2011 Pearson Education, Inc.

Transcription

1 Overview: The Fundamental Units of Life All organisms are made of cells The cell is the simplest collec=on of ma>er that can be alive Cell structure is correlated to cellular func=on All cells are related by their descent from earlier cells

2 Figure m 1 m 0.1 m 1 cm Human height Length of some nerve and muscle cells Chicken egg Unaided eye 1 mm Frog egg 100 m 10 m 1 m 100 nm 10 nm 1 nm Human egg Most plant and animal cells Nucleus Most bacteria Mitochondrion Smallest bacteria Viruses Ribosomes Proteins Lipids Small molecules Light microscopy Superresolution microscopy Electron microscopy 0.1 nm Atoms

3 Figure 6.3 Light Microscopy (LM) Electron Microscopy (EM) Brightfield (unstained specimen) Confocal Longitudinal section of cilium Cross section of cilium Cilia 50 m Brightfield (stained specimen) Phase-contrast Differential-interferencecontrast (Nomarski) Fluorescence 10 m 1 m 10 m 50 m Deconvolution Super-resolution Scanning electron microscopy (SEM) 2 m 2 m Transmission electron microscopy (TEM)

4 Concept 6.2: Eukaryo=c cells have internal membranes that compartmentalize their func=ons The basic structural and func=onal unit of every organism is one of two types of cells: prokaryo=c or eukaryo=c Only organisms of the domains Bacteria and Archaea consist of prokaryo=c cells Pro=sts, fungi, animals, and plants all consist of eukaryo=c cells

5 Comparing Prokaryo=c and Eukaryo=c Cells Basic features of all cells Plasma membrane Semifluid substance called cytosol Chromosomes (carry genes) Ribosomes (make proteins)

6 Prokaryo,c cells are characterized by having No nucleus DNA in an unbound region called the nucleoid No membrane-bound organelles Cytoplasm bound by the plasma membrane

7 Figure 6.5 Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial chromosome Cell wall Capsule (a) A typical rod-shaped bacterium Flagella (b) 0.5 m A thin section through the bacterium Bacillus coagulans (TEM)

8 Figure 6.8dc Protistan Cells 1 m Flagella Nucleus Nucleolus Vacuole Chloroplast Chlamydomonas (colorized TEM) Cell wall

9 Figure 6.8a Flagellum Centrosome CYTOSKELETON: Microfilaments Intermediate filaments Microtubules ENDOPLASMIC RETICULUM (ER) Rough ER Smooth ER Nuclear envelope Nucleolus Chromatin NUCLEUS Plasma membrane Ribosomes Microvilli Peroxisome Golgi apparatus Mitochondrion Lysosome

10 NUCLEUS Figure 6.8c Nuclear envelope Nucleolus Chromatin Rough endoplasmic reticulum Smooth endoplasmic reticulum Ribosomes Golgi apparatus Central vacuole Microfilaments Intermediate filaments Microtubules CYTOSKELETON Mitochondrion Peroxisome Plasma membrane Chloroplast Cell wall Plasmodesmata Wall of adjacent cell

11 A Panoramic View of the Eukaryo=c Cell A eukaryo=c cell has internal membranes that par==on the cell into organelles Plant and animal cells have most of the same organelles BioFlix: Tour of an Animal Cell BioFlix: Tour of a Plant Cell

12 Concept 6.3: The eukaryo=c cell s gene=c instruc=ons are housed in the nucleus and carried out by the ribosomes The nucleus contains most of the DNA in a eukaryo=c cell Ribosomes use the informa=on from the DNA to make proteins

13 The Nucleus: Informa=on Central The nucleus contains most of the cell s genes and is usually the most conspicuous organelle The nuclear envelope encloses the nucleus, separa=ng it from the cytoplasm The nuclear membrane is a double membrane; each membrane consists of a lipid bilayer

14 1 m Figure 6.9 Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Rough ER Surface of nuclear envelope Ribosome Pore complex 0.25 m Close-up of nuclear envelope Chromatin Pore complexes (TEM) 1 m Nuclear lamina (TEM)

15 Figure 6.9a Nucleolus Nucleus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Rough ER Ribosome Close-up of nuclear envelope Chromatin

16 Ribosomes: Protein Factories Ribosomes are par=cles made of ribosomal RNA and protein Ribosomes carry out protein synthesis in two loca=ons In the cytosol (free ribosomes) On the outside of the endoplasmic re=culum or the nuclear envelope (bound ribosomes)

17 Figure m Free ribosomes in cytosol Endoplasmic reticulum (ER) Ribosomes bound to ER Large subunit TEM showing ER and ribosomes Small subunit Diagram of a ribosome

18 Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic func=ons in the cell Components of the endomembrane system Nuclear envelope Endoplasmic re=culum Golgi apparatus Lysosomes Vacuoles Plasma membrane These components are either con=nuous or connected via transfer by vesicles

19 The Endoplasmic Re=culum: Biosynthe=c Factory The endoplasmic re,culum (ER) accounts for more than half of the total membrane in many eukaryo=c cells The ER membrane is con=nuous with the nuclear envelope There are two dis=nct regions of ER Smooth ER, which lacks ribosomes Rough ER, surface is studded with ribosomes

20 Figure 6.11 Rough ER Smooth ER Nuclear envelope ER lumen Cisternae Ribosomes Transport vesicle Smooth ER Rough ER Transitional ER 200 nm

21 Figure 6.11a Smooth ER Rough ER Nuclear envelope ER lumen Cisternae Ribosomes Transport vesicle Transitional ER

22 Figure 6.11b Smooth ER Rough ER 200 nm

23 Func%ons of Smooth ER The smooth ER Synthesizes lipids Metabolizes carbohydrates Detoxifies drugs and poisons Stores calcium ions

24 Func%ons of Rough ER The rough ER Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates) Distributes transport vesicles, proteins surrounded by membranes Is a membrane factory for the cell

25 The Golgi Apparatus: Shipping and Receiving Center The Golgi apparatus consists of fla>ened membranous sacs called cisternae Func=ons of the Golgi apparatus Modifies products of the ER Manufactures certain macromolecules Sorts and packages materials into transport vesicles

26 Figure 6.12 cis face ( receiving side of Golgi apparatus) Cisternae 0.1 m trans face ( shipping side of Golgi apparatus) TEM of Golgi apparatus

27 Figure 6.12a 0.1 m TEM of Golgi apparatus

28 Lysosomes: Diges=ve Compartments A lysosome is a membranous sac of hydroly=c enzymes that can digest macromolecules Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids Lysosomal enzymes work best in the acidic environment inside the lysosome Anima=on: Lysosome Forma=on

29 Some types of cell can engulf another cell by phagocytosis; this forms a food vacuole A lysosome fuses with the food vacuole and digests the molecules Lysosomes also use enzymes to recycle the cell s own organelles and macromolecules, a process called autophagy

30 Figure 6.13 Nucleus 1 m Vesicle containing two damaged organelles 1 m Mitochondrion fragment Lysosome Peroxisome fragment Digestive enzymes Lysosome Lysosome Plasma membrane Digestion Peroxisome Food vacuole Vesicle Mitochondrion Digestion (a) Phagocytosis (b) Autophagy

31 Vacuoles: Diverse Maintenance Compartments A plant cell or fungal cell may have one or several vacuoles, derived from endoplasmic re=culum and Golgi apparatus

32 Food vacuoles are formed by phagocytosis Contrac,le vacuoles, found in many freshwater pro=sts, pump excess water out of cells Central vacuoles, found in many mature plant cells, hold organic compounds and water Video: Paramecium Vacuole

33 Figure 6.14 Central vacuole Cytosol Nucleus Central vacuole Cell wall Chloroplast 5 m

34 The Endomembrane System: A Review The endomembrane system is a complex and dynamic player in the cell s compartmental organiza=on

35 Figure Nucleus Rough ER Smooth ER Plasma membrane

36 Figure Nucleus Rough ER Smooth ER cis Golgi trans Golgi Plasma membrane

37 Figure Nucleus Rough ER Smooth ER cis Golgi trans Golgi Plasma membrane

38 Concept 6.5: Mitochondria and chloroplasts change energy from one form to another Mitochondria are the sites of cellular respira=on, a metabolic process that uses oxygen to generate ATP Chloroplasts, found in plants and algae, are the sites of photosynthesis Peroxisomes are oxida=ve organelles

39 The Evolu=onary Origins of Mitochondria and Chloroplasts Mitochondria and chloroplasts have similari=es with bacteria Enveloped by a double membrane Contain free ribosomes and circular DNA molecules Grow and reproduce somewhat independently in cells

40 The Endosymbiont theory An early ancestor of eukaryo=c cells engulfed a nonphotosynthe=c prokaryo=c cell, which formed an endosymbiont rela=onship with its host The host cell and endosymbiont merged into a single organism, a eukaryo=c cell with a mitochondrion At least one of these cells may have taken up a photosynthe=c prokaryote, becoming the ancestor of cells that contain chloroplasts

41 Figure 6.16 Engulfing of oxygenusing nonphotosynthetic prokaryote, which becomes a mitochondrion Mitochondrion Endoplasmic reticulum Nuclear envelope Nucleus Ancestor of eukaryotic cells (host cell) Nonphotosynthetic eukaryote At least one cell Engulfing of photosynthetic prokaryote Chloroplast Mitochondrion Photosynthetic eukaryote

42 Mitochondria: Chemical Energy Conversion Mitochondria are in nearly all eukaryo=c 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 respira=on are catalyzed in the mitochondrial matrix Cristae present a large surface area for enzymes that synthesize ATP

43 Figure m Intermembrane space Outer membrane Mitochondria Free ribosomes in the mitochondrial matrix DNA Inner membrane Cristae Matrix (a) Diagram and TEM of mitochondrion 0.1 m Mitochondrial DNA Nuclear DNA (b) Network of mitochondria in a protist cell (LM)

44 Chloroplasts: Capture of Light Energy Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that func=on in photosynthesis Chloroplasts are found in leaves and other green organs of plants and in algae

45 Chloroplast structure includes Thylakoids, membranous sacs, stacked to form a granum Stroma, the internal fluid The chloroplast is one of a group of plant organelles, called plas,ds

46 Figure 6.18 Ribosomes Stroma 50 m Inner and outer membranes Granum DNA Thylakoid Intermembrane space (a) Diagram and TEM of chloroplast 1 m Chloroplasts (red) (b) Chloroplasts in an algal cell

47 Peroxisomes: Oxida=on Peroxisomes are specialized metabolic compartments bounded by a single membrane Peroxisomes produce hydrogen peroxide and convert it to water Peroxisomes perform reac=ons with many different func=ons How peroxisomes are related to other organelles is s=ll unknown

48 Figure m Chloroplast Peroxisome Mitochondrion

49 Concept 6.6: The cytoskeleton is a network of fibers that organizes structures and ac=vi=es in the cell The cytoskeleton is a network of fibers extending throughout the cytoplasm It organizes the cell s structures and ac=vi=es, anchoring many organelles It is composed of three types of molecular structures Microtubules Microfilaments Intermediate filaments

50 Figure m

51 Roles of the Cytoskeleton: Support and Mo=lity The cytoskeleton helps to support the cell and maintain its shape It interacts with motor proteins to produce mo=lity Inside the cell, vesicles can travel along monorails provided by the cytoskeleton Recent evidence suggests that the cytoskeleton may help regulate biochemical ac=vi=es

52 Figure 6.21 ATP Vesicle Receptor for motor protein (a) Motor protein (ATP powered) Microtubule of cytoskeleton Microtubule Vesicles 0.25 m (b)

53 Components of the Cytoskeleton Three main types of fibers make up the cytoskeleton Microtubules are the thickest of the three components of the cytoskeleton Microfilaments, also called ac=n filaments, are the thinnest components Intermediate filaments are fibers with diameters in a middle range

54 Table m 10 m 5 m Column of tubulin dimers 25 nm Actin subunit Keratin proteins Fibrous subunit (keratins coiled together) Tubulin dimer 7 nm 8 12 nm

55 Microtubules Microtubules are hollow rods about 25 nm in diameter and about 200 nm to 25 microns long Func=ons of microtubules Shaping the cell Guiding movement of organelles Separa=ng chromosomes during cell division

56 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

57 Figure 6.22 Centrosome Microtubule Centrioles 0.25 m Longitudinal section of one centriole Microtubules Cross section of the other centriole

58 Cilia and Flagella Microtubules control the bea=ng of cilia and flagella, locomotor appendages of some cells Cilia and flagella differ in their bea=ng pa>erns Video: Chlamydomonas Video: Paramecium Cilia

59 Figure 6.23 Direction of swimming (a) Motion of flagella 5 m Direction of organism s movement Power stroke Recovery stroke (b) Motion of cilia 15 m

60 Cilia and flagella share a common structure 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 Anima=on: Cilia and Flagella

61 Figure m Outer microtubule doublet Dynein proteins Plasma membrane Central microtubule Radial spoke Microtubules Plasma membrane (b) Cross section of motile cilium Cross-linking proteins between outer doublets Basal body 0.5 m 0.1 m (a) Longitudinal section of motile cilium Triplet (c) Cross section of basal body

62 Microfilaments (Ac%n Filaments) Microfilaments are solid rods about 7 nm in diameter, built as a twisted double chain of ac,n subunits The structural role of microfilaments is to bear tension, resis=ng pulling forces within the cell They form a 3-D network called the cortex just inside the plasma membrane to help support the cell s shape Bundles of microfilaments make up the core of microvilli of intes=nal cells

63 Figure 6.26 Microvillus Plasma membrane Microfilaments (actin filaments) Intermediate filaments 0.25 m

64 Microfilaments that func=on in cellular mo=lity contain the protein myosin in addi=on to ac=n In muscle cells, thousands of ac=n filaments are arranged parallel to one another Thicker filaments composed of myosin interdigitate with the thinner ac=n fibers

65 Figure 6.27 Muscle cell Actin filament Myosin filament Myosin head (a) Myosin motors in muscle cell contraction 0.5 m Cortex (outer cytoplasm): gel with actin network Inner cytoplasm: sol with actin subunits 100 m Extending pseudopodium (b) Amoeboid movement Chloroplast (c) Cytoplasmic streaming in plant cells 30 m

66 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

67 Concept 6.7: Extracellular components and connec=ons between cells help coordinate cellular ac=vi=es 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 junc=ons

68 Cell Walls of Plants The cell wall is an extracellular structure that dis=nguishes plant cells from animal cells Prokaryotes, fungi, and some pro=sts also have cell walls 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

69 Plant cell walls may have mul=ple layers Primary cell wall: rela=vely 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

70 Figure 6.28 Secondary cell wall Primary cell wall Middle lamella 1 m Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata

71 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 fibronec,n ECM proteins bind to receptor proteins in the plasma membrane called integrins

72 Figure 6.30 Collagen EXTRACELLULAR FLUID Polysaccharide molecule Proteoglycan complex Carbohydrates Fibronectin Core protein Integrins Plasma membrane Proteoglycan molecule Proteoglycan complex Microfilaments CYTOPLASM

73 Func=ons of the ECM Support Adhesion Movement Regula=on

74 Cell Junc=ons Neighboring cells in =ssues, organs, or organ systems ohen adhere, interact, and communicate through direct physical contact Intercellular junc=ons facilitate this contact There are several types of intercellular junc=ons Plasmodesmata Tight junc=ons Desmosomes Gap junc=ons

75 Plasmodesmata in Plant Cells Plasmodesmata are channels that perforate plant cell walls Through plasmodesmata, water and small solutes (and some=mes proteins and RNA) can pass from cell to cell

76 Figure 6.31 Cell walls Interior of cell Interior of cell 0.5 m Plasmodesmata Plasma membranes

77 Plasmodesmata in Plant Cells Plasmodesmata are channels that perforate plant cell walls Through plasmodesmata, water and small solutes (and some=mes proteins and RNA) can pass from cell to cell

78 Figure 6.31 Cell walls Interior of cell Interior of cell 0.5 m Plasmodesmata Plasma membranes

79 Tight Junc%ons, Desmosomes, and Gap Junc%ons in Animal Cells At,ght junc,ons, membranes of neighboring cells are pressed together, preven=ng leakage of extracellular fluid Desmosomes (anchoring junc=ons) fasten cells together into strong sheets Gap junc,ons (communica=ng junc=ons) provide cytoplasmic channels between adjacent cells

80 The Cell: A Living Unit Greater Than the Sum of Its Parts Cells rely on the integra=on of structures and organelles in order to func=on For example, a macrophage s ability to destroy bacteria involves the whole cell, coordina=ng components such as the cytoskeleton, lysosomes, and plasma membrane

81 Figure m