Week # 8 Lecture – pp 15-128

1. Lecture Presentations for Integrated Biology and Skills for Success in ScienceBanks, Montoya, Johns, & Eveslage Week # 8 Lecture – pp 15-128

2. Cells and Their Membranes • By the end of the lecture today, students will be able to: • State the cell theory • Define cell biology • Describe the different classes of cells in the human body • Describe the functions of the plasma membrane • Describe the components of the plasma membrane and explain the role of each component, including lipids and proteins • Differentiate between microvilli, cilia and flagellum

3. Modern Cell Theory • All organisms are composed of cells and cell products • Cell is the simplest structural and functional unit of life • cells are alive • An organism’s structure and functions are due to the activities of its cells • Cells come only from preexisting cells, not from nonliving matter • therefore, all life traces its ancestry to the same original cells • Cells of all species have many fundamental similarities in their chemical composition and metabolic mechanisms • Cell biology  study of cells (i.e., their morphology, physiological properties, organelles, interactions with the environment, life cycles, division and death)

4. http://www.youtube.com/watch?v=4OpBylwH9DU

5. Cell Shapes • about 200 types of cells in the human body • Squamous - thin and flat with nucleus creating bulge • Polygonal - irregularly angular shapes with 4 or more sides • Stellate – starlike shape • Cuboidal – squarish and about as tall as they are wide • Columnar - taller than wide • Spheroid to Ovoid – round to oval • Discoid - disc-shaped • Fusiform - thick in middle, tapered toward the ends • Fibrous – threadlike shape • Note: some of these shapes are cell appearance in tissue sections, but not their 3 dimensional shape

6. Cell Shapes Squamous Cuboidal Columnar Polygonal Stellate Spheroid Discoid Fusiform (spindle-shaped) Fibrous

7. Two Classes of cells in the Human Body • Sex cells, also known as germ cells or reproductive cells, are either sperm cells of males or oocyte cells of females. • Somatic cells are the cells that make up everything else in the body.

8. Cell Size • Human cell size • most from 10 - 15 micrometers (µm) in diameter • egg cells (very large)100 µm diameter • barely visible to the naked eye • nerve cell at 1 meter long • longest human cell • too slender to be seen with naked eye • Limitations on cell size • cell growth increases volume more than surface area • surfaceareaof a cell is proportional to the square of its diameter • volume of a cell is proportional to the cube of its diameter • nutrient absorption and waste removal utilize surface area • if cell becomes too large, may rupture like overfilled water balloon • http://projects.cbe.ab.ca/ict/udlsci/udlscience/biology/cells/saVol/notes/saVol.htm

9. Major Constituents of Cell • plasma (cell) membrane • surrounds cell • made of proteins and lipids • composition and function can vary from oneregion of the cell to another • cytoplasm • organelles • cytoskeleton • cytosol (intracellularfluid - ICF) • extracellular fluid – ECF • fluid outside of cell Apical cell surface Microfilaments Microvillus Terminal web Desmosome Secretory vesicle undergoing Fat droplet exocytosis Secretory vesicle Intercellular space Golgi vesicles Centrosome Centrioles Golgi complex Lateral cell surface Free ribosomes Intermediate filament Lysosome Nucleus Nucleolus Microtubule Nuclear envelope Rough endoplasmic reticulum Smooth endoplasmicreticulum Mitochondrion Plasma membranes Hemidesmosome Basement membrane Basal cell surface

10. Plasma Membrane unit membrane – forms the border of the cell and many of its organelles -appears as a pair of dark parallel lines around cell (viewed with the electron microscope) plasma membrane – unit membrane at cell surface -defines cell boundaries -governs interactions with other cells -controls passage of materials in and out of cell -intracellular face – side that faces cytoplasm -extracellular face – side that faces outward . Plasma membrane of upper cell Intercellular space Plasma membrane of lower cell Nuclear envelope Nucleus ( a ) 100 nm .

11. Membrane Lipids • 98% of molecules in plasma membrane are lipids • Phospholipids • 75% of membrane lipids are phospholipids • amphiphilic molecules arranged in a bilayer • hydrophilic phosphate heads face water on each side of membrane • hydrophobic tails – directed toward the center, avoiding water • drift laterally from place to place • movement keeps membrane fluid

12. Plasma Membrane Extracellular fluid Peripheral protein Glycolipid Glycoprotein Carbohydrate chains Extracellular face of membrane • Oily film of lipids with diverse proteins embedded Phospholipid bilayer Channel Peripheral protein Intracellular face of membrane Cholesterol Transmembrane protein Proteins of cytoskeleton Intracellular fluid (b)

13. Membrane Protein Functions • receptors, second-messenger systems, enzymes, ion channels, carriers, cell-identity markers, cell-adhesion molecules . Breakdown products Chemical messenger Ions CAM of another cell (c) Ion Channel A channel protein that is constantly open and allows ions to pass into and out of the cell (a) Receptor A receptor that binds to chemical messengers such as hormones sent by other cells (b) Enzyme An enzyme that breaks down a chemical messenger and terminates its effect (d) Gated ion channel A gated channel that opens and closes to allow ions through only at certain times (e) Cell-identity marker A glycoprotein acting as a cell- identity marker distinguishing the body’s own cells from foreign cells (f) Cell-adhesion molecule (CAM) A cell-adhesion molecule (CAM) that binds one cell to another

14. http://www.youtube.com/watch?v=y31DlJ6uGgE

15. Microvilli • Extensions of membrane (1-2 m) • serves to increase cell’s surface area • best developed in cells specialized in absorption • gives 15 – 40 times more absorptive surface area • on some cells they are very dense and appear as a fringe – “brush border” • milking action of actin • actin filaments shorten microvilli • pushing absorbed contents down into cell

16. Microvilli . Glycocalyx Microvillus Actin microfilaments (a) (b) 1 . 0 µm 0 . 1 µm . Actin microfilaments are found in center of each microvilli.

17. Cilia • Hairlike processes 7-10m long • single, nonmotile primary cilium found on nearly every cell • “antenna’ for monitoring nearby conditions • sensory in inner ear, retina, nasal cavity, and kidney • Motile cilia – respiratory tract, uterine tubes, ventricles of the brain, efferent ductules of testes • beat in waves • sweep substances across surface in same direction • power strokes followed by recovery strokes . Mucus Saline layer Epithelial cells 1 2 3 4 5 6 7 Power stroke Recovery stroke (a) (b)

18. Structure of Cilia . Cilia (a) 10 m .

19. Flagella • tail of the sperm - only functional flagellum • whiplike structure with axoneme identical to cilium • much longer than cilium • stiffened by coarse fibers that supports the tail • movement is more undulating, snakelike • no power stroke or recovery stroke as in cilia

20. Exit Quiz • 1). Name the three fundamental parts of the cell theory and identify who introduced each of these parts to the scientific community. • 2). Why are the majority of cells observed to be so small? • 3). What are the major components to a cell? What are the primary functions of each of these components? • 4). What are the seven major functions of proteins in a cell membrane? • 5). What are the fundamental differences between cilia and flagella?