• Relate advances in microscope technology to discoveries about cells and cell structure.

Section Objectives:

• Compare the operation of a microscope with that of an electron microscope.

• Identify the main ideas of the cell theory.

The History of the Cell TheoryThe History of the Cell Theory• Before microscopes were invented, people

believed that diseases were caused by curses and supernatural spirits.

• Microscopes enabled scientists to view and study cells, the basic units of living organisms.

• As scientists began using microscopes, they quickly realized they were entering a new world–one of microorganisms.

• The first person to record looking at water under a microscope was Anton van Leeuwenhoek.

• The microscope van Leeuwenhoek used is considered a simple light microscope because it contained one lens and used natural light to view objects.

Development of Light MicroscopesDevelopment of Light Microscopes

Compound light microscopes use a series of lenses to magnify objects in steps.

These microscopes can magnify objects up to 1 500 times.

Development of Light MicroscopesDevelopment of Light Microscopes

Microscope Lab TechniquesMicroscope Lab Techniques

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• Robert Hooke was an English scientist who lived at the same time as van Leeuwenhock.

The Cell TheoryThe Cell Theory

• Hooke used a compound light microscope to study cork, the dead cells of oak bark.

Cells are the basic building blocks of all living things.

2 Other Scientists

• Matthis Schleiden – concluded that all plants are made of cells

• Theodor Schwann – concluded that all animals are made of cells

What are cells?• Smallest living things• Made of carbohydrates, proteins, lipids and other

molecules• Make up multi-cellular organisms and specialize• Contain DNA and in multi-cellular organisms have

copies of the same DNA• Cells are like little bodies.

What are cells?• Size - mostly microscopic with some large

enough to see with eye• Bacteria cells smaller than all other cells• Shape – not all cells are “bubbles”• Shape represents function or movement

(example: amoebas are amorphous because of their movement. Skin cells are flat because they are layered)

The cell theory is made up of three main ideas:

All cells come from preexisting cells.

The cell is the basic unit of organization of organisms.

All organisms are composed of one or more cells.

• The electron microscope was invented in the 1940s.

• This microscope uses a beam of electrons to magnify structures up to 500 000 times their actual size.

Development of Electron MicroscopesDevelopment of Electron Microscopes

Cells that do not contain internal membrane-bound structures are called prokaryotic cells.

• The cells of most unicellular organisms such as bacteria do not have membrane bound structures and are therefore called prokaryotes.

Two Basic Cell TypesTwo Basic Cell Types

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• Most of the multi-cellular plants and animals we know are made up of cells containing membrane-bound structures

and are therefore called eukaryotes.

Cells containing membrane-bound structures are called eukaryotic cells.

7.17.1

Two Basic Cell TypesTwo Basic Cell Types

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The membrane-bound structures within eukaryotic cells are called organelles.

• Each organelle has a specific function that contributes to cell survival.

Two Basic Cell TypesTwo Basic Cell Types

The nucleus is the central membrane-bound organelle that manages cellular functions.

• Separation of organelles into distinct compartments benefits the eukaryotic cells.

Two Basic Cell TypesTwo Basic Cell Types

Question 1 How did the invention of the microscope

impact society's understanding of disease?

B. Microscopes were invented after the development of the cell theory.

A. Scientists were able to view microorganisms that were previously unknown.

D. Scientists could view membrane-bound organelles of prokaryotes.

C. It was once believed that viruses, not bacteria, caused diseases.

How did the invention of the microscope impact society's understanding of disease?

Question 1

The answer is A. Before microscopes were invented, people believed that curses and supernatural spirits caused diseases. Microscopes enabled scientists to view cells, which led to the discovery that microorganisms cause some diseases.

Which of the following uses a beam of light and a series of lenses to magnify objects in steps?

Question 2

D. simple light microscope

C. transmission electron microscope

B. scanning electron microscope

A. compound light microscope

The answer is A. Most microscopes use at least two convex lenses. Compound light microscopes use a light beam and a series of lenses and can magnify objects up to about 1500 times. Electron microscopes use a beam of electrons and can magnify structures up to 500 000 times.

Plasma membrane

Nucleus

Nucleolus

Chromosomes

Organelles

Question 3 What makes this cell eukaryotic?

A. Because it has a cell wall.

B. Because it contains DNA.

Plasma membrane

Nucleus

Nucleolus

Chromosomes

Organelles

Question 3 What makes this cell eukaryotic?

C. Because it has membrane-bound organelles.

D. Because it does not have DNA.

Plasma membrane

Nucleus

Nucleolus

Chromosomes

Organelles

Question 3 The Answer is C. Eukaryotic cells contain

membrane-bound organelles that have specific functions in the cell; prokaryotic cells do not.

End of Chapter 7 Show