A
- a pentose sugar
- a nitrogen-containing organic base
- a phosphate group
4
Q
Components of a nucleotide for DNA
A
o A deoxyribose sugar with hydrogen at the 2’ position
o A phosphate group
o One of four nitrogenous bases - adenine (A), cytosine(C), guanine(G) or thymine(T)
5
Q
Where is the hydrogen on the DNA nucleotide
A
2nd position
6
Q
Nitrogenous Bases in DNA nucleotide
A
adenine (A), cytosine(C), guanine(G) or thymine(T)
7
Q
Components of RNA nucleotides
A
o A ribose sugar with a hydroxyl (OH) group at the 2’ position
o A phosphate group
o One of four nitrogenous bases - adenine (A), cytosine(C), guanine(G) or uracil (U)
8
Q
What is the function of the hydroxyl group on the 2nd carbon in RNA nucleotide
A
- makes RNA more susceptible to hydrolysis
- This is why DNA is the storage molecule and RNA is the transport molecule with a shorter molecular lifespan
9
Q
Draw RNA nucleotide
A
10
Q
Draw DNA nucleotide
A
11
Q
Define purine
A
A nitrogenous base that has two rings in their structure that are made up of carbon and nitrogen atoms.
One larger ring is hexagonal while the other smaller ring is pentagonal in structure.
12
Q
What shape is the larger ring in purines
A
Hexagonal
13
Q
What shape is the smaller ring in purines
A
Pentagonal
14
Q
What bases are purine
A
Adenine + guanine
15
Q
Define pyrimidines
A
A nitrogenous base that contains only one ring made up of both carbon and nitrogen atoms.
Their ring is also hexagonal.
16
Q
What bases are pyrimidines
A
Cytosine
Thymine
Uracil
17
Q
Flow chart of different structure of nucleotides = visual
A
18
Q
Differences between DNA and RNA = sugar/bases/number of strands
A
19
Q
How does RNA and DNA form
A
Condensation reaction
20
Q
Where does the condensation reaction occur between nucleotides
A
between the phosphate group of one nucleotide and the pentose sugar of the next nucleotide
21
Q
What type of bond does the condensation reaction form
A
Phosphodiester bonds
22
Q
Draw a polynucleotide
A
23
Q
Why is it called a phosphodiester bond
A
because it consists of a phosphate group and two ester bonds
24
Q
• The chain of alternating phosphate groups and pentose sugars produced as a result of many phosphodiester bonds is known as….
A
the sugar-phosphate backbone (of the DNA or RNA molecule)
25
What do organisms use ATP for
o Anabolic reactions (building larger molecules from smaller molecules)
o Moving substances across the cell membrane or moving substances within the cell
• In animals, energy is also required for:
o Muscle contraction – to coordinate movement at the whole-organism level
o The conduction of nerve impulses
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Examples of nucleotides
DNA
RNA
ATP
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ATP is a type of..
Nucleic acid
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What is ATP specifically
A phosphorylated nucleotide
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Structure of ATP
o Three phosphate groups = adenosine triphosphate(ATP)
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Adenosine with 1 phosphate group
adenosine monophosphate(AMP)
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Adenosine with 2 phosphate groups
adenosine diphosphate(ADP)
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What is adenosine
A nucleoside
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What is DNA molecules made up of
two polynucleotide strands lying side by side, running in opposite directions
– the strands are said to be antiparallel
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What is each DNA polynucleotide strand made up of
alternating deoxyribose sugars and phosphate groups bonded together to form the sugar-phosphate backbone.
35
What are the bonds in the sugar phosphate backbone
Phosphodiester bonds = covalent bonds
36
Where does the Phosphodiester bond occur
o The phosphodiester bonds link the 5-carbon of one deoxyribose sugar molecule to the phosphate group from the same nucleotide, which is itself linked by another phosphodiester bond to the 3-carbon of the deoxyribose sugar molecule of the next nucleotide in the strand
37
What does 3’ and 5’ mean
o Each DNA polynucleotide strand is said to have a 3’ end and a 5’ end (these numbers relate to which carbon on the pentose sugar could be bonded with another nucleotide)
o As the strands run in opposite directions (they are antiparallel), one is known as the 5’ to 3’ strand and the other is known as the 3’ to 5’ strand
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How are the two antiparallel polynucleotide strands held together
Hydrogen bonds between bases
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Complementary base: purine adenine
Pyrimidine Thymine
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How many hydrogen bonds are formed between A and T
2
41
Complimentary base: pyrimidine cytosine
purine guanine
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How many hydrogen bonds between G and C
3
43
What shape is DNA
Double helix
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What process is dna copied via
semi-conservative replication
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Why is it called semi-conservative replication
because in each new DNA molecule produced, one of the polynucleotide DNA strands (half of the new DNA molecule) is from the original DNA molecule being copied
• The other polynucleotide DNA strand (the other half of the new DNA molecule) has to be newly created by the cell
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What is the importance of semi-conservative replication
• Retaining one original DNA strand ensures there is genetic continuity (i.e. genetic information is conserved) between generations of cells
47
Describe the process of semi-conservative replication
• The enzyme helicase unwinds the DNA double helix by breaking the hydrogen bonds between the base pairs on the two antiparallel polynucleotide DNA strands to form two single polynucleotide DNA strands
• Each of these single polynucleotide DNA strands acts as a template for the formation of a new strand made from free nucleotides that are attracted to the exposed DNA bases by base pairing
• The new nucleotides are then joined together by the enzyme DNA polymerase which catalyses condensation reactions between the deoxyribose sugar and phosphate groups of adjacent nucleotides to form a sugar-phosphate backbone (5 to 3 direction)
• The original strand and the new strand join together through hydrogen bonding between base pairs to form the new DNA molecule
48
Which enzyme beaks the hydrogen bonds
Helicase
49
Which enzyme catalyses condensation reaction between deoxyribose sugar and phosphate groups
DNA polymerase
50
What direction does DNA polymerase work I’m
5 to 3
51
How often do mistakes get made in dna replication (mutations)
Very very rarely
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How would mistakes occur if they do
o Bases being inserted into the complementary strand in the wrong order
o An extra base being inserted by accident
o A base being left out by accident
53
Define gene
sequence of nucleotides that forms part of a DNA molecule, which codes for the production of a specific polypeptide (protein)
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What is a codon
A triplet
55
Some of the triplets code for..
Start and stop
56
Features of the genetic code
Non-overlapping
Degenerate
Universal
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What does non-overlapping mean
o Each base is only read once in which codon it is part of
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What does degenerate mean
multiple codons can code for the same amino acid
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What does universal mean
almost every organism uses the same code
o The same triplet codes code for the same amino acids in all living things
o + is why genetic engineering is possible
60
Role of tRNA
tRNA molecules that transfer amino acids possess anticodons which are complementary to the codons on mRNA
61
Stages of protein synthesis
o Transcription – DNA is transcribed and an mRNA molecule is produced
o Translation – mRNA (messenger RNA) is translated and an amino acid sequence is produced
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Where does transcription occur
Nucleus
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How does transcription occur
• Part of a DNA molecule unwinds (the hydrogen bonds between the complementary base pairs break)
• The exposed gene can then be transcribed (the gene from which a particular polypeptide will be produced)
• A complimentary copy of the code from the gene is made by building a single-stranded nucleic acid molecule known as mRNA (messenger RNA)
• Free RNA nucleotides pair up (via hydrogen bonds) with their complementary (now exposed) bases on one strand (the template strand) of the ‘unzipped’ DNA molecule
• The sugar-phosphate groups of these RNA nucleotides are then bonded together (by phosphodiester bonds) by the enzyme RNA polymerase to form the sugar-phosphate backbone of the mRNA molecule
• When the gene has been transcribed (when the mRNA molecule is complete), the hydrogen bonds between the mRNA and DNA strands break and the double-stranded DNA molecule re-forms
• The mRNA molecule then leaves the nucleus via a pore in the nuclear envelope
64
What is the template strand
• RNA nucleotides only pair with the bases on one strand of the DNA molecule
o This strand of the DNA molecule is known as the template strand (or the transcribed strand) and it is used to produce the mRNA molecule
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The other strand is the
Coding strand
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What direction does RNA polymerase move
3 to 5
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Therefore what direction does mRNA molecule Grow
5 to 3
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Where does translation occur
Cytoplasm = ribosomes
69
How does translation occur
• In the cytoplasm, there are free molecules of tRNA(transfer RNA
• These tRNA molecules have a triplet of unpaired bases at one end (known as the anticodon) and a region where a specific amino acid can attach at the other
• The tRNA molecules bind with their specific amino acids(also in the cytoplasm) and bring them to the mRNA molecule on the ribosome
• The triplet of bases (anticodon) on each tRNA molecule pairs with a complementary triplet (codon) on the mRNA molecule
• Two tRNA molecules fit onto the ribosome at any one time, bringing the amino acid they are each carrying side by side
• A peptide bond is then formed (via a condensation reaction) between the two amino acids
• This process continues until a ‘stop’ codon on the mRNA molecule is reached – this acts as a signal for translation to stop and at this point the amino acid chain coded for by the mRNA molecule is complete
• The amino acid chain then forms the final polypeptide
70
How many codons can fit in the ribosome at once
2
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+ name process in step 6
= precipitation
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Condensation
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84
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C
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D
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B
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C
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A
90
What type of sugar does ATP have
Ribose - OH on second carbon
91
What type of sugar does DNA have
Deoxyribose - H on 2nd carbon
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What type of sugar does RNA have
Ribose - OH on second carbon
93
Is ATP recycled
YES
94
Instead of calling them free nucleotides what should we call them
Free, activated nucleotides
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Is there a difference in helicase between DNA and RNA
YES
