Transcript Cell Structure and Function

Cell Structure and
Function
Chapter 3
The Cell--Considerations
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Basic unit of life
Protection and support
Movement
Communication
Metabolism and energy release
Inheritance
Cell Theory
All living things are made up of
cell(s)
Cells are smallest living unit of
structure and function for all
organisms
All cells arise from preexisting cells
(No spontaneous generation)
Why Are Cell So Small?
Sizes of living things
Prokaryotes vs Eukaryotes
• Prokaryotes
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“Before nucleus”
DNA in nucleoid region
Ribosomes
Cell membrane
No membrane–bound
organelles
• Eukaryotes
– “True nucleus”
– DNA in double
membrane bound
nucleus
– Ribosomes
– Cell membrane
– Membrane –bound
organelles
Typical Bacterium---A Prokaryote
Typical Animal Cell-A Eukaryote
Plasma Membrane
Animal cell anatomy
Plant cell anatomy
Nucleus--The Brains of the Cell
Nucleus
• DNA dispersed throughout
• Consists of :
– Nuclear envelope: Separates nucleus from
cytoplasm and regulates movement of materials in
and out
– Chromatin: Condenses to form chromosomes
during cell division
– Nucleolus: Assembly site of large and small
ribosomal units
Ribosomes
• Sites of protein
synthesis
• Composed of a
large and small
subunit
• Types
– Free
– Attached to
endoplasmic
reticulum
Composition of
eukaryotic and
prokaryotic
ribosomes
Cryoelectron microscopy–based image of
the E. coli ribosome at ~25 Å resolution.
Mol. Biol. Gene, Fig. 14-21
The Endomembrane System
• Nuclear envelope
• Endoplasmic reticulum
• Golgi apparatus
• Vesicles
Endoplasmic Reticulum
• Types
– Rough
• Attached
ribosomes
• Proteins produced
and modified
– Smooth
• No attached
ribosomes
• Manufacture lipids
• Cisternae or Lumen:
Interior spaces isolated
from rest of cytoplasm
Golgi Apparatus—Traffic Cop
• Modification,
packaging,
distribution of
proteins and lipids
for secretion or
internal use
• Flattened
membrane sacs
stacked on each
other
Function of Golgi Apparatus
Action of Lysosomes
Peroxisomes and
Proteasomes
• Peroxisomes
– Smaller than lysosomes
– Contain enzymes to break down fatty and
amino acids
– Hydrogen peroxide is a by-product of
breakdown
• Proteasomes
– Consist of large protein complexes
– Include several enzymes that break down
and recycle proteins in cell
Energy Management
Organelles
• Mitochondria
–Aerobic Respiration
• Chloroplasts
–Photosynthesis
Circle of Life
Energy
Respiration
Mitochondria
Carbon
Complex>>Simple
CO2, H2O
compounds, O2
Chloroplasts
Photosynthesis
Energy
Mitochondria—Powerhouse of the Cell
• In all eukaryotes
• Major site of ATP
synthesis
• Membranes
– Outer
– Cristae: Infoldings of
inner membrane
• Matrix: Substance
located in space
formed by inner
membrane
Chloroplast
Animal cell anatomy
Plant cell anatomy
The Cytoskeleton
• Function:
– Maintenance of cells shape
– Movement within cytoplasm
– Cell movement
– Intracellular communication?
• Three components
– Actin filaments
– Microtubules
– Intermediate filaments
CYTOSKELETON= complex network of filamentous
proteins extending throughout the cytoplasm
Three types of filaments: Microtubules
Microfilaments
Intermediate Filaments
Cell shape
FUNCTION:
Anchoring of organelles
and cellular structures
Motility:
Organelle movement
crawling,
chemokinesis
chemotaxis
endo- and exo-cytosis)
Tensile strength
Cell polarity
Chromosome movement
ACTIN FILAMENTS
helical structure, diameter ~ 7 nm
EX. intestinal microvilli
MICROFILAMENTS
ACTIN STRUCTURES IN CELLS:
MICROVILLI
STRESS FIBRES
FOCAL ADHESIONS
LAMELLIPODIA
FILOPODIA
(or MICROSPIKES
CONTRACTILE
RING
(cell division)
hollow cyllinders, diameter ~ 25 nm, emanating from the MTOC
Microtubule structure
Made of  and β Tubulin
rope-like fibres, diameter ~ 10 nm,
nuclear, cytoplasmic, connecting cell-cell junctions
Structure of intermediate
filaments
Cytoskeleton Elements
microtubules
microfilaments
intermediate
filaments
Centrioles
Centrioles
• In specialized zone
near nucleus:
Centrosome
• Each unit consists of
microtubules
• Before cell division,
centrioles divide,
move to ends of cell
and become spindle
fibers
Cilia and flagella
• Cilia (small and numerous) and
flagella (large and single)
–9 + 2 pattern of microtubules
– Iinvolved in cell movement.
–Each has a basal body at its
base.
• Plant cells lack centrioles
Structure of a flagellum or cilium
Prokaryotes vs Eukaryotes
• Prokaryotes
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–
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“Before nucleus”
DNA in nucleoid region
Ribosomes
Cell membrane
No membrane–bound
organelles
• Eukaryotes
– “True nucleus”
– DNA in double
membrane bound
nucleus
– Ribosomes
– Cell membrane
– Membrane –bound
organelles
Evolution of the eukaryotic cellEndosymbiotic Hypothesis
SUMMARY
• Cell Theory
• Physics of Cell Size
• Eukaryotes
– Nucleus
– Membrane Bound Organelles
• ER
• Golgi
• Vesicles, ex. Lysosomes
– Energy Management Organelles
– Cytoskeleton
– Prokaryotes
– Endosymbiosis