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Chapter 4 A Tour of the Cell PowerPoint Lectures Campbell Biology: Concepts & Connections, Eighth Edition REECE •TAYLOR • SIMON•DICKEY• HOGAN © 2015 Pearson Education, Inc. Lecture by Edward J. Zalisko INTRODUCTION TO THE CELL © 2015 Pearson Education, Inc. 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells • Bacteria and archaea are prokaryotic cells. • All other forms of life are composed of eukaryotic cells. • Eukaryotic cells are distinguished by having • a membrane-enclosed nucleus and • many membrane-enclosed organelles that perform specific functions. • Prokaryotic cells are smaller and simpler in structure. © 2015 Pearson Education, Inc. 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells • Prokaryotic and eukaryotic cells have • a plasma membrane, • an interior filled with a thick, jellylike fluid called the cytosol, • one or more chromosomes, which carry genes made of DNA, and • ribosomes, tiny structures that make proteins according to instructions from the genes. © 2015 Pearson Education, Inc. 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells • The inside of both types of cells is called the cytoplasm. • However, in eukaryotic cells, this term refers only to the region between the nucleus and the plasma membrane. © 2015 Pearson Education, Inc. 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells • In a prokaryotic cell, • the DNA is coiled into a region called the nucleoid (nucleus-like) and • no membrane surrounds the DNA. © 2015 Pearson Education, Inc. 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells • Outside the plasma membrane of most prokaryotes is a fairly rigid, chemically complex cell wall, which • protects the cell and • helps maintain its shape. • Some prokaryotes have surface projections. • Short projections help attach prokaryotes to each other or their substrate. • Longer projections called flagella (singular, flagellum) propel a prokaryotic cell through its liquid environment. © 2015 Pearson Education, Inc. Figure 4.3-0 Fimbriae Ribosomes Nucleoid Plasma membrane Cell wall Bacterial chromosome A typical rod-shaped bacterium © 2015 Pearson Education, Inc. Capsule A colorized TEM of the bacterium Escherichia coli Flagella 4.4 Eukaryotic cells are partitioned into functional compartments • A eukaryotic cell contains • a membrane-enclosed nucleus and • various other organelles (“little organs”), which perform specific functions in the cell. © 2015 Pearson Education, Inc. 4.4 Eukaryotic cells are partitioned into functional compartments • The structures and organelles of eukaryotic cells perform four basic functions. 1. The nucleus and ribosomes are involved in the genetic control of the cell. 2. The endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and peroxisomes are involved in the manufacture, distribution, and breakdown of molecules. © 2015 Pearson Education, Inc. 4.4 Eukaryotic cells are partitioned into functional compartments 3. Mitochondria in all cells and chloroplasts in plant cells are involved in energy processing. 4. Structural support, movement, and communication between cells are functions of the cytoskeleton, plasma membrane, and cell wall. © 2015 Pearson Education, Inc. 4.4 Eukaryotic cells are partitioned into functional compartments • The internal membranes of eukaryotic cells partition it into compartments. • Cellular metabolism, the many chemical activities of cells, occurs within organelles. © 2015 Pearson Education, Inc. 4.4 Eukaryotic cells are partitioned into functional compartments • Almost all of the organelles and other structures of animals cells are present in plant cells. • A few exceptions exist. • Lysosomes and centrosomes containing centrioles are not found in plant cells. • Only the sperm cells of a few plant species have flagella. © 2015 Pearson Education, Inc. 4.4 Eukaryotic cells are partitioned into functional compartments • Plant but not animal cells have • a rigid cell wall that contains cellulose, • plasmodesmata, cytoplasmic channels through cell walls that connect adjacent cells, • chloroplasts, where photosynthesis occurs, and • a central vacuole, a compartment that stores water and a variety of chemicals. © 2015 Pearson Education, Inc. Figure 4.4a Rough endoplasmic reticulum NUCLEUS Nuclear envelope Nucleolus Chromatin Ribosomes CYTOSKELETON Microtubule Microfilament Intermediate filament Peroxisome Smooth endoplasmic reticulum Plasma membrane Golgi apparatus Lysosome Mitochondrion © 2015 Pearson Education, Inc. Centrosome with pair of centrioles Figure 4.4b Smooth endoplasmic reticulum NUCLEUS Nuclear envelope Nucleolus Chromatin Rough endoplasmic reticulum Mitochondrion CYTOSKELETON Microfilament Microtubule Central vacuole Ribosomes Chloroplast Cell wall Plasmodesma Cell wall of adjacent cell Golgi apparatus Peroxisome Plasma membrane © 2015 Pearson Education, Inc. THE NUCLEUS AND RIBOSOMES © 2015 Pearson Education, Inc. 4.5 The nucleus contains the cell’s genetic instructions • The nucleus • contains most of the cell’s DNA and • controls the cell’s activities by directing protein synthesis by making messenger RNA (mRNA). • DNA is associated with many proteins and is organized into structures called chromosomes. • When a cell is not dividing, this complex of proteins and DNA, called chromatin, appears as a diffuse mass within the nucleus. © 2015 Pearson Education, Inc. 4.5 The nucleus contains the cell’s genetic instructions • The double membrane nuclearenvelope has pores that • regulate the entry and exit of large molecules and • connect with the cell’s network of membranes called the endoplasmic reticulum. © 2015 Pearson Education, Inc. 4.5 The nucleus contains the cell’s genetic instructions • The nucleolus is • a prominent structure in the nucleus and • the site of ribosomal RNA (rRNA) synthesis. © 2015 Pearson Education, Inc. Figure 4.5 Nuclear envelope Endoplasmic reticulum Ribosome © 2015 Pearson Education, Inc. Nucleolus Pore Chromatin 4.6 Ribosomes make proteins for use in the cell and export • Ribosomes are involved in the cell’s protein synthesis. • Ribosomes are the cellular components that use instructions from the nucleus, written in mRNA, to build proteins. • Cells that make a lot of proteins have a large number of ribosomes. © 2015 Pearson Education, Inc. 4.6 Ribosomes make proteins for use in the cell and export • Some ribosomes are free ribosomes; others are bound. • Free ribosomes are suspended in the cytosol. • Bound ribosomes are attached to the outside of the endoplasmic reticulum or nuclear envelope. © 2015 Pearson Education, Inc. Figure 4.6 Rough ER Bound ribosome Endoplasmic reticulum Protein Ribosome Free ribosome mRNA © 2015 Pearson Education, Inc. THE ENDOMEMBRANE SYSTEM © 2015 Pearson Education, Inc. 4.7 Many organelles are connected in the endomembrane system • Many of the membranes within a eukaryotic cell are part of the endomembrane system. • Some of these membranes are physically connected, and others are linked when tiny vesicles (sacs made of membrane) transfer membrane segments between them. © 2015 Pearson Education, Inc. 4.7 Many organelles are connected in the endomembrane system • Many of these organelles interact in the • • • • synthesis, distribution, storage, and export of molecules. © 2015 Pearson Education, Inc. 4.7 Many organelles are connected in the endomembrane system • The endomembrane system includes the • • • • • • nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, and plasma membrane. © 2015 Pearson Education, Inc. 4.7 Many organelles are connected in the endomembrane system • The largest component of the endomembrane system is the endoplasmic reticulum (ER), an extensive network of flattened sacs and tubules. © 2015 Pearson Education, Inc. 4.8 The endoplasmic reticulum is a biosynthetic workshop • There are two kinds of endoplasmic reticulum, which differ in structure and function. 1. SmoothER lacks attached ribosomes. 2. RoughERhas bound ribosomes that stud the outer surface of the membrane. © 2015 Pearson Education, Inc. Figure 4.8a Rough ER Smooth ER Ribosomes Rough ER Smooth ER © 2015 Pearson Education, Inc. Figure 4.8b Transport vesicle buds off 4 Secretory protein inside transport vesicle mRNA Bound ribosome 3 Sugar chain 1 2 Growing polypeptide © 2015 Pearson Education, Inc. Glycoprotein Rough ER 4.8 The endoplasmic reticulum is a biosynthetic workshop • Smooth ER is involved in a variety of metabolic processes, including • the production of enzymes important in the synthesis of lipids, oils, phospholipids, and steroids, • the production of enzymes that help process drugs, alcohol, and other potentially harmful substances, and • the storage of calcium ions. © 2015 Pearson Education, Inc. 4.8 The endoplasmic reticulum is a biosynthetic workshop • Rough ER makes • additional membrane for itself and • secretory proteins. © 2015 Pearson Education, Inc. 4.9 The Golgi apparatus modifies, sorts, and ships cell products • The Golgi apparatus serves as a molecular warehouse and processing station for products manufactured by the ER. • Products travel in transport vesicles from the ER to the Golgi apparatus. • One side of the Golgi stack serves as a receiving dock for transport vesicles produced by the ER. © 2015 Pearson Education, Inc. 4.9 The Golgi apparatus modifies, sorts, and ships cell products • Products of the ER are modified as a Golgi sac progresses through the stack. • The “shipping” side of the Golgi functions as a depot, where products in vesicles bud off and travel to other sites. ©© 2015 Pearson Education, Inc. 2012 Pearson Education, Inc. Figure 4.9 “Receiving” side of Golgi apparatus Transport vesicle from the ER 1 2 3 Golgi apparatus 4 Transport vesicle from the Golgi “Shipping” side of Golgi apparatus © 2015 Pearson Education, Inc. 4.10 Lysosomes are digestive compartments within a cell • A lysosome is a membrane-enclosed sac of digestive enzymes • made by rough ER and • processed in the Golgi apparatus © 2015 Pearson Education, Inc. 4.10 Lysosomes are digestive compartments within a cell • Lysosomes • fuse with food vacuoles and digest food, • destroy bacteria engulfed by white blood cells, or • fuse with other vesicles containing damaged organelles or other materials to be recycled within a cell. © 2015 Pearson Education, Inc. Figure 4.10b-3 Lysosome Digestion Vesicle containing damaged mitochondrion © 2015 Pearson Education, Inc. 4.11 Vacuoles function in the general maintenance of the cell • Vacuoles are large vesicles that have a variety of functions. • Some protists have contractile vacuoles, which help to eliminate water from the protist. • In plants, vacuoles may • have digestive functions, • contain pigments, or • contain poisons that protect the plant. © 2015 Pearson Education, Inc. Figure 4.11a Contractile vacuoles Nucleus © 2015 Pearson Education, Inc. Figure 4.11b Central vacuole Chloroplast Nucleus © 2015 Pearson Education, Inc. 4.12 A review of the structures involved in manufacturing and breakdown • The following figure summarizes the relationships among the major organelles of the endomembrane system. © 2015 Pearson Education, Inc. Figure 4.12 Nucleus Smooth ER Nuclear envelope Rough ER Golgi apparatus Transport vesicle Plasma membrane Lysosome Transport vesicle © 2015 Pearson Education, Inc. 4.12 A review of the structures involved in manufacturing and breakdown • Peroxisomes are metabolic compartments that do not originate from the endomembrane system. • How they are related to other organelles is still unknown. • Some peroxisomes break down fatty acids to be used as cellular fuel. © 2015 Pearson Education, Inc. ENERGY-CONVERTING ORGANELLES © 2015 Pearson Education, Inc. 4.13 Mitochondria harvest chemical energy from food • Mitochondria are organelles that carry out cellular respiration in nearly all eukaryotic cells. • Cellular respiration converts the chemical energy in foods to chemical energy in ATP (adenosine triphosphate). © 2015 Pearson Education, Inc. 4.13 Mitochondria harvest chemical energy from food • Mitochondria have two internal compartments. 1. The intermembrane space is the narrow region between the inner and outer membranes. 2. The mitochondrialmatrix contains • the mitochondrial DNA, • ribosomes, and • many enzymes that catalyze some of the reactions of cellular respiration. © 2015 Pearson Education, Inc. 4.13 Mitochondria harvest chemical energy from food • Folds of the inner mitochondrial membrane, called cristae, increase the membrane’s surface area, enhancing the mitochondrion’s ability to produce ATP. © 2015 Pearson Education, Inc. Figure 4.13 Mitochondrion Intermembrane space Outer membrane Inner membrane Crista Matrix © 2015 Pearson Education, Inc. 4.14 Chloroplasts convert solar energy to chemical energy • Photosynthesis is the conversion of light energy from the sun to the chemical energy of sugar molecules. • Chloroplasts are the photosynthesizing organelles of plants and algae. © 2015 Pearson Education, Inc. 4.14 Chloroplasts convert solar energy to chemical energy • Chloroplasts are partitioned into compartments. • Between the outer and inner membrane is a thin intermembrane space. • Inside the inner membrane is a thick fluid called stroma, which contains the chloroplast DNA, ribosomes, many enzymes, and a network of interconnected sacs called thylakoids, where green chlorophyll molecules trap solar energy. • In some regions, thylakoids are stacked like poker chips. Each stack is called a granum. © 2015 Pearson Education, Inc. Figure 4.14 Chloroplast Granum Stroma Inner and outer membranes © 2015 Pearson Education, Inc. Thylakoid 4.15 EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by endosymbiosis • Mitochondria and chloroplasts contain • DNA and • ribosomes. • The structure of this DNA and these ribosomes is very similar to that found in prokaryotic cells. © 2015 Pearson Education, Inc. 4.15 EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by endosymbiosis • The endosymbionttheory states that • mitochondria and chloroplasts were formerly small prokaryotes and • they began living within larger cells. © 2015 Pearson Education, Inc. Figure 4.15 Endoplasmic reticulum Nucleus Engulfing of oxygenusing prokaryote Ancestor of eukaryotic cells (host cell) Mitochondrion Engulfing of photosynthetic prokaryote Mitochondrion At least one cell Nonphotosynthetic eukaryote Chloroplast Photosynthetic eukaryote © 2015 Pearson Education, Inc. THE CYTOSKELETON AND CELL SURFACES © 2015 Pearson Education, Inc. 4.16 The cell’s internal skeleton helps organize its structure and activities • Cells contain a network of protein fibers, called the cytoskeleton, which organize the structures and activities of the cell. © 2015 Pearson Education, Inc. 4.16 The cell’s internal skeleton helps organize its structure and activities • Microtubules (made of tubulin) • shape and support the cell and • act as tracks along which organelles equipped with motor proteins move. • In animal cells, microtubules grow out from a region near the nucleus called the centrosome, which contains a pair of centrioles, each composed of a ring of microtubules. © 2015 Pearson Education, Inc. 4.16 The cell’s internal skeleton helps organize its structure and activities • Intermediatefilaments • are found in the cells of most animals, • reinforce cell shape and anchor some organelles, and • are often more permanent fixtures in the cell. © 2015 Pearson Education, Inc. 4.16 The cell’s internal skeleton helps organize its structure and activities • Microfilaments (actin filaments) • support the cell’s shape and • are involved in motility. © 2015 Pearson Education, Inc. Figure 4.16-0 Nucleus Nucleus 10 nm 7 nm 25 nm Intermediate filament Microtubule © 2015 Pearson Education, Inc. Microfilament 4.17 SCIENTIFIC THINKING: Scientists discovered the cytoskeleton using the tools of biochemistry and microscopy • In the 1940s, biochemists first isolated and identified the proteins actin and myosin from muscle cells. • In 1954, scientists, using newly developed techniques of microscopy, established how filaments of actin and myosin interact in muscle contraction. • In the next decade, researchers identified actin filaments in all types of cells. © 2015 Pearson Education, Inc. 4.17 SCIENTIFIC THINKING: Scientists discovered the cytoskeleton using the tools of biochemistry and microscopy • In the 1970s, scientists were able to visualize actin filaments using fluorescent tags and in living cells. • In the 1980s, biologists were able to record the changing architecture of the cytoskeleton. © 2015 Pearson Education, Inc. Figure 4.17 © 2015 Pearson Education, Inc. 4.18 Cilia and flagella move when microtubules bend • The short, numerous appendages that propel protists such as Paramecium are called cilia (singular, cilium). • Other protists may move using flagella, which are longer than cilia and usually limited to one or a few per cell. • Some cells of multicellular organisms also have cilia or flagella. © 2015 Pearson Education, Inc. Figure 4.18b Flagellum © 2015 Pearson Education, Inc. 4.18 Cilia and flagella move when microtubules bend • A flagellum, longer than cilia, propels a cell by an undulating, whiplike motion. • Cilia work more like the oars of a boat. • Although differences exist, flagella and cilia have a common structure and mechanism of movement. © 2015 Pearson Education, Inc. 4.18 Cilia and flagella move when microtubules bend • Both flagella and cilia are composed of microtubules wrapped in an extension of the plasma membrane. • In nearly all eukaryotic cilia and flagella, a ring of nine microtubule doublets surrounds a central pair of microtubules. • This arrangement is called the 9 2 pattern. • The microtubule assembly is anchored in a basal body with nine microtubule triplets arranged in a ring. © 2015 Pearson Education, Inc. Figure 4.18c-0 Outer microtubule doublet Central microtubules Cross-linking proteins Motor proteins (dyneins) Plasma membrane © 2015 Pearson Education, Inc. 4.18 Cilia and flagella move when microtubules bend • Cilia and flagella move by bending motor proteins called dynein feet. • These feet attach to and exert a sliding force on an adjacent doublet. • This “walking” causes the microtubules to bend. © 2015 Pearson Education, Inc. 4.19 The extracellular matrix of animal cells functions in support and regulation • Animal cells synthesize and secrete an elaborate extracellularmatrix (ECM), which • helps hold cells together in tissues and • protects and supports the plasma membrane. © 2015 Pearson Education, Inc. 4.19 The extracellular matrix of animal cells functions in support and regulation • The ECM may attach to the cell through other glycoproteins that then bind to membrane proteins called integrins. • Integrins • span the membrane and • attach on the other side to proteins connected to microfilaments of the cytoskeleton. © 2015 Pearson Education, Inc. Figure 4.19 Glycoprotein complex with long polysaccharide EXTRACELLULAR FLUID Collagen fiber Connecting glycoprotein Integrin Plasma membrane CYTOPLASM Microfilaments of cytoskeleton © 2015 Pearson Education, Inc. 4.20 Three types of cell junctions are found in animal tissues • Adjacent cells adhere, interact, and communicate through specialized junctions between them. • Tight junctions prevent leakage of fluid across a layer of epithelial cells. • Anchoring junctions fasten cells together into sheets. • Gap junctions are channels that allow small molecules to flow through protein-lined pores between cells. © 2015 Pearson Education, Inc. Figure 4.20 Tight junctions prevent fluid from moving across a layer of cells Tight junction Anchoring junction Gap junction Plasma membranes of adjacent cells Ions or small molecules © 2015 Pearson Education, Inc. Extracellular matrix 4.21 Cell walls enclose and support plant cells • A plant cell, but not an animal cell, has a rigid cellwall that • protects and provides skeletal support that helps keep the plant upright and • is primarily composed of cellulose. • Plant cells have cell junctions called plasmodesmata that allow plants tissues to share • water, • nourishment, and • chemical messages. © 2015 Pearson Education, Inc. Figure 4.21 Plant cell walls Vacuole Plasmodesmata Primary cell wall Secondary cell wall Plasma membrane Cytosol © 2015 Pearson Education, Inc. 4.22 Review: Eukaryotic cell structures can be grouped on the basis of four main functions • Eukaryotic cell structures can be grouped on the basis of four functions: 1. genetic control, 2. manufacturing, distribution, and breakdown of materials, 3. energy processing, and 4. structural support, movement, and intercellular communication. © 2015 Pearson Education, Inc. Table 4-22-0 © 2015 Pearson Education, Inc.