Water (H2O)

Water's Molecular Structure

- 2 hydrogens 1 oxygen
- Shared by covalent bonds
- V shaped

- Oxygen atoms, slight negative charge, meaning they are greedy for electrons.
- Hydrogen atoms,slight positive charge, meaning they want to give away their electrons.

Due to this polarity, all water molecules are attracted to one another and once they're all stuck together, those are called hydrogen bonds. The positive pole around one hydrogen atom will bond to the negative pole around the oxygen atoms of another water molecule.

Properties of Water

Cohesion -Water molecules are attracted to each other due to hydrogen bonding.
-Creating surface tension, allowing insects to walk on water.

Adhesion
-Water molecules stick to other polar or charged surfaces.
-Leads to capillary action, which helps water move through plant roots and blood vessels.

High Heat of Vaporization
-Takes lots of energy to convert water from liquid to gas.
-Sweating and transpiration help organisms cool down as water evaporates.

Universal Solvent
-Water dissolves polar and ionic compounds
-Important for transporting nutrients and chemical reactions in cells.

Proteins

Functions

Enzymatic Activity

- Proteins act as enzymes to speed up chemical reactions.
- Ex. Amylase breaks down starch into sugars.

Structural Support

Proteins like collagen and keratin provide strength and structure

Transport

Hemoglobin carries oxygen in red blood cells

Signaling

Hormones like insulin act as chemical messengers

Immune Defense

Antibodies are proteins that help protect against pathogens

Structure

Amino Acids (Building Blocks)

20 types of amino acids

Amino group (NH₂)

Carboxyl group (COOH)

R group (side chain, varies for each amino acid)

Peptide Bond

Levels of Protein Structure

Primary Structure

Sequence of amino acids (polypeptide chain)

Quaternary

Multiple polypeptide chains interacting

Tertiary Structure

3D folding due to interactions between R groups

Secondary Structure

Alpha helices or beta sheets formed by hydrogen bonding

Hydrophobicity
- Non-polar and repel water
- Hydrophobic molecules form separate layers rather than dissolving

Lipids

Types

Triglycerides (Fats & Oils)

- 1 glycerol + 3 fatty acids
- Long-term energy storage, insulation, protection

Saturated fats

No double bonds (solid at room temp)

Unsaturated fats

One or more double bonds (liquid at room temp

Phospholipids

- 1 glycerol + 2 fatty acids + phosphate group
- Form cell membranes (phospholipid bilayer)
- Hydrophilic head & Hydrophobic tail → Forms selective barrier