Chapter 5: Cell Structure and Function
The Development of Cell Theory
Cell Function Limits Cell Size
Types of Cells:
Prokaryotic & Eukaryotic
Characteristics of Prokaryotes and Eukaryotes
There are two general
classes of cells: prokaryotic and eukaryotic. The evolution
of prokaryotic cells preceded that of eukaryotic cells by 2 billion years.
Additional obvious differences between prokaryotes and eukaryotes include:
Eukaryotic cells are, on average, ten times the size of prokaryotic cells.
composition and length
The DNA of eukaryotes is much more complex (in both size and organisation) and than the DNA of prokaryotes.
Prokaryotes have a cell wall composed of peptidoglycan, a single large polymer of amino acids and sugar. Many types of eukaryotic cells also have cell walls, but none made of peptidoglycan.
Control Center of the Cell
Chloroplasts & Mitochondria:
Energy Capture and Extraction
Storage and Elimination
Shape, Support, and Movement
Association of plectin with
myosin II. (a) REF-52 cytoskeleton with actin
filaments decorated by myosin S1 (black arrow). An intermediate filament (white
arrow) associates with an actin filament bundle via plectin sidearms (10 nm
immunogold labeling, white arrowheads). (b-e) Gelsolin-treated cells immunogold
labelled for plectin (b,e) or myosin II (d). After actin depletion, intermediate
filaments (white arrows) with plectin sidearms (white arrowheads) remain
associated with myosin-rich remnants of stress fibers (b, black arrowhead), and
also bind to clusters of myosin filaments (c, black arrowheads) and individual
myosin bipolar filaments (d, black arrowheads). (e) Nocodazole-treated cell with
actin depleted by gelsolin. Individual plectin molecules in lamella (white
arrowheads) cross-link myosin filaments (black arrowheads) and their clusters.
Some plectin molecules bind to each other (asterisk). Bars, 0.1 µm.
The mitotic spindle
is the structure responsible for the segregation of chomosomes
at mitosis. How is the spindle assembled? What factors regulate the dynamics of
microtubules during the cell cycle?
The following images
show the localization of microtubules and DNA in interphase
and mitotic Xenopus XL-177 cells. Tubulin (detected with an anti-tubulin antibody)
is shown in green; DNA (detected with DAPI) is shown in blue. Images by Claire
This image shows
the localization of microtubules and DNA in a mitotic spindle
assembled in vitro in a cytoplasmic extract from Xenopus laeviseggs. Tubulin
(detected with an anti-tubulin antibody) is shown in red; DNA (detected with
DAPI) is shown in blue. Image by Claire Walczak.
People and Projects
Walczak and Ann Yonetani are studying the role of kinesin-like proteins
spindle assembly. Lisa Belmont is characterizing a protein that regulates the
catastrophe rate of microtubules. Heather Deacon is looking for novel factors that
regulate microtubule dynamics. Mimi Shirasu is looking for novel factors involved
in spindle assembly. Jennifer Frazier is looking for molecular and structural
evidence of microtubules in prokaryotes and Archae.
Last updated: March
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Cross-section of cilia
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Last modified on: 31 January, 2000 by Dave Ussery