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Cells: The Living Units

Based on Human Anatomy & Physiology, 6th Edition, Elaine N. Marieb

Part B

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Cytoplasmic Organelles

• Specialized cellular compartments

• Membranous – Mitochondria, peroxisomes, lysosomes,

endoplasmic reticulum, and Golgi apparatus

• Nonmembranous – Cytoskeleton, centrioles, and ribosomes

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Mitochondria

• Double membrane structure ith shel!like

cristae

• "ro#ide most o! the cell$s %&" #ia aerobic

cellular respiration

• Contain their on DN% and 'N%

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Mitochondria

(igure )*+

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Ribosomes

• Site o! protein synthesis

• Membrane-bound ribosomes synthesize

proteins to be incorporated into membranes

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Endoplasmic Reticulum (ER)

(igure )*+.a and c

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Endoplasmic Reticulum (ER)

• /nterconnected tubes and parallel

membranes enclosing cisternae

• Continuous ith the nuclear membrane

•&o #arieties – rough 0' and smooth 0'

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Rough (ER)

• 0xternal sur!ace studded ith ribosomes

• Manu!actures all secreted proteins

• 'esponsible !or the synthesis o! integral

membrane proteins and phospholipids !orcell membranes

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mooth ER

• &ubules arranged in a looping netork

• Catalyzes the !olloing reactions in #ariousorgans o! the body – /n the li#er – lipid and cholesterol metabolism,

breakdon o! glycogen and, along ith the kidneys,detoxi!ication o! drugs

 – /n the testes – synthesis o! steroid-based hormones

 – /n the intestinal cells – absorption, synthesis, andtransport o! !ats

 – /n skeletal and cardiac muscle – storage and releaseo! calcium

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!olgi "pparatus

• Stacked and !lattened membranous sacs

• (unctions in modi!ication, concentration, and

packaging o! proteins

•&ransport #essels !rom the 0' !use ith theGolgi apparatus

• "roteins then pass through the Golgi

apparatus to be packaged as a secretory

#esicle

• Secretory #esicles lea#e the Golgi stack and

mo#e to designated parts o! the cell

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Role o# the !olgi "pparatus

(igure )*1+

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Lysosomes

• Spherical membranous bags containing

digesti#e enzymes

• Digest ingested bacteria, #iruses, and toxins

• Degrade non!unctional organelles

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Endomembrane ystem

• System o! organelles that !unction to2 – "roduce, store, and export biological molecules

 – Degrade potentially harm!ul substances

• System includes2 – Nuclear en#elope, smooth and rough 0', lysosomes,

#acuoles, transport #esicles, Golgi apparatus, and the

plasma membrane

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Endomembrane ystem

(igure )*1)

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$ero%isomes

• Membranous sacs containing oxidases and

catalases

• Detoxi!y harm!ul or toxic substances

• Neutralize dangerous !ree radicals – (ree radicals – highly reacti#e chemicals ith

unpaired electrons 3i*e*, 41 –5

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Cytos&eleton

• &he 6skeleton7 o! the cell

• Dynamic, elaborate series o! rods running

through the cytosol

• Consists o! microtubules, micro!ilaments,

and intermediate !ilaments

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Cytos&eleton

(igure )*18

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Microtubules

• Dynamic, hollo tubes made o! the spherical

protein tubulin

• Determine the o#erall shape o! the cell and

distribution o! organelles

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Micro#ilaments

• Dynamic strands o! the protein actin

•  %ttached to the cytoplasmic side o! the

plasma membrane

• 9races and strengthens the cell sur!ace

• (unction in endocytosis and exocytosis

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Centrioles

• Small barrel-shaped organelles located in

the centrosome near the nucleus

• "inheel array o! nine triplets o!

microtubules

• 4rganize mitotic spindle during mitosis

• (orm the bases o! cilia and !lagella

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Centrioles

(igure )*1:a, b

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Cilia

• ;hiplike, motile cellular extensions on exposed

sur!aces o! certain cells• Mo#e substances in one direction across cell

sur!aces

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'ucleus

• Contains nuclear en#elope, nucleoli and

chromatin

• Gene-containing control center o! the cell

• Contains the genetic library ith blueprints

!or nearly all cellular proteins

• Dictates the kinds and amounts o! proteins

to be synthesized

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'ucleus

(igure )*1.a

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'uclear Envelope

• Selecti#ely permeable double membrane

barrier containing pores

• 0ncloses

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Chromatin

• &hreadlike strands o!DN% and histones

• (orm condensed,barlike bodies o!

chromosomes henthe nucleus starts todi#ide

(igure )*1=

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'ucleoli

• Dark-staining spherical bodies ithin the nucleus

• Site o! ribosome production