Nucleotides and Nucleic Acids (2.1.3) Flashcards
Name the two types of bases and the individual bases.
Purines: Adenine, Guanine
Pyrimidines: Cytosine, Thymine, Uracil
What is the structural difference between a purine and pyrimidine?
Purine: Two carbon-nitrogen rings joined together.
Pyrimidine: One carbon-nitrogen ring.
What are ADP and ATP?
Phosphorylated nucleotides.
What base is present in ADP and ATP?
Adenine
What substance is used to make ATP and why is ATP produced.
Glucose. Cells cannot get energy directly from Glucose so it has to be converted to ATP first.
How is a polynucleotide formed?
Condensation reaction.
A bond between the phosphate group of one nucleotide and the sugar of another.
Describe the structure of DNA
Two polynucleotide strands joined together by hydrogen bonding between the bases, forming a double helix shape.
Name the complementary base pairings and the number of hydrogen bonds between them.
Apple turnover with Gloopy Custard.
Adenine - Thymine (2)
Guanine - Cytosine (3)
Outline the steps involved in purifying DNA.
1) Break up the cell sample.
2) Add the broken up cells to a solution of detergent, sodium chloride and distilled water.
3) Incubate the beaker in a water bath at 60 degrees for 15 minutes.
4) Cool the mixture in an ice bath.
5) Filter the mixture then add protease enzymes.
6) Dribble cold ethanol down the side of the tube so it forms a layer on top of the solution.
7) Leave the tube and wait for a white precipitate to form.
8) Remove using a glass rod or hooked instrument.
Purifying DNA - When heating the cells in the detergent mixture. What exactly is happening?
The detergent breaks down the cell membranes. The salt binds to the DNA causing it to clump together.
Purifying DNA - The temperature of the water bath should be high enough for what reason?
To stop enzymes in the cells from working properly and breaking down the DNA.
What are the stages of DNA replication?
The enzyme DNA helicase breaks hydrogen bonds between two polynucleotide DNA strands.
The helix unzips.
Each separated strand acts as a template.
Free-floating DNA nucleotides attach to the exposed bases by complementary base pairing.
The enzyme DNA polymerase joins the nucleotides on the strands together creating a sugar-phosphate backbone.
Hydrogen bonds form between the bases.
The strands twist together to form a double-helix.
Describe semi-conservative replication.
Half of the strands in each new DNA molecule are from the original piece of DNA.
What is a random, spontaneous change in DNA replication called and what might this lead to?
Mutation
They can alter the sequence of amino acids in a protein causing an abnormal protein to be produced.
It might have no change, be worse, or better.
Define ‘gene’
A sequence of DNA nucleotides that codes for a polypeptide.
