Cell Theory, Structures, and Processes: Biology Basics for Beginners

Cell Theory

All living things are made of one or more cells

Plant Cells

Have a cell wall

Animal Cells

Do NOT have a cell wall or chloroplasts.

Nucleus

Stores/protects DNA and controls many cell activities.

Cell Membrane

Controls what enters and leaves the cell.

Mitochondria

Produces usable energy (ATP).

Cytoplasm

Jelly-like material where organelles are suspended and reactions occur.

Ribosomes

Make proteins.

DNA

Contains genetic instructions.

Chloroplast

Performs photosynthesis in plant cells.

Cell Wall

Provides support and protection in plant cells.

Vacuole

Stores water

Prokaryotic Cells

No nucleus and no membrane-bound organelles.

Eukaryotic Cells

Have a nucleus and membrane-bound organelles.

Hierarchy of Organization

Cell → Tissue → Organ → Organ System → Organism.

Selectively Permeable

The cell membrane allows some substances to pass through while preventing others.

Diffusion

Movement of particles from an area of high concentration to low concentration.

Osmosis

Diffusion of water across a selectively permeable membrane.

Isotonic

Equal solute concentration; water moves in and out at roughly equal rates.

Hypertonic

More solute outside the cell; water moves out and the cell shrinks.

Hypotonic

Less solute outside the cell; water moves in and the cell swells.

Endocytosis

The cell membrane surrounds material and brings it into the cell.

Exocytosis

The cell uses a vesicle to release material outside the cell.

Phagocytosis

A type of endocytosis where a cell takes in large particles by engulfing them.

Phospholipid Bilayer

The cell membrane is mainly made of a phospholipid bilayer.