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Chapter 4 – A Tour of the Cell
Intro
The Microscopic World of Cells
• Organisms are either:
– Single-celled, such as
most bacteria and
protists
– Multicelled, such as
plants, animals, and
most fungi
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Life’s 3 Domains
Scientist’s study of different organisms’ cell
structure and DNA lead them to group
organisms into 3 different domains
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Life’s 3 Domains
Plants Animals Fungi
Eubacteria:
common bacteria First Eukaryotes -- Protists
Archaebacteria: Oldest
bacteria
First cells (prokaryotic) 3.5 billion years ago
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
My Thoughts
(Complete one of the following statements on the left side opposite the
notes you just took)
I can picture…
A question I have is…
This is like…
This reminds me of…
I am confused about…
The big idea here is…
I think/wonder….
I predict that…
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
The Microscopic World of Cells
•
The human body is made up of trillions of cells many of which are
specialized
–
Muscle cells, Nerve cells, & blood cells…
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
The Cell Theory
• Cells were first discovered in 1665 by Robert Hooke.
• The accumulation of scientific evidence led to the cell theory
- All living things are composed of one or more cells
- All cells are formed from previously existing cells
Cell theory 6 minute video: http://ed.ted.com/lessons/the-wackyhistory-of-cell-theory
Microscopes provide windows to the
world of the cell
The Light Microscope
 Light passes through the
specimen
 Lenses enlarge, or magnify,
the image
Magnification – the increase
in the specimen’s apparent
size
Resolving power – the ability
to show 2 objects as being
separate
Microscopes provide windows to the
world of the cell
The Electron Microscope
 Uses a beam of electrons
 Resolving power is higher
than the light microscope
 Can magnify up to
100,000X
The Size of Cells
 Most cells are 10-100
micrometers (µm) in size
 Cell size and shape are
related to their function
 Ex: red blood cells, nerve
cells, eggs
The Size of Cells
30 µm
10 µm
• The lower limit of cell size is determined by the fact that a cell
must be large enough to house the parts (DNA, organelles) it
needs to survive and reproduce.
• The maximum size of a cell is limited by the amount of surface
needed to obtain nutrients from the environment and dispose
of wastes.
The Two Major Categories of Cells
The Two Major Categories of Cells
• There are 2 major categories of cells
- Prokaryotic cells
- Eukaryotic cells
• Both cells
- Are surrounded by a plasma membrane
- Consist of cytoplasm and organelles and contain DNA
• Prokaryotic and eukaryotic cells differ in several ways
Comparing Eukaryotic and Prokaryotic
CellsProkaryotes
Eukaryotes
Differences
Differences
Commonalities
Prokaryotic Cells
• Smaller than eukaryotic cells
•
•
•
•
•
(2-8 um)
Enclosed by a plasma
membrane that is usually
surrounded by a rigid cell wall
The cell wall may be covered
by a sticky capsule
DNA is found inside the cell
but it is not housed in a
nucleus
Ribosomes (70S) are present
Internal structures surrounded
by membranes are not present
Eukaryotic Cells
 Larger than




prokaryotic cells
(10-100 um)
More complex in
structure
DNA housed in the
nucleus
Ribosomes (80S)
Membrane bound
organelles
Comparing Animal and Plant Cells
 Animal cells contain
centrioles, lysosomes,
flagella
 Plant cells contain a central
vacuole, cell wall,
chloroplasts
Comparing Eukaryotic and Prokaryotic
CellsProkaryotes
Eukaryotes
Differences
Differences
Commonalities
Comparing Eukaryotic and Prokaryotic Cells- Differences in parallel
Eukaryotic Cells
statements
Prokaryotic Cells
 Descended from ancient prokaryotes
 Date back at least 3.5 BYA
2.1 BYA
 Ex include: Bacteria &
 Ex organisms: plants, animals, fungi,
Archaeabacteria
protists
 Simpler Structure (all single celled More Complex Structure (mostly
organisms)
multicellular organisms but some single
 Naked DNA (not wrapped around histone
celled organism)
proteins)
 DNA associated with histone proteins
 Circular Chromosomes
 DNA in cytoplasm (nucleoid
region)
 70S ribosomes
 No internal membrane
compartments (no membrane bound
organelles)-ex: no mitochondria, no
Rough ER
 Chromosomes linear
 DNA separated from cytoplasm (in
nucleus)
 80S ribosomes
 Internal membrane compartments
(membrane bound organelles) –ex: yup
mitochondria and Rough ER
Comparing Eukaryotic and Prokaryotic CellsCommonalities: Prokaryotes & Eukaryotes
 Smallest units of Life (therefore has the characteristics of life
Chapter 1!)
 Requires energy (to run metabolic reactions of life)
 Grows and develops
 Independently reproduce
 DNA stores genetic information
 Can evolve over generations
 Order: internal organization
 Responds to environmental stimuli
 Ribosomes build proteins for the cells
 Contains plasma membrane to regulate what enters and
leaves the cell
 Filled with cytosol (fluid)