2.1.3 Nucleotides and Nucleic acids Flashcards
(62 cards)
What are nucleotides?
The monomer that makes nucleic acids consists of a pentose sugar,
nitrogenous base and phosphate group.
What are Purine nitrogenous bases?
2 carbon ring structures (adenine and guanine)
What are Pyrimidine nitrogenous bases?
1 carbon ring structure (Cytosine, Thymine and Uracil)
What is Thymine (Or Uracil in RNA) complementary to?
Adenine
What is Guanine complementary to?
Cytosine
What is the bond called between two nucleotide monomers?
Phosphodiester bonds
What is the reaction that nucleotides undergo to form phosphodiester bonds?
Condensation Reaction
What do phosphodiester bonds form between?
The pentose sugar and phosphate of the two nucleotides.
What’s a gene?
A sequence of DNA nucleotides that codes for the production of a specific
sequence of amino acids, that in turn make up a specific polypeptide (protein)
What is semi-conservative replication?
The replication of DNA to produce two new DNA
molecules which both contain one new strand and one old strand from the original DNA
molecule.
What is a Degenerate genetic code?
A term used to describe the fact that some amino acids
can be coded for by multiple different codons.
What is a non-overlapping genetic code?
A term used to describe the fact that each base is
only part of one codon and that each codon is read one at a time in order.
What is the structure ATP (Adenosine triphosphate)?
Composed of adenine, ribose, and 3 inorganic phosphate groups.
-Phosphate groups link with
ribose in a row.
-The two last bonds among
phosphates act as high
energy bonds. Each of these
contains 30.5 kJ/mol.
-This energy is released when
ATP is subjected to hydrolysis
by the enzyme ATPase.
How does ATP link to energy?
When a phosphate group is removed
from ATP, adenosine diphosphate (ADP)
is formed and 30.5 kJ/mol of energy is
released.
Removal of a second phosphate produces
adenosine monophosphate (AMP), and
30.5 kJ/mol of energy is again released.
Removal of the last phosphate, leaving
adenosine, releases only 14.2 kJ/mol.
Describe how ATP is good for energy release
It is readily hydrolysed to release energy
It is small and water soluble - This allows it to be readily transported around the cell.
The hydrolysis of ATP can be carried out quickly and easily whenever
Energy is required within the cell by the action of just one enzyme, ATPase
ATP is relatively stable at cellular pH levels
What are the names of the 2 polynucleotides?
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are polynucleotides, which are polymers of nucleotides
What’s the difference between DNA and RNA?
DNA is a double-stranded polynucleotide, whereas RNA is a single-stranded polynucleotide
What is a phosphodiester bond?
A phosphodiester bond is the linkage which occurs when exactly two of the hydroxyl groups in phosphoric acid react with hydroxyl groups on the pentose sugars of two adjacent nucleotides to form two ester bonds
What’s the difference in bases between DNA and RNA?
DNA nucleotides and RNA nucleotides can contain the organic bases adenine, cytosine and guanine. However, only DNA contains thymine, whereas RNA- uracil
Is DNA parallel or anti-parallel?
DNA is antiparallel - the strands of DNA run in opposite directions.
Name some similarities between DNA and ATP
Both have 5 Carbon sugar - pentose
Both contain a phosphate
Both contain adenine as their base
Name some differences between DNA and ATP
DNA has a deoxyribose sugar whereas ATP has a ribose sugar
DNA can involve all four bases, ATP only adenine
DNA has 1 phosphate, ATP has three phosphates
What was Meselsohn and Stahl (1958)’s theory?
The semi conservative hypothesis was shown to be the true mechanism by the work of Meselsohn and Stahl (1958).
-They grew the bacteria Escherichia coli with different isotopes of nitrogen.
-The bacteria was exposed to N15 for several generations until it was exposed to a lighter N14.
-Scientists could then distinguish between the different DNA densities by centrifuging them.
All the bases in DNA contain nitrogen
Nitrogen has two forms:
Light 14N
Heavy isotope 15N
Bacteria will incorporate nitrogen from their growing medium into any new DNA they make
What are the steps for semi-conservative replication?
- A representative portion of DNA, which is about to undergo replication.
- The two strands of the DNA separate. The hydrogen bonds between the bases break.
- Free nucleotides are attracted to their complementary bases.
- Once the new nucleotides have lined up, they are joined together by the enzyme DNA polymerase.
- Finally, all the nucleotides are joined to form a complete polynucleotide chain using DNA polymerase. In this way, two identical strands of DNA are formed. As each strand retains half of the original DNA material, this method of replication is called the semi-conservative method.
