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7-1 Life Is Cellular
Photo Credit: © Quest/Science Photo Library/Photo Researchers, Inc.
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2. Figure 7.0 Fluorescent stain of cell

3. The Discovery of the Cell
Early Microscopes
In 1665, Robert Hooke used an early compound microscope to look at a thin slice of cork, a plant material.
Cork looked like thousands of tiny, empty chambers.
Hooke called these chambers “cells.”
Cells are the basic units of life.
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4. The Discovery of the Cell
Hooke’s Drawing of Cork Cells
hoto Credit: © Peter Arnold, Inc.
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5. The Discovery of the Cell
The Cell Theory In 1838, Matthias Schleiden concluded that all plants were made of cells. In 1839, Theodor Schwann stated that all animals were made of cells. In 1855, Rudolph Virchow concluded that new cells were created only from division of existing cells. These discoveries led to the cell theory.
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6. The Discovery of the Cell
The cell theory states:
All living things are composed of cells.
Cells are the basic units of structure and function in living things.
New cells are produced from existing cells.
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8. Prokaryotes and Eukaryotes
Cells come in a variety of shapes and sizes.
All cells:
are surrounded by a barrier called a cell membrane.
at some point contain DNA.
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9. Figure 7.4 A prokaryotic cell

10. Figure 7.4x1 Bacillus polymyxa

11. Figure 7.4x2 E. coli

12. Prokaryotes and Eukaryotes
Cells are classified into two categories, depending on whether they contain a nucleus. The nucleus is a large membrane-enclosed structure that contains the cell's genetic material in the form of DNA. The nucleus controls many of the cell's activities.
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13. Prokaryotes and Eukaryotes
Prokaryotic cells have genetic material that is not contained in a nucleus.
Prokaryotes do not have membrane-bound organelles.
Prokaryotic cells are generally smaller and simpler than eukaryotic cells.
Bacteria are prokaryotes.
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14. Prokaryotes and Eukaryotes
Eukaryotic cells contain a nucleus in which their genetic material is separated from the rest of the cell.
Eukaryotic cells are generally larger and more complex than prokaryotic cells.
Eukaryotic cells generally contain dozens of structures and internal membranes.
Many eukaryotic cells are highly specialized.
Plants, animals, fungi, and protists are eukaryotes.
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7-1
The cell theory states that new cells are produced from
nonliving material.
existing cells.
cytoplasm.
animals.
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7-1
The person who first used the term cell was
Matthias Schleiden.
Lynn Margulis.
Anton van Leeuwenhoek.
Robert Hooke.
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7-1
Which organism listed is a prokaryote?
protist
bacterium
fungus
plant
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7-1
One way prokaryotes differ from eukaryotes is that they
contain DNA, which carries biological information.
have a surrounding barrier called a cell membrane.
do not have a membrane separating DNA from the rest of the cell.
are usually larger and more complex.
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19. Eukaryotic Cell Structures
Structures within a eukaryotic cell that perform important cellular functions are known as organelles.
Cell biologists divide the eukaryotic cell into two major parts: the nucleus and the cytoplasm.
The Cytoplasm is the portion of the cell outside the nucleus.
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20. Eukaryotic Cell Structures
Plant Cell
Nucleolus
Nucleus
Smooth endoplasmic reticulum
Nuclear envelope
Ribosome (free)
Rough endoplasmic reticulum
Ribosome (attached)
Cell wall
Golgi apparatus
Cell membrane
Chloroplast
Mitochondrion
Vacuole
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21. Eukaryotic Cell Structures
Animal Cell
Smooth endoplasmic reticulum
Nucleolus
Nucleus
Ribosome (free)
Nuclear envelope
Cell membrane
Rough endoplasmic reticulum
Ribosome (attached)
Centrioles
Golgi apparatus
Mitochondrion
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Nucleus
Nucleus
The nucleus is the control center of the cell.
The nucleus contains nearly all the cell's DNA and with it the coded instructions for making proteins and other important molecules.
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Nucleus
The Nucleus
Chromatin
Nuclear envelope
Nucleolus
The nucleus controls most cell processes and contains the hereditary information of DNA. The DNA combines with protein to form chromatin, which is found throughout the nucleus. The small, dense region in the nucleus is the nucleolus.
Nuclear pores
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Ribosomes
Ribosomes
One of the most important jobs carried out in the cell is making proteins.
Proteins are assembled on ribosomes.
Ribosomes are small particles of RNA and protein found throughout the cytoplasm.
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25. Endoplasmic Reticulum
There are two types of ER—rough and smooth.
Endoplasmic Reticulum
Ribosomes
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Golgi Apparatus
The Golgi apparatus appears as a stack of closely opposed membranes.
The Golgi apparatus modifies, sorts, and packages proteins. Notice the stacklike membranes that make up the Golgi apparatus.
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Vacuoles
In many plant cells there is a single, large central vacuole filled with liquid.
Vacuole
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Vacuoles
Contractile vacuole
Vacuoles are also found in some unicellular organisms and in some animals. The paramecium contains a contractile vacuole that pumps excess water out of the cell.
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29. Mitochondria and Chloroplasts
Mitochondria Nearly all eukaryotic cells contain mitochondria. Mitochondria convert the chemical energy stored in food into compounds that are more convenient for the cell to use.
Mitochondrion
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30. Mitochondria and Chloroplasts
Plants and some other organisms contain chloroplasts.
Chloroplasts capture energy from sunlight and convert it into chemical energy in a process called photosynthesis.
Chloroplast
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31. Mitochondria and Chloroplasts
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The cytoskeleton is a network of protein filaments that helps the cell to maintain its shape. The cytoskeleton is also involved in movement.
The cytoskeleton is made up of:
microfilaments
microtubules
Cytoskeleton
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Cytoskeleton
Cytoskeleton
Cell membrane
Endoplasmic reticulum
Microtubule
The cytoskeleton is a network of protein filaments that helps the cell to maintain its shape and is involved in many forms of cell movement. Microtubules are part of the cytoskeleton that help maintain cell shape.
Microfilament
Ribosomes
Mitochondrion
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Centrioles are located near the nucleus and help to organize cell division.
Cell Organelle Interactive
Plant and Animal Model Interactive
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7-2
In the nucleus of a cell, the DNA is usually visible as
a dense region called the nucleolus.
the nuclear envelope.
granular material called chromatin.
condensed bodies called chloroplasts.
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7-2
Two functions of vacuoles are storing materials and helping to
break down organelles.
assemble proteins.
maintain homeostasis.
make new organelles.
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7-2
Chloroplasts are found in the cells of
plants only.
plants and some other organisms.
all eukaryotes.
most prokaryotes.
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7-2
Which of the following is NOT a function of the Golgi apparatus?
synthesize proteins.
modify proteins.
sort proteins.
package proteins.
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7-2
Which of the following is a function of the cytoskeleton?
manufactures new cell organelles
assists in movement of some cells from one place to another
releases energy in cells
modifies, sorts, and packages proteins
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40. Unicellular Organisms: One cell carries out all life functions.
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Colonial Organisms: Groups of single celled organisms live together. Larger size makes it harder for organisms to eat. All/most cells do most functions.
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Multicellular Organisms: Groups of specialized cells working together. The simplest multicellular organism:
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But what is a slime mold?
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46. Organization Within An Organism
Nature has levels of organization
Unique properties emerge at successively higher levels
Atoms are organized into molecules
In multicelled species, cells are organized into tissues, organs, and organ systems
All organisms consist of one or more cells
Emergent properties: Life emerges at the cellular level

47. Levels of Organization

48. Levels of Organization

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Microscopes
Microscopes
Microscopes are devices that produce magnified images of structures that are too small to see with the unaided eye.
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Microscopes
Light Microscopes
The most commonly used microscope is the light microscope.
Light microscopes produce clear images of objects at a magnification of about 1000 times.
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Microscopes
Compound light microscopes allow light to pass through the specimen and use two lenses to form an image.
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Microscopes
Electron Microscopes
To study even smaller objects, scientists use electron microscopes.
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Exploring the Cell
Electron Microscopes
Electron microscopes reveal details 1000 times smaller than those visible in light microscopes.
Electron microscopy can be used to visualize only nonliving, preserved cells and tissues.
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Exploring the Cell
Transmission electron microscopes (TEMs)
Used to study cell structures and large protein molecules
Specimens must be cut into ultra-thin slices
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Exploring the Cell
Scanning electron microscopes (SEMs)
Produce three-dimensional images of cells
Specimens do not have to be cut into thin slices
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Exploring the Cell
Scanning Electron Micrograph of Neurons
Photo Credit: © Dr. Dennis Kunkel/Phototake
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7-1
Electron microscopes are capable of revealing more details than light microscopes because
electron microscopes can be used with live organisms.
light microscopes cannot be used to examine thin tissues.
the wavelengths of electrons are longer than those of light.
the wavelengths of electrons are shorter than those of light.
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59. Estimating Field Diameter of a Microscope
(1) Set up so that the finely divided part overlaps one edge of the field
(2) Line up major division on opposite edge
Estimating Field Diameter of a Microscope
To determine field diameter using a stage micrometer, one places the stage micrometer on the microscope stage. Next, looking through the eyepiece (using the lowest magnification), one uses the mechanical stage controls to line up a major division of the scale with one edge of a microscope field so that the finely etched portion of the scale overlaps the other edge. By counting divisions, one can estimate true field diameter to the nearest 0.01 or 0.02 mm. Once a microscope is calibrated at one magnification, it should not be necessary to repeat calibration for other objective lenses. The scale is inversely proportional to the magnification itself. For example, if the field diameter at 40x total magnification is measured to be 5.2 mm, then the diameter at 400x must be 0.52 mm.
(field of view 1) X (magnification 1) = (field of view 2) X (magnification 2)
Knowing field diameter, one can determine the actual surface area of the specimen in view, count objects in the field, and determine the number of objects per unit area. For accuracy, one may count multiple randomly-selected fields. Often an object will overlap the edge of a field, and counting all overlapping objects results in overestimating the density. A good practice is to set criteria in advance for accepting or rejecting an object. For example, you can divide the field into four imaginary quadrants. If an object overlaps the top or right edge of the field it is accepted, but it is rejected if it overlaps the bottom or left of the field.
References:
Alberts, B., et al. (2002). Molecular Biology of the Cell, 4th ed. New York: Garland Science.
Caprette, D. (1995). Light Microscopy. Retrieved from
Lodish, H., et al. (2000). Molecular Cell Biology, 4th ed. New York: W.H. Freeman and Co.
Wolfe, S.L. (1993). Molecular and Cellular Biology. Belmont, CA: Wadsworth Publishing Company.
Image Reference:
Caprette, D. (2006). Field diameter.
Field diameter= 0.52 mm

60. Estimating Field Diameter of a Microscope
(1) Set up so that the finely divided part overlaps one edge of the field
(2) Line up major division on opposite edge
Estimating Field Diameter of a Microscope
To determine field diameter using a stage micrometer, one places the stage micrometer on the microscope stage. Next, looking through the eyepiece (using the lowest magnification), one uses the mechanical stage controls to line up a major division of the scale with one edge of a microscope field so that the finely etched portion of the scale overlaps the other edge. By counting divisions, one can estimate true field diameter to the nearest 0.01 or 0.02 mm. Once a microscope is calibrated at one magnification, it should not be necessary to repeat calibration for other objective lenses. The scale is inversely proportional to the magnification itself. For example, if the field diameter at 40x total magnification is measured to be 5.2 mm, then the diameter at 400x must be 0.52 mm.
(field of view 1) X (magnification 1) = (field of view 2) X (magnification 2)
Knowing field diameter, one can determine the actual surface area of the specimen in view, count objects in the field, and determine the number of objects per unit area. For accuracy, one may count multiple randomly-selected fields. Often an object will overlap the edge of a field, and counting all overlapping objects results in overestimating the density. A good practice is to set criteria in advance for accepting or rejecting an object. For example, you can divide the field into four imaginary quadrants. If an object overlaps the top or right edge of the field it is accepted, but it is rejected if it overlaps the bottom or left of the field.
References:
Alberts, B., et al. (2002). Molecular Biology of the Cell, 4th ed. New York: Garland Science.
Caprette, D. (1995). Light Microscopy. Retrieved from
Lodish, H., et al. (2000). Molecular Cell Biology, 4th ed. New York: W.H. Freeman and Co.
Wolfe, S.L. (1993). Molecular and Cellular Biology. Belmont, CA: Wadsworth Publishing Company.
Image Reference:
Caprette, D. (2006). Field diameter.
Field diameter= 0.52 mm