Eukaryotic Cells Organelles l Eukaryotic cells are compartmentalized

  • Slides: 38
Download presentation
Eukaryotic Cells: Organelles l Eukaryotic cells are compartmentalized l They contain small structures called

Eukaryotic Cells: Organelles l Eukaryotic cells are compartmentalized l They contain small structures called organelles l l l Perform specific functions Isolates reactions from others Two classes of organelles: l Endomembrane system: l Organelles that communicate with one another l l l Via membrane channels Via small vesicles Energy related organelles l l Mitochondria & chloroplasts Basically independent & self-sufficient 1

Plasma Membrane Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or

Plasma Membrane Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. protein molecules phospholipid bilayer 2

Cell Fractionation and Differential Centrifugation l Cell fractionation is the breaking apart of cellular

Cell Fractionation and Differential Centrifugation l Cell fractionation is the breaking apart of cellular components l Differential centrifugation: l Allows separation of cell parts l Separated out by size & density l Works like spin cycle of washer l The faster the machine spins, the smaller the parts that are settled out 3

Animal Cell Anatomy Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction

Animal Cell Anatomy Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Plasma membrane: outer surface that regulates entrance and exit of molecules protein phospholipid Nucleus: command center of cell Cytoskeleton: maintains cell shape and assists movement of cell parts: Microtubules: protein cylinders that move organelles Intermediate filaments: protein fibers that provide stability of shape Nuclear envelope: double membrane with nuclear pores that encloses nucleus Chromatin: diffuse threads containing DNA and protein Nucleolus: region that produces subunits of ribosomes Endoplasmic reticulum: protein and lipid metabolism Rough ER: studded with ribosomes that synthesize proteins Actin filaments: protein fibers that play a role in change of shape Smooth ER: lacks ribosomes, synthesizes lipid molecules Peroxisome: vesicle that is involved in fatty acid metabolism Centrioles*: short cylinders of microtubules of unknown function Centrosome: microtubule organizing center that contains a pair of centrioles Ribosomes: particles that carry out protein synthesis Lysosome*: vesicle that digests macromolecules and even cell parts Vesicle: small membranebounded sac that stores and transports substances Cytoplasm: semifluid matrix outside nucleus that contains organelles *not in plant cells Polyribosome: string of ribosomes simultaneously synthesizing same protein Mitochondrion: organelle that carries out cellular respiration, producing ATP molecules Golgi apparatus: processes, packages, and secretes modified proteins 4

Plant Cell Anatomy Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction

Plant Cell Anatomy Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Nucleus: command center of cell Nuclear envelope: double membrane with nuclear pores that encloses nucleus Nucleolus: produces subunits of ribosomes Central vacuole*: large, fluid-filled sac that stores metabolites and helps maintain turgor pressure Cell wall of adjacent cell Chromatin: diffuse threads containing DNA and protein Middle lamella: cements together the primary cell walls of adjacent plant cells Nuclear pore: permits passage of proteins into nucleus and ribosomal subunits out of nucleus Ribosomes: carry out protein synthesis Chloroplast*: carries out photosynthesis, producing sugars Centrosome: microtubule organizing center (lacks centrioles) Endoplasmic reticulum: protein and lipid metabolism Granum*: a stack of chlorophyll-containing thylakoids in a chloroplast Rough ER: studded with ribosomes that synthesize proteins Mitochondrion: organelle that carries out cellular respiration, producing ATP molecules Smooth ER: lacks ribosomes, synthesizes lipid molecules Peroxisome: vesicle that is involved in fatty acid metabolism Golgi apparatus: processes, packages, and secretes modified proteins Cytoplasm: semifluid matrix outside nucleus that contains organelles Microtubules: protein cylinders that aid movement of organelles Actin filaments: protein fibers that play a role in movement of cell and organelles Plasma membrane: surrounds cytoplasm, and regulates entrance and exit of molecules Cell wall*: outer surface that shapes, supports, and protects cell *not in animal cells 5

Nucleus Command center of cell, usually near center l Separated from cytoplasm by nuclear

Nucleus Command center of cell, usually near center l Separated from cytoplasm by nuclear envelope l l Consists of double layer of membrane Nuclear pores permit exchange between nucleoplasm & cytoplasm Contains chromatin in semifluid nucleoplasm l l Chromatin contains DNA of genes, and proteins Condenses to form chromosomes l l Chromosomes are formed during cell division Dark nucleolus composed of r. RNA l Produces subunits of ribosomes 6

Anatomy of the Nucleus Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

Anatomy of the Nucleus Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. nuclear envelope nucleolus Nuclear envelope: inner membrane outer membrane nuclear pore chromatin nucleoplasm phospholipid (Bottom): Courtesy Ron Milligan/Scripps Research Institute; (Top right): Courtesy E. G. Pollock 7

Ribosomes l Are the site of protein synthesis in the cell l Composed of

Ribosomes l Are the site of protein synthesis in the cell l Composed of r. RNA l l Consists of a large subunit and a small subunit l Subunits made in nucleolus May be located: l On the endoplasmic reticulum (thereby making it “rough”), or l Free in the cytoplasm, either singly or in groups, called polyribosomes 8

Nucleus, Ribosomes, & ER Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

Nucleus, Ribosomes, & ER Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Cytoplasm Endoplasmic reticulum (ER) ER membrane protein 4. An enzyme removes the signal peptide. 5. Ribosomal subunits and m. RNA break away. The protein remains in the ER and folds into its final shape. Lumen of ER enzyme receptor m. RNA SRP signal recognition particle (SRP) 2. Signal recognition particle (SRP) binds to signal peptide. 3. SRP attaches to receptor (purple); a channel opens; and the polypeptide enters ER. . signal peptide ribosomal subunits nuclear pore ribosome m. RNA 1. m. RNA is leaving the nucleus and is attached to the ribosome; protein synthesis is occurring. DNA Nucleus 9

Endomembrane System Series of intracellular membranes that compartmentalize the cell l Restrict enzymatic reactions

Endomembrane System Series of intracellular membranes that compartmentalize the cell l Restrict enzymatic reactions to specific compartments within cell l Consists of: l l l Nuclear envelope Membranes of endoplasmic reticulum Golgi apparatus Vesicles l l Several types Transport materials between organelles of system 10

Endomembrane System: The Endoplasmic Reticulum A system of membrane channels and saccules (flattened vesicles)

Endomembrane System: The Endoplasmic Reticulum A system of membrane channels and saccules (flattened vesicles) continuous with the outer membrane of the nuclear envelope l Rough ER l l l Studded with ribosomes on cytoplasmic side Protein anabolism l l Synthesizes proteins Modifies and processes proteins l l l Adds sugar to protein Results in glycoproteins Smooth ER l l No ribosomes Synthesis of lipids Site of various synthetic processes, detoxification, and storage Forms transport vesicles 11

Endoplasmic Reticulum Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or

Endoplasmic Reticulum Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. ribosomes nuclear envelope rough endoplasmic reticulum smooth endoplasmic reticulum 0. 08 m © R. Bolender & D. Fawcett/Visuals Unlimited 12

Endomembrane System: The Golgi Apparatus l Consists of 3 -20 flattened, curved saccules l

Endomembrane System: The Golgi Apparatus l Consists of 3 -20 flattened, curved saccules l Resembles stack of hollow pancakes l Modifies proteins and lipids l Receives vesicles from ER on cis (or inner face) l Packages them in vesicles l Prepares for “shipment” in v Packages them in vesicles from trans (or outer face) l Within cell l Export from cell (secretion, exocytosis) 13

Golgi Apparatus Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or

Golgi Apparatus Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. secretion transport vesicle saccules transport vesicle trans face cis face Golgi apparatus Nucleus 0. 1 m Courtesy Charles Flickinger, from Journal of Cell Biology 49: 221 -226, 1971, Fig. 1 page 224 14

Endomembrane System: Lysosomes l l Membrane-bound vesicles (not in plants) l Produced by the

Endomembrane System: Lysosomes l l Membrane-bound vesicles (not in plants) l Produced by the Golgi apparatus l Contain powerful digestive enzymes and are highly acidic l Digestion of large molecules l Recycling of cellular resources l Apoptosis (programmed cell death, like tadpole losing tail) Some genetic diseases l Caused by defect in lysosomal enzyme l Lysosomal storage diseases (Tay-Sachs) 15

Lysosomes Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.

Lysosomes Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. lysosome mitochondrion peroxisome fragment a. Mitochondrion and a peroxisome in a lysosome b. Storage bodies in a cell with defective lysosomes a: Courtesy Daniel S. Friend; b: Courtesy Robert D. Terry/Univ. of San Diego School of Medicine 16

Endomembrane System: Summary Proteins produced in rough ER and lipids from smooth ER are

Endomembrane System: Summary Proteins produced in rough ER and lipids from smooth ER are carried in vesicles to the Golgi apparatus. l The Golgi apparatus modifies these products and then sorts and packages them into vesicles that go to various cell destinations. l Secretory vesicles carry products to the membrane where exocytosis produces secretions. l Lysosomes fuse with incoming vesicles and digest macromolecules. l 17

Endomembrane System: A Visual Summary Copyright © The Mc. Graw-Hill Companies, Inc. Permission required

Endomembrane System: A Visual Summary Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. secretion plasma membrane incoming vesicle brings substances into the cell that are digested when the vesicle fuses with a lysosome secretory vesicle fuses with the plasma membrane as secretion occurs enzyme Golgi apparatus modifies lipids and proteins from the ER; sorts them and packages them in vesicles lysosome contains digestive enzymes that break down worn-out cell parts or substances entering the cell at the plasma membrane protein transport vesicle shuttles proteins to various locations such as the Golgi apparatus transport vesicle shuttles lipids to various locations such as the Golgi apparatus lipid rough endoplasmic reticulum synthesizes proteins and packages them in vesicles; vesicles commonly go to the Golgi apparatus smooth endoplasmic reticulum synthesizes lipids and also performs various other functions ribosome Nucleus 18

Peroxisomes l Similar to lysosomes l l l Membrane-bounded vesicles Enclose enzymes However l

Peroxisomes l Similar to lysosomes l l l Membrane-bounded vesicles Enclose enzymes However l l l Enzymes synthesized by free ribosomes in cytoplasm (instead of ER) Active in lipid metabolism Catalyze reactions that produce hydrogen peroxide H 2 O 2 l l Toxic Broken down to water & O 2 by catalase 19

Peroxisomes Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.

Peroxisomes Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 100 nm © S. E. Frederick & E. H. Newcomb/Biological Photo Service 20

Vacuoles l Membranous sacs that are larger than vesicles l l l Store materials

Vacuoles l Membranous sacs that are larger than vesicles l l l Store materials that occur in excess Others very specialized (contractile vacuole) Plants cells typically have a central vacuole l l Up to 90% volume of some cells Functions in: l l l Storage of water, nutrients, pigments, and waste products Development of turgor pressure Some functions performed by lysosomes in other eukaryotes 21

Vacuoles Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.

Vacuoles Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 100 nm © Newcomb/Wergin/Biological Photo Service 22

Energy-Related Organelles: Mitochondria l Smaller than chloroplast l Contain ribosomes and their own DNA

Energy-Related Organelles: Mitochondria l Smaller than chloroplast l Contain ribosomes and their own DNA l Surrounded by a double membrane l Inner membrane surrounds the matrix and is convoluted (folds) to form cristae. l Matrix – Inner semifluid containing respiratory enzymes l Break down carbohydrates l Involved in cellular respiration l Produce most of ATP utilized by the cell 23

Mitochondrial Structure Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or

Mitochondrial Structure Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 200 nm a. double membrane outer membrane inner membrane cristae matrix b. a: Courtesy Dr. Keith Porter 24

The Cytoskeleton l Maintains cell shape l Assists in movement of cell and organelles

The Cytoskeleton l Maintains cell shape l Assists in movement of cell and organelles l Three types of macromolecular fibers l l Actin Filaments l Intermediate Filaments l Microtubules Assemble and disassemble as needed 25

The Cytoskeleton: Actin Filaments Extremely thin filaments like twisted pearl necklace l Dense web

The Cytoskeleton: Actin Filaments Extremely thin filaments like twisted pearl necklace l Dense web just under plasma membrane maintains cell shape l Support for microvilli in intestinal cells l Intracellular traffic control l l l For moving stuff around within cell Cytoplasmic streaming Function in pseudopods of amoeboid cells Pinch mother cell in two after animal mitosis Important component in muscle contraction (other is myosin) 26

The Cytoskeleton: Actin Filament Operation Copyright © The Mc. Graw-Hill Companies, Inc. Permission required

The Cytoskeleton: Actin Filament Operation Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. actin filament ADP + ATP tail myosin molecules P head membrane 27

The Cytoskeleton: Intermediate Filaments l Intermediate in size between actin filaments and microtubules l

The Cytoskeleton: Intermediate Filaments l Intermediate in size between actin filaments and microtubules l Rope-like assembly of fibrous polypeptides l Vary in nature l l From tissue to tissue l From time to time Functions: l Support nuclear envelope l Cell-cell junctions, like those holding skin cells tightly together 28

The Cytoskeleton: Microtubules Hollow cylinders made of two globular proteins called a and b

The Cytoskeleton: Microtubules Hollow cylinders made of two globular proteins called a and b tubulin l Spontaneous pairing of a and b tubulin molecules form structures called dimers l Dimers then arrange themselves into tubular spirals of 13 dimers around l Assembly: l l Under control of Microtubule Organizing Center (MTOC) Most important MTOC is centrosome Interacts with proteins kinesin and dynein to cause movement of organelles 29

The Cytoskeleton: Microtubule Operation Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

The Cytoskeleton: Microtubule Operation Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. ATP vesicle kinesin receptor vesicle moves, not microtubule 30

The Cytoskeleton Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or

The Cytoskeleton Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. actin subunit Chara a. Actin filaments fibrous subunits peacock b. Intermediate filaments tubulin dimer chameleon c. Microtubules a(Actin): © M. Schliwa/Visuals Unlimited; b, c(Intermediate, Microtubules): © K. G. Murti/Visuals Unlimited; a(Chara): The Mc. Graw-Hill Companies, Inc. /photo by Dennis Strete and Darrell Vodopich; b(Peacock): © Vol. 86/Corbis; c(Chameleon): © Photodisc/Vol. 6/Getty Images 31

Microtubular Arrays: Centrioles l l l Short, hollow cylinders l Composed of 27 microtubules

Microtubular Arrays: Centrioles l l l Short, hollow cylinders l Composed of 27 microtubules l Microtubules arranged into 9 overlapping triplets One pair per animal cell l Located in centrosome of animal cells l Oriented at right angles to each other l Separate during mitosis to determine plane of division May give rise to basal bodies of cilia and flagella 32

Cytoskeleton: Centrioles Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or

Cytoskeleton: Centrioles Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. empty center of centriole one microtubule triplet one centrosome: one pair of centrioles two centrosomes: two pairs of centrioles 200 nm (Middle): Courtesy Kent Mc. Donald, University of Colorado Boulder; (Bottom): Journal of Structural Biology, Online by Manley Mc. Gill et al. Copyright 1976 by Elsevier Science & Technology Journals. Reproduced with permission of Elsevier Science & Technology Journals in the format Textbook via Copyright Clearance Center 33

Microtubular Arrays: Cilia and Flagella Hair-like projections from cell surface that aid in cell

Microtubular Arrays: Cilia and Flagella Hair-like projections from cell surface that aid in cell movement l Very different from prokaryote flagella l l l Outer covering of plasma membrane Inside this is a cylinder of 18 microtubules arranged in 9 pairs In center are two single microtubules This 9 + 2 pattern used by all cilia & flagella In eukaryotes, cilia are much shorter than flagella l l Cilia move in coordinated waves like oars Flagella move like a propeller or cork screw 34

Structure of a Flagellum Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for

Structure of a Flagellum Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. outer microtubule doublet Flagellum radial spoke central microtubules The shaft of the flagellum has a ring of nine microtubule doublets anchored to a central pair of microtubules. shaft dynein side arm Flagellum cross section Sperm plasma membrane triplets Basal body cross section 100 nm The basal body of a flagellum has a ring of nine microtubule triplets with no central microtubules. 25 nm The side arms of each doublet are composed of dynein, a motor molecule. dynein side arms ATP In the presence of ATP, the dynein side arms reach out to their neighbors, and bending occurs. (Flagellum, Basal body): © William L. Dentler/Biological Photo Service 35

Comparison of Prokaryotic and Eukaryotic Cells 36

Comparison of Prokaryotic and Eukaryotic Cells 36

Review l Cellular Level of Organization l l Cell theory Cell size Prokaryotic Cells

Review l Cellular Level of Organization l l Cell theory Cell size Prokaryotic Cells l Eukaryotic Cells l l l l Organelles Nucleus and Ribosome Endomembrane System Other Vesicles and Vacuoles Energy related organelles Cytoskeleton l Centrioles, Cilia, and Flagella 37

Reference Cell Structure and Function Chapter 4: pp. 59 -84 Sylvia S. Mader 38

Reference Cell Structure and Function Chapter 4: pp. 59 -84 Sylvia S. Mader 38