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Transcript
Chapter 4 – A Tour of the Cell
And comparison to viruses
Intro
Intro
Intro
Intro
Intro
State Standards
Standard 1.c. – Prokaryotic cells, eukaryotic cells (including those
from plant and animals), and viruses differ in complexity and general
structure
Standard 1.e. – The endoplasmic reticulum and Golgi apparatus play
a role in the secretion of proteins
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
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
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
Microscopes provide windows to the
world of the cell
Scanning Electron
Microscope (SEM)
 Used to study the details of
the surface of the cell
 Produces a 3D image
 Used to study cell and
organelle surfaces
Microscopes provide windows to the
world of the cell
Transmission Electron
Microscope (TEM)
 An electron beam is aimed
through a thin section
 Used to explore the
internal structures of the
cell
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
The Size of Cells
 Most cells are 10-100
micrometers in size
 Cell size and shape are
related to their function
 Ex: red blood cells, nerve
cells, eggs
The Size of Cells
• 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.
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
Structures of the Prokaryotic Cell
Nucleoid region – area where DNA is coiled in the cytoplasm. DNA
is in direct contact with the rest of the cell
Plasmid – smaller circular DNA molecules
Ribosomes – where proteins are made
Plasma membrane – encloses the cytoplasm of the prokaryotic cell
Structures of the Prokaryotic Cell
Cell wall – rigid, composed of lipids, carbohydrates and protein.
Protects the cell and maintains its shape
•
Cell Wall components determine if bacteria is classified as
• gram positive (+)
• or gram negative (-)..In
general more toxic and resistant to
antibiotics
http://www.bio.upenn.edu/computing/media/Instructional.Stain.Gram.php
Structures of the Prokaryotic Cell
Capsule – sticky outer coat that surrounds some prokaryotes.
Protects the cell surface. Helps bacteria attach to surfaces
Pili – short surface projections found in some prokaryotes. Helps
attach bacteria to surfaces
Flagella – long whiplike extensions found in some prokaryotes.
Propel cell through liquid environments
The Role of Bacteria in the Nitrogen Cycle
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 statements
Prokaryotic Cells
Eukaryotic Cells
 Date back at least 3.5 BYA
 Descended from ancient prokaryotes 2.1 BYA
 Ex include: Bacteria & Archaeabacteria
 Ex organisms: plants, animals, fungi, protists
 Simpler Structure (all single celled
 More Complex Structure (mostly multicellular
organisms)
 Naked DNA (not wrapped around 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
organisms but some single celled organism)
 DNA associated with histone proteins
 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)