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Water, other inorganic chemicals,biomoleculesuniversal components of cells
All cells have 2 major subdivisions:plasmamembrane, cytoplasm
Many biomolecules need to be flexible tofunction and to be regulated, but easilydisturbed by changes in environmentalfactorsneed for homeostasis
3 domains: Archaea, Bacteria (prokayotes),Eukaryotes
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Contains materials for genetic instructionsand inheritance
Genescodes for making RNAs and proteinsDifferent genes are expressed in different
tissues and organsProtein-coding genes make up only a small
percentage of the total DNA (1.5% inhumans); the rest had been called junk
Telomeres(stretches of repeated, noncodingDNA sequences) protect chromosome endsand their loss is associated with aging
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Rough ER and its ribosomes synthesize
protein for secretion and membrane
construction
Smooth ER packages new proteins in
transport vesicles
Rough ER and smooth ER are connected
making one continuous organelleTransport vesicles carry their cargo to the
Golgi complex for further processing
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Newly synthesized raw materials continueto travel via vesicles through the layers ofthe Golgi stack during which they are:
1. Processed into finished products2. Sorted and directed to their final
destinations: a. cells exterior, b. newplasma membrane, c. other organelles
Secretory vesicles are released byexocytosis
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Secretory proteins contain a sorting signaland bind to the interior surface of the Golgimembrane that contains recognition markers
Coat proteins (coatomer) from cytosol bindwith specific protein on the outer surface ofthe Golgi sac and causes it to curve and budoff, exposing docking markers (v-SNAREs)
v-SNAREs bind with t-SNAREs of theplasma membrane; membranes fuse; contentis emptied to exterior of cell
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Lysosomes:
1. Digest extracellular material brought into
the cell by phagocytosis
2. Remove aged or damaged organelles
3. Cause intentional self-destruction of
healthy cells as a normal part of
embryonic development (apoptosis orprogrammed cell death)
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Proteasomes:1. Large, tunnel-like protein structures2. Many thousands per cell
3. Chop internal proteins (only those taggedwith a tiny protein called ubiquitin) intoreusable amino acidsa. Those that are no longer neededb. As emergency energy supplies inextreme starvationc. Misfolded proteins
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Smaller than lysosomes
Contain powerful oxidative enzymes and
most of the cells catalase
Oxidative enzymes use oxygen to strip
hydrogen from certain organic molecules
detoxifies wastes produced within cell or
foreign toxic compounds that have enteredthe cell H2O2is produced
decomposed into H2O and O2by catalase
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Cellular power plantsContain DNA (mtDNA) exclusively
inherited from the maternal side
Required for aerobic metabolism ineukaryotes
Densities vary among tissues and organtypes (1-10% of skeletal muscle volume;30-50% of heart)
Mitochondrial metabolism can createoxidative stress
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Occurs when production of reactiveoxygen species (ROS) overwhelms thebodys antioxidant defenses
ROSsuperoxide anions, hydroxyl (-OH)radicals, peroxynitrite, hydrogen peroxide
Antioxidant systemssuperoxidedismutase, catalase, glutathione, vit C,derivatives of vit A and E, flavonoids, uricacid
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Octagonal barrels 3x larger thanribosomes
Found in many but not all animal groups
Thousands in cells, but do not show upwith ordinary staining techniques
Proposed to act as cellular trucksdocking at nuclear pores to pick up cargo(may be mRNAs or ribosomal subunits)from the nucleus and deliver them to thecytoplasm
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Semiliquid (gelatinous) portion of thecytoplasm that surrounds the organelles
55% of total cell volumeAssociated with:1. Enzymatic regulation of intermediary
metabolism (catabolism, anabolism,transformation of simple sugars, aminoacids, fatty acids)
2. Protein synthesis3. Storage of fat and glycogen4. Temporary storage of secretory, transport,
and endocytic vesicles
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Cell bone and muscleComplex protein network; intracellular
scaffolding to
1. Support and organize cell componentsinto an appropriate arrangement
2. Control their movements Components:1. Microtubules2. Microfilaments3. Intermediate filaments
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Largest element made up of tubulinVery slender, long, hollow, unbranched
tubes
Position many organellesMaintain distinct shape and size of cellsCoordinate complex cell movements:1. Transport of secretory vesicles2. Movement of cilia and flagella3. Distribution of chromosomes during cell
division
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Kinesin
1
2
3
4
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Dynein
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Cells main microtubule organizing center
(MTOC)
Located near the nucleus
Consists of centrioles (pair, short,
cylindrical, at right angles to each other,
form the spindle apparatus)
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Smallest elements
Functions:
1. Vital to cellular contractile systems
2. Act as mechanical stiffeners to specific
cellular projections (microvilli)
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Tough, durable, highly stableRoles:1. Maintain structural integrity of a cell2. Resist mechanical stresses applied to a cell Only one class is found in a particular cell
type:1. Neurofilamentsin nerve cell axons (85% of
total proteins)
2. In skeletal muscle cells, holding actin-myosin units in proper alignment3. Keratinin skin cells (85% of total proteins)
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1. Cell adhesion molecules (CAMs) in plasmamembranes
2. Extracellular matrix (ECM) secreted by thefibroblasts with 3 major types of fibers:
collagen(provides tensile strength), elastin(provides elasticity), fibronectin(promotescell adhesion and holds cells in place;reduced in cancerous tissue) Cells
are able to function normally and survive only whenassociated with their normal matrix components, except thecirculating blood cells.
3. Cell junctions
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Desmosomesspot welds or adhering junctions;abundant is tissues that are subject toconsiderable stretching (skin, heart, uterus)
Tight junctionsimpermeable junctions; join
sheets of epithelial tissueGap junctionscommunicating junctions formed
by 2 small connecting tunnels (connexons) madeup of connexinproteins; permits small ions to pass
between cells to transmit electrical activitythroughout an entire muscle mass ,as well assmall signal molecules between cells
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