Cell Discovery Unknown before the invention of the microscope – Cells too small to see with eyes Robert Hooke – 1665 – Simple microscope to look at cork – Looked like “cells” or small rooms Anton van Leeuwenhoek – 1685 – Designed his own microscope and looked at single celled organisms

Cell Theory A summary of experimental findings about cells 1.All living things are composed of one or more cells 2.Cells are the basic unit of structure and organization of all living organisms 3.Cells arise only from previously existing cells, with cells passing on copies of their genetic material

Prokaryotic Cells No organelles – Cellular functions take place anywhere in cell No nucleus – Genetic material (DNA) is free floating in cell – DNA is circular Single celled Bacteria

Eukaryotic Cells Have organelles – Membrane bound structures – Allows cellular functions to take place in specific places Have nucleus – Contains genetic information – DNA is linear Multicellular animals or plants Some unicellular – Yeast and algae

Both Prokaryotic and Eukaryotic Have cell membranes

Prokaryotic and Eukaryotic ProkaryoticEukaryotic

Plasma Membrane Separate the cell from the environment Selective Permeability – Allows some molecules to pass through – Keeps some molecules in – Keeps some molecules out

Structure of the Plasma Membrane Phospholipid bilayer – Two layers of phospholipids – Water-loving “heads” – Water-hating “tails” – Water soluble substances do not move through Transport proteins – Move some things in or out of the cell – Like tunnels through the membrane

What else is stuck in the plasma membrane? Cholesterol – Maintains fluidity Carbohydrates – Help identify cells

Cell Organelles – All Eukaryotes Nucleus – Control Center Ribosomes - Makes proteins Endoplasmic Reticulum- Makes proteins Golgi Apparatus – Packages proteins Vacuole – Stores cell materials Mitochondria- Supplies energy to cell Cell membrane - Flexible boundary

Eukaryotic Cell Structures Found…. Only in Animal Cells Lysosome – Digestive enzymes Centriole – Plays a role in cell division Only in Plant Cells Cell Wall – Inflexible barrier Chloroplast – Where photosynthesis takes place