© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              © 2005 Pearson Education, Inc., publishing as Benjamin Cummings   Nucleus Most bacteria Measurements 1 centimeter (cm) = 102 meter (m) = 0.4 inch 1 millimeter (mm) = 10–3 m 1 micrometer (µm) = 10–3 mm = 106 m 1 nanometer (nm) = 10–3 µm = 10 9 m 10 m 1 m 0.1 m 1 cm 1 mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm 0.1 nm Human height Length of some nerve and muscle cells Chicken egg Frog egg Most plant and animal cells Mitochondrion Smallest bacteria Viruses Ribosomes Proteins Lipids Small molecules Atoms Unaided eye Light microscope Electron microscope nucleus Chapter 6: A Tour of the Cell What is a cell? Simplest collection of matter that can live How can researchers study cells? Microscopes (Appendix C) Light microscope Electron microscope Scanning EM – surface details of cells Transmission EM – internal structures

Differential centrifugation                                              Chapter 6: A Tour of the Cell What is a cell? Simplest collection of matter that can live 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 Tissue cells Homogenization Homogenate 1000 g (1000 times the force of gravity) 10 min Differential centrifugation Supernatant poured into next tube 20,000 g 20 min Pellet rich in nuclei and cellular debris mitochondria (and chloro- plasts if cells are from a plant) “microsomes” (pieces of plasma mem- branes and cells’ internal membranes) ribosomes 150,000 g 3 hr 80,000 g 60 min   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell What is a cell? How can researchers study cells? 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 Flagella: locomotion organelles of some bacteria (a) A typical rod-shaped bacterium (b) A thin section through the bacterium Bacillus coagulans (TEM) 0.5 µm   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Chapter 6: A Tour of the Cell What is a cell? How can researchers study cells? 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

Intermediate filaments Figure 6.9 Animal Cell ENDOPLASMIC RETICULUM (ER) Rough ER Smooth ER Centrosome CYTOSKELETON Microfilaments Microtubules Microvilli Peroxisome Mitochondrion Lysosome Golgi apparatus Ribosomes Plasma membrane In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm) Nuclear envelope Nucleolus Chromatin NUCLEUS Flagellum Intermediate filaments

Ribosomes ( small brown dots ) Figure 6.9 Plant Cell Ribosomes ( small brown dots ) Central vacuole Microfilaments Intermediate filaments Microtubules Rough endoplasmic reticulum Smooth Chromatin NUCLEUS Centrosome Nuclear envelope Nucleolus Chloroplast Plasmodesmata Wall of adjacent cell Cell wall Plasma membrane Mitochondrion Golgi apparatus Peroxisome In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Tonoplast CYTOSKELETON

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell 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)   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 6.10 The nucleus and its 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. Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Rough ER Pore complex Surface of nuclear envelope. TEM of a specimen prepared by a special technique known as freeze-fracture. Close-up of nuclear envelope Ribosome 1 µm 0.25 µm

TEM showing ER and ribosomes                                              Chapter 6: A Tour of the Cell 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 Small TEM showing ER and ribosomes Diagram of a ribosome 0.5 µm   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell 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, vacuoles, plasma membrane What is the role of the smooth ER? Make lipids (oils, phospholipids, & steroids) Metabolism of carbs Detoxification of drugs & poisons Ca+2 ion storage What is the role of the rough ER? Studded with ribosomes Makes secreted proteins, membranes & glycoproteins Smooth ER Rough ER ER lumen Cisternae Ribosomes Transport vesicle Transitional ER 200 µm Nuclear envelope   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell 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   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 6.13 The Golgi apparatus cis face (“receiving” side of Golgi apparatus) Vesicles move from ER to Golgi Vesicles also transport certain proteins back to ER Vesicles coalesce to form new cis Golgi cisternae Cisternal maturation: Golgi cisternae move in a cis- to-trans direction Vesicles form and leave Golgi, carrying specific proteins to other locations or to the plasma mem- brane for secretion Vesicles transport specific proteins backward to newer Cisternae trans face (“shipping” side of TEM of Golgi apparatus 0.1 0 µm 1 6 5 2 3 4

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell 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? What do lysosomes do? Digestion & recycling at pH 5 Hydrolytic enzymes break bonds of all macromolecules   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 6.14 Lysosomes 1 µm Nucleus Lysosome containing Lysosome contains active hydrolytic enzymes Food vacuole fuses with lysosome Hydrolytic enzymes digest food particles Lysosome containing two damaged organelles 1 µ m Mitochondrion fragment Peroxisome Lysosome fuses with vesicle containing damaged organelle Hydrolytic enzymes digest organelle components Vesicle containing damaged mitochondrion Digestion Food vacuole Plasma membrane Digestive (a) Phagocytosis: lysosome digesting food (b) Autophagy: lysosome breaking down damaged organelle

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell 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? What do lysosomes do? 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……   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 6.16 Review: relationships among organelles of the endomembrane system Nuclear envelope is connected to rough ER, which is also continuous with smooth ER 1 Nucleus Rough ER Smooth ER Nuclear envelope 3

Figure 6.16 Review: relationships among organelles of the endomembrane system Golgi pinches off transport vesicles and other vesicles that give rise to lysosomes and vacuoles Membranes and proteins produced by the ER flow in the form of transport vesicles to the Golgi 3 4 5 Nuclear envelope Nuclear envelope is connected to rough ER, which is also continuous with smooth ER 2 Nucleus Rough ER Smooth ER cis Golgi trans Golgi Lysosome available for fusion with another vesicle for digestion Transport vesicle carries proteins to plasma membrane for secretion Transport vesicle 1

Figure 6.16 Review: relationships among organelles of the endomembrane system Plasma membrane expands by fusion of vesicles; proteins are secreted from cell Golgi pinches off transport vesicles and other vesicles that give rise to lysosomes and vacuoles Membranes and proteins produced by the ER flow in the form of transport vesicles to the Golgi 3 4 5 6 Nuclear envelope Nuclear envelope is connected to rough ER, which is also continuous with smooth ER 2 Nucleus Rough ER Smooth ER cis Golgi trans Golgi Plasma membrane Lysosome available for fusion with another vesicle for digestion Transport vesicle carries proteins to plasma membrane for secretion Transport vesicle 1

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell 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? What do lysosomes do? What do vacuoles do? 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   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 6.17 The mitochondrion, site of cellular respiration Intermembrane space Outer membrane Free ribosomes in the mitochondrial matrix Mitochondrial DNA Inner Cristae Matrix 100 µm

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell 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? What do lysosomes do? What do vacuoles do? What is the role of a mitochondria? 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   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 6.18 The chloroplast, site of photosynthesis Granum Chloroplast DNA Ribosomes Stroma Inner and outer membranes Thylakoid 1 µm

Absent

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell 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? What do lysosomes do? What do vacuoles do? What is the role of a mitochondria? What do chloroplasts do? What about peroxisomes? Enzymes that transfer hydrogen to oxygen forming peroxide Beta oxidation of fatty acids for energy Detoxifying alcohol in liver How does the cell keep its shape? Cytoskeleton made of Microtubules Microfilaments Intermediate filaments Role – support, motility & regulation   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Table 6.1 The Structure and Function of the Cytoskeleton

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell 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? What do lysosomes do? What do vacuoles do? What is the role of a mitochondria? What do chloroplasts do? What about peroxisomes? How does the cell keep its shape? 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   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 6.29 Extracellular matrix (ECM) of an animal cell A proteoglycan complex consists of hundreds of proteoglycan molecules attached noncovalently to a single long polysac- charide molecule. Collagen fibers are embedded in a web of complexes. Fibronectin attaches the ECM to integrins embedded in the plasma membrane. Plasma membrane EXTRACELLULAR FLUID Micro- filaments 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 Carbo- hydrates Proteoglycan Core protein Integrin

© 2005 Pearson Education, Inc., publishing as Benjamin Cummings                                              Chapter 6: A Tour of the Cell 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? What do lysosomes do? What do vacuoles do? What is the role of a mitochondria? What do chloroplasts do? What about peroxisomes? How does the cell keep its shape? What important structures lie outside of the cell? 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   © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

Figure 6.31 Exploring Intercellular Junctions in Animal Tissues Tight junctions prevent fluid from moving across a layer of cells Tight junction 0.5 µm 1 µm Space between cells Plasma membranes of adjacent cells Extracellular matrix Gap junction Tight junctions 0.1 µm Intermediate filaments Desmosome Gap junctions At tight junctions, the membranes of neighboring cells are very tightly pressed against each other, bound together by specific proteins (purple). Forming continu- ous seals around the cells, tight junctions prevent leakage of extracellular fluid across a layer of epithelial cells. 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. 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 commu- nication between cells in many types of tissues, including heart muscle and animal embryos. TIGHT JUNCTIONS DESMOSOMES GAP JUNCTIONS