2.3 Nucleic acids Flashcards
What is a double helix?
Shape of DNA molecule, due to coding of two sugar phosphate backbone strands into right-handed spiral configiration
What is a monomer?
Molecule that when repeated makes a polymer
What is a nucleotide?
A molecule consisting of five-carbon ring (pentose) sugar, a phosphate group and a nitrogenous base
What is a polynucleotide?
A large molecule containing nucleotides
What do nucleotides do?
Form monomers of nucleic acid, DNA and RNA
- In DNA pentose sugar = deoxyribose
- In RNA pentose sugar = ribose
They become phospholysed nucleotides when they contain more than one phosphate group
Help regulate many metabolic pathways
May be components of coenzymes
What is the structure of DNA?
6x
- It is a polymer as it is made up of many repeating units called nucleotides
- A molecule of DNA consists of two polynucleotide strands
- The two strands run in opposite directions so they are described as parallel
- Each DNA nucleotide consists of a phosphate group, a pentose sugar called deoxyribose and one of four nitrogenous bases
- The covalent bond between the sugar residue and the phosphate group in the nucleotide is called a phosphodiester bond - These bonds are broken when polynucleotides are synthesised
- DNA molecules are long and so they can carry a lot of encoded genetic information
What are is a purine?
- 2 rings
- adenine and guanine
What is a pyrimidene?
- 1 ring
- thymine and cytosine
What holds the two antiparallel DNA strands between the nitrogenous base together?
Hydrogen bonds
This allows the molecule to unzip for transcription and replication
How much hydrogen bonds do each base pairs have?
A-T has 2
C-G has 3
Why does a purine always pair up with a pyrimidene?
This is because it gives it equal sized rungs on the DNA ladder. They can then twist into the double helix.
This gives the molecule stability
What is the 5’ end?
Where the phosphate group is attached to the fifth carbon atom of the deoxyribose sugar
What is the 3’ end?
Where the phosphate group is attached to the third carbon atom of the deoxyribose sugar
What is on the rungs of the ladder?
The complementary base pairs joined by hydrogen bonds
What are the 4 proteins involved in DNA replication
DNA gyrase
DNA helicase
DNA polymerase
DNA ligase