Macromolecules - nucleic acids and lipids

Central dogma of molecular biology

DNA -> RNA -> Protein

- called gene expression

Primary role of DNA

Information carrier

Primary roles of RNA

Information carrier and cellular control

Nucleic acids

Comprise both DNA and RNA

Polymers made of nucleotide monomers

Nucleotide

Made up of a phosphate group, a sugar and a nucleoside

Double helix structure

2 complimentary strands of DNA assembled together as a twisted ladder

Nucleotide positioning

Rungs - bases

Backbone - alternating phosphate and sugars

DNA replication

old strands act as a template which directs the assembly of the new strand by base complimentary

Transcription to RNA

Genetic information copied into a complementary molecule of messenger RNA. Complementary base pairing goes: G-C and A-U

Genetic code

3 nucleotides in DNA transcribed of mRNA (codon), base-pair to 3 nucleotides in tRNA (anticodon), which is linked to a specific amino acid

Lipids

hydrophobic molecules

1. fats

2. phospholipids

3. steroids

Functions of lipids

Mainly energy storage, also membrane lipids, signalling molecules and electric insulation

Fats or triglycerides

3 fatty acids linked through an ester bond to a glycerol molecule. 3 long non polar hydrocarbon chains (hydrophobicity)

Saturated fats

Only single bonds between carbons, flexible molecules that pack tightly. Solid at room temperature.

Unsaturated fats

One or more double bonds, which bend the molecule, liquid at room temperature

Functions of fats

energy storage, form droplets in adipose cells

Phospholipids

A polar group (head) replaces one of the fatty acid tails. Molecule has both a polar and nonpolar portion. Causes various types of self assembly to minimise water exposure

Steroids

Carbon skeleton made of 4 linked rings - different chemical groups are attached to the rings