Characteristics of Life & Biochemistry: Cell Structure, Chemical Compounds, and pH

Science

We use science to answer questions we have about our world.

Biology

The study of life and the places and processes that support it.

Living things

All living things are made of cells and have organization.

Cells

The smallest unit of life; can be unicellular or multicellular.

Prokaryotic cells

Cells that do not have a nucleus.

Eukaryotic cells

Cells that have a nucleus.

Homeostasis

The ability to maintain stable internal conditions.

Evolution

The capability of living things to change over time.

Universal genetic code

All living things have DNA as their genetic material.

Metabolism

The process of obtaining and using materials and energy.

Autotrophs

Organisms that make their own food.

Heterotrophs

Organisms that consume other living things for food.

Phototropism

The response of plants to light.

Gravitropism

The response of plants to gravity.

Thigmotropism

The response of plants to touch.

Compound

A substance formed by two or more different elements.

Chemical formula

Shows the number of each element in a compound.

Mixture

When 2+ elements or compounds are physically mixed together but not chemically combined.

Suspension

A mixture of water and non-dissolved materials that will separate over time.

Solution

A mixture in which all the components are evenly distributed.

Solute

The substance that is dissolved in a solution.

Solvent

The substance in which the solute dissolves.

Chemical bonds

Atoms in compounds are held together by chemical bonds.

Valence electrons

Electrons that are available to form bonds.

Covalent bonds

Form when electrons are shared between atoms.

Molecule

When atoms are joined together by a covalent bond.

Ionic bonds

Form when one or more electrons are transferred from one atom to another.

Acid

Any compound that forms H+ ions in solution (pH less than 7).

Base

Any compound that forms OH- ions in solution (pH greater than 7).

Neutral

Any compound that has an equal concentration of H+ and OH- ions.

pH scale

A measurement system that indicates the concentration of H+ ions in a solution (0-14).

Buffer

Weak acids or bases that react with strong acids or bases to prevent sudden changes in pH.

Water dissociation

Water naturally dissociates into H+ and OH- ions.