Discovery of Discovery of CellsCells

First to View CellsFirst to View Cells• In 1665, Robert Hooke

used a microscope to examine a thin slice of cork

• What he saw looked like small boxes so he called them “cells”

Anton van LeeuwenhoekAnton van Leeuwenhoek

• In 1673, Leeuwenhoek was first to view organisms under a microscope

• He looked at pond water & plaque he scraped from his teeth

Development of Light Microscope

• Leeuwenhoek was the first scientist to describe living cells as seen through a simple microscope

• Simple Light Microscope - One lens and uses natural light

• Compound Light Microscope - More than one lens to magnify–Magnifies up to 1500 times.

CELL THEORYCELL THEORY•All living things are made of cells

•Cells are the basic unit of structure and function in an organism (basic unit of life)

•Cells come from the reproduction of existing cells (cell division)

NEED TO KNOW!!! NEED TO KNOW!!!

Cell ClassificationCell Classification

• Prokaryotes– NO Membrane

bound organelles

– NO nucleus– Bacteria

• Eukaryotes– Most cells– True nucleus– Membrane

bound organelles

– Plants, fungi, animals

ProkaryotesProkaryotes• Simplest type of cell

• Lack a nucleus or membrane bound organelles

• Single, circular chromosome

• Bacteria and Archaebacteria

ProkaryotesProkaryotes• DNA located in the

center

• Cell membrane AND cell wall

• Ribosomes to make proteins

• May have cilia/pilli/flagella to aid in movement

EukaryotesEukaryotes

• HAVE a nucleus and membrane bound organelles

• Protists, fungi, plants, and animals

• Larger and more complex type of cells

EukaryoticEukaryotic CellCell

• Nucleus that contains DNA

• Cell membrane

• Specialized organelles– Where chemical

reactions occur

Number of Cells• Unicellular Organisms

– Organism is only one single cell

• Multicellular Organisms– Complex organisms with cells

organized into tissues, organs, systems

Looking at Cells Looking at Cells

• A cell’s shape reflects its function– Can be long and flat, branched, round,

etc

• Cell size is limited by the cell’s surface area to volume ratio– The larger the cell, the more nutrients it

needs and waste it produces