The Historyand

Organelles of

Cells

• 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 inventor of the microscope was Anton van Leeuwenhoek in the 1600’s. It was based on Galileo’s telescope

• He looked at organisms living in water.

• 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

• 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.

He saw many small boxes or chambers that he called “CELLS”.

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A Brief History of Cells

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

There are two basic types of electron microscopes.

The transmission electron microscope allows scientists to study the structures contained within a cell.

The scanning electron microscope scans the surface of cells to learn their three dimensional shape.

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

Basic Cell Structure

Section Objectives

• Compare and contrast the structures of plant and animal cells.

• Explain the advantages of highly folded membranes.

• Understand the structure and function of the parts of a typical eukaryotic cell.

The plasma or cell membrane acts as a selectively permeable membrane to control what goes in and out of the cell.

Cellular Boundaries

The cell wall The cell wall is a fairly rigid structure located outside the plasma membrane that provides additional support and protection for plant cells.

Nucleus and cell control

Chromatin

Nucleolus

Nuclear Envelope

Assembly, Transport, and Storage

The endoplasmic reticulum (ER) is an organelle that is suspended in the cytoplasm and is the site of cellular chemical reactions.

Assembly, Transport, and Storage Endoplasmic

Reticulum (ER)

Ribosomes

Assembly, Transport, and Storage

Golgi Apparatus

Vacuoles and storage Vacuoles are membrane-bound spaces used for temporary storage of materials. Notice the difference between vacuoles in plant and animal cells.

VacuoleAnimalCell

PlantCell

Lysosomes and recycling

Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria.

Energy Transformers:

Chloroplasts are cell organelles that capture light energy and produce food to store for a later time.

Chloroplasts and energy

The chloroplasts belongs to a group of plant organelles called plastids, which are used for storage.

Chloroplasts contain green pigment called chlorophyll. Chlorophyll traps light energy and gives leaves and stems their green color.

Chloroplasts and energy

Mitochondria are membrane-bound organelles in plant and animal cells that transform energy for the cell.

Mitochondria and energy

A mitochondria, like the endoplasmic reticulum, has a highly folded inner membrane. Energy storing molecules are produced on inner folds.

Mitochondria and energy

Cells have a support structure called the cytoskeleton within the cytoplasm. The cytoskeleton is composed of microtubules and microfilaments. Microtubules are thin, hollow cylinders made of protein and microfilaments are thin solid protein fibers.

Structures for Support and Locomotion

Some cell surfaces have cilia and flagella, which are structures that aid in locomotion or feeding. Cilia and flagella can be distinguished by their structure and by the nature of their action.

Cilia and flagella

Cilia are short, numerous, hair-like projections that move in a wavelike motion.

Cilia and flagella Cilia

Flagella are long projections that move in a whip-like motion. Flagella and cilia are the major means of locomotion in unicellular organisms.

Cilia and flagella

Flagella

Check for Understanding

Answer the following

questions on your paper

What is the primary function of the cell wall?

Question 1

D. acquire nutrients from environment

C. control activity of organelles

B. provide support

A. act as selectively permeable membrane

Question 2

DNA

Plasma membrane

Cell wall

Describe the control center of a prokaryotic cell.

Ribosomes

Question 3 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.

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

Question 4

D. simple light microscope

C. transmission electron microscope

B. scanning electron microscope

A. compound light microscope

Plasma membrane

Nucleus

Nucleolus

Chromosomes

Organelles

Question 5 What makes this cell eukaryotic?

A. Because it has a cell wall. B. Because it contains DNA. C. Because it has membrane-bound organelles. D. Because it does not have DNA.

Which of the following structures is the site of protein synthesis?

Question 6

D. Lysosome

C. Vacuole

B. Ribosome

A. Golgi apparatus

What is the advantage of having numerous folds in the ER?

Question 7

B. It can create more vesicles in a smaller space.

A. It enables the ER to lie snugly against the nucleolus.

C. It can capture more light energy with more folds.

D. A large amount of work can be done in a small space.

B. It contains a greater number of plastids.

What could you predict about a plant cell that contains fewer chloroplasts than other plant cells?

Question 8

A. It contains less chlorophyll.

D. It will appear darker green in color.

C. It will have an increased rate of light energy capture.

A mutation results in the inner membranes of a liver cell’s mitochondria being smooth, rather than folded. Which of the following would you expect?

Question 9

B. it can create more vesicles in a smaller space

A. more efficient storage of cellular energy

C. decreased energy available to the cell

D. fewer ribosomes available for protein synthesis

Question 10

Which of the following is a main idea of the cell theory?

D. All cells come from preexisting cells.

C. All cells come from two parent cells.

B. The organelle is the basic unit structure and organization of organisms.

A. All organisms are composed of one cell.

Question 11

In what type of cell would you find chlorophyll?

D. fungus

C. plant

B. animal

A. prokaryote

Question 12

Which of these structures packs proteins into membrane-bound structures?

A. B.

C. D.

Question 13

What is the difference between the cell wall and the plasma membrane?

Cell wall

Plasma membrane

Inside cell

Outside cell

Question 14

Which of the following organelles is not bound by a membrane?

D. lysosome

C. vacuole

B. Golgi apparatus

A. ribosome

Question 15

In which of the following pairs are the terms related?

D. plastid – storage

C. microfilaments – locomotion

B. prokaryote – mitochondria

A. cell wall – selective permeability

Question 16

Which of the following structures is found in both plant and animal cells?

D. thylakoid membrane

C. mitochondrion

B. cell wall

A. chloroplast

Question 17

Compare the cytoskeleton of a cell to the skeleton of the human body.

Main Ideas• Eukaryotic cells have a nucleus and

organelles, are enclosed by a plasma membrane, and some have a cell wall that provides support and protection.

• Cells make proteins on ribosomes that are often attached to the highly folded endoplasmic reticulum. Cells store materials in the Golgi apparatus and vacuoles.

• The cytoskeleton helps maintain cell shape, is involved in the movement of organelles and cells, and resists stress placed on cells.

Main Ideas Continued

• Mitochondria break down food molecules to release energy. Chloroplasts convert light energy into chemical energy.

A prokaryotic cell does not have internal organelles surrounded by a membrane. Most of a prokaryote’s metabolism takes place in the cytoplasm. Click to see 4 parts.

1. Ribosomes

2. DNA 3. Plasma membrane

4. Cell wall

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This eukaryotic cell from an animal has distinct membrane-bound organelles that allow different parts of the cell to perform different functions. Click to see the 7 parts.

4. Plasma membrane

1. Nucleus

2. Nucleolus

3. Chromosomes

6. ERClick

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5. Golgi7. Mitochondria

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