1. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Chp 3 Cells

2. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Cell Theory  The cell is the basic structural and functional unit of life  Organismal activity depends on individual and collective activity of cells  Biochemical activities of cells are dictated by subcellular structure  Continuity of life has a cellular basis

3. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Cell Basics  Cells are composed of: Carbon, Hydrogen, Nitrogen, Oxygen  Basic Parts of Cells:  Plasma Membrane – barrier/boundary  Cytoplasm – intracellular fluid  Nucleus – controls cellular activities

4. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.2 Secretion being released from cell by exocytosis Peroxisome Ribosomes Rough endoplasmic reticulum Nucleus Nuclear envelope Chromatin Golgi apparatus Nucleolus Smooth endoplasmic reticulum Cytosol Lysosome Mitochondrion Centrioles Centrosome matrix Microtubule Microvilli Microfilament Intermediate filaments Plasma membrane

5. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Plasma Membrane  Separates intracellular fluids from extracellular fluids  (Boundary between internal/external environment)  Plays a dynamic role in cellular activity (refer to as plasma membrane rather than cell membrane – many organelles have a membrane)  Glycocalyx is a glycoprotein area abutting the cell that provides highly specific highly specific biological markers by which cells recognize one another  Carbohydrates form a cell coat (glycocalyx) outside the membrane – protection & cell recognition (antigens like ABO on blood cells)

6. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glycocalyx  “Sugar Coating” of cell  Sperm recognizes ovum, immune system identify a bacterium,  Changes in glycocalyx occur in a cell becoming cancerous – may change continuously, therefore ‘keeping ahead’ of the immune system

7. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fluid Mosaic Model  Thin (7-10 nm) Double bilayer of lipids with imbedded, dispersed proteins  Constantly changing mosaic pattern (due to proteins floating in bilayer)  Bilayer consists of phospholipids, cholesterol, and glycolipids  Glycolipids are lipids with bound carbohydrate  Phospholipids have hydrophobic (two fatty acid ‘tails’) and hydrophilic bipoles PLAY Membrane Structure

8. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fluid Mosaic Model  Result of Lipid Bilayer arrangement:  Sandwich-like structure like two parallel sheet, lying tail to tail  Self-orienting – membranes self-assemble into closed, spherical, structures that can reseal themselves if damaged  Majority of membrane phospholipids are unsaturated.

9. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fluid Mosaic Model Figure 3.3

10. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Functions of Membrane Proteins  Transport  Enzymatic activity  Receptors for signal transduction Figure 3.4.1 PLAY Receptor Proteins PLAY Enzymes PLAY Transport Protein http://www.biologymad.com/c ells/cellmembrane.htm

11. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Functions of Membrane Proteins  Intercellular adhesion  Cell-cell recognition  Attachment to cytoskeleton and extracellular matrix Figure 3.4.2 PLAY Structural Proteins

12. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Plasma Membrane Surfaces  Differ in the kind and amount of lipids they contain  Glycolipids (5% of total membrane lipid) are found only in the outer membrane surface  20% of all membrane lipid is cholesterol – between phospholipid tails  Decreases orderliness and increases mobility of phospholipids.

13. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipid Rafts  Make up 20% of the outer membrane surface  Composed of sphingolipids and cholesterol  Provide more stable and orderly and less fluid than the rest of the membrane  Lipid Rafts are concentrating platforms for cell- signaling molecules

14. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 2 Types of Membrane Proteins  Integral  Firmly inserted in lipid bilayer.  Some protrude from one side of membrane, most are transmembrane proteins  Mainly involved with transport – channels  Some are carriers – bind to substance and move it through membrane.  Some are receptors for hormones

15. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 2 Types of Membrane Proteins  Peripheral – not imbedded in lipid – attached to integral proteins or membrane lipids.  Easily removed – without damage to membrane  Includes network of filaments – support membrane  Some are enzymes  Some involved in mechanical functions – changing shape during cell division, muscle contraction

16. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Specialization of Plasma Membrane  Microvilli – fingerlike extensions of plasma membrane  Increase surface area and absorptive surface (intestines, kidney tubule)  Actin filaments – contractile protein – stiffens p.m.  3 factors that bind cells together  Glycoproteins (glycocalyx acts as adhesive)  Wavy contours of adjacent membranes  Special membrane junctions *Most importnat

17. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Membrane Junctions (see pics on slides)  Tight junction – impermeable junction that encircles the cell. Forms impermeable junction  Prevents molecules from passing through extracellular space, between the cells. (epithelial cells of digestive tract keep digestive enzymes and microorganisms in GI tract from seeping into blood stream  Desmosome – anchoring junction scattered along the sides of cells (like rivets)  Prevent separation of cells and reduces tear during pulling forces (skin, heart muscle)

18. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Membrane Junctions  Gap junction – a nexus that allows chemical substances to pass between cells  Connexons (hollow cylinders) connect cells – transmembrane (integral) proteins.  Many different types.  Ions, simple sugars, other small molecules pass through.

19. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Membrane Junctions: Tight Junction Figure 3.5a

20. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Membrane Junctions: Desmosome Figure 3.5b

21. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Membrane Junctions: Gap Junction Figure 3.5c

22. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Plasma Membrane Functions  Membrane Transport  Cells bathed in interstitial fluid – rich in nutrients (amino acids, sugars, fatty acids, vitamins, hormones & neurotransmitters, salts, wastes)  Selectively Permeable – allows some things into cell, keeps others out, also keeps substances in the cell but wastes can exit.  Damaged cells (burns) – ruin permeability – fluids, proteins, ions exit dead or damaged cell.