Bio 178 Lecture 7
Cell Structure
Copyright: J. Elson-Riggins
Reading
•
Chapter 5 (& P 550)
Quiz Material
•
Questions on P 104
•
Chapter 5 Quiz on Text Website
(www.mhhe.com/raven7)
Outline
• Microscopy (Cntd.)
• Prokaryotes
• Eukaryotes
Characteristics of Principle Cell Types
2 structurally different types of cells:
PROKARYOTE
EUKARYOTE
True Nucleus?
No
Yes
Membrane bound
organelles?
No
Yes
Bacteria
Archaebacteria
Protista
Fungi
Plantae
Animalia
Kingdoms
SEM - Dinoflagellate, Gonyaulax polyedra
http://www.mcb.harvard.edu/hastings/dino.html
Immunofluorescence Microscopy
Green =
Anti-tubulin
Red = Antivimentin
http://www.img.cas.cz/dbc/gallery.htm
Prokaryotic Cells (Bacteria)
Prokaryotes
Characteristics
• Simple Organization
1. Little compartmentalization.
2. Nucleoid region with a simple circle of DNA.
3. Ribosomes.
• Size
~ 1 to 10 µm.
Prokaryote Characteristics (Cntd.)
• Support
Most prokaryotes have a strong cell wall (instead of
internal support structures).
• Cell Shape
Variable - rod (bacillus), sphere (coccus), comma (vibrio),
spiral (spirillum).
Staphylococcus epidermidis
Dr. Dennis Kunkel / Visuals Unlimited,
http://www.visualsunlimited.com/browse/vu285/vu285886.html
Spirillum
http://web.grcc.cc.mi.us/biosci/pictdata/103contents.htm
Bacillus
http://web.grcc.cc.mi.us/biosci/pictdata/103contents.htm
Vibrio
Vibrio cholerae
http://bioaulas.tioale.pro.br/aula_bacterias.php
Prokaryote Cell Walls
• Bacteria have cell walls of peptidoglycan (proteincarbohydrate), but Archaebacteria use other materials.
• Gram Staining
Gram Positive:
A thick wall with many layers of peptidoglycan that blocks
the escape of the gram stain  Purple.
Gram Negative:
Only a thin peptidoglycan layer that allows the escape of
the gram stain  Red.
Prokaryote Cell Walls
Importance of Prokaryotes
• Decomposition
• Photosynthesis
• Disease
• Tools for molecular biology
Eukaryotic Cells
Key Characteristic:
COMPARTMENTALIZATION:
• Membrane-bound organelles (including the
endomembrane system).
• Nucleus.
• Plasma membrane.
Eukaryote - Animal Cell
Eukaryote - Plant Cell
The Nucleus
Function
Control center of cell.
Structure
• Nuclear Envelope
1. 2 phospholipid bilayers.
2. Internal bilayer continuous with ER.
3. Nuclear pores that allow selective passage of proteins
and RNA.
Nuclear Envelope
Nuclear Structure (Cntd.)
• Nucleolus
1. Dark staining region of nucleus.
2. Contains genes that encode rRNA.
3. Function - rRNA synthesis and assembly of ribosomal
subunits.
• Chromosomes
DNA and protein (histones).
Nucleolus
http://cellbio.utmb.edu/cellbio/nucleus3.htm
Chromosome Structure
Ribosomes
Function
Protein synthesis.
Composition
2 subunits of rRNA and protein.
The Endomembrane system
Structure
Interior membranes that are connected by either:
• direct physical continuity or
• vesicular transport
Function
Compartmentalization, large surface area, and trafficking.
Components
• Endoplasmic reticulum
• Golgi apparatus
• Lysosomes
The Endomembrane System
The Endomembrane System
Endoplasmic Reticulum
Structure
• Lipid bilayer with embedded proteins that forms an
intracellular network.
• Cisternal space.
Intracellular Location
Continuous with nuclear envelope and concentrated
around it.
Rough Endoplasmic Reticulum (RER)
Structure
ER with attached ribosomes.
Functions
• Lipid/membrane synthesis.
• Synthesis of proteins to be secreted from the cell determined by the presence of a signal sequence on the
polypeptide chain.
• Synthesis of proteins that will be embedded in the cell
membrane or sent to lysosomes.
RER Structure
Synthesis of Secreted Proteins
Signal sequence composed of hydrophobic aa.
RER
http://trc.ucdavis.edu/mjguinan/apc100/modules/TermsCells&Tissue
s/structures/ER.html
Smooth Endoplasmic Reticulum (SER)
Structure
Few attached ribosomes.
Functions
• Lipid/membrane synthesis.
• Detoxification.
SER
http://cellbio.utmb.edu/cellbio/ser.htm