Visual Anatomy & Physiology First Edition Martini & Ober Chapter 3 Cellular Level of Organization Lecture 5 Slides 1-15; 80 min (with review of syllabus and Web sites) [Lecture 1] Slides 16 – 38; 50 min [Lecture 2] 118 min (38 slides plus review of course Web sites and syllabus)

Lecture Overview 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

Cells Are Specialized vary in size vary in shape vary in function measured in micrometers

A Composite Cell hypothetical cell major parts nucleus cytoplasm cell membrane

Cell Membrane outer limit of cell; isolates cell controls what moves in and out of cell - selectively permeable self-sealing 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

Cell Membranes

A Transmembrane Protein Hydrophilic channel Membrane Lipids

Cellular Organelles Table 1 of 2 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 SMOOTH ER Membranous network lacking ribosomes lipid & cholesterol synthesis GOLGI “Stack of Pancakes”; cisternae modification, transport, and packaging of proteins

Cellular Organelles Table 2 of 2 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

Cell Death Two mechanisms of cell death Necrosis Programmed cell death (PCD or apoptosis) 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

Necrosis vs. Apoptosis Necrosis Apoptosis Figure from: Alberts et al., Essential Cell Biology, Garland Press, 1998

Cellular Pathways of Apoptosis Figure from: http://www.ambion.com/tools/pathway/pathway.php?pathway=Cellular%20Apoptosis%20Pathway

Cellular Pathways of Apoptosis Figure from: http://www.ambion.com/tools/pathway/pathway.php?pathway=Cellular%20Apoptosis%20Pathway

Failure of Apoptosis - Syndactyly Photo from: http://en.wikipedia.org/wiki/Apoptosis

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

Figure from: Hole’s Human A&P, 12th edition, 2010

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

Cancer is a Genetic Disorder Figure from: Hole’s Human A&P, 12th edition, 2010

Cancer Cancers are due to: Figure from: Hole’s Human A&P, 12th edition, 2010

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

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

Simple Diffusion Solutes will evenly disperse in a solvent with time by diffusion. This is the lowest energy state.

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

Where Would You Rather Be? “Spread out, would ya!?”

Facilitated Diffusion Figure from: Hole’s Human A&P, 12th edition, 2010 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

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

Diffusion and the Cell Membrane Carrier/channel proteins required for all but fat-soluble molecules and small uncharged molecules oxygen, carbon dioxide and other lipid-soluble substances diffuse freely through the membrane

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

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% NaCl 5.0% Glucose Crenation The O in hypotonic

Filtration smaller molecules are forced through porous membranes hydrostatic pressure important in the body molecules leaving blood capillaries Think ‘sprinkler hose’

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

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

Lecture Review 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 TRANSPORT PROCESS IS ENERGY NEEDED? CONCEN- TRATION GRADIENT GENERAL DESCRIPTION EXAMPLE IN HUMANS SIGNIFICANCE SIMPLE DIFFUSION NO [HIGH] TO [LOW] spreading out of molecules to equilibrium O2 into cells; CO2 out of cells. Cellular Respiration FACILITATED DIFFUSION Using a special cm carrier protein to move something through the cell membrane (cm) Process by which glucose enters cells OSMOSIS water moving through the cm to dilute a solute maintenance of osmotic pressure of 0.9%. Same FILTRATION using pressure to push something through a cm (sprinkler hose) manner in which the kidney filters things from blood removal of metabolic wastes

Lecture Review TRANSPORT PROCESS IS ENERGY NEEDED? CONCEN- TRATION GRADIENT GENERAL DESCRIPTION EXAMPLE IN 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 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 expelling a substance from the cell into ECF Exporting proteins; dumping waste Same