Biological molecules: nucleic acids Flashcards
What does a nucleotide contain?
- A phosphate group
- A pentose sugar
- A nitrogen-containing base
What does a DNA nucleotide contain?
- A DEOXYRIBOSE sugar
- A phosphate group
- A nitrogen-containing base
What is the pentose sugar in RNA called?
Ribose
What are purines?
(nitrogenous base)
- Adenine
- Guanine
They have a double ring
What are pyrimidines?
(nitrogenous bases)
- Thymine
- Cytosine
- Uracil (RNA)
They have a single ring
What is the bond between the phosphate group and the sugar?
Phosphodiester bond
- joins the monomers to make the polymer DNA
What is the reaction the makes the phosphodiester bond?
Condensation reaction
What are complementary base pairs held together by?
Hydrogen bonds
What base pairs have 3 hydrogen bonds?
- Cytosine
- Guanine
What base pairs have 2 hydrogen bonds?
- Adenine
- Thymine
What is DNA used for in our body?
(deoxyribonucleic acid) is the store of genetic information that codes for proteins to help us grow and develop.
What is the function of RNA?
(ribonucleic acid) comes in the form of transfer (tRNA) or messenger (mRNA), or ribosomal (rRNA).
It transfers genetic information of the DNA to ribosomes to make proteins.
What is semi-conservative replication?
‘Unzipping’ DNA so that new polynucleotides can use it as a template and synthesise. This is how DNA is copied.
Explain the process of semi-conservative replication
- The enzyme Helicase breaks the hydrogen bonds between the 2 polynucleotide strands, the point of separation is called the replication fork.
- The original strands act as a template, and the formation of the new strand is catalysed by DNA polymerase.
- The bases are read and free floating polynucleotides then bond (hydrogen) to their complementary base pair on the original strand by condensation reactions.
So each new DNA molecule now has one new and one original strand.
Explain why DNA polymerase works in opposite ways during semi-conservative replication
DNA polymerase reads the parent strand in a 3’ to 5’ direction therefore builds the Leading strand in a 5’ to 3’ direction as the strands are opposites, towards the replication fork.
Because they are opposites, that means the the other parent strand is facing the opposite way in a 5’ to 3’ direction so the Lagging strand is now built in 3’ to 5’, away from the replication fork.
The strands are antiparallel.