Chapter 4: A Tour of the Cell PDF

Chapter 4 A Tour of the Cell PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko  http://imgur.com/FGYUR Figure 4.0_1 Chapter...

Chapter 4 A Tour of the Cell PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko  http://imgur.com/FGYUR Figure 4.0_1 Chapter 4: Big Ideas Introduction to the Cell The Nucleus and Ribosomes The Endomembrane Energy-Converting The Cytoskeleton System Organelles and Cell Surfaces Cells were first observed by Robert Hooke in 1665. Invented the microscope Little rooms or “cellulae” Working with more refined lenses, Antoni van Leeuwenhoek later described blood, sperm, and organisms living in pond water Figure 4.0_2  INTRODUCTION TO THE CELL © 2012 Pearson Education, Inc. 4.1 Microscopes reveal the world of the cell  A variety of microscopes have been developed for a clearer view of cells and cellular structure.  The most frequently used microscope is the light microscope (LM)—like the one used in biology laboratories. – Light passes through a specimen, then through glass lenses, and finally light is projected into the viewer’s eye. – Specimens can be magnified up to 1,000 times the actual size of the specimen. © 2012 Pearson Education, Inc. 4.1 Microscopes reveal the world of the cell  Magnification is the increase in the apparent size of an object.  Resolution is a measure of the clarity of an image. In other words, it is the ability of an instrument to show two close objects as separate. © 2012 Pearson Education, Inc. 4.1 Microscopes reveal the world of the cell  Microscopes have limitations. – The human eye and the microscope have limits of resolution—the ability to distinguish between small structures. – Therefore, the light microscope cannot provide the details of a small cell’s structure. © 2012 Pearson Education, Inc. 4.1 Microscopes reveal the world of the cell  In the 1800s, these studies led to cell theory, which states that – all living things are composed of cells and – all cells come from other cells. © 2012 Pearson Education, Inc. Figure 4.1A Figure 4.1B 10 m Human height 1m Length of some nerve and muscle Unaided eye cells 100 mm (10 cm) Chicken egg 10 mm (1 cm) Frog egg 1 mm Paramecium Light microscope Human egg 100 m Most plant and animal cells 10 m Nucleus Most bacteria Electron microscope Mitochondrion 1 m Smallest bacteria 100 nm Viruses Ribosome 10 nm Proteins Lipids 1 nm Small molecules 0.1 nm Atoms Figure 4.1B_1 10 m Human height 1m Length of some nerve and muscle Unaided eye 100 mm cells (10 cm) Chicken egg 10 mm (1 cm) Frog egg 1 mm Paramecium 100 m Figure 4.1B_2 Frog egg 1 mm Paramecium Light microscope Human egg 100 m Most plant and animal cells 10 m A normal size range for a Nucleus typical eukaryotic cell is __ Most bacteria Electron microscope Mitochondrion 1 m A)1 to 10 nanometers B) 10 to 100 100 nm Smallest bacteria Viruses nanometers C) 1 to 10 Ribosome 10 nm micrometers Proteins D) 10 to 100 Lipids micrometers 1 nm Small molecules 0.1 nm Atoms Figure 4.1B_3 4.1 Microscopes reveal the world of the cell  Beginning in the 1950s, scientists started using a very powerful microscope called the electron microscope (EM) to view the ultrastructure of cells. – Instead of light, EM uses a beam of electrons.  Electron microscopes can – resolve biological structures as small as 2 nanometers and – magnify up to 1,000,000 times. © 2012 Pearson Education, Inc. 4.1 Microscopes reveal the world of the cell  Scanning electron microscopes (SEM) study the detailed architecture of cell surfaces.  Transmission electron microscopes (TEM) study the details of internal cell structure. © 2012 Pearson Education, Inc. Figure 4.1D  Cells must – be large enough to house DNA, proteins, and structures needed to survive and reproduce, © 2012 Pearson Education, Inc. Figure 4.1B_2 Frog egg 1 mm Paramecium Light microscope Human egg 100 m Most plant and animal cells 10 m A normal size range for a Nucleus typical eukaryotic cell is __ Most bacteria Electron microscope Mitochondrion 1 m A)1 to 10 nanometers B) 10 to 100 100 nm Smallest bacteria Viruses nanometers C) 1 to 10 Ribosome 10 nm micrometers Proteins D) 10 to 100 Lipids micrometers 1 nm Small molecules 0.1 nm Atoms  So, why are they so small? © 2012 Pearson Education, Inc. Figure 4.2A 3 1 1 3 Total volume Lxwxh Total surface 6 x (L x w) area Surface-to- volume ratio Figure 4.2A 3 1 1 3 Total volume 27 units3 27 units3 Total surface area 54 units2 162 units2 Surface-to- 6 2 volume ratio As cell size increases, the ANSWER: A) volume and surface area decrease. B) volume increases proportionally more than the surface area. C) ratio of surface area to volume stays the same. D) surface area increases proportionally more than the volume. 4.2 The small size of cells relates to the need to exchange materials across the plasma membrane – Many people think of plasma membranes as mainly containment, like that of a plastic bag – Think of them more like skin. © 2012 Pearson Education, Inc. Which part of the mitochondrion shown enhances its ability to produce ATP by increasing the surface area of a mitochondrial membrane? structure A structure B structure C structure D 4.2 The small size of cells relates to the need to exchange materials across the plasma membrane – For example, membranes and our skin both detect stimuli, engage in gas exchange, and serve as sites of excretion and absorption.) © 2012 Pearson Education, Inc. 4.2 The small size of cells relates to the need to exchange materials across the plasma membrane  The plasma membrane forms a flexible boundary between the living cell and its surroundings.  Phospholipids form a two-layer sheet called a phospholipid bilayer in which – hydrophilic heads face outward, exposed to water, and – hydrophobic tails point inward, shielded from water. © 2012 Pearson Education, Inc. 4.2 The small size of cells relates to the need to exchange materials across the plasma membrane  Membrane proteins are either – attached to the membrane surface or – embedded in the phospholipid bilayer.  Some proteins form channels or tunnels that shield ions* and other hydrophilic molecules as they pass through the hydrophobic center of the membrane.  Other proteins serve as pumps, using energy to actively transport molecules into or out of the cell. © 2012 Pearson Education, Inc. An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Figure 4.2B Outside cell Hydrophilic Hydrophobic heads region of a protein Hydrophobic tails Hydrophilic region of Phospholipid Inside cell a protein Channel protein Proteins How is a cell membrane like a peanut butter and jelly bean sandwich? 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. – Prokaryotic and eukaryotic cells have – a plasma membrane (cell membrane) and – one or more chromosomes and ribosomes. – Eukaryotic cells have a – membrane-bound nucleus and – number of other organelles. – Prokaryotes have a nucleoid and no true organelles. © 2012 Pearson Education, Inc. 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells  The DNA of prokaryotic cells is coiled into a region called the nucleoid, but no membrane surrounds the DNA.  The surface of prokaryotic cells may – be surrounded by a chemically complex cell wall, – have a capsule surrounding the cell wall, – have short projections that help attach to other cells or the substrate, or – have longer projections called flagella that may propel the cell through its liquid environment. © 2012 Pearson Education, Inc. Figure 4.UN01 Figure 4.3 Fimbriae Ribosomes Nucleoid Plasma membrane Cell wall Bacterial chromosome Capsule Flagella A TEM of the bacterium A typical rod-shaped Bacillus coagulans bacterium 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. (The Endomembrane system, however, consists of Nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles and the plasma (cell) membrane.) © 2012 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. © 2012 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. © 2012 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 centrioles are not found in plant cells. – Plant but not animal cells have – a rigid cell wall, and anything that has to do with the cell wall like plasmodesmata. – chloroplasts, and – a central vacuole. © 2012 Pearson Education, Inc. Concept Check The three domains of life described by biologists today include the bacteria, the archaea, and the eukarya (all other forms of life). What is the basic difference between the eukarya or eukaryotes and the prokaryotes (archaea and bacteria)? a) The prokaryotes do not have a plasma membrane surrounding the cell. b) The prokaryotes use RNA and not DNA to pass on the genetic message. c) The interior of the cell of eukaryotes is divided by internal membranes into specialized compartments. d) The eukaryotes engage in cellular metabolism while the prokaryotes do not. © 2012 Pearson Education, Inc. Answer The three domains of life described by biologists today include the bacteria, the archaea, and the eukarya (all other forms of life). What is the basic difference between the eukarya or eukaryotes and the prokaryotes (archaea and bacteria)? c) The interior of the cell of eukaryotes is divided by internal membranes into specialized compartments. © 2012 Pearson Education, Inc. Figure 4.4A Smooth Rough NUCLEUS: endoplasmic endoplasmic Nuclear reticulum reticulum envelope Chromatin Nucleolus NOT IN MOST PLANT CELLS: Centriole Lysosome Peroxisome Ribosomes Golgi apparatus CYTOSKELETON: Microtubule Mitochondrion Intermediate filament Microfilament Plasma membrane Figure 4.4B Rough NUCLEUS: endoplasmic Nuclear envelope Chromatin reticulum Ribosomes Nucleolus Smooth Golgi endoplasmic apparatus reticulum NOT IN ANIMAL CYTOSKELETON: CELLS: Microtubule Central vacuole Intermediate Chloroplast filament Cell wall Microfilament Plasmodesma Mitochondrion Peroxisome Plasma membrane Cell wall of adjacent cell Concept Check The cell is sometimes described as a protein factory. Using the cell- as-factory analogy, which of the following accurately describes the functions of the endomembrane system? a) The ribosomes on the rough endoplasmic reticulum are analogous to a production line in a factory. b) The Golgi apparatus is analogous to the packaging and shipping department. c) The nucleus is analogous to management offices. d) All of the above. © 2012 Pearson Education, Inc. Answer The cell is sometimes described as a protein factory. Using the cell-as- factory analogy, which of the following accurately describes the functions of the endomembrane system? d) All of the above. © 2012 Pearson Education, Inc.  THE NUCLEUS AND RIBOSOMES © 2012 Pearson Education, Inc. 4.5 The nucleus is the cell’s genetic control center  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 in structures called chromosomes. © 2012 Pearson Education, Inc. 4.5 The nucleus is the cell’s genetic control center  The nuclear envelope (also known as the nuclear membrane) – is a double membrane and – has pores that allow material to flow in and out of the nucleus. (The plasma membrane doesn’t have pores, what does it have instead?)  The nuclear envelope is attached to a network of cellular membranes called the endoplasmic reticulum. © 2012 Pearson Education, Inc. 4.5 The nucleus is the cell’s genetic control center  The nucleolus is – a prominent structure in the nucleus and – the site of ribosomal RNA (rRNA) synthesis. © 2012 Pearson Education, Inc. Figure 4.5 Nucleus Two membranes of nuclear envelope Chromatin Nucleolus Pore Endoplasmic reticulum Ribosomes Figure 4.5_1 Two membranes of nuclear envelope Chromatin Nucleolus Pore Endoplasmic reticulum 4.6 Ribosomes make proteins for use in the cell and export  Ribosomes are involved in the cell’s protein synthesis. – Ribosomes are synthesized from rRNA produced in the nucleolus. – Cells that must synthesize large amounts of protein have a large number of ribosomes. © 2012 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 cytoplasm and – typically involved in making proteins that function within the cytoplasm. (Make proteins for use within the cell.) – Bound ribosomes are – attached to the endoplasmic reticulum (ER) associated with the nuclear envelope and – associated with proteins packed in certain organelles or exported from the cell. (Make proteins that are transported out of the cell.) © 2012 Pearson Education, Inc. Figure 4.6 Ribosomes ER Cytoplasm Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Colorized TEM showing ER and ribosomes mRNA Protein Diagram of a ribosome Figure 4.6_1 Cytoplasm Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Colorized TEM showing ER and ribosomes  THE ENDOMEMBRANE SYSTEM © 2012 Pearson Education, Inc. Figure 4.12 Nucleus Nuclear membrane Rough ER Transport vesicle from Smooth Golgi to ER Transport plasma vesicle from ER membrane to Golgi Golgi Lysosome Vacuole Plasma apparatus membrane 4.7 Overview: Many cell organelles are connected through 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 some are related by the transfer of membrane segments by tiny vesicles (sacs made of membrane).  Many of these organelles work together in the – synthesis, – storage, and – export of molecules. © 2012 Pearson Education, Inc. Studies of the endomembrane system often involve the use of a protein that can emit a green fluorescence (glow). A researcher wants to make a video of cell behavior, so she initially labels the outer nuclear envelope of a cell with the fluorescent tag and records a video for several hours. Later, she sees that the tag is part of a transport vesicle very close to the plasma membrane. Which organ is least likely to incorporate the fluorescent tag? 4.7 Overview: Many cell organelles are connected through the endomembrane system  The endomembrane system includes  the nuclear envelope,  endoplasmic reticulum (ER),  Golgi apparatus,  lysosomes,  vacuoles, and  the plasma membrane. © 2012 Pearson Education, Inc. 4.8 The endoplasmic reticulum is a biosynthetic factory  There are two kinds of endoplasmic reticulum— smooth and rough. – Smooth ER lacks attached ribosomes. – Rough ER lines the outer surface of membranes. – Although physically interconnected, smooth and rough ER differ in structure and function. © 2012 Pearson Education, Inc. Figure 4.8A Nuclear envelope Ribosomes Smooth ER Rough ER Figure 4.8B Transport vesicle buds off 4 Secretory mRNA protein inside trans- Ribosome port vesicle 3 1 Sugar chain Glycoprotein 2 Polypeptide Rough ER Figure 4.8A_1 Ribosome Smooth ER Rough ER  4.8 The endoplasmic reticulum is a biosynthetic factory  Smooth ER is involved in a variety of diverse metabolic processes. – Smooth ER produces enzymes important in the synthesis of lipids, oils, phospholipids, and steroids. – Other enzymes made by the smooth ER help process drugs, alcohol, and other potentially harmful substances. – Some smooth ER helps store calcium ions. (Important in muscle contraction.) © 2012 Pearson Education, Inc. 4.8 The endoplasmic reticulum is a biosynthetic factory  Rough ER makes – additional membrane for itself and – proteins destined for secretions. © 2012 Pearson Education, Inc. The two main functions of the rough endoplasmic reticulum are the production of A) mitochondria and proteins secreted by the cell. B) hydrogen peroxide and steroid hormones secreted by the cell. C) ribosomes and steroid hormones. D) membrane and proteins secreted by the cell. You are told that the cells on a microscope slide are plant, animal, or bacterial. You look at them through a microscope and see cell walls and membrane-bound organelles. You conclude correctly that the cells A) are plant cells. B) are animal cells. C) are bacterial cells. D) could be either plant or bacterial cells 4.9 The Golgi apparatus finishes, sorts, and ships cell products  The Golgi apparatus serves as a molecular warehouse and finishing factory for products manufactured by the ER. – Products travel in transport vesicles from the ER to the Golgi apparatus. – One side of the Golgi apparatus functions as a receiving dock for the product and the other as a shipping dock. – Products are modified as they go from one side of the Golgi apparatus to the other and travel in vesicles to other sites. © 2012 Pearson Education, Inc. Figure 4.9 “Receiving” side of Golgi apparatus Golgi Golgi apparatus apparatus 1 Transport Transport vesicle vesicle from from ER 2 the Golgi 3 4 4 “Shipping” side of Golgi apparatus Figure 4.9_1 Golgi apparatus These are flattened sacs and are Not connected More secretion of proteins =more golgi sacs Transport vesicle from the Golgi The Golgi apparatus A) is composed of stacks of membranous vesicles that are continuous with one another. B) stores, modifies, and packages proteins. C) strings together amino acids to produce proteins. D) is the site of carbohydrate breakdown. An immune system cell called the plasma cell produces thousands of antibodies (proteins) per second for release into the body. What type of intracellular structure would you expect to be very prominent within the cell? A) nucleus B) rough endoplasmic reticulum C) peroxisome D) microtubules 4.10 Lysosomes are digestive compartments within a cell  A lysosome is a membranous sac containing digestive enzymes. (lysosomes are not found in plants) – The enzymes and membrane are produced by the rough ER and transferred to the Golgi apparatus for processing. – The membrane serves to safely isolate these potent enzymes from the rest of the cell. © 2012 Pearson Education, Inc. 4.10 Lysosomes are digestive compartments within a cell  Lysosomes help digest food particles engulfed by a cell. 1. A food vacuole binds with a lysosome. 2. The enzymes in the lysosome digest the food. 3. The nutrients are then released into the cell. © 2012 Pearson Education, Inc. Figure 4.10A_s1 Digestive enzymes Acidic! Lysosome About a pH of 5, instead of 7.2 in cytoplasm Plasma membrane To maintain their acidic internal pH, lysosomes must actively concentrate H+ ions (protons). Figure 4.10A_s2 Digestive enzymes Lysosome Food vacuole Plasma membrane Figure 4.10A_s3 Digestive enzymes Lysosome Food vacuole Plasma membrane Figure 4.10A_s4 Digestive enzymes Lysosome Digestion Food vacuole Plasma membrane 4.10 Lysosomes are digestive compartments within a cell  Lysosomes also help remove or recycle damaged parts of a cell. 1. The damaged organelle is first enclosed in a membrane vesicle. 2. Then a lysosome – fuses with the vesicle, – dismantles its contents, and – breaks down the damaged organelle. © 2012 Pearson Education, Inc. Which of the following statements about lysosomes is false? A) Lysosomes help to digest worn-out or damaged organelles. B) Lysosomes synthesize proteins from the recycled amino acids. C) Lysosomes fuse with food vacuoles to expose nutrients to lysosomal enzymes. D) Lysosomes destroy harmful bacteria engulfed by white blood cells. When a cell is deprived of oxygen, its lysosomes tend to burst and release their contents into the cell. As a result of this, that cell will A) recycle damaged organelles. B) undergo cell division. C) produce replacement lysosomes. D) undergo self-digestion and die.  Animation: Lysosome Formation Right click on animation / Click play © 2012 Pearson Education, Inc. Figure 4.10B_s1 Lysosome Vesicle containing damaged mitochondrion Figure 4.10B_s2 Lysosome Vesicle containing damaged mitochondrion Figure 4.10B_s3 Lysosome Vesicle containing Digestion damaged mitochondrion 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 that help to eliminate water from the protist. – In plants, vacuoles may – have digestive functions, – contain pigments, or – contain poisons that protect the plant. – Maintain pressure in the plant (holds water) © 2012 Pearson Education, Inc. Figure 4.11A Contractile vacuoles If an organism lives in pure water, it would need to Nucleus use these vacuoles often, in order to pump water out of itself. Figure 4.11B Central vacuole Chloroplast Nucleus Contractile vacuoles A) are generally found in protists that inhabit salt water. B) help in the excretion of excess salt. C) prevent cells from bursting as a result of the influx of excess water. D) allow organisms to avoid dehydration by absorbing water from the environment. A manufacturing company dumps its wastes into a nearby pond. One of the wastes is found to paralyze the contractile vacuoles of certain protists. A biologist looking at individual samples of these organisms taken from the pond would find that they ANSWER: A)have gained water and burst. B)have died because wastes C)have built up in the cytoplasm. D) have lost water and shrunk. E) have died of malnutrition.  ENERGY-CONVERTING ORGANELLES © 2012 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). © 2012 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 mitochondrial matrix contains – the mitochondrial DNA, – ribosomes, and – many enzymes that catalyze some of the reactions of cellular respiration. © 2012 Pearson Education, Inc. Figure 4.13 Mitochondrion Outer membrane Intermembrane space Inner membrane Cristae Matrix Figure 4.13_1 Outer membrane Inner membrane Cristae Matrix 4.14 Chloroplasts convert solar energy to chemical energy  Chloroplasts are the photosynthesizing organelles of all photosynthesizing eukaryotes.  Photosynthesis is the conversion of light energy from the sun to the chemical energy of sugar molecules. © 2012 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 that contains the chloroplast DNA, ribosomes, and many enzymes and – a network of interconnected sacs called thylakoids. – In some regions, thylakoids are stacked like poker chips. Each stack is called a granum,where green chlorophyll molecules trap solar energy. © 2012 Pearson Education, Inc. Figure 4.14 Inner and Chloroplast Granum Stroma outer membranes Thylakoid Figure 4.14_1 Inner and Granum Stroma outer membranes 4.15 EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by endosymbiosis  Mitochondria and chloroplasts have – DNA and – ribosomes.  The structure of this DNA and these ribosomes is very similar to that found in prokaryotic cells. © 2012 Pearson Education, Inc. 4.15 EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by endosymbiosis  The endosymbiont theory proposes that – mitochondria and chloroplasts were formerly small prokaryotes and – they began living within larger cells. © 2012 Pearson Education, Inc. Figure 4.15 Mitochondrion Nucleus Endoplasmic reticulum Engulfing of photosynthetic Some prokaryote cells Engulfing Chloroplast of oxygen- Host cell using prokaryote Mitochondrion Host cell  THE CYTOSKELETON AND CELL SURFACES © 2012 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 functions in structural support and motility.  Scientists believe that motility and cellular regulation result when the cytoskeleton interacts with proteins called motor proteins. © 2012 Pearson Education, Inc.  Video: Cytoplasmic Streaming Use window controls to play © 2012 Pearson Education, Inc. 4.16 The cell’s internal skeleton helps organize its structure and activities  The cytoskeleton is composed of three kinds of fibers. 1. Microfilaments (actin filaments) support the cell’s shape and are involved in motility. 2. Intermediate filaments reinforce cell shape and anchor organelles. 3. Microtubules (made of tubulin) give the cell rigidity and act as tracks for organelle movement. © 2012 Pearson Education, Inc. Figure 4.16 Nucleus Nucleus Actin subunit Fibrous subunits Tubulin subunits 7 nm 10 nm 25 nm Microfilament Intermediate filament Microtubule Figure 4.16_1 Actin subunit 7 nm Microfilament Figure 4.16_2 Nucleus Fibrous subunits 10 nm Intermediate filament Figure 4.16_3 Nucleus Tubulin subunits 25 nm Microtubule Figure 4.16_4 Figure 4.16_5 Figure 4.16_6 4.17 Cilia and flagella move when microtubules bend  While some protists have flagella and cilia that are important in locomotion, some cells of multicellular organisms have them for different reasons. – Cells that sweep mucus out of our lungs have cilia. – Animal sperm are flagellated. – Are protists eukaryotic or prokaryotic? © 2012 Pearson Education, Inc. Figure 4.17A Cilia Figure 4.17B Flagellum Figure 4.17C Outer microtubule doublet Central microtubules Radial spoke Dynein proteins Plasma membrane Figure 4.17C_1 Outer microtubule doublet Central microtubules Radial spoke Dynein proteins 4.17 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 crew boat.  Although differences exist, flagella and cilia have a common structure and mechanism of movement. © 2012 Pearson Education, Inc. 4.17 Cilia and flagella move when microtubules bend  Both flagella and cilia are made of microtubules wrapped in an extension of the plasma membrane.  A ring of nine microtubule doublets surrounds a central pair of microtubules. This arrangement is – called the 9 + 2 pattern and – anchored in a basal body with nine microtubule doublets arranged in a ring. © 2012 Pearson Education, Inc.  Animation: Cilia and Flagella Right click on animation / Click play © 2012 Pearson Education, Inc. 4.17 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. – The arms then release and reattach a little further along and repeat this time after time. – This “walking” causes the microtubules to bend. © 2012 Pearson Education, Inc. 4.18 CONNECTION: Problems with sperm motility may be environmental or genetic  In developed countries over the last 50 years, there has been a decline in sperm quality.  The causes of this decline may be – environmental chemicals or – genetic disorders that interfere with the movement of sperm and cilia. Primary ciliary dyskinesia (PCD) is a rare disease characterized by recurrent infections of the respiratory tract and immotile sperm. © 2012 Pearson Education, Inc. Figure 4.18 4.19 The extracellular matrix of animal cells functions in support and regulation  Animal cells synthesize and secrete an elaborate extracellular matrix (ECM) that – helps hold cells together in tissues and – protects and supports the plasma membrane. © 2012 Pearson Education, Inc. 4.19 The extracellular matrix of animal cells functions in support and regulation  The ECM may attach to a cell through glycoproteins that then bind to membrane proteins called integrins. Integrins span the plasma membrane and connect to microfilaments of the cytoskeleton. © 2012 Pearson Education, Inc. Figure 4.19 Glycoprotein EXTRACELLULAR FLUID complex with long polysaccharide Collagen fiber Connecting glycoprotein Integrin Plasma membrane CYTOPLASM Microfilaments of cytoskelton 4.20 Three types of cell junctions are found in animal tissues  Adjacent cells communicate, interact, and adhere through specialized junctions between them. – Tight junctions prevent leakage of extracellular fluid across a layer of epithelial cells. – Anchoring junctions fasten cells together into sheets. – Gap junctions are channels that allow molecules to flow between cells. © 2012 Pearson Education, Inc.  Animation: Desmosomes Right click on animation / Click play © 2012 Pearson Education, Inc.  Animation: Gap Junctions Right click on animation / Click play © 2012 Pearson Education, Inc.  Animation: Tight Junctions Right click on animation / Click play © 2012 Pearson Education, Inc. Figure 4.20 Tight junctions prevent fluid from moving between cells Tight junction prevent leakage of extracellular fluid across a layer of Anchoring epithelial cells. junction fasten cells together into sheets. Gap junction are channels that allow molecules Plasma membranes to flow of adjacent cellsbetween cells. Extracellular matrix Channel between our cells Allows water to move between plant cells Allows solutes to move between plant cells Holds animal cells together Connects our cells into a strong sheet Keeps animal cells from leaking Tight Junction Plasmodesma Gap junction Anchoring junction 4.21 Cell walls enclose and support plant cells  A plant cell, but not an animal cell, has a rigid cell wall that – protects and provides skeletal support that helps keep the plant upright against gravity and – is primarily composed of cellulose.  Plant cells have cell junctions called _____ that serve in communication between cells. © 2012 Pearson Education, Inc. 4.21 Cell walls enclose and support plant cells  A plant cell, but not an animal cell, has a rigid cell wall that – protects and provides skeletal support that helps keep the plant upright against gravity and – is primarily composed of cellulose.  Plant cells have cell junctions called plasmodesmata that serve in communication between cells. © 2012 Pearson Education, Inc. Figure 4.21 Plant cell walls Vacuole Plasmodesmata Primary cell wall Secondary cell wall Plasma membrane Cytoplasm 4.22 Review: Eukaryotic cell structures can be grouped on the basis of four basic functions  Eukaryotic cell structures can be grouped on the basis of four functions: 1. genetic control, 2. manufacturing, distribution, and breakdown, 3. energy processing, and 4. structural support, movement, and communication between cells. © 2012 Pearson Education, Inc. Table 4.22 Table 4.22_1 Table 4.22_2 You should now be able to 1. Describe the importance of microscopes in understanding cell structure and function. 2. Describe the two parts of cell theory. 3. Distinguish between the structures of prokaryotic and eukaryotic cells. 4. Explain how cell size is limited. 5. Describe the structure and functions of cell membranes. © 2012 Pearson Education, Inc. You should now be able to 6. Explain why compartmentalization is important in eukaryotic cells. 7. Compare the structures of plant and animal cells. Note the function of each cell part. 8. Compare the structures and functions of chloroplasts and mitochondria. 9. Describe the evidence that suggests that mitochondria and chloroplasts evolved by endosymbiosis. © 2012 Pearson Education, Inc. You should now be able to 10. Compare the structures and functions of microfilaments, intermediate filaments, and microtubules. 11. Relate the structure of cilia and flagella to their functions. 12. Relate the structure of the extracellular matrix to its functions. 13. Compare the structures and functions of tight junctions, anchoring junctions, and gap junctions. © 2012 Pearson Education, Inc. You should now be able to 14. Relate the structures of plant cell walls and plasmodesmata to their functions. 15. Describe the four functional categories of organelles in eukaryotic cells. © 2012 Pearson Education, Inc. Figure 4.UN02 Figure 4.UN03 a. l. b. c. k. j. i. h. d. g. e. f. Interpreting Data Images generated by the Hubble telescope or the planetary probes like Voyager telescope give us a very limited view of the universe. Likewise, looking at cells under a light microscope is limited by the ability to resolve cellular parts. Which of the following cell parts are visible under a light microscope? a) ribosomes b) large macromolecules c) microtubules d) mitochondria—just barely © 2012 Pearson Education, Inc. Answer Images generated by the Hubble telescope or the planetary probes like Voyager telescope give us a very limited view of the universe. Likewise, looking at cells under a light microscope is limited by the ability to resolve cellular parts. Which of the following cell parts are visible under a light microscope? d) mitochondria—just barely © 2012 Pearson Education, Inc. Looking at the following cells: Which of the following is correct? A)Cell A has the greatest surface area, Cell B has the greater volume, Cell A has the greater surface area to volume ratio B) Cell A has the greatest surface area, Cell A has the greater volume, Cell A has the greater surface area to volume ratio C) Cell B has the greater surface area, Cell B has the greater volume, Cell A has the greater surface area to volume ratio D) Cell A has the greater surface area, Cell A has the greater volume, Cell B has the greater surface area to volume ratio If photosynthesis is related to light energy, then the portions of a leaf shaded from light will test negative for starch, since starch is a product of photosynthesis. What is the independent and dependent variable in this experiment? A) photosynthesis, light exposure B) Light exposure, leaf growth C) Light exposure, starch production D) Starch production, Light exposure The smallest unit at which the properties of life can be established: A)Molecule B) Cell C) Organelle D) Organism