Bases in DNA
adenine, guanine, cytosine, thymine
Bases in RNA
adenine, guanine, cytosine , uracil
Difference in base pairing in nucleic acids
Adenine - thymine or uracil form 2 hydrogen bonds between them
Guanine - cytosine form 3 hydrogen bonds between them
Differences between DNA and RNA
In DNA, two long polynucleotide chains form a double helix, whereas in RNA is consists of one single helix short polynucleotide chain
RNA has uracil as a nitrogenous base rather than thymine
What does semi conservative DNA replication mean and why is it important
One strand of one of the new DNA chain is from the original DNA, and the other is a newly synthesised strand
it ensures that the genetic code remains identical between generations of cells
Whole process of semi-conservative replication
- DNA helicase will unzip the original DNA strand by breaking the H bonds between all the bases leaving two separate template strands
- New free DNA nucleotides will attach to the exposed bases on the template strands by complementary base pairing
- DNA polymerase will join adjacent nucleotides 5’-3’ to form phosphodiester bonds on the new strand of nucleotides
Why is DNA antiparallel
as the sugar phosphate backbone runs 3’-5’ up one strand and 3’-5’ down the other strand
What is the meselson-stahl experiment
Its evidence for semi-conservative replication
Added DNA of E coli in two separate test tubes in and grew them in 14n and 15n nitrogen isotopes.
then allowed DNA to replicate one generation to allow nitrogen isotopes to be incorporated into the DNA
then took a sample from each test tube and grew them together and allowed one generation of replication
then took all three tubes and spun in a centrifuge to allow DNA to form bands
14n showed a band at the high point
15n showed a band at a lower point
14n+15n showed a band in between, suggesting that the replication was semi conservative as both isotopes of nitrogen were incorporated into the DNA
Structure of ATP
Adenine, ribose and 3 phosphates
adenosine triphosphate
what is ATP broken into and how
ADP + Pi
its hydrolysed using the enzyme ATP hydrolase
How is ATP synthesised
ADP + Pi = ATP
Condensation reaction to form a bond between to inorganic phosphates using the enzyme ATP synthase
Adaptation of ATP (x2)
- it can be rapidly resynthesized after it has been broken down so can be recycled to be used in various functions in the body
- the inorganic phosphate can phosphorylate other compounds to make them more reactive
Properties of ATP (x4)
-Releases small amounts of energy at a time to prevent cell death by heat as energy can be wasted through heat
- cannot leave the cell that it is synthesised in, so is constantly available for use in respiration
- it is an immediate source of energy as hydrolysis of ATP involves only 1 step
- Is soluble
