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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.

• Matthias Schleiden

concluded that all

plants are made of

cells.

Theodor Schwann

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 1-

millionth 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, two-dimensional 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 three-

dimensional

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

Has membrane-bound organelles

Some ribosomes Has ribosomes

Very small (1-10 µm)

Small (2-1000 µm)

Has cytoplasm, DNA, cell membrane

Has cytoplasm, DNA, cell membrane