Visual Anatomy & PhysiologyFirst Edition
Martini & Ober
Chapter 3Cellular Level of
OrganizationLecture 5
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• Specialization and differentiation of cells
• General characteristics of cells
• The cell membrane
• Cellular organelles (summary table)
• Cell death; necrosis and apoptosis
• Stem cells and progenitor cells
• Cancer
• Movement of substances into and out of the cell
Lecture Overview
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Cells Are Specialized
• vary in size• vary in shape• vary in function• measured in micrometers
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A Composite Cell
• hypothetical cell• major parts
• nucleus• cytoplasm• cell membrane
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Cell Membrane
• outer limit of cell; isolates cell• controls what moves in and out of cell - selectively permeable
•phospholipid bilayer • water-soluble “heads” form outer surfaces• water-insoluble “tails” form interior• permeable to lipid-soluble substances only
• cholesterol stabilizes the membrane• proteins
• receptors• pores, channels, carriers• enzymes• CAMS• self-markers
• self-sealing
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Cell Membranes
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A Transmembrane Protein
Membrane Lipids
Hydrophilic channel
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Cellular Organelles
CELL COMPONENT DESCRIPTION/STRUCTURE
FUNCTION(S)
CELL MEMBRANE Bilayer of phospholipids with proteins dispersed throughout
cell boundary; selectively permeable (i.e. controls what enters and leaves the cell; membrane transport)
CYTOPLASM jelly-like fluid (70% water) suspends organelles in cell
NUCLEUS Central control center of cell; bound by lipid bilayer membrane; contains chromatin (loosely colied DNA and proteins)
controls all cellular activity by directing protein synthesis (i.e. instructing the cell what proteins/enzymes to make.
NUCLEOLUS dense spherical body(ies) within nucleus; RNA & protein
Ribosome synthesis
RIBOSOMES RNA & protein; dispersed throughout cytoplasm or studded on ER
protein synthesis
ROUGH ER Membranous network studded with ribosomes
protein synthesis
SMOOTH ER Membranous network lacking ribosomes
lipid & cholesterol synthesis
GOLGI “Stack of Pancakes”; cisternae modification, transport, and packaging of proteins
Table 1 of 2
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Cellular Organelles
CELL COMPONENT DESCRIPTION/STRUCTURE
FUNCTION(S)
LYSOSOMES Membranous sac of digestive enzymes destruction of worn cell parts (“autolysis) and foreign particles
PEROXISOMES Membranous sacs filled with oxidase enzymes (catalase)
detoxification of harmful substances (i.e. ethanol, drugs, etc.)
MITOCHONDRIA Kidney shaped organelles whose inner membrane is folded into “cristae”.
Site of Cellular Respiration; “Powerhouse of Cell”
FLAGELLA long, tail-like extension; human sperm locomotion
CILIA short, eyelash extensions;human trachea & fallopian tube
to allow for passage of substances through passageways
MICROVILLI microscopic ruffling of cell membrane increase surface area
CENTRIOLES paired cylinders of microtubules at right angles near nucleus
aid in chromosome movement during mitosis
Table 2 of 2
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Cell Death• Two mechanisms of cell death
– Necrosis– Programmed cell death (PCD or apoptosis)
• Necrosis– Tissue degeneration following cellular injury or
destruction– Cellular contents released into the environment
causing an inflammatory response
• Programmed Cell Death (Apoptosis)– Orderly, contained cell disintegration– Cellular contents are contained and cell is
immediately phagocytosed
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Necrosis vs. Apoptosis
Necrosis
ApoptosisFigure from: Alberts et al., Essential Cell Biology, Garland Press, 1998
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Cellular Pathways
of Apoptosis
Figure from: http://www.ambion.com/tools/pathway/pathway.php?pathway=Cellular%20Apoptosis%20Pathway
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Failure of Apoptosis - Syndactyly
Photo from: http://en.wikipedia.org/wiki/Apoptosis
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Stem and Progenitor Cells
Stem cell • can divide to form two new stem cells• can divide to form a stem cell and a progenitor cell• totipotent – can give rise to any cell type (Embryonic stem cells)• pluripotent – can give rise to a restricted number of cell types
Progenitor cell • committed cell• can divide to become any of a restricted number of cells • pluripotent
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Figure from: Hole’s Human A&P, 12th edition, 2010
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Cancer
Two types of tumors• benign – usually remains localized• malignant – invasive and can metastasize; cancerous
Genes that cause cancer• oncogenes – activate other genes that increase cell division• tumor suppressor genes – normally regulate mitosis; if inactivated they will not regulate mitosis
Oncology is the study of tumors
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Cancer is a Genetic Disorder
Figure from: Hole’s Human A&P, 12th edition, 2010
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Cancer
Cancers are due to:
Figure from: Hole’s Human A&P, 12th edition, 2010
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Cancer
Metastasis is the spread of a cancer from its site of origin to other areas of the body
Figure from: Hole’s Human A&P, 12th edition, 2010
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Movements Into and Out of the Cell
Passive (Physical) Processes• require no cellular energy• simple diffusion• facilitated diffusion• osmosis
Active (Physiological) Processes• require cellular energy• active transport• endocytosis• exocytosis• transcytosis
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Solutes will evenly disperse in a solvent with time by diffusion. This is the lowest energy state.
Simple Diffusion
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Simple Diffusion
• movement of substances from regions of higher concentration to regions of lower concentration (a physical process)
Figure from: Hole’s Human A&P, 12th edition, 2010
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Where Would You Rather Be?
“Spread out, would ya!?”
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Facilitated Diffusion
• diffusion across a membrane with the help of a channel or carrier molecule• e.g, transport of glucose across cell membrane
BUT…still from a region of higher concentration to a region of lower concentration
Figure from: Hole’s Human A&P, 12th edition, 2010
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Factors Influencing Diffusion Rates
• Distance (shorter is faster)
• Gradient size (bigger difference in concentration is faster)
• Molecule size (smaller is faster)
• Temperature (warmer is faster)
• Electrical forces (repulsion is better)
In the body, diffusion distances are typically limited to a maximum of about 125 µm
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Diffusion and the Cell Membrane
oxygen, carbon dioxide and other lipid-soluble substances diffuse freely through the membrane
Carrier/channel proteins required for all but fat-soluble molecules and small uncharged molecules
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Osmosis (Special case of passive diffusion)
• movement of water (solvent) through a selectively permeable membrane from regions of higher water concentration to regions of lower water concentration• *water moves toward a higher concentration of solutes
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Osmotic Pressure/Tonicity
Osmotic Pressure (Osmolarity) – ability of solute to generate enough pressure to move a volume of water by osmosis
*Osmotic pressure increases as the number of nonpermeable solutes particles increases
• isotonic – same osmotic pressure as a second solution
• hypertonic – higher osmotic pressure
• hypOtonic – lower osmotic pressure
0.9% NaCl5.0% Glucose
Crenation
The O in
hypotonic
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Filtration
• smaller molecules are forced through porous membranes• hydrostatic pressure important in the body• molecules leaving blood capillaries
Think ‘sprinkler hose’
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Active Transport
• carrier molecules transport substances across a membrane from regions of lower concentration to regions of higher concentration, i.e., against a concentration gradient
• sugars, amino acids, sodium ions, potassium ions, etc.
Active transport is a physiological process since it requires cellular energy
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Endocytosis and Exocytosis• cell engulfs a substance by forming a vesicle around the substance• three types
• pinocytosis – substance is mostly water• phagocytosis – substance is a solid• receptor-mediated endocytosis – requires the substance to bind to a membrane-bound receptor
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• The cell is– The structural and functional unit of all living matter– Smallest body structure that can perform the functions of
‘life’
• Cells must specialize and differentiate, e.g., neurons (nerve cells) and muscle cells
• All eukaryotic cells have several major components in common– Nucleus– Cell membrane– Cytosol– Organelles– Inclusions
Lecture Review
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Lecture Review
TRANSPORTPROCESS
ISENERGYNEEDED?
CONCEN-TRATIONGRADIENT
GENERALDESCRIPTION
EXAMPLEIN HUMANS
SIGNIFICANCE
SIMPLEDIFFUSION
NO [HIGH]TO[LOW]
spreading out of molecules to equilibrium
O2 into cells; CO2
out of cells.
Cellular Respiration
FACILITATED DIFFUSION
NO [HIGH]TO[LOW]
Using a special cm carrier protein to move something through the cell membrane (cm)
Process by which glucose enters cells
OSMOSIS NO [HIGH]TO[LOW]
water moving through the cm to dilute a solute
maintenance of osmotic pressure of 0.9%.
Same
FILTRATION NO [HIGH]TO[LOW]
using pressure to push something through a cm (sprinkler hose)
manner in which the kidney filters things from blood
removal of metabolic wastes
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Lecture Review
TRANSPORTPROCESS
ISENERGYNEEDED?
CONCEN-TRATIONGRADIENT
GENERALDESCRIPTION
EXAMPLEIN HUMANS
SIGNIFICANCE
ACTIVE TRANSPORT
YES [LOW]TO[HIGH]
opposite of diffusion at the expense of energy
K+-Na+-ATPase pump
maintenance of the resting membrane potential
ENDOCYTOSIS YES [LOW]TO[HIGH]
bringing a substance into the cell that is too large to enter by any of the above ways;
Phagocytosi: cell eating;
Pinocytosis: cell drinking.
Phagocytosed (foreign) particles fuse with lysosomes to be destroyed
help fight infection
EXOCYTOSIS YES [LOW]TO[HIGH]
expelling a substance from the cell into ECF
Exporting proteins; dumping waste
Same