BB10A: Cells, Biomolecules & Genetics Semester 1 Tuesday 30 Sept. Lecture 3 Biomolecules & their interactions with Water Andrew Pearson

Life on our planet has evolved to cope with a predominantly aqueous environment: roughly 70% of the Earths surface & animal bodies are H 2 O Biomolecules & their interactions with Water

The properties of H 2 O have therefore had a powerful effect upon the forces of natural selection at the level of the Biomolecule. Let us look at some properties of H 2 O. Biomolecules & their interactions with Water

In contrast to hydrophobic substances, many biochemically important ions and molecules are so hydrophilic that Osmotic pressure results. Biomolecules & their interactions with Water

Another important property of H 2 O is its ability to dissociate into both a weak acid and a weak base. Biomolecules & their interactions with Water

The effect of water upon natural selection is quite marked even at the molecular level: the case of the most abundant biosynthesised molecule, Glucose. Biomolecules & their interactions with Water

Proteoglycan aggregate Chondroitin sulphateKeratan sulphate Hyaluronic Acid core

The less it is allowed to interact with aqueous media, the stronger a H-bond can be. This is important in the stability of macromolecules such as DNA: Biomolecules & their interactions with Water

All things naturally prefer (are more stable in) the lowest possible energy state. For H 2 O in the biosphere (i.e. between 0 o C and 100 o C) this means random motion, not an ordered structure. Biomolecules & their interactions with Water

This effect is important in the stabilisation of biomembranes Biomolecules & their interactions with Water

Relative abundances of elements in the universe Biomolecules & their interactions with Water

Relative abundances of elements in Earths crust Biomolecules & their interactions with Water

Relative abundances of elements in humans Biomolecules & their interactions with Water

Universal Earths crust Human body Biomolecules & their interactions with Water

Apart from photosynthesising organisms, which take energy from e/m radiation, all the biochemical needs of the biosphere for life come from: chemical elements, salts and molecules found in the lower regions of the atmosphere, the hydrosphere and the upper parts of the lithosphere. Biomolecules & their interactions with Water

Ecology studies are often enhanced by under- standing how and why elements cycle through different systems in the biosphere, & recent perturbations of ecological balances by human activities have brought these matters into sharp focus. Biomolecules & their interactions with Water