Cells: The Basic Unit of Life
Cells, the most basic unit of a living thing, were discovered in 1665 by Robert Hooke. Hooke contributed
greatly to The Cell Theory.
The Cell Theory
1. All organisms are composed of one or more cells.
2. The cell is the most basic unit of life in all living things.
3. All cells come from existing cells.
Cells can be found living alone or grouped with other cells:
Unicellular: made of a single cell. Must carry out all functions needed to survive in one cell.
Multicellular: made of many cells. Are able to have groups of cells that specialize for certain functions
(muscle, nerves, etc)
Some cells are simpler in structure than other cells.
Prokaryotic Cells
No Nucleus
No membrane-covered organelles
Circular DNA
Bacteria
Eukaryotic Cells
Nucleus
Membrane-covered organelles
Linear DNA
All cells other than bacteria
Cells have many components called organelles that enable the cell to live, grow, & reproduce.
Cytoplasm: cellular fluid surrounding a cell’s organelles
Cell Membrane: phospholipid barrier that controls what enters & exits a cell
Cell Wall: provides strength & support to the cell membrane in a plant cell and bacterial cell. Plant cell walls
are made of cellulose.
Nucleus: stores the cell’s DNA, which stores the information for how to make proteins.
Ribosome: small grain-like organelles that make proteins from amino acids
Endoplasmic Reticulum: transports materials, makes lipids & breaks down drugs and other chemicals.
Mitochondria: makes the ATP(cellular energy) through cellular respiration
Chloroplast: found in plants & algae, this organelle takes the energy from sunlight and is used to make sugar
through the process of photosynthesis
Golgi Complex: modifies & packages lipids & proteins for export from the cell.
Vacuole: large chamber to store water while supporting the cell in plant cells
Lysosome: digest food particles, wastes, cell parts, & foreign invaders
Types of Cells
Eukaryotic/Plant
Prokaryotic/Bacteria
Eukaryotic/Animal