+

Introduction to Cells B-2.1: Recall 3 major tenets of cell theory B-2.3: Compare structures and organelles of prokaryotic and eukaryotic cells.

+Discovery of the Cell

n  Robert Hooke – 1665 n  Looked at cork under a simple microscope n  Saw tiny boxes and termed them “cells”

n  Based off of a monastery or prison

n  Matthias Schleiden – 1838 n  Concluded ALL plants must be composed of cells

n  Theodor Schwann – 1839 n  Concluded ALL animals must be composed of cells

n  Rudolph Virchow – 1855 n  Stated his theory that “All cells from from preexisting cells”

+Cell Theory

n The work of early scientists contributed to our current understanding of cells.

n The Cell Theory has 3 tenets: 1.  All living things are composed of cell 2.  The cell is the basic unit of structure and

function in living organisms 3.  New cells are produced from preexisting cells

+Unicellular vs. Multicellular n  Cell:

n  Lowest level of structure capable of performing ALL activities of life

n  Unicellular organism: composed of only ONE cell n  This one cell must perform all the functions necessary to support

life

n  Obtain energy, grow, reproduce, expel waste, respond to environment

n  Examples: Bacteria, Amoebas, Yeast, Algae

+Unicellular vs. Multicellular

n Multicellular Organism: n Composed of many cells. n Some become specialized to perform certain

functions

n Cells à Tissues à Organs à Organ Systems

n Multicellular organisms are complex and can usually be seen with the naked eye

n Examples: All animals, all plants, mushrooms

Bone cells (osteocytes) Nerve cells

Red blood cells Leaf cross section

+Types of Cells

n There are two basic types of cells:

1.  Prokaryotic: n “Pro” = before n “Karyo” = nucleus

2.  Eukaryotic: n “eu” = True

+Prokaryotic Cells

n  No true nucleus

n  DNA is not separated from rest of cell by a nuclear membrane

n  DNA not arranged in strands called chromosomes n  DNA: deoxyribonucleic acid

n  Chemical compound that stores and transmits genetic information

+Prokaryotic vs. Eukaryotic Cells

n  Prokaryotes have few organelles n  Eukaryotes have many organelles in the cytoplasm

n  Prokaryotes do NOT contain mitochondria n  They obtain energy from sunlight or chemicals in their

environment

n  Prokaryotes contain ribosomes

n  Most prokaryotes are unicellular n  i.e. bacteria

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+Eukaryotic Cells

n  DNA is organized into structures called chromosomes n  We will discuss chromosomes in detail soon!

n  Chromosomes are separated from the cytoplasm by nuclear membrane

Plant cell

Animal cell