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7-1 Life Is Cellular
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Figure 7.0 Fluorescent stain of cell
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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The Discovery of the Cell
Hooke’s Drawing of Cork Cells
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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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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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Prokaryotes and Eukaryotes
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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Figure 7.4 A prokaryotic cell
Figure 7.4x1 Bacillus polymyxa
Figure 7.4x2 E. coli
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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Prokaryotes and Eukaryotes
Prokaryotes
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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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
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nonliving material.
existing cells.
cytoplasm.
animals.
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7-1
The person who first used the term cell was
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Matthias Schleiden.
Lynn Margulis.
Anton van Leeuwenhoek.
Robert Hooke.
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7-1
Which organism listed is a prokaryote?
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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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Eukaryotic Cell Structures
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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Eukaryotic Cell Structures
Plant Cell
Nucleolus
Nucleus
Smooth
endoplasmic
reticulum
Nuclear envelope
Ribosome (free)
Rough endoplasmic
reticulum
Ribosome
(attached)
Golgi
apparatus
Cell wall
Cell membrane
Chloroplast
Mitochondrion
Vacuole
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Eukaryotic Cell Structures
Animal Cell
Nucleolus
Smooth endoplasmic
reticulum
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
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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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.
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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
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.
Contractile vacuole
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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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Mitochondria and Chloroplasts
Chloroplasts
Chloroplast
Plants and some other
organisms contain
chloroplasts.
Chloroplasts capture energy
from sunlight and convert it
into chemical energy in a
process called
photosynthesis.
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Mitochondria and Chloroplasts
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Cytoskeleton
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
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Cytoskeleton
Cytoskeleton
Cell membrane
Endoplasmic
reticulum
Microtubule
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
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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
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break down organelles.
assemble proteins.
maintain homeostasis.
make new organelles.
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7-2
Chloroplasts are found in the cells of
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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?
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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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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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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
Levels of Organization
Levels of Organization
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
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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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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
Field diameter= 0.52 mm
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
Field diameter= 0.52 mm