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Lesson Overview
7.1 Life is Cellular
Lesson Overview
Life Is Cellular
The Discovery of the Cell
• The cell theory states:
- All living things are
made up of cells.
- Cells are the basic
units of structure and
function in living things.
- New cells are
produced from existing
cells.
Lesson Overview
Life Is Cellular
Early Microscopes
• Robert Hooke
• 1st person to use
the microscope to
look at a nonliving
specimen.
• He looked at a thin
slice of cork, a plant
material.
Lesson Overview
Life Is Cellular
Early Microscopes
• He called the
empty chambers
he looked at “cells”.
Lesson Overview
Life Is Cellular
Early Microscopes
– Anton van Leeuwenhoek
examined pond water and
other things, including a
sample taken from a human
mouth.
– He called the organisms
bacteria.
Lesson Overview
Life Is Cellular
The Cell Theory
• Theodor Schwann
stated that all animals
were made of cells.
Theodor Schwann
• Matthias Schleiden
concluded that all
plants are made of
cells.
Matthias Schleiden
Lesson Overview
Life Is Cellular
The Cell Theory
• Rudolf Virchow
concluded that new
cells could be
produced only from
the division of existing
cells.
Rudolf Virchow
Lesson Overview
Life Is Cellular
Exploring the Cell
• Most microscopes
use lenses to
magnify the image
of an object by
focusing light or
electrons.
Lesson Overview
Life Is Cellular
Light Microscopes and Cell Stains
• A typical light
microscope allows light
to pass through a
specimen and uses two
lenses to form an
image.
• The first set of lenses,
located just above the
specimen, produces an
enlarged image of the
specimen.
Lesson Overview
Life Is Cellular
• The second set of
lenses magnifies this
image still further.
• Light microscopes are
able to produce
images of objects
only to a
magnification of about
1000 times because
light waves are
diffracted or scattered
as they pass through
matter.
Lesson Overview
Life Is Cellular
Light Microscopes and Cell Stains
– It is difficult to see
most living cells
through a light
microscope because
they are nearly
transparent.
– Using chemical
stains or dyes can
usually solve this
problem.
Lesson Overview
Life Is Cellular
Light Microscopes and Cell Stains-R-Track
– Fluorescence- when
dyes give off light of a
particular color when
viewed under specific
wavelengths of light.
– Fluorescence
microscopy makes it
possible to see the
locations of molecules
and watch them move
about in a living cell.
Lesson Overview
Life Is Cellular
Electron Microscopes
– Used to study objects
smaller than 1millionth of a meter.
– Use beams of
electrons, not light,
that are focused by
magnetic fields.
Lesson Overview
Life Is Cellular
Electron Microscopes
There are two
major types of
electron
microscopes:
transmission
and scanning.
Lesson Overview
Life Is Cellular
Transmission Electron
Microscopes
– Used to
explore
inside the cell
(ex. Cell
structures
and large
protein
molecules).
– produce flat,
twodimensional
images.
Lesson Overview
Life Is Cellular
Scanning Electron
Microscopes
– Used to scan the
entire surface of a
specimen without
cutting them into
thin slices.
– produce threedimensional
images of the
specimen’s
surface.
ANTENNA OF AN ANT
Lesson Overview
Life Is Cellular
Electron Microscopes – R-Track
• Electron microscopy can be used to examine only
nonliving cells and tissues because samples need to be
dehydrated and chemically preserve first before placing
them in the microscope.
Lesson Overview
Life Is Cellular
Prokaryotes and Eukaryotes
– All cells are
surrounded by a
thin, flexible barrier
called a cell
membrane.
– Cells are prokaryotes
or eukaryotes
depending on whether
they contain a
nucleus.
Lesson Overview
Life Is Cellular
Prokaryotes and Eukaryotes
– Eukaryotes are cells that enclose their DNA in nuclei.
– Prokaryotes are cells that do not enclose DNA in nuclei.
Lesson Overview
Life Is Cellular
Prokaryotes
– Prokaryotic cells are generally smaller and simpler
than eukaryotic cells.
– Example: bacteria.
Lesson Overview
Life Is Cellular
Eukaryotes
– Eukaryotic cells are generally larger and more complex
than prokaryotic cells.
– Examples: plants, animals, fungi, and organisms
commonly called “protists.”
Lesson Overview
Life Is Cellular
Differences & Similarities between
Prokaryotes & Eukaryotes
Prokaryotes
Eukaryotes
No nucleus
Has nucleus
No membrane-bound
organelles
Some ribosomes
Has membrane-bound
organelles
Has ribosomes
Very small (1-10 µm)
Small (2-1000 µm)
Has cytoplasm, DNA,
cell membrane
Has cytoplasm, DNA,
cell membrane