1. Lecture #3Date _________ Chapter 7~ A Tour of the Cell Chapter 7~ A Tour of the Cell

2. Cell size As cell size increases, the surface area to volume ratio decreases As cell size increases, the surface area to volume ratio decreases Rates of chemical exchange may then be inadequate for cell size Rates of chemical exchange may then be inadequate for cell size Cell size, therefore, remains small Cell size, therefore, remains small

3. Nucleus The command center The command center Contains Contains Chromatin which can coil and condense into ChromosomesChromatin which can coil and condense into Chromosomes Nuclear envelope with nuclear poresNuclear envelope with nuclear pores Shape maintained by lamina Shape maintained by lamina Nucleolus: rRNA and proteins for making ribosome'sNucleolus: rRNA and proteins for making ribosome's

4. Ribosomes Protein manufacturing Protein manufacturing Can have free or bound ribosome's Can have free or bound ribosome's Free- suspended in cytosol- makes proteins to function in cytosolFree- suspended in cytosol- makes proteins to function in cytosol Bound- bound to ER or nuclear env.- makes proteins for export from cell of to function within organellesBound- bound to ER or nuclear env.- makes proteins for export from cell of to function within organelles

5. Endomembrane system, I Endoplasmic reticulum (ER) Endoplasmic reticulum (ER) Continuous with nuclear envelope Continuous with nuclear envelope Smooth ER Smooth ER no ribosome's, synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisonsno ribosome's, synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons Rough ER Rough ER with ribosomes, synthesis of secretory proteins (glycoproteins), membrane productionwith ribosomes, synthesis of secretory proteins (glycoproteins), membrane production

6. Endomembrane system, II Golgi apparatus Golgi apparatus ER products are modified, stored, and then shippedER products are modified, stored, and then shipped Cisternae: flattened membranous sacs Cisternae: flattened membranous sacs trans face (shipping) & cis face (receiving)trans face (shipping) & cis face (receiving) Transport vesicles Transport vesicles

7. Endomembrane system, III Lysosomes Lysosomes sac of hydrolytic enzymes; digestion of macromoleculessac of hydrolytic enzymes; digestion of macromolecules Phagocytosis Phagocytosis Autophagy: recycle cell’s own organic material Autophagy: recycle cell’s own organic material Tay-Sachs disease- lipid-digestion disorder Tay-Sachs disease- lipid-digestion disorder

8. Endomembrane system, IV Vacuoles Vacuoles membrane-bound sacs (larger than vesicles)membrane-bound sacs (larger than vesicles) Food (phagocytosis) Food (phagocytosis) Contractile vacuole (pump excess water- protists) Contractile vacuole (pump excess water- protists) Central (storage in plants) Central (storage in plants) tonoplast membranetonoplast membrane

9. Other membranous organelles, I Mitochondria Mitochondria quantity in cell correlated with metabolic activityquantity in cell correlated with metabolic activity cellular respirationcellular respiration double membranedouble membrane cristae/matrix cristae/matrix intermembrane space intermembrane space contain own DNAcontain own DNA

10. Organelles Chloroplast Chloroplast double membranousdouble membranous thylakoids (flattened disks)thylakoids (flattened disks) grana (stacked thylakoids grana (stacked thylakoids StromaStroma own DNAown DNA

11. Peroxisomes Single membrane Single membrane Produce hydrogen peroxide in cells Produce hydrogen peroxide in cells Metabolism of fatty acids; detoxification of alcohol (liver) Metabolism of fatty acids; detoxification of alcohol (liver) Hydrogen peroxide then converted to water through enzymes ( catalase) Hydrogen peroxide then converted to water through enzymes ( catalase)

12. The Cytoskeleton Fibrous network in cytoplasm Fibrous network in cytoplasm Types of network fibers Types of network fibers Microtubules:Microtubules: Thickest, tubulin protein Thickest, tubulin protein shape, support, and transport shape, support, and transport chromosome separation chromosome separation Microfilaments :Microfilaments : Thinnest, actin protein filaments Thinnest, actin protein filaments motility, cell division, shape motility, cell division, shape Intermediate filaments:Intermediate filaments: middle diameter- keratin middle diameter- keratin shape, nucleus anchorage shape, nucleus anchorage

13. Cell surfaces & junctions Cell wall: Cell wall: not in animal cellsnot in animal cells protection, shape, regulationprotection, shape, regulation Plant cell: Plant cell: primary cell wall produced firstprimary cell wall produced first middle lamella of pectinmiddle lamella of pectin (polysaccharide) holds cells together some plants have a secondary cell wallsome plants have a secondary cell wall

14. Extracellular matrix (ECM) Glycoproteins: proteins covalently bonded to carbohydrate Glycoproteins: proteins covalently bonded to carbohydrate Collagen (50% of proteins in human body) Collagen (50% of proteins in human body) embedded in proteoglycanembedded in proteoglycan

15. Intracellular junctions PLANTS: PLANTS: Plasmodesmata: Plasmodesmata: cell wall perforations; water and solute passage in plantscell wall perforations; water and solute passage in plants ANIMALS: ANIMALS: Tight junctions- fusion of neighboring cells; prevents leakage between cells Tight junctions- fusion of neighboring cells; prevents leakage between cells Desmosomes- riveted, anchoring junction; strong sheets of cells Desmosomes- riveted, anchoring junction; strong sheets of cells Gap junctions- cytoplasmic channels; allows passage of materials or current between cells Gap junctions- cytoplasmic channels; allows passage of materials or current between cells