A Tour of the Cell PDF

A Tour of the Cell Introduction to the Cell The Nucleus and Ribosomes PowerPoint Lectures f...

A Tour of the Cell Introduction to the Cell The Nucleus and Ribosomes PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey The Endomembrane Energy-Converting The Cytoskeleton © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko System Organelles and Cell Surfaces 4.1 Microscopes reveal the world of the cell INTRODUCTION TO THE CELL ▪ Using light microscopes, scientists studied – microorganisms, – animal and plant cells, and – some structures within cells. ▪ In the 1800s, these studies led to cell theory, which states that – all living things are composed of cells and – cell is the basic structural and functional unit of life – all cells come from other cells. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 1 Figure 4.1B Figure 4.1A 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 4.1C Figure 4.1D 2 4.2 The small size of cells relates to the need to 4.2 The small size of cells relates to the need to exchange materials across the plasma membrane exchange materials across the plasma membrane ▪ The plasma membrane forms a flexible boundary ▪ Membrane proteins are either between the living cell and its surroundings. – attached to the membrane surface or ▪ Phospholipids form a two-layer sheet called a – embedded in the phospholipid bilayer. phospholipid bilayer in which ▪ Some proteins form channels or tunnels that shield – hydrophilic heads face outward, exposed to water, and ions and other hydrophilic molecules as they pass – hydrophobic tails point inward, shielded from water. 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. © 2012 Pearson Education, Inc. Figure 4.2B 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells ▪ Bacteria and archaea are prokaryotic cells. Outside cell ▪ All other forms of life are composed of eukaryotic cells. Hydrophilic Hydrophobic heads region of – Prokaryotic and eukaryotic cells have a protein – a plasma membrane and Hydrophobic tails Hydrophilic – one or more chromosomes and ribosomes. region of Phospholipid Inside cell a protein – Eukaryotic cells have a Channel protein Proteins – membrane-bound nucleus and – number of other organelles. – Prokaryotes have a nucleoid and no true organelles. © 2012 Pearson Education, Inc. 3  Figure 4.3 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells Fimbriae Ribosomes ▪ The DNA of prokaryotic cells is coiled into a region called the nucleoid, but no membrane surrounds Nucleoid the DNA. Plasma membrane ▪ The surface of prokaryotic cells may Cell wall – be surrounded by a chemically complex cell wall, Bacterial chromosome Capsule – have a capsule surrounding the cell wall, Flagella A TEM of the bacterium – have short projections that help attach to other cells or A typical rod-shaped Bacillus coagulans bacterium the substrate, or – have longer projections called flagella that may propel the cell through its liquid environment. © 2012 Pearson Education, Inc. 4.4 Eukaryotic cells are partitioned into 4.4 Eukaryotic cells are partitioned into functional compartments functional compartments ▪ The structures and organelles of eukaryotic cells 3. Mitochondria in all cells and chloroplasts in plant cells perform four basic functions. are involved in energy processing. 1. The nucleus and ribosomes are involved in the genetic 4. Structural support, movement, and communication control of the cell. between cells are functions of the cytoskeleton, plasma membrane, and cell wall. 2. The endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and peroxisomes are involved in the manufacture, distribution, and breakdown of molecules. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 4 4.4 Eukaryotic cells are partitioned into 4.4 Eukaryotic cells are partitioned into functional compartments functional compartments ▪ The internal membranes of eukaryotic cells ▪ Almost all of the organelles and other structures of partition it into compartments. animals cells are present in plant cells. ▪ Cellular metabolism, the many chemical activities ▪ A few exceptions exist. of cells, occurs within organelles. – Lysosomes and centrioles are not found in plant cells. – Plant but not animal cells have – a rigid cell wall, – chloroplasts, and – a central vacuole. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. Figure 4.4A Figure 4.4B Smooth Rough NUCLEUS: Rough NUCLEUS: endoplasmic endoplasmic Nuclear endoplasmic Nuclear envelope reticulum reticulum envelope reticulum Chromatin Ribosomes Chromatin Nucleolus Nucleolus NOT IN MOST PLANT CELLS: Smooth Golgi endoplasmic Centriole apparatus reticulum Lysosome NOT IN ANIMAL CYTOSKELETON: CELLS: Microtubule Central vacuole Intermediate Chloroplast filament Cell wall Microfilament Plasmodesma Peroxisome Ribosomes Mitochondrion Golgi apparatus Peroxisome CYTOSKELETON: Plasma membrane Microtubule Mitochondrion Intermediate filament Cell wall of adjacent cell Microfilament Plasma membrane 5  4.5 The nucleus is the cell’s genetic control center THE NUCLEUS AND RIBOSOMES ▪ 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. © 2012 Pearson Education, Inc. 4.5 The nucleus is the cell’s genetic control center 4.5 The nucleus is the cell’s genetic control center ▪ The nuclear envelope ▪ The nucleolus is – is a double membrane and – a prominent structure in the nucleus and – has pores that allow material to flow in and out of the – the site of ribosomal RNA (rRNA) synthesis. nucleus. ▪ The nuclear envelope is attached to a network of cellular membranes called the endoplasmic reticulum. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 6 Figure 4.5 4.6 Ribosomes make proteins for use in the cell and export ▪ Ribosomes are involved in the cell’s protein synthesis. Nucleus Two membranes – Ribosomes are synthesized from rRNA produced in the of nuclear envelope nucleolus. Chromatin Nucleolus – Cells that must synthesize large amounts of protein Pore have a large number of ribosomes. Endoplasmic reticulum Ribosomes © 2012 Pearson Education, Inc. Figure 4.6 4.6 Ribosomes make proteins for use in the cell and export Ribosomes ER Cytoplasm ▪ Some ribosomes are free ribosomes; others are Endoplasmic reticulum (ER) bound. Free ribosomes Bound – Free ribosomes are ribosomes – suspended in the cytoplasm and – typically involved in making proteins that function within the cytoplasm. Colorized TEM showing – Bound ribosomes are ER and ribosomes – attached to the endoplasmic reticulum (ER) associated with mRNA the nuclear envelope and Protein Diagram of a ribosome – associated with proteins packed in certain organelles or exported from the cell. © 2012 Pearson Education, Inc. 7  4.7 Overview: Many cell organelles are connected through the endomembrane system THE ENDOMEMBRANE ▪ Many of the membranes within a eukaryotic cell are part of the endomembrane system. 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. © 2012 Pearson Education, Inc. 4.7 Overview: Many cell organelles are connected 4.8 The endoplasmic reticulum is a biosynthetic through the endomembrane system factory ▪ The endomembrane system includes ▪ There are two kinds of endoplasmic reticulum— – the nuclear envelope, smooth and rough. – endoplasmic reticulum (ER), – Smooth ER lacks attached ribosomes. – Golgi apparatus, – Rough ER lines the outer surface of membranes. – lysosomes, – Although physically interconnected, smooth and rough ER differ in structure and function. – vacuoles, and – the plasma membrane. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 8 Figure 4.8A Figure 4.8B Transport vesicle Nuclear buds off 4 envelope Secretory mRNA protein inside trans- Ribosome port vesicle Ribosomes Smooth ER 3 Rough ER 1 Sugar chain Glycoprotein 2 Polypeptide Rough ER 4.8 The endoplasmic reticulum is a biosynthetic 4.8 The endoplasmic reticulum is a biosynthetic factory factory ▪ Smooth ER is involved in a variety of diverse ▪ Rough ER makes metabolic processes. – additional membrane for itself and – Smooth ER produces enzymes important in the – proteins destined for secretions. synthesis of lipids, oils, phospholipids, and steroids. – Other enzymes help process drugs, alcohol, and other potentially harmful substances. – Some smooth ER helps store calcium ions. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 9  Figure 4.9 4.9 The Golgi apparatus finishes, sorts, and ships cell products “Receiving” side of Golgi ▪ The Golgi apparatus serves as a molecular apparatus warehouse and finishing factory for products Golgi Golgi apparatus apparatus manufactured by the ER. 1 Transport Transport – Products travel in transport vesicles from the ER to the vesicle vesicle from Golgi apparatus. from ER 2 the Golgi – One side of the Golgi apparatus functions as a receiving 3 dock for the product and the other as a shipping dock. 4 – Products are modified as they go from one side of the “Shipping” 4 Golgi apparatus to the other and travel in vesicles to side of Golgi other sites. apparatus © 2012 Pearson Education, Inc. 4.10 Lysosomes are digestive compartments 4.10 Lysosomes are digestive compartments within a cell within a cell ▪ A lysosome is a membranous sac containing ▪ Lysosomes help digest food particles engulfed by a digestive enzymes. cell. – The enzymes and membrane are produced by the ER 1. A food vacuole binds with a lysosome. and transferred to the Golgi apparatus for processing. 2. The enzymes in the lysosome digest the food. – The membrane serves to safely isolate these potent enzymes from the rest of the cell. 3. The nutrients are then released into the cell. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 10 Figure 4.10A_s1 Figure 4.10A_s2 Digestive Digestive enzymes enzymes Lysosome Lysosome Food vacuole Plasma membrane Plasma membrane Figure 4.10A_s3 Figure 4.10A_s4 Digestive Digestive enzymes enzymes Lysosome Lysosome Digestion Food vacuole Food vacuole Plasma membrane Plasma membrane 11  Figure 4.10B_s1 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. Lysosome 2. Then a lysosome – fuses with the vesicle, Vesicle containing damaged mitochondrion – dismantles its contents, and – breaks down the damaged organelle. © 2012 Pearson Education, Inc. Figure 4.10B_s2 Figure 4.10B_s3 Lysosome Lysosome Vesicle containing Vesicle containing Digestion damaged mitochondrion damaged mitochondrion 12  Figure 4.11A 4.11 Vacuoles function in the general maintenance of the cell ▪ Vacuoles are large vesicles that have a variety of functions. Contractile vacuoles – Some protists have contractile vacuoles that help to eliminate water from the protist. – In plants, vacuoles may – have digestive functions, Nucleus – contain pigments, or – contain poisons that protect the plant. © 2012 Pearson Education, Inc. Figure 4.11B 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 Central vacuole system. Chloroplast Nucleus © 2012 Pearson Education, Inc. 13 Figure 4.12 Nucleus Nuclear membrane Rough ER Transport ENERGY-CONVERTING vesicle from Smooth ER Golgi to ORGANELLES Transport plasma vesicle from ER membrane to Golgi Golgi Lysosome Vacuole Plasma apparatus membrane © 2012 Pearson Education, Inc. 4.13 Mitochondria harvest chemical energy from 4.13 Mitochondria harvest chemical energy from food food ▪ Mitochondria are organelles that carry out cellular ▪ Mitochondria have two internal compartments. respiration in nearly all eukaryotic cells. 1. The intermembrane space is the narrow region between ▪ Cellular respiration converts the chemical energy in the inner and outer membranes. foods to chemical energy in ATP (adenosine 2. The mitochondrial matrix contains triphosphate). – the mitochondrial DNA, – ribosomes, and – many enzymes that catalyze some of the reactions of cellular respiration. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 14 Figure 4.13 4.14 Chloroplasts convert solar energy to Mitochondrion chemical energy ▪ Chloroplasts are the photosynthesizing organelles Outer of all photosynthesizing eukaryotes. membrane ▪ Photosynthesis is the conversion of light energy Intermembrane space from the sun to the chemical energy of sugar molecules. Inner membrane Cristae Matrix © 2012 Pearson Education, Inc. Figure 4.14 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 Inner and Stroma Chloroplast Granum – a thick fluid called stroma that contains the chloroplast DNA, outer ribosomes, and many enzymes and membranes – 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. Thylakoid © 2012 Pearson Education, Inc. 15 4.15 EVOLUTION CONNECTION: 4.15 EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by Mitochondria and chloroplasts evolved by endosymbiosis endosymbiosis ▪ Mitochondria and chloroplasts have ▪ The endosymbiont theory proposes that – DNA and – mitochondria and chloroplasts were formerly small prokaryotes and – ribosomes. – they began living within larger cells. ▪ The structure of this DNA and these ribosomes is very similar to that found in prokaryotic cells. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. Figure 4.15 Mitochondrion Nucleus Endoplasmic THE CYTOSKELETON AND reticulum Engulfing of photosynthetic CELL SURFACES Some prokaryote cells Engulfing Chloroplast of oxygen- Host cell using prokaryote Mitochondrion Host cell © 2012 Pearson Education, Inc. 16 4.16 The cell’s internal skeleton helps organize 4.16 The cell’s internal skeleton helps organize its structure and activities its structure and activities ▪ Cells contain a network of protein fibers, called the ▪ The cytoskeleton is composed of three kinds of cytoskeleton, which functions in structural support fibers. and motility. 1. Microfilaments (actin filaments) support the cell’s ▪ Scientists believe that motility and cellular shape and are involved in motility. regulation result when the cytoskeleton interacts 2. Intermediate filaments reinforce cell shape and anchor with proteins called motor proteins. organelles. 3. Microtubules (made of tubulin) give the cell rigidity and act as tracks for organelle movement. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. Figure 4.16 4.17 Cilia and flagella move when microtubules bend Nucleus ▪ While some protists have flagella and cilia that are Nucleus 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. Actin subunit Fibrous subunits Tubulin subunits 7 nm 10 nm 25 nm Microfilament Intermediate filament Microtubule © 2012 Pearson Education, Inc. 17 Figure 4.17A Figure 4.17B Flagellum Cilia Figure 4.17C Figure 4.17C_1 Outer microtubule doublet Central microtubules Outer Radial spoke microtubule doublet Dynein proteins Central microtubules Radial spoke Dynein proteins Plasma membrane 18 4.17 Cilia and flagella move when microtubules 4.17 Cilia and flagella move when microtubules bend bend ▪ A flagellum, longer than cilia, propels a cell by an ▪ Both flagella and cilia are made of microtubules undulating, whiplike motion. wrapped in an extension of the plasma membrane. ▪ Cilia work more like the oars of a crew boat. ▪ A ring of nine microtubule doublets surrounds a central pair of microtubules. This arrangement is ▪ Although differences exist, flagella and cilia have a common structure and mechanism of movement. – called the 9 + 2 pattern and – anchored in a basal body with nine microtubule triplets arranged in a ring. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 4.17 Cilia and flagella move when microtubules 4.18 CONNECTION: Problems with sperm bend motility may be environmental or genetic ▪ Cilia and flagella move by bending motor proteins ▪ In developed countries over the last 50 years, there called dynein feet. has been a decline in sperm quality. – These feet attach to and exert a sliding force on an ▪ The causes of this decline may be adjacent doublet. – environmental chemicals or – The arms then release and reattach a little further along and repeat this time after time. – genetic disorders that interfere with the movement of sperm and cilia. Primary ciliary dyskinesia (PCD) is a – This “walking” causes the microtubules to bend. rare disease characterized by recurrent infections of the respiratory tract and immotile sperm. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 19 4.19 The extracellular matrix of animal cells 4.19 The extracellular matrix of animal cells functions in support and regulation functions in support and regulation ▪ Animal cells synthesize and secrete an elaborate ▪ The ECM may attach to a cell through extracellular matrix (ECM) that glycoproteins that then bind to membrane proteins called integrins. Integrins span the plasma – helps hold cells together in tissues and membrane and connect to microfilaments of the – protects and supports the plasma membrane. cytoskeleton. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. Figure 4.19 4.20 Three types of cell junctions are found in Glycoprotein EXTRACELLULAR FLUID animal tissues complex with long polysaccharide ▪ Adjacent cells communicate, interact, and adhere Collagen fiber through specialized junctions between them. Connecting – Tight junctions prevent leakage of extracellular fluid glycoprotein across a layer of epithelial cells. Integrin – Anchoring junctions fasten cells together into sheets. Plasma – Gap junctions are channels that allow molecules to membrane flow between cells. CYTOPLASM Microfilaments of cytoskelton © 2012 Pearson Education, Inc. 20 Figure 4.20 Tight junctions 4.21 Cell walls enclose and support plant cells prevent fluid from moving between cells ▪ A plant cell, but not an animal cell, has a rigid cell wall that Tight junction – protects and provides skeletal support that helps keep the plant upright against gravity and Anchoring junction – is primarily composed of cellulose. Gap junction ▪ Plant cells have cell junctions called plasmodesmata that serve in communication Plasma membranes between cells. of adjacent cells Extracellular matrix © 2012 Pearson Education, Inc. Figure 4.21 Plant cell walls Vacuole Plasmodesmata Primary cell wall Secondary cell wall Plasma membrane Cytoplasm 21