Discovering Cells…

Anton van Leenwenhoek Dutch scientist The first person to look at water using a single-lens microscope in the mid-1600’s. He was surprised to see the water was full of living things: “animalcules”

van Leenwenhoek Microscope

Robert Hooke English scientist Studied cork using a compound light microscope.

Hooke Microscope

CELLS He observed tiny geometric shapes and named them “cells” because they reminded him of the small rooms monks lived in at the monastery.

Robert Hooke published 'Micrographia' in 1665 Robert Hooke published 'Micrographia' in 1665. It is his most famous work, and is notable for the stunning illustrations, drawn by Hooke himself.

The picture of the flea shown is one of his most famous images; the original is 18 inches across.

Additional Hooke drawings

Matthias Schleiden German scientist Observed different plants and concluded that all plants are composed of cells in the 1830’s.

Theodore Schwann German scientist Made observations that all animals are composed of cells.

Robert Brown Scottish scientist Observed that all cells contained a prominent structure that appeared to be a “blob” in the center of the cell…the nucleus.

Rudolf Virchow Concluded that the nucleus was the structure responsible for cell division.

Together, these men developed The Cell Theory:

The Cell Theory 1. All organisms are composed of one or more cells. 2. The cell is the basic unit of organization of organisms. 3. All cells come from preexisting cells.

Compound Light Microscopes Uses 2 or more glass lenses to magnify objects. Can magnify up to 1500 times.

Compound Light Microscopes

Scanning Electron Microscope Sweeps a beam of electrons over the surface of a specimen causing electrons to be emitted from the specimen. Produce a realistic, 3D image…but only on the surface. Can magnify about 60,000 times.

Scanning Electron Microscope

Transmission Electron Microscope Aims a beam of electrons through a specimen Two-dimensional images are used to study details of cells Can magnify hundreds of thousands of times.

Transmission Electron Microscope

Blood Cells Compound Microscope TEM SEM

LOOKING AT CELLS FORM DEFINES FUNCTION VARIOUS SHAPES A cell’s shape reflects its function. VARIOUS SHAPES Branched Flat Round Rectangular Irregular Change shapes

CELL SIZE Cell size is limited by a cell’s surface area-to-volume ratio Cells get larger…need more nutrients…release more waste. The substances have to move farther to reach their destination

CELL FEATURES (Venn Diagram?) ALL cells share common structural features: Cell membrane Cytoplasm Ribosomes DNA

Two Types of Cells Prokaryotes Pro = before Karyon = nucleus Lacks a nucleus Pro = before Karyon = nucleus Eukaryotes Has a nucleus Eu = true Karyon = nucleus

Two Types of Cells Prokaryotes Small, simple, single-celled organisms BACTERIA Eukaryotes Complex, multi-celled organisms PLANTS & ANIMALS

Internal compartments (membrane-bound organelles) Two Types of Cells Prokaryotes Do NOT have: Eukaryotes DO have: Internal compartments (membrane-bound organelles)

Eukaryotic cells can carry out more specialized functions because of their complex organization (organelles).

Cell Division Cell Membrane Ribosomes Nucleus No Nucleus Complex, multi-celled organisms Small, simple, single-celled organisms DNA Cell Division Cell Division— Binary Fission Cell Division— Mitosis No Internal Compartments—membrane-bound organelles Cell Membrane Has Internal Compartments—membrane-bound organelles Ribosomes Earliest cells Cells evolved later Smaller ribosomes Larger ribosomes