1.1 Water

Water as a solvent

• Helps multicellular organisms transport molecules around the body

• Acts as a medium where chemical reactions of life can occur

Water as a metabolite

• Water is either a reactant or a product of a reaction

• eg. Photosynthesis, digestion, aerobic respiration

Water is a temperature buffer

Helps buffer/slow down temperature changed in cells due to enzymatic activity because of its relatively high specific heat capacity

Formation of Cell Membrane

Phospholipid heads interact with water while tails avoid water. Seeking these interaction phospholipids spontaneously form bilayers.

Impacts Protein Folding

Water drives the folding of amino acid chain because different types of amino acids seek and avoid interactions with water. Additionally, without proper shape, proteins can’t perform proper functions.

Surrounds DNA to support the double-helix

Without this shape cells wouldn’t be able to perform instructions encoded by DNA.

Charge of Oxygen

Negative

Charge of Hydrogen

Positive

Polar Molecule

A molecule where there is unequal distribution of electrical charge. One end is slightly more positive, the other end is slightly more negative.

Hydrogen Bonds

A weak intermolecular force. In water, electropositive hydrogen atoms attract electronegative oxygen atoms in other water molecules.

Cohesion

Forces by which individual molecules of the same type attract and associate.

Cohesion of water molecules

• allows for water to be drawn up the Xylem vessels in plants by evaporative loss of water from the leaves.

• Retains water on Earth’s surface to serve habitats

• Contributes to physical properties of water important to living organisms

Cohesion-Tension Hypothesis

1. Transpiration (evaporation) occurs because stomata are open to allow gas exchange for photosynthesis. As it occurs, negative pressure is created (tension/suction)

2. Tension pulls water in the plant xylem drawing water upwards.

3. Cohesion pulls up water molecules in chains as the top-most water is pulled up and out of the stomata.

Surface Tension

A property of the surface of a liquid that allows it to resist an external force due to the molecules cohesive nature.

Adhesion

the force by which individual molecules stick to surrounding surfaces and materials.

Hydrophilic

attract to water

Adhesion of water molecules

• Allows plants to move water using capillary action.

• Permits water to move through soil