Discovering Discovering CellsCells

Life ScienceLife Science

Chapter 2 Section 3Chapter 2 Section 3

pp. 50- 57pp. 50- 57

What are Cells?What are Cells?

Cells are the basic units of Cells are the basic units of structure and function in living structure and function in living thingsthings Structure: what living things are Structure: what living things are

made ofmade of Function: the processes that Function: the processes that

keep an organism alive keep an organism alive

One square cm of skin One square cm of skin contains over contains over

100,000 cells100,000 cellsSkin CellsSkin Cells

First Observation of CellsFirst Observation of Cells

MICROSCOPE MICROSCOPE

is an instrument that makes is an instrument that makes smallsmall things look things look bigbigThe invention of the microscope made it The invention of the microscope made it

possible for …possible for …people to discover people to discover

and learn about cellsand learn about cells

First Observation of CellsFirst Observation of Cells

A A SIMPLESIMPLE microscope has only one lens microscope has only one lens

A A COMPOUNDCOMPOUND microscopemicroscope

has more than one lenshas more than one lens

Robert HookeRobert Hooke In 1633, one of the first to observe cells In 1633, one of the first to observe cells

with a microscope that he madewith a microscope that he made Hooke used his microscope to look at

the structure of a thin slice of cork (the bark of the cork oak tree)

He felt the small empty spaces looked like tiny rectangular rooms, so he called the empty spaces “cells” which is a word meaning “small rooms.”

Cork Cells as Drawn by HookeCork Cells as Drawn by Hooke

Cork Cells under 100x Cork Cells under 100x MagnificationMagnification

Anton van LeeuwenhoekAnton van Leeuwenhoek(pronounced 'vahn Laywenhook')(pronounced 'vahn Laywenhook') Dutch tradesman and scientist Dutch tradesman and scientist

from the Netherlands. from the Netherlands. He is commonly known as "the He is commonly known as "the

Father of Microbiology". Father of Microbiology". Using his handmade Using his handmade

microscopes, he was the first microscopes, he was the first to observe and describe single to observe and describe single celled organismscelled organisms

Anton van LeeuwenhoekAnton van Leeuwenhoek

Uses the microscope Uses the microscope he built to look at:he built to look at:

Drops of lake waterDrops of lake waterScrapings from teeth Scrapings from teeth

and gumsand gumsWater from rain Water from rain

guttersgutters

““Little Animals”Little Animals”

• Anton van Anton van Leeuwenhoek Leeuwenhoek saw moving saw moving little animals little animals he called:he called:

AnimalculesAnimalcules

Schleiden, Schwann, and VirchowSchleiden, Schwann, and Virchow

1838 1838 SchleidenSchleiden concludes: ALL plants are made of cells concludes: ALL plants are made of cells 1839 1839 SchwannSchwann concludes: ALL animals are made of concludes: ALL animals are made of

cellscells Therefore, Therefore, ALL LIVING THINGS ARE MADE OF CELLSALL LIVING THINGS ARE MADE OF CELLS However, no one could explain where cells come fromHowever, no one could explain where cells come from 1855 1855 VirchowVirchow writes: New cells are only formed from writes: New cells are only formed from

cells that already exist…cells that already exist… or or ALL CELLS COME FROM CELLSALL CELLS COME FROM CELLS

The Cell TheoryThe Cell Theory Schleiden, Schwann, Virchow and others helped develop Schleiden, Schwann, Virchow and others helped develop

the the cell theory.cell theory. Cell Theory Cell Theory is a widely accepted explanation for the

relationship between cells and living things.

THE CELL THEORY STATES THE FOLLOWING:THE CELL THEORY STATES THE FOLLOWING: All living things are composed of cellsAll living things are composed of cells Cells are the basic units of structure and Cells are the basic units of structure and

function in living things.function in living things. All cells are produced from other cellsAll cells are produced from other cells..

Microscope TimelineMicroscope Timeline

1590 one of the first compound microscope- uses two lenses

Microscope TimelineMicroscope Timeline

1660Hooke’s compound microscope uses light to help see

Microscope TimelineMicroscope Timeline

1674Leeuwenhoek’s simple microscope can magnify 266 times

Microscope Microscope Timeline

1886Modern Compound Light Microscope can magnify up to 1,000 times

Microscope TimelineMicroscope Timeline

1933Transmission Electron Microscope (TEM)

using electrons, it can magnify up to 500,000 times

Microscope TimelineMicroscope Timeline

1965 SEM -Scanning Electron Microscope can see in 3D and magnify up to 150,000

times

Microscope TimelineMicroscope Timeline

1981 STM Scanning Tunneling Microscope can magnify up to 1,000,000

times

Light and Electron MicroscopesLight and Electron Microscopes

The lenses in light microscopes magnify The lenses in light microscopes magnify an object byan object bybending the light bending the light

that passes through that passes through

themthem

Compound Microscope Compound Microscope MagnificationMagnification

20x

30x

Total magnification is equal to the two lenses multiplied together

So 20 x 30 =So 20 x 30 =600 times larger600 times larger

Electron MicroscopeElectron Microscope

A microscope that uses a beam of electrons instead of light to produce a magnified image is called an

ELECTRON microscopeELECTRON

Hidden Worlds…Hidden Worlds…

An image of a streptococcus bacteria taken by a scanning

electron microscope. Magnified around 2,000,000x

Fly Foot

Alien Life???Alien Life???

Weevil pyralidae moth

Electric guitar string

You Know These!!!You Know These!!!Edge of a dime

Sponge (only 23x)

leaf

Snowflake

Strand of hair