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Chapter 6: A Tour of the Cell 10 m Human height 1m Length of some nerve and muscle cells Unaided eye 0.1 m Chicken egg 1 cm Frog egg 1 mm Most plant and animal cells 10 µm 1 µm 100 nm nucleus Nucleus Most bacteria Most bacteria Mitochondrion Smallest bacteria Viruses Ribosomes 10 nm Measurements 1 centimeter (cm) = 102 meter (m) = 0.4 inch 1 nm 1 millimeter (mm) = 10–3 m 1 micrometer (µm) = 10–3 mm = 106 m 1 nanometer (nm) = 10–3 µm = 10 9 m 0.1 nm Proteins Lipids Small molecules Atoms Electron microscope 100 µm Light microscope 1. What is a cell? - Simplest collection of matter that can live 2. How can researchers study cells? - Microscopes (Appendix C) - Light microscope - Electron microscope - Scanning EM – surface details of cells - Transmission EM – internal structures Chapter 6: A Tour of the Cell 1. What is a cell? - Simplest collection of matter that can live 2. How can researchers study cells? - Microscopes (Appendix C) - Cell fractionation - Used to isolate cellular components based on size & density - Cells are homogenized - Organelles separated by differential centrifugation Homogenization Tissue cells 1000 g Homogenate (1000 times the force of gravity) Differential centrifugation 10 min Supernatant poured into next tube 20,000 g 20 min Pellet rich in nuclei and cellular debris 80,000 g 60 min 150,000 g 3 hr Pellet rich in mitochondria (and chloroplasts if cells are from a Pellet rich in plant) “microsomes” (pieces of plasma membranes and Pellet rich in cells’ internal ribosomes membranes) Chapter 6: A Tour of the Cell 1. What is a cell? 2. How can researchers study cells? 3. What is the difference between prokaryotic & eukaryotic cells? - Prokaryotic - No true nucleus or other membrane-bound organelles - Bacteria & Archaebacteria Pili: attachment structures on the surface of some prokaryotes Nucleoid: region where the cell’s DNA is located (not enclosed by a membrane) Ribosomes: organelles that synthesize proteins Plasma membrane: membrane enclosing the cytoplasm Cell wall: rigid structure outside the plasma membrane Capsule: jelly-like outer coating of many prokaryotes 0.5 µm (a) A typical rod-shaped bacterium Flagella: locomotion organelles of some bacteria (b) A thin section through the bacterium Bacillus coagulans (TEM) Chapter 6: A Tour of the Cell 1. What is a cell? 2. How can researchers study cells? 3. What is the difference between prokaryotic & eukaryotic cells? - Prokaryotic - No true nucleus or other membrane-bound organelles - Bacteria & Archaebacteria - Eukaryotic - Nucleus & other membrane-bound organelles are present - Plants, animals, fungi, protists Figure 6.9 Animal Cell ENDOPLASMIC RETICULUM (ER) Rough ER Smooth ER Nuclear envelope Nucleolus NUCLEUS Chromatin Flagellum Plasma membrane Centrosome CYTOSKELETON Microfilaments Intermediate filaments Ribosomes Microtubules Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm) Figure 6.9 Plant Cell Nuclear envelope Nucleolus Chromatin NUCLEUS Centrosome Rough endoplasmic reticulum Smooth endoplasmic reticulum Ribosomes ( small brown dots ) Central vacuole Tonoplast Golgi apparatus Microfilaments Intermediate filaments CYTOSKELETON Microtubules Mitochondrion Peroxisome Plasma membrane Chloroplast Cell wall Plasmodesmata Wall of adjacent cell In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Cell wall Plasmodesmata Chapter 6: A Tour of the Cell 1. 2. 3. 4. What is a cell? How can researchers study cells? What is the difference between prokaryotic & eukaryotic cells? What is the role of the nucleus? - Houses most of the genes on chromosomes made of chromatin - Chromatin = DNA wrapped around proteins - Surrounded by nuclear envelope - Double membrane lined with pores - Pore complexes regulate movement of RNA & proteins into & out of nucleus - Nuclear lamina – inner lining of nuclear envelope used for support - Nucleolus - Site of ribosome production - rRNA + imported ribosomal proteins (through pore complexes) Figure 6.10 The nucleus and its envelope Nucleus Nucleus 1 µm Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Rough ER Surface of nuclear envelope. TEM of a specimen prepared by a special technique known as freeze-fracture. 0.25 µm Ribosome 1 µm Close-up of nuclear envelope Pore complexes (TEM). Each pore is ringed by protein particles. Nuclear lamina (TEM). The netlike lamina lines the inner surface of the nuclear envelope. Chapter 6: A Tour of the Cell 1. 2. 3. 4. 5. What is a cell? How can researchers study cells? What is the difference between prokaryotic & eukaryotic cells? What is the role of the nucleus? What is the role of the ribosome? - Protein synthesis (aka…translation) - Made in nucleolus - Large & small subunit - Free ribosomes in cytosol - Bound ribosomes on rough ER or nucleus Ribosomes ER Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit 0.5 µm Small subunit TEM showing ER and ribosomes Diagram of a ribosome Chapter 6: A Tour of the Cell 1. 2. 3. 4. 5. 6. What is a cell? How can researchers study cells? What is the difference between prokaryotic & eukaryotic cells? What is the role of the nucleus? What is the role of the ribosome? What is the endomembrane system & who are its members? - Collection of membranes inside a eukaryotic cell related through direct contact or by transfer vesicles - Nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, Smooth ER vacuoles, plasma membrane Nuclear Rough ER 7. What is the role of the smooth ER? envelope - Make lipids (oils, phospholipids, & steroids) - Metabolism of carbs - Detoxification of drugs & poisons ER lumen - Ca+2 ion storage Cisternae 8. What is the role of the rough ER? Ribosomes Transitional ER - Studded with ribosomes Transport vesicle - Makes secreted proteins, membranes & Smooth ER Rough ER 200 µm glycoproteins Chapter 6: A Tour of the Cell 1. 2. 3. 4. 5. 6. 7. 8. 9. What is a cell? How can researchers study cells? What is the difference between prokaryotic & eukaryotic cells? What is the role of the nucleus? What is the role of the ribosome? What is the endomembrane system & who are its members? What is the role of the smooth ER? What is the role of the rough ER? What is the role of the Golgi apparatus? - Center of manufacturing, warehousing, sorting & shipping - ER products get modified & sent along - Membrane phospholipids - Sugars of glycoproteins - Targets proteins for other organelles - Sorts products for secretion Figure 6.13 The Golgi apparatus Golgi apparatus cis face (“receiving” side of Golgi apparatus) 1 Vesicles move 2 Vesicles coalesce to 6 Vesicles also from ER to Golgi form new cis Golgi cisternae transport certain Cisternae proteins back to ER 3 Cisternal maturation: Golgi cisternae move in a cisto-trans direction 5 Vesicles transport specific proteins backward to newer Golgi cisternae 0.1 0 µm 4 Vesicles form and leave Golgi, carrying specific proteins to other locations or to the plasma membrane for secretion trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus Chapter 6: A Tour of the Cell 1. What is a cell? 2. How can researchers study cells? 3. What is the difference between prokaryotic & eukaryotic cells? 4. What is the role of the nucleus? 5. What is the role of the ribosome? 6. What is the endomembrane system & who are its members? 7. What is the role of the smooth ER? 8. What is the role of the rough ER? 9. What is the role of the Golgi apparatus? 10. What do lysosomes do? - Digestion & recycling at pH 5 - Hydrolytic enzymes break bonds of all macromolecules Figure 6.14 Lysosomes Nucleus 1 µm Lysosome containing two damaged organelles 1µm Mitochondrion fragment Peroxisome fragment Lysosome Lysosome contains Food vacuole fuses Hydrolytic active hydrolytic enzymes digest with lysosome enzymes food particles Digestive enzymes Lysosome fuses with vesicle containing damaged organelle Lysosome Plasma membrane Lysosome Lysosome Hydrolytic enzymes digest organelle components Digestion Food vacuole (a) Phagocytosis: lysosome digesting food Digestion Vesicle containing damaged mitochondrion (b) Autophagy: lysosome breaking down damaged organelle Chapter 6: A Tour of the Cell 1. What is a cell? 2. How can researchers study cells? 3. What is the difference between prokaryotic & eukaryotic cells? 4. What is the role of the nucleus? 5. What is the role of the ribosome? 6. What is the endomembrane system & who are its members? 7. What is the role of the smooth ER? 8. What is the role of the rough ER? 9. What is the role of the Golgi apparatus? 10. What do lysosomes do? 11. What do vacuoles do? - Food vacuoles – lysosomes - Contractile vacuoles – FW protists use these to pump out excess water - Central vacuole – reserve of many different substances or ions for plants - Let’s review the endomembrane system…… Figure 6.16 Review: relationships among organelles of the endomembrane system 1 Nuclear envelope is connected to rough ER, which is also continuous with smooth ER Nucleus Rough ER Smooth ER Nuclear envelope 3 Figure 6.16 Review: relationships among organelles of the endomembrane system 1 Nuclear envelope is connected to rough ER, which is also continuous with smooth ER Nucleus Rough ER 2 Membranes and proteins produced by the ER flow in the form of transport vesicles to the Golgi Smooth ER cis Golgi Nuclear envelope Transport vesicle 3 Golgi pinches off transport vesicles and other vesicles that give rise to lysosomes and vacuoles trans Golgi 4 Lysosome available 5 Transport vesicle carries for fusion with another proteins to plasma vesicle for digestion membrane for secretion Figure 6.16 Review: relationships among organelles of the endomembrane system 1 Nuclear envelope is connected to rough ER, which is also continuous with smooth ER Nucleus Rough ER 2 Membranes and proteins produced by the ER flow in the form of transport vesicles to the Golgi Smooth ER cis Golgi Nuclear envelope Transport vesicle 3 Golgi pinches off transport vesicles and other vesicles that give rise to lysosomes and vacuoles trans Golgi Plasma membrane 4 Lysosome available 5 Transport vesicle carries 6 Plasma membrane expands for fusion with another proteins to plasma by fusion of vesicles; proteins vesicle for digestion membrane for secretion are secreted from cell Chapter 6: A Tour of the Cell 1. What is a cell? 2. How can researchers study cells? 3. What is the difference between prokaryotic & eukaryotic cells? 4. What is the role of the nucleus? 5. What is the role of the ribosome? 6. What is the endomembrane system & who are its members? 7. What is the role of the smooth ER? 8. What is the role of the rough ER? 9. What is the role of the Golgi apparatus? 10. What do lysosomes do? 11. What do vacuoles do? 12. What is the role of a mitochondria? - Site of cellular respiration - Double membrane (inner & outer) & mitochondrial matrix - Has DNA & ribosomes & can reproduce on their own Figure 6.17 The mitochondrion, site of cellular respiration Mitochondrion Intermembrane space Outer membrane Free ribosomes in the mitochondrial matrix Inner membrane Cristae Matrix Mitochondrial DNA 100 µm Chapter 6: A Tour of the Cell 1. What is a cell? 2. How can researchers study cells? 3. What is the difference between prokaryotic & eukaryotic cells? 4. What is the role of the nucleus? 5. What is the role of the ribosome? 6. What is the endomembrane system & who are its members? 7. What is the role of the smooth ER? 8. What is the role of the rough ER? 9. What is the role of the Golgi apparatus? 10. What do lysosomes do? 11. What do vacuoles do? 12. What is the role of a mitochondria? 13. What do chloroplasts do? - Photosynthesis for plant energy transformations - Double membrane (inner & outer) & stroma - Has DNA & ribosomes & can reproduce on their own - Thylakoids have chlorophyll & harness light energy Figure 6.18 The chloroplast, site of photosynthesis Chloroplast Ribosomes Stroma Chloroplast DNA Inner and outer membranes Granum 1 µm Thylakoid Absent Chapter 6: A Tour of the Cell 1. What is a cell? 2. How can researchers study cells? 3. What is the difference between prokaryotic & eukaryotic cells? 4. What is the role of the nucleus? 5. What is the role of the ribosome? 6. What is the endomembrane system & who are its members? 7. What is the role of the smooth ER? 8. What is the role of the rough ER? 9. What is the role of the Golgi apparatus? 10. What do lysosomes do? 11. What do vacuoles do? 12. What is the role of a mitochondria? 13. What do chloroplasts do? 14. What about peroxisomes? - Enzymes that transfer hydrogen to oxygen forming peroxide - Beta oxidation of fatty acids for energy - Detoxifying alcohol in liver 15. How does the cell keep its shape? - Cytoskeleton made of - Microtubules - Microfilaments - Intermediate filaments - Role – support, motility & regulation Table 6.1 The Structure and Function of the Cytoskeleton Chapter 6: A Tour of the Cell 1. What is a cell? 2. How can researchers study cells? 3. What is the difference between prokaryotic & eukaryotic cells? 4. What is the role of the nucleus? 5. What is the role of the ribosome? 6. What is the endomembrane system & who are its members? 7. What is the role of the smooth ER? 8. What is the role of the rough ER? 9. What is the role of the Golgi apparatus? 10. What do lysosomes do? 11. What do vacuoles do? 12. What is the role of a mitochondria? 13. What do chloroplasts do? 14. What about peroxisomes? 15. How does the cell keep its shape? 16. What important structures lie outside of the cell? - Plants – primary cell wall (initially thin & flexible) & secondary cell wall in mature cells - Animals – Extra cellular matrix (ECM) – glycoproteins from cell - Collagen embedded in proteoglycans - Fibronectin & integrins Figure 6.29 Extracellular matrix (ECM) of an animal cell Collagen fibers are embedded in a web of proteoglycan complexes. A proteoglycan complex consists of hundreds of proteoglycan molecules attached noncovalently to a single long polysaccharide molecule. EXTRACELLULAR FLUID Fibronectin attaches the ECM to integrins embedded in the plasma membrane. Plasma membrane Integrin Microfilaments CYTOPLASM Integrins are membrane proteins that are bound to the ECM on one side and to associated proteins attached to microfilaments on the other. This linkage can transmit stimuli between the cell’s external environment and its interior and can result in changes in cell behavior. Polysaccharide molecule Carbohydrates Core protein Proteoglycan molecule Chapter 6: A Tour of the Cell 1. What is a cell? 2. How can researchers study cells? 3. What is the difference between prokaryotic & eukaryotic cells? 4. What is the role of the nucleus? 5. What is the role of the ribosome? 6. What is the endomembrane system & who are its members? 7. What is the role of the smooth ER? 8. What is the role of the rough ER? 9. What is the role of the Golgi apparatus? 10. What do lysosomes do? 11. What do vacuoles do? 12. What is the role of a mitochondria? 13. What do chloroplasts do? 14. What about peroxisomes? 15. How does the cell keep its shape? 16. What important structures lie outside of the cell? 17. How are neighboring cells connected? - Plants – plasmodesmata – openings in cell walls that cytosol can pass through - Animals - Tight junctions – membranes of neighboring cells bound by specific proteins - Desmosomes – function like rivets fastening cells together into strong sheets - Gap junctions – cytoplasmic channels between cells Figure 6.31 Exploring Intercellular Junctions in Animal Tissues TIGHT JUNCTIONS At tight junctions, the membranes of neighboring cells are very tightly pressed against each other, bound together by specific proteins (purple). Forming continuous seals around the cells, tight junctions prevent leakage of extracellular fluid across a layer of epithelial cells. Tight junction Tight junctions prevent fluid from moving across a layer of cells 0.5 µm DESMOSOMES Desmosomes (also called anchoring junctions) function like rivets, fastening cells together into strong sheets. Intermediate filaments made of sturdy keratin proteins anchor desmosomes in the cytoplasm. Tight junctions Intermediate filaments Desmosome Gap junctions Space between Plasma membranes cells of adjacent cells 1 µm Extracellular matrix Gap junction 0.1 µm GAP JUNCTIONS Gap junctions (also called communicating junctions) provide cytoplasmic channels from one cell to an adjacent cell. Gap junctions consist of special membrane proteins that surround a pore through which ions, sugars, amino acids, and other small molecules may pass. Gap junctions are necessary for communication between cells in many types of tissues, including heart muscle and animal embryos.