Cells
The Universal Subunits of Life
Cellular Structure
• all life is cellular
• Cell Theory
– Cells are the fundamental units of life.
– All organisms are composed of cells.
– All cells come from preexisting cells.
• each cell possesses the different molecules
necessary for sustaining life & specializations
(≥10,000)
Cellular Structure
• all life is cellular
– all cells belong to one of two structural
categories
• prokaryotic cells - relatively simple
• eukaryotic cells - more complex
Cellular Structure
• prokaryotic cells
– cytoplasm surrounded by plasma membrane
• cytosol + insoluble particles
– DNA in nucleoid
– no membrane-bound organelles
– cell wall (most)
– complex, highly regulated metabolism
– distinguished by many non-universal
characteristics
some common prokaryotic characters
Figure 4.5
Bacterial Flagellum
Figure 4.6
relative
sizes
of
organisms
and
their
constituents
Figure 4.2
Cellular Structure
• eukaryotic cells
– larger, but still small
cell size is limited by surface area/volume ratio
Figure 4.3
Cellular Structure
• eukaryotic cells
– larger, but still small
– plasma membrane
– cytoskeleton
– membrane-bound organelles
Animal & Plant Cells
Figure 4.7
cell fractionation
by
centrifugation
permits
biochemical
analysis
that supplements
microscopic
observations
Figure 4.8
Organelle Functions
• information processing organelles
– nucleus
• an envelope of two membranes
–perforated by pores
–the outer membrane is linked to the ER
• contains
–nucleoplasm
–chromatin
–nucleoli
nuclear
structures
Figure
4.9
Organelle Functions
• information processing organelles
– nucleus
– chloroplasts (cp) & mitochondria (mt)
• contain DNA like prokaryotic cells
• express some essential proteins
Organelle Functions
• information processing organelles
– nucleus
– chloroplasts (cp) & mitochondria (mt)
– ribosomes
• complex RNA-protein bodies
• translate instructions into polypeptides
• in cytoplasm, on ER, in cp & mt
Organelle Functions
• energy processing organelles
– mitochondria
• major site of oxidative energy production
• two membranes surround aqueous matrix
that contains energy-processing enzymes
• the highly folded inner membrane
(cristae) bears energy-processing enzymes
Mitochondrion
Figure 4.14
chromoplasts
leucoplasts
Figure 4.17
Organelle Functions
• energy processing organelles
– mitochondria
– plastids
• a two-membrane envelope
• store/produce energy or display colors
• chloroplasts
–thylakoid membranes are suspended in
the stroma
–each contains enzymes of energy
production
Chloroplast
Figure 4.15
endosymbiotic origin of cp & mt
Figure 4.18
Organelle Functions
• the endomembrane system
– a system of interacting membranes located
throughout the cell
• endoplasmic reticulum (ER)
–continuous with the nuclear outer
membrane
–the membrane encloses the lumen
–translates & processes proteins headed
for organelles, membranes, outside
–RER (rough), SER (smooth)
rough & smooth endoplasmic reticulum
(RER, SER)
Figure 4.11
Organelle Functions
• endomembrane system
– interacting membrane organelles throughout
the cell
• endoplasmic reticulum (ER)
• Golgi apparatus
–flattened sacks (cisternae) + vesicle
shuttles
–proteins travel from ER to cis face to
trans face
endomembrane system function
Figure 4.12
Organelle Functions
• endomembrane system
– interacting membrane organelles throughout
the cell
• endoplasmic reticulum (ER)
• Golgi apparatus
• lysosome
–vesicle with digestive enzymes
–fuses with phagosome
lysosome function
Figure 4.13
Organelle Functions
• other organelles
– peroxisome
• detoxifies peroxides
Figure 4.19
Organelle Functions
• other organelles
– peroxisome
• detoxifies peroxides
– glyoxysome (plants only)
• converts lipids to carbohydrates
– vacuole (plants)
• maintains turgor pressure
• stores reserves, wastes
• visual attractant (anthocyanins)
Figure 4.20
microfilaments
stabilize
cell shape
Figure 4.22
9+2
arrangement
of
microtubules
in cilium
Figure 4.23
mechanism of microtubular movement
Figure 4.24
Extracellular Structures
• plant, fungi cell wall
– prevents cell from bursting
Plant Cell Wall
Figure 4.25
Extracellular Structures
• plant, fungi cell wall
• animal extracellular matrix
– secreted by adjacent cells
– differs from tissue to tissue
An extracellular matrix
Figure 4.26