4-1 Introduction to the Cell

Important events in the discovery of the cell and the development of the cell theory…..

1665 – Robert Hooke Coined the term "cells”. Observed cells in cork. Cork Cells

1673- Anton van Leeuwenhoek Created a powerful microscope

1827-33 - Robert Brown -noticed that pollen grains in water jiggled around called “Brownian motion” -discovered the nucleus Nucleus Human Cheek Cell

A botanist who concluded that all plants are made of cells. 1838 - Matthias Schleiden A botanist who concluded that all plants are made of cells. Typical Plant Cell

1839 - Theodor Schwann A zoologist who concluded that all animals are made of cells. Nerve Cells

1855 - Rudolph Virchow A physician who did research on cancer cells and concluded “Omnis cellula e cellula”. “All cells are from other pre-existing cells.”

The Cell Theory 1. All living things are composed of one or more cells. 2. Cells are the basic units of structure and function in an organism. 3. Cells come only from existing cells.

both in size, shape, and internal organization. Cells are Diverse… both in size, shape, and internal organization.

Why Are Cells So Small? Transport- Cell volume to surface area ratios favor small size. Control- Nucleus to cytoplasm consideration. Metabolic requirements- ……..we’ll come back to this later.

Note: 1.0 mm = one millionth of a meter How small can a cell be? Mycoplasmas - bacteria that are 0.1 to 1.0 mm. (1/10 the size of regular bacteria). Note: 1.0 mm = one millionth of a meter

All cells have…… Plasma (cell) Membrane Nucleus (eukaryotes only) Cytoplasm (an area) Organelles (structures with specialized functions)

Cell Types Prokaryotes- simple cells that do not have internal membranes example = bacteria Eukaryotes- more complex cells that do have internal, membrane-bound structures examples = plants and animals

Eukaryotic Organisms: include protists, fungi, plants and animals Timeline Prokaryotic Organisms: First appeared 3.5 BYA include bacteria and cyanobacteria Eukaryotic Organisms: First appeared 2.0 BYA include protists, fungi, plants and animals

Key Differences: Eukaryotes Prokaryotes Have a nucleus and other membrane bounded structures. Have large ribosomes DNA is organized into chromosomes Flagella are made of microtubules and have a 9+2 structure Cell walls are made of cellulose Prokaryotes Lack a nucleus and other membrane bounded structures. Have small ribosomes DNA is not organized into chromosomes Flagella are not made of microtubules and does not have a 9+2 structure Cell walls are made of peptidoglycan, not cellulose

Examples Prokaryotic Eukaryotic Nucleus

Eukaryotic Prokaryotic