Cell Theory

1665 Robert Hooke Used a compound microscope to examine thin slices of cork (bark from an oak tree). He saw it had hollow compartments, so he called them cells (he was the one that named cells).

1674 Anton van Leeuwenhoek He developed a much more powerful microscope. He was able to describe living cells when he observed single celled organisms swimming in a drop of pond water.

1838 Schleiden and Schwann Matthias Schleiden studied plant tissue. He proposed that plants are made up of cells. He showed his results to another scientist, Theodor Schwann, who saw similarities between plant and animal cells. Schwann concluded that all animals are made of cells.

1855 Rudolf Virchow He stated that all cells come from preexisting cells.

Cell Theory: Three Parts All organisms are made of cells All existing cells are produced by other living cells The cell is the most basic unit of life

How Theories are Made and Changed All of the scientists that studied cells built on each other’s findings. This is how theories are made, and how they get changed when scientists discover new evidence.

Prokaryotic and Eukaryotic Cells

Prokaryotic and Eukaryotic Cells: -They are both enclosed by a membrane that controls movement of materials into and out of the cell -Have similar building blocks -Both contain ribosomes and DNA

Cytoplasm Cytoplasm is found in the membrane and is a jellylike substance that contains dissolved building blocks (like proteins). In some cells, the cytoplasm contains organelles. Organelles are structures specialized to perform processes in the cell.

Prokaryotic vs. Eukaryotic Cells Prokaryotic Cells Eukaryotic Cells Have a nucleus and other membrane bound organelles (attached to the membrane) The nucleus contains the genetic information Can be single celled or multicellular Bigger, complex Animal and plant cells Don’t have a nucleus or other membrane bound organelles (not attached to the membrane) The cell’s DNA is suspended in the cytoplasm All are single-celled organisms Small, simple Bacteria