AP Biology Unit 1: Foundations of Biochemistry

Water (H₂O)

A molecule consisting of two hydrogen atoms and one oxygen atom, crucial for life.

Polarity

The uneven distribution of charge in a molecule, leading to partial negative and positive charges.

Electronegativity

The measure of an atom's affinity for electrons; oxygen is highly electronegative.

Hydrogen Bond

A weak electrical attraction between a partial positive hydrogen atom and a partial negative atom in neighboring molecules.

Cohesion

The attraction of molecules for other molecules of the same kind, significant in water transport.

Adhesion

The clinging of one substance to another; important in water's interaction with surfaces.

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid; water has a high surface tension.

High Specific Heat

The amount of heat required to raise the temperature of 1 gram of a substance by 1°C, which is high for water.

Evaporative Cooling

The cooling of a liquid as it evaporates, helping to regulate temperature in organisms.

Density of Ice

Ice is less dense than liquid water, allowing it to float and insulate aquatic life.

Universal Solvent

Water's ability to dissolve many substances due to its polarity.

Hydration Shells

Sphere of water molecules surrounding ions when an ionic compound dissolves in water.

Hydrophilic

Substances that have an affinity for water, such as ions and polar molecules.

Hydrophobic

Substances that repel water, typically nonpolar molecules like oils.

CHNOPS

The six key elements essential for life: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur.

Carbon Backbone

The structural framework of organic molecules, formed by carbon atoms.

Tetravalence

The ability of carbon to form four covalent bonds with various atoms.

Nitrogen Cycle

The series of processes by which nitrogen and its compounds are interconverted in the environment.

Phosphorus Cycle

The movement of phosphorus through the lithosphere, biosphere, and hydrosphere.

Biological Relevance of Specific Heat

Water's specific heat helps maintain stable temperatures for organisms and ecosystems.

Transpiration

The process by which water evaporates from plant leaves, aiding in nutrient transport.

Crystalline Lattice

The structured arrangement of molecules in solid ice, keeping them less dense than liquid water.

Water's High Surface Tension

Results from hydrogen bonding, leading to phenomena like the ability of some insects to walk on water.

Conservation of Energy Law

In living systems, matter cannot be created or destroyed, only rearranged.

Biomolecules and CHNOPS

Different macromolecules utilize specific elements from the CHNOPS group.

Mistake: Bond Types

Confusion between polar covalent bonds (within molecules) and hydrogen bonds (between molecules).

Mistake: Phase Changes

Understanding that only hydrogen bonds break when water changes phase, not covalent bonds.

Mistake: Cohesion vs. Adhesion

Cohesion refers to water-to-water attraction; adhesion refers to water's attraction to other surfaces.

Mnemonic for Element Identification

CHO for Carbohydrates, CHO for Lipids, CHON for Proteins, CHONP for Nucleic Acids.