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Cell Organelles
By
Diana L. Duckworth
Rustburg High School
Campbell County
Nucleus
• Enclosed by nuclear envelope
– Double membrane, each a lipid bilayer
– Two membranes merge in pores
• Protein lined channels for exit of mRNA and ribosomes from
nucleus
• Within nucleus one or more nucleoli
– Site for the manufacture of ribosomes
• Chromatin – DNA in combination with proteins
– Diffuse mass uncoiled chromatin so DNA can be
transcribed; condensed (tightly coiled) during cell
division
Nucleus
Ribosomes
Pores
Chromatin
http://biology.about.com/library/weekly/aa032300a.htm
Nucleoli (nucleolus – singular)
Nuclear Envelope
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL2.html
Endoplasmic Reticulum (ER)
• Membrane system within cytoplasm
• Connected to nuclear envelope
• Two kinds of ER
– Smooth endoplasmic reticulum
• Synthesis of lipids, phospholipids, steroids
• Detoxifies drugs (good & bad)
• Stores calcium ions in muscle cells
– Rough Endoplasmic Reticulum
• Ribosomes attached to ER
• Synthesis of proteins and hormones for sectretion
Rough Endoplasmic Reticulum
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL2.html
Ribosomes – Free or Attached to ER
Free manufacture proteins for use in cytoplasm; attached to
ER they manufacture proteins for export outside cell.
http://biology.about.com/library/weekly/aa033000a.htm
Golgi Apparatus
• Stack of flattened membranous sacs
(cisternae)
• Finishing and distribution of export products
& does make some polysaccharides for
export
• Vesicles from ER bud off and merge with one
side of Golgi apparatus (near E.R.)
• Cisternae mature through the stack
• Finished products bud off from other side in
transport vesicles
Golgi Apparatus
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossD.html
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL2.html
Formation of Golgi & export of
products
http://employees.csbsju.edu/hjakubowski/classes/ch331/cho/ergolgi.jpeg
Lysosomes
• Digestive vesicle produced by Golgi
– Acidic environment in lysosome
– Contains enzymes that break down
macromolecules & recycle components
• Function by engulfing material from
cytoplasm (autocytosis) or by merging with
food vacuoles
– Food vacuoles form when cell engulfs
something from outside cell (phagocytosis)
Vacuoles
• Membrane bound sacs serve a variety of
purposes
• Food vacuoles form when cell engulfs material
from outside cell (phagocytosis)
• Plant cell vacuoles surrounded by membrane
called tonoplast
– Used as storage for cell wastes, water
– Get larger by merging with smaller vacuoles
– Occupy most of volume of plant cell, cytosol is thin
region between vacuole & membrane
Mitochondria
• Site of cellular respiration
– Generate ATP from extracting energy from sugars,
fats & other fuels
• Enclosed by membranes that are not part of
cellular membrane system
– Has at least 2 membranes separating interior from
cytosol
– Contain both ribosomes and DNA
– Some membrane proteins are imported from cytosol
• Grow and reproduce within cell, separate from
cellular reproduction
Mitochondria
http://desertfiddlekate.blogspot.com/2007/06/compendium-reviewone.html
http://www.answers.com/topic/mitochondria-1?cat=technology
Chloroplasts
• Conversion of light energy to
chemical energy in sugars
• One of group of organelles –
plastids
• Surrounded by 2 membranes (not
ER)
• Internal membrane system called
thylakoids
• Stacked thylakoids called granas
• Surrounding fluid called stroma &
contains DNA, ribosomes,
enzymes
http://www.williamsclass.com/Seve
nthScienceWork/CellTheoryParts.
htm
Peroxisomes
• Single membrane bound vesicles
• Contain enzymes initiate breakdown of
complex molecules into smaller molecules
– By-product is hydrogen peroxide (toxic)
– Enzymes convert this to water
• Do NOT form by budding from ER
– Grow larger by adding proteins formed in
cytosol & lipids made in ER
– Split in two when become too large
Cytoskeleton – 3 components
• Microtubules – largest; hollow rods
–
–
–
–
function in cell division
Mobility of organelles
Shape & support cell
Responsible for beating of cilia & flagella
• Microfilaments (Actin filaments & Myosin
filaments)
– Resist tensional forces on cell
– Contractile apparatus in muscle cells, cell motility
• Intermediate filaments
– Control shape of cell; more permanent
http://www.williamsclass.com/SeventhScienceWork/CellTheoryParts.htm
Extracellular Components of Cells
• Plant cell walls
– Protection; prevents excessive water uptake;
maintains shape
– Cellulose (polysaccharide) fibrils embedded in
matrix of other polysaccharides and proteins
• Extracellular matrix of animal cells (ECM)
– Glycoproteins (collagen) secreted by cells
– Communicates with cytoskeleton & can affect
development & differentiation of cells
Generalized Animal Cell
http://sun.menloschool.org/~cweaver/cells/
Generalized Plant Cell
http://sun.menloschool.org/~cweaver/cells/