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Biochapter6notes 151125141544-lva1-app6892
- 1. Chapter 6 A Tour of the Cell
- 2. •All organisms are made of cells •The cell is the simplest collection of matter that can live •Cell structure is correlated to cellular function •All cells are related by their descent from earlier cells
- 3. Microscopy • Scientists use microscopes to visualize cells too small to see with the naked eye • In a light microscope (LM), visible light passes through a specimen and then through glass lenses, which magnify the image by refracting (bending) the light • The minimum resolution of an LM is about 200 nanometers (nm), the size of a small bacterium
- 4. Figure 6.2 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 Atoms Small molecules Lipids Proteins Ribosomes Viruses Smallest bacteria Mitochondrion Most bacteria Nucleus Most plant and animal cells Human egg Frog egg Chicken egg Length of some nerve and muscle cells Human height Unaidedeye LM EM Super- resolution microscopy •LMs can magnify effectively to about 1,000 times the size of the actual specimen
- 5. Figure 6.3 50 µm 10 µm 50µm 10µm 1µm 2 µm 2 µm Brightfield (unstained specimen) Brightfield (stained specimen) Phase-contrast Differential- interference-contrast (Nomarski) Fluorescence Confocal (without) Confocal (with) Deconvolution Super-resolution (without) Super-resolution (with) Scanning electron microscopy (SEM) Transmission electron microscopy (TEM)
- 6. 1 µm 1 µm Scanning electron microscopy (SEM) Cilia Longitudinal section of cilium Transmission electron microscopy (TEM) Cross section of cilium • Two basic types of electron microscopes (EMs) are used to study subcellular structures • Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3D • Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen • TEMs are used mainly to study the internal ultrastructure of cells
- 7. Thin section Freeze fracture Cortical granule in egg cell TEM
- 8. Isolating Organelles by Cell Fractionation • Cell fractionation takes cells apart and separates the major organelles from one another • Ultracentrifuges fractionate cells into their component parts Homogenization Homogenate Tissue cells Differential centrifugation
- 9. LE 6-5b Pellet rich in nuclei and cellular debris Pellet rich in mitochondria (and chloro- plasts if cells are from a plant) Pellet rich in “microsomes” (pieces of plasma membranes and cells’ internal membranes) Pellet rich in ribosomes 150,000 g 3 hr 80,000 g 60 min 20,000 g 20 min 1000 g (1000 times the force of gravity) 10 min Supernatant poured into next tube
- 10. Comparing Prokaryotic and Eukaryotic Cells • Basic features of all cells: – Plasma membrane – Semifluid substance called the cytosol – Chromosomes (carry genes) – Ribosomes (make proteins)
- 11. • Prokaryotic cells have no nucleus • In a prokaryotic cell, DNA is in an unbound region called the nucleoid • Prokaryotic cells lack membrane-bound organelles Cell wall of the gram-negative bacterium Leptothrix discophora. Visible are the inner and outer membranes and the peptidoglycan cell wall. (Transmission electron micrograph.) [© T. J. Beveridge/BPS.]
- 12. Figure 6.5Fimbriae Nucleoid Ribosomes Plasma membrane Cell wall Capsule Flagella A typical rod-shaped bacterium (a) Bacterial chromosome 0.5 µm A thin section through the bacterium Bacillus coagulans (TEM) (b)
- 13. • Eukaryotic cells have DNA in a nucleus that is bounded by a membranous nuclear envelope • Eukaryotic cells have membrane-bound organelles Name 2 in micrograph above. • Eukaryotic cells are generally much larger than prokaryotic cells Type of microscope? Why? Animal, plant, bacteria, or fungi? Why?
- 14. LE 6-7 Total surface area (height x width x number of sides x number of boxes) 6 125 125 150 750 1 1 1 5 1.2 66 Total volume (height x width x length X number of boxes) Surface-to-volume ratio (surface area ÷ volume) Surface area increases while Total volume remains constant The logistics of carrying out cellular metabolism sets limits on the size of cells
- 15. Hydrophilic region Hydrophobic region Carbohydrate side chain Structure of the plasma membrane Hydrophilic region Phospholipid Proteins Outside of cell Inside of cell 0.1 µm TEM of a plasma membrane •The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of the cell •The general structure of a biological membrane is a double layer of phospholipids
- 16. Figure 6.8a Flagellum Centrosome CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Microvilli Peroxisome Mitochondrion Lysosome Golgi apparatus Ribosomes Plasma membrane Nuclear envelope Nucleolus Chromatin NUCLEUS ENDOPLASMIC RETICULUM (ER) Rough ER Smooth ER In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm)
- 17. Figure 6.8bNUCLEUS Nuclear envelope Nucleolus Chromatin Rough ER Smooth ER Ribosomes Central vacuole Microfilaments Microtubules CYTOSKELETON Chloroplast Plasmodesmata Wall of adjacent cell Cell wall Plasma membrane Peroxisome Mitochondrion Golgi apparatus In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Cell wall Plasmodesmata
- 18. Figure 6.8cAnimalCells FungalCells PlantCells Unicellular Eukaryotes Human cells from lining of uterus (colorized TEM) Yeast cells budding (colorized SEM) A single yeast cell (colorized TEM) Cells from duckweed (colorized TEM) Chlamydomonas (colorized SEM) Chlamydomonas (colorized TEM) Cell Nucleus Nucleolus Parent cell Buds Cell wall Vacuole Nucleus Mitochondrion Cell wall Cell Chloroplast Mitochondrion Nucleus Nucleolus Flagella Vacuole Cell wall Chloroplast Nucleus Nucleolus 10μm 5μm 5μm 1μm 8μm 1 μm
- 19. The Nucleus: Genetic Library of the Cell • The nucleus contains most of the cell’s genes and is usually the most conspicuous organelle • The nuclear envelope encloses the nucleus, separating it from the cytoplasm
- 20. LE 6-10 Close-up of nuclear envelope Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Ribosome Pore complexes (TEM) Nuclear lamina (TEM) 1 µm Rough ER Nucleus 1 µm 0.25 µm Surface of nuclear envelope
- 21. Ribosomes: Protein Factories in the Cell • Ribosomes are particles made of ribosomal RNA and protein • Ribosomes carry out protein synthesis in two locations: – In the cytosol (free ribosomes) – On the outside of the endoplasmic reticulum (ER) or the nuclear envelope (bound ribosomes)
- 22. LE 6-11 Ribosomes 0.5 µm ER Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit Diagram of a ribosome TEM showing ER and ribosomes
- 23. Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell • Components of the endomembrane system: – Nuclear envelope – Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane • These components are either continuous or connected via transfer by vesicles Inner life of a cell
- 24. The Endoplasmic Reticulum: Biosynthetic Factory • The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells • The ER membrane is continuous with the nuclear envelope • There are two distinct regions of ER: – Smooth ER, which lacks ribosomes – Rough ER, with ribosomes studding its surface
- 25. LE 6-12 Ribosomes Smooth ER Rough ER ER lumen Cisternae Transport vesicle Smooth ER Rough ER Transitional ER 200 nm Nuclear envelope
- 26. • The smooth ER – Synthesizes lipids – Metabolizes carbohydrates – Stores calcium – Detoxifies poison (organ with cells loaded with smooth ER?) • The rough ER – Has bound ribosomes – Produces proteins and membranes, which are distributed by transport vesicles – Is a membrane factory for the cell
- 27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The Golgi apparatus consists of flattened membranous sacs called cisternae • Functions of the Golgi apparatus: – Modifies products of the ER – Manufactures certain macromolecules – Sorts and packages materials into transport vesicles The Golgi Apparatus: Shipping and Receiving Center
- 28. LE 6-13 trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus 0.1 µm Golgi apparatus cis face (“receiving” side of Golgi apparatus) Vesicles coalesce to form new cis Golgi cisternaeVesicles also transport certain proteins back to ER Vesicles move from ER to Golgi Vesicles transport specific proteins backward to newer 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 Cisternae
- 29. Lysosomes: Digestive Compartments • A lysosome is a membranous sac of hydrolytic enzymes • Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids • Lysosomes also use enzymes to recycle organelles and macromolecules, a process called autophagy
- 30. Figure 6.13 1 μm (a) Nucleus Vesicle containing two damaged organelles Mitochondrion fragment Peroxisome fragment Lysosome Peroxisome Mitochondrion Vesicle Digestion Autophagy: lysosome breaking down damaged organelles (b) Digestion Phagocytosis: lysosome digesting food Food vacuole Plasma membrane Digestive enzymes Lysosome Lysosome 1 μm
- 31. Vacuoles: Diverse Maintenance Compartments • Vesicles and vacuoles (larger versions of vacuoles) are membrane-bound sacs with varied functions • A plant cell or fungal cell may have one or several vacuoles • Food vacuoles are formed by phagocytosis • Contractile vacuoles, found in many freshwater protists, pump excess water out of cells • Central vacuoles, found in many mature plant cells, hold organic compounds and water
- 32. LE 6-15 5 µm Central vacuole Cytosol Tonoplast Central vacuole Nucleus Cell wall Chloroplast Video: Paramecium VacuoleVideo: Paramecium Vacuole
- 33. Concept 6.5: Mitochondria and chloroplasts change energy from one form to another • Mitochondria are the sites of cellular respiration • Chloroplasts, found only in plants and algae, are the sites of photosynthesis • Mitochondria and chloroplasts are not part of the endomembrane system • Peroxisomes are oxidative organelles
- 34. The Evolutionary Origins of Mitochondria and Chloroplasts • Mitochondria and chloroplasts have similarities with bacteria – Enveloped by a double membrane – Contain free ribosomes and circular double stranded DNA molecules – Grow and reproduce somewhat independently in cells • These similarities led to the endosymbiont theory
- 35. • The endosymbiont theory suggests that an early ancestor of eukaryotes engulfed an oxygen-using nonphotosynthetic prokaryotic cell • The engulfed cell formed a relationship with the host cell, becoming an endosymbiont • The endosymbionts evolved into mitochondria • At least one of these cells may have then taken up a photosynthetic prokaryote, which evolved into a chloroplast
- 36. Figure 6.16 Endoplasmic reticulum Nucleus Nuclear envelope Ancestor of eukaryotic cells (host cell) Engulfing of oxygen- using nonphotosynthetic prokaryote, which becomes a mitochondrion Nonphotosynthetic eukaryote Engulfing of photosynthetic prokaryote Mitochondrion Mitochondrion Chloroplast Photosynthetic eukaryote At least one cell
- 37. Mitochondria: Chemical Energy Conversion • Mitochondria are in nearly all eukaryotic cells • They have a smooth outer membrane and an inner membrane folded into cristae • The inner membrane creates two compartments: intermembrane space and mitochondrial matrix • Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix • Cristae present a large surface area for enzymes that synthesize ATP
- 38. Figure 6.17 Mitochondrion Intermembrane space Outer membrane DNA Inner membrane Free ribosomes in the mitochondrial matrix Cristae Matrix (a) Diagram and TEM of mitochondrion 0.1 μm 10 μm Mitochondria Mitochondrial DNA Nuclear DNA Network of mitochondria in Euglena (LM) (b)
- 39. Chloroplasts: Capture of Light Energy • The chloroplast is a member of a family of organelles called plastids • Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis • Chloroplasts are found in leaves and other green organs of plants and in algae • Chloroplast structure includes: – Thylakoids, membranous sacs – Stroma, the internal fluid
- 40. Figure 6.18 Chloroplast Ribosomes Stroma Inner and outer membranes Granum DNA Thylakoid Intermembrane space Diagram and TEM of chloroplast(a) (b) Chloroplasts in an algal cell (b) 1 μm 50 μm Chloroplasts (red)
- 41. Peroxisomes: Oxidation • Peroxisomes are specialized metabolic compartments bounded by a single membrane • Peroxisomes produce hydrogen peroxide and convert it to water Chloroplast Peroxisome Mitochondrion
- 42. • The cytoskeleton is a network of fibers extending throughout the cytoplasm • It organizes the cell’s structures and activities, anchoring many organelles • It is composed of three types of molecular structures: – Microtubules (red) – Microfilaments (green) – Intermediate filaments (yellow)
- 44. Roles of the Cytoskeleton: Support, Motility, and Regulation • The cytoskeleton helps to support the cell and maintain its shape • It interacts with motor proteins to produce motility • Inside the cell, vesicles can travel along “monorails” provided by the cytoskeleton • Recent evidence suggests that the cytoskeleton may help regulate biochemical activities
- 45. Figure 6.21 0.25 μmVesiclesMicrotubule SEM of a squid giant axon(b) (a) Motor proteins “walk” vesicles along cytoskeletal fibers. (a) Motor protein (ATP powered) Microtubule of cytoskeleton Receptor for motor protein Vesicle ATP
- 49. Microtubules • Microtubules are hollow rods about 25 nm in diameter and about 200 nm to 25 microns long • Functions of microtubules: – Shaping the cell – Guiding movement of organelles – Separating chromosomes during cell division Cross-section MT
- 50. The motile apparatus of the sperm (Part 1) 9 + 2
- 51. Centrosomes and Centrioles • In many cells, microtubules grow out from a centrosome near the nucleus • The centrosome is a “microtubule- organizing center” • In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring
- 52. LE 6-22 0.25 µm Microtubule Centrosome Centrioles Longitudinal section of one centriole Microtubules Cross section of the other centriole
- 54. Cilia and Flagella • Microtubules control the beating of cilia and flagella, locomotor appendages of some cells • Cilia and flagella differ in their beating patterns Video: ChlamydomonasVideo: Chlamydomonas Video: Paramecium CiliaVideo: Paramecium Cilia Cilia in inner ear
- 55. LE 6-23a 5 µm Direction of swimming Motion of flagella
- 56. LE 6-23b 15 µm Direction of organism’s movement Motion of cilia Direction of active stroke Direction of recovery stroke
- 57. • Cilia and flagella share a common ultrastructure: – A core of microtubules sheathed by the plasma membrane – A basal body that anchors the cilium or flagellum – A motor protein called dynein, which drives the bending movements of a cilium or flagellum
- 58. Figure 6.240.1 μm 0.5 μm 0.1 μm Microtubules Plasma membrane Basal body Longitudinal section of motile cilium (a) Triplet Cross section of motile cilium (b) Outer microtubule doublet Motor proteins (dyneins) Central microtubule Radial spoke Cross-linking proteins between outer doublets Plasma membrane Cross section of basal body(c)
- 59. • How dynein “walking” moves flagella and cilia: – Dynein arms alternately grab, move, and release the outer microtubules – Protein cross-links limit sliding – Forces exerted by dynein arms cause doublets to curve, bending the cilium or flagellum
- 60. LE 6-25a Dynein “walking” Microtubule doublets ATP Dynein arm
- 61. LE 6-25b Wavelike motion Cross-linking proteins inside outer doublets ATP Anchorage in cell Effect of cross-linking proteins
- 62. Microfilaments (Actin Filaments) • Microfilaments are solid rods about 7 nm in diameter, built as a twisted double chain of actin subunits • The structural role of microfilaments is to bear tension, resisting pulling forces within the cell • They form a 3D network just inside the plasma membrane to help support the cell’s shape • Bundles of microfilaments make up the core of microvilli of intestinal cells
- 63. LE 6-26 Microfilaments (actin filaments) Microvillus Plasma membrane Intermediate filaments 0.25 µm
- 64. • Microfilaments that function in cellular motility contain the protein myosin in addition to actin • In muscle cells, thousands of actin filaments are arranged parallel to one another • Thicker filaments composed of myosin interdigitate with the thinner actin fibers
- 65. Figure 6.26 Muscle cell 0.5 µm Actin filament Myosin filament Myosin head Chloroplast (a) (b) (c)Myosin motors in muscle cell contraction Cytoplasmic streaming in plant cells Amoeboid movement Extending pseudopodium Cortex (outer cytoplasm): gel with actin network Inner cytoplasm (more fluid) 100 µm 30 µm
- 66. • Localized contraction brought about by actin and myosin also drives amoeboid movement • Pseudopodia (cellular extensions) extend and contract through the reversible assembly and contraction of actin subunits into microfilaments
- 67. LE 6-27b Cortex (outer cytoplasm): gel with actin network Amoeboid movement Inner cytoplasm: sol with actin subunits Extending pseudopodium
- 68. • Cytoplasmic streaming is a circular flow of cytoplasm within cells • This streaming speeds distribution of materials within the cell • In plant cells, actin-myosin interactions and sol-gel transformations drive cytoplasmic streaming Video: Cytoplasmic StreamingVideo: Cytoplasmic Streaming
- 69. LE 6-27c Nonmoving cytoplasm (gel) Cytoplasmic streaming in plant cells Chloroplast Streaming cytoplasm (sol) Cell wall Parallel actin filaments Vacuole
- 70. Intermediate Filaments • Intermediate filaments range in diameter from 8–12 nanometers, larger than microfilaments but smaller than microtubules • They support cell shape and fix organelles in place • Intermediate filaments are more permanent cytoskeleton fixtures than the other two classes
- 71. Concept 6.7: Extracellular components and connections between cells help coordinate cellular activities • Most cells synthesize and secrete materials that are external to the plasma membrane • These extracellular structures include: – Cell walls of plants – The extracellular matrix (ECM) of animal cells – Intercellular junctions
- 72. Cell Walls of Plants • The cell wall is an extracellular structure that distinguishes plant cells from animal cells • The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water • Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein
- 73. Cell Walls of Plants • Plant cell walls may have multiple layers: – Primary cell wall: relatively thin and flexible – Middle lamella: thin layer between primary walls of adjacent cells – Secondary cell wall (in some cells): added between the plasma membrane and the primary cell wall • Plasmodesmata are channels between adjacent plant cells
- 74. Figure 6.27 Secondary cell wall Primary cell wall Middle lamella Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata 1 μm
- 75. The Extracellular Matrix (ECM) of Animal Cells • Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM) • The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin and other macromolecules. ECM proteins bind to receptor proteins in the plasma membrane called integrins. • Functions of the ECM: – Support – Adhesion – Movement – Regulation
- 76. LE 6-29a EXTRACELLULAR FLUID Proteoglycan complexCollagen fiber Fibronectin Integrin Micro- filaments CYTOPLASM Plasma membrane
- 78. Location and formation of extracellular matrices in the chick embryo
- 79. Speculative diagram of the fibronectin receptor complex
- 80. 6.33 Role of the extracellular matrix in cell differentiation Basal lamina in B induces differentiation
- 81. Intercellular Junctions • Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact • Intercellular junctions facilitate this contact
- 82. Plants: Plasmodesmata • Plasmodesmata are channels that perforate plant cell walls • Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell Cross-section
- 83. LE 6-30 Interior of cell Interior of cell 0.5 µm Plasmodesmata Plasma membranes Cell walls
- 84. Animals: Tight Junctions, Desmosomes, and Gap Junctions • At tight junctions, membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid • Desmosomes (anchoring junctions) fasten cells together into strong sheets • Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells
- 85. LE 6-31 Tight junctions prevent fluid from moving across a layer of cells Tight junction 0.5 µm 1 µm 0.1 µm Gap junction Extracellular matrix Space between cells Plasma membranes of adjacent cells Intermediate filaments Tight junction Desmosome Gap junctions
- 86. Tight junctions
- 87. Gap Junctions
- 88. Connexin proteins create gap junctions 6 connexins/channel A compartment of several cells In center
- 89. The Cell: A Living Unit Greater Than the Sum of Its Parts • Cells rely on the integration of structures and organelles in order to function • Inner Life of A Cell
- 90. Nuclear Pore Complex is much more complicated than just a simple protein like the connexin protein of gap junctions—Groups of scientists are uncovering just how many proteins interact to make up this complex. http://lab.rockefeller.edu/rout/resproj1
Notas do Editor
- Figure 6.2 The size range of cells
- Figure 6.3 Exploring microscopy Concept Check 6.1 1. How do stains used for light microscopy compare with those used for electron microscopy? ➢Stains used for light microscopy are colored molecules that bind to cell components, affecting the light passing through, while stains used for electron microscopy involve heavy metals that affect the beams of electrons passing through 2. Which type of microscope would you use to study (a) the changes in shape of a living white blood cell and (b) the details of surface texture of a hair? ➢ a) light microscope (no damage to cell) b) scanning electron microscope (to study the detailed architecture of cell surfaces)
- Both the SEM and TEM use electromagnets as lenses to bend the paths of the electrons, ultimately focusing the image onto a monitor for viewing.
- Freeze fracture: making the specimen cold and then breaking it. Pic C has a flat surface of the membrane.
- We’ve had separation via chromatography, polarity before. Now we can do it via centrifugation. It is actually common. Application Cell fractionation is used to isolate (fractionate) cell components based on size and density. Technique Cells are homogenized in a blender to break them up. The resulting mixture (homogenate) is centrifuged. The supernatant (liquid) is poured into another tube and centrifuged at a higher speed for a longer period. This process is repeated several times. This “differential centrifugation” results in a series of pellets, each containing different cell components. ➢The faster the centrifuge spins the smaller the pellets will be
- Cell fractionation enables researchers to prepare specific cell components in bulk and identify their functions, a task not usually possible with intact cells.
- Write an essay about these four common features in ALL cells
- Figure 6.5 A prokaryotic cell Bacteria have a cell wall (peptidoglycan is only present in cell walls) Classification based on the type of cell wall (done via gram stain) Thick Peptidoglycan Layer-- Cell Wall are long strains of sugar. Gram Positive absorb the stain and turn purple N-acetylglucosamine (NAG) N-acetylnuramic acid (NAM) Thin Peptidoglycan Cell Wall – gram negative cell wall is composed of a thin layer plus an outer layer (more complex structure than Gram positive) Right outside the plasma membrane is a cell wall. Plasma membrane controls what goes in and out of the cell Cell wall provides structure and keeps protection via osmotic pressure Capsule (not on all bacteria) is a thick coating outside of the cell wall and secrete capsules to Not involved in immune response 2 types-- simple polysaccharides which don’t elicit an immediate response Ribosomes: different in eukaryotic (ads) than bacteria (7ds) Prokaryotic Fimbriae: made of the protein pilin. Used to attach to other things—function. Chromosomes: “blueprint to life”coding for all of the biological models than need to be made and passes it down from cell to cell Flagella: have little embedded motors causing them to twirl. Function is for movement Clockwise twirl = forward counter Sex Pilis: to pass a small portion of the genome. bacterial conjugation made by male bacteria composed of pillin
- Transmission Electron Microscope because it’s a slice and you can see the cell Animal Cell Nuclear Envelope: protein and phospholipids. Function is to house the genetic material Eukaryotic cells have compartmentalization that allow them to have bigger cells Compartments = organelles
- A high surface-to-volume ratio facilitates the exchange of materials between a cell and its environment.
- Figure 6.8a Exploring eukaryotic cells (part 1: animal cell cutaway) Concept Check 6.2 1 Briefly describe the structure and function of the nucleus, the mitochondrion, the chloroplast, and the endoplasmic reticulum. ➢Nucleus: Nuclear envelope: is a double membrane enclosing the nucleus; perforated by pores; continuous with ER. Nucleolus: structure involved in production of ribosomes; a nucleus has one or more nucleoli. Chromatin: material consisting of DNA and proteins; visible as individual chromosomes in a dividing cell Mitochondrion: organelle where cellular respiration occurs and most ATP is generated; double-bound membrane; folded inner membrane; has some individual DNA Chloroplast: photosynthetic organelle; converts energy of sunlight to chemical energy stored in sugar molecules; double bound membrane; inner thylakoids; individual DNA ER: network of membranous sacs and tubes; active in membrane synthesis and other synthetic ad metabolic processes; has rough (ribosomal studded) and smooth regions 2. Imagine an elongated cell (such as a nerve cell) that measures 125 * 1 * 1 arbitrary units. Predict how its surface-to-volume ratio would compare with thosein Figure 6.7.Then calculate the ratio and check your prediction. ➢This cell would have the same volume as the cells in columns 2 and 3 but proportionally more surface area than in column 2 and less than in column 3. Thus, the surface-to-volume ratio should be greater than 1.2 but less than 6. To obtain the surface area, you'd have to add he area of the six sides 125 +125 +125 +125+1+1 = 502. The surface-to-volume ratio equals 502 divided by a volume of 125, or 4.0
- Figure 6.8b Exploring eukaryotic cells (part 2: plant cell cutaway)
- Figure 6.8b Exploring eukaryotic cells (part 3: micrographs)
- The nucleus houses most of the cell’s DNA and Ribosomes. (Some genes are located in mitochondria and chloroplasts.) ➢use information from the DNA to make proteins ➢DNA is organized into discrete units called chromosomes
- Mitochondria, Chloroplast, and Nucleus have a double membrane. ➢chromatin: The complex of DNA and proteins making up chromosomes ➢nucleolus: nuclear subdomain that assembles ribosomal subunits. proteins imported from the cytoplasm are assembled with rRNA into large and small subunits of ribosomes. The nucleus directs protein synthesis by synthesizing messenger RNA (mRNA) according to instructions provided by the DNA. Once an mRNA molecule reaches the cytoplasm, ribosomes translate the mRNA’s genetic message into the primary structure of a specific polypeptide.
- ➢ribosomes are not membrane bounded and thus are not considered organelles. ➢cells active in protein synthesis also have prominent nucleoli
- Endomembrane System Carries out many tasks: ➢synthesis of proteins ➢transport of proteins into membranes and organelles or out of the cell ➢metabolism and movement of lipids ➢detoxification of poisons Vesicles: sacs made of membrane
- Smooth ER: outer surface lacks ribosomes ➢Functions include: synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, and storage of calcium ions. ➢ Rough ER: studded with ribosomes on the outer surface of the membrane, thus appearing “rough” through an electron microscope ➢membrane factory for the cell–it grows in place by adding membrane proteins and phospholipids to its own mem- brane. ➢glycoproteins: proteins with carbohydrates covalently bonded to them… most secretory proteins
- Cis: Receiving; located near the ER Trans: Shipping; gives rise to vesicles that pinch off and travel to other sites. Products of the endoplasmic reticulum are usually modified during their transit from the cis region to the trans region of the Golgi apparatus.
- Figure 6.13 Lysosomes
- Chloroplast transfer solar energy from the sun to chemical energy. Mitochondria is where cellular respiration occurs. Endosymbiotic Theory
- Figure 6.16 The endosymbiont theory of the origins of mitochondria and chloroplasts in eukaryotic cells
- Figure 6.17 The mitochondrion, site of cellular respiration
- Figure 6.18 The chloroplast, site of photosynthesis Thylakoid Stack = Granum Stromo: bat
- Intermediate filaments are composed of a variety of proteins Microtubules are made of tubulin
- TEM because the resolution is too good for it to be SEM
- Figure 6.21 Motor proteins and the cytoskeleton
- Microtubule Large, alpha and beta tubulin, cilia, flagella, and the spindle body are composed of microtubules Responsible for cell and organelle movements
- Microfilaments
- Eukaryotic Cilia and Flagella have the 9+2
- A lysosome is a vesicle that has a specific job
- The basal body has nine triplets, anchors the organelle in the plasma membrane The flagella and cilia have microtubules columns in the middle
- Figure 6.24 Structure of a flagellum or motile cilium
- Intermediate filaments are thicker than microfilaments
- Figure 6.26 Microfilaments and motility
- Figure 6.27 Plant cell walls Middle Lamina = Extracellular Matrix
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- devbio8e-fig-06-32-0.jpg
- The extracellular matrix send signals
- Intermediate filaments hold Desmosomes together
- 1. 2.
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- Figures\Chapter06\DevBio7e06381.jpg