Ib Biology Hl: A1.2 - Nucleic Acid

What are nucleic acid chains made of

Repeating monomers ( nucleotides ) that have undergone a polymerisation ( a condensation reaction)

monomer of nucleid acid

nucleotide

Two main types of nucleic acid

Déoxyribonucleic acid ( DNA )

Ribonucleic acid ( RNA )

Components of a nucleotide

• pentose sugar

• Nitrogenous base

• A phosphate group

Sugar phosphate bonding

The nucleotide links together through polymerisation. This requires energy and gives out a water molecule. The bond is phosphodi-ester bond.? covalent bond

Two main types of bases

• purines ( two rings in their structure )( A, G)

• Pyrimidines ( on ring in their structure )( T, C, U)

How are the two strands of DNA linked to each other

Complimentary base pairing between nitrogenous bases

Differences between RNA and DNA

• Thymine is replaced by uracil in RNA

• RNA used Deoxyribose as a sugar, while RNA uses ribose

• RNA on C2 has -OH, DNA on C2 has -H

• RNA is a single stranded molecule, while DNA is a double stranded molecule connected by hydrogen bonding

• Thus RNA is less table, usually temporary

structure of DNA polymer

nitrogenous base attached to C1 atom, other attachment to phosphate group at C3, and own phosphate group is C5

difference between DNA and RNA

RNA:

• used ribose

• single stranded

• has uracil

• is less stable

DNA:

• uses deoxyribose

• double stranded

• has thymine

• more stable

nucleosomes

dna wrapped around 8 histone proteins/ histone octamer

different histone proteins

H2A H2B H3 H4

chromatin

many nucleosomes together

Chargaff’s rues

the amount of guanine is equal to the amount of cytosine, and the amount of adesine is the same as the amount of thymine

amino acid structure

amino group : NH2,

carboxyl acid : COOH

R group

central carbon .

condensation of amino acids