CHAPTER 4 A Tour of the Cell
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings If you stacked up 8000 cell membranes, they would be only as thick as a page in this book Every second, your body produces about 2 million red blood cells
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings An electron microscope can visualize objects a million times smaller than the head of a pin The cells of a whale are about the same size as the cells of a mouse
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Antibiotics are one of the great marvels of modern medicine BIOLOGY AND SOCIETY: DRUGS THAT TARGET CELLS –Treatment with these drugs will kill invading bacteria –The drugs don’t harm the human cells of the host
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Cells are the building blocks of all life THE MICROSCOPIC WORLD OF CELLS Cells must be tiny for materials to move in and out of them fast enough to meet the cell’s metabolic needs
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Organisms are either: –Single-celled, such as most bacteria and protists –Mult-icelled, such as plants, animals, and most fungi
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The light microscope is used by many scientists Microscopes as Windows to Cells –Light passes through the specimen –Lenses enlarge, or magnify, the image (a) Light micrograph (LM) of a white blood cell (stained purple) surrounded by red blood cells
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Magnification –An increase in the specimen’s apparent size Resolving power –The ability of an optical instrument to show two objects as separate
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Cells were first discovered in 1665 by Robert Hooke The accumulation of scientific evidence led to the cell theory –All living things are composed of cells –All cells form from previously existing cells
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The electron microscope (EM) uses a beam of electrons –It has a higher resolving power than the light microscope
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The electron microscope can magnify up to 100,000X –Such power reveals the diverse parts within a cell Human height Length of some nerve and muscle cells Frog eggs Chicken egg Plant and animal cells Nucleus Most bacteria Mitochondrion Smallest bacteria Viruses Ribosomes Proteins Lipids Small molecules Atoms Unaided eye Light microscope Electron microscope
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings SEM The scanning electron microscope (SEM) is used to study the detailed architecture of the surface of a cell (b) Scanning electron micrograph (SEM) of cilia (above) And a white blood cell
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings TEM The transmission electron microscope (TEM) is useful for exploring the internal structure of a cell (c) Transmission electron micrograph (TEM) of a white blood cell & cilial
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The countless cells on earth fall into two categories The Two Major Categories of Cells –Prokaryotic cells –Eukaryotic cells
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Cell Size is Limited Surface to Volume Ratio limits upper size Larger cells have less surface area relative to volume
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic and eukaryotic cells differ in several respects Prokaryotic cell Nucleoid region Eukaryotic cell Nucleus Organelles
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic cells –Are smaller than eukaryotic cells –Lack internal structures surrounded by membranes –Lack a nucleus
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Prokaryotic flagella Nucleoid region (DNA) Ribosomes Plasma membrane Cell wall Capsule Pili
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings A Generic Animal Cell
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings An idealized plant cell
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Surrounded by a double membrane called the nuclear envelope Structure and Function of the Nucleus –It contains –chromatin -a DNA-protein structure –a nucleolus - which produces ribosomal parts –Nucleoplasm Occurs only in eukaryotic cells
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Nuclear Pore Complex Allows movement of material into and out of nucleus
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Ribosomes build all the cell’s proteins –Are not membrane bound Ribosomes
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings DNA controls the cell by transferring its coded information into RNA How DNA Controls the Cell –The information in the RNA is used to make proteins Synthesis of mRNA in the nucleus 1 2 Movement of mRNA into cytoplasm via nuclear pore 3 Synthesis of protein in the cytoplasm DNA mRNA Nucleus Cytoplasm mRNA Ribosome Protein
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Many of the membranous organelles in the cell belong to the endomembrane system –Endoplasmic reticulum - rough and smooth –Golgi Apparatus –Lysosomes –Vacuoles THE ENDOMEMBRANE SYSTEM: MANUFACTURING AND DISTRIBUTING CELLULAR PRODUCTS
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The endoplasmic reticulum (ER) The Endoplasmic Reticulum –Greek for ‘network within a cell’ –Produces an enormous variety of molecules –Is composed of smooth and rough ER Nuclear envelope Ribosomes Rough ER Smooth ER
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The “roughness” of the rough ER is due to ribosomes that stud the outside of the ER membrane Rough ER
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The functions of the rough ER include –Producing proteins –Producing new membrane
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings After the rough ER synthesizes a molecule it packages the molecule into transport vesicles 1
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Smooth ER The smooth ER lacks the surface ribosomes of ER Produces lipids, including steroids and sex hormones Regulates sugar Detoxifies drugs Stores calcium
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The Golgi apparatus The Golgi Apparatus –Works in partnership with the ER –Refines, stores, and distributes the products of cells Transport vesicle from ER “Receiving” side of Golgi apparatus New vesicle forming Transport vesicle from the Golgi “Shipping” side of Golgi apparatus Plasma membrane
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings A lysosome is a membrane-enclosed sac Lysosomes –Greek for ‘breakdown body’ –It contains digestive enzymes Isolated by membrane –The enzymes break down Macromolecules Old organelles
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Lysosomes have several types of digestive functions They exit the Golgi apparatus
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings –They fuse with food vacuoles to digest the food
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings –They fuse with old organelles to recycle parts –Digest bacteria in white blood cells
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Lysosomal diseases Genetic disorders Recipe is messed up Enzyme doesn’t work what should get broken down doesn’t Tay-Sachs lipids aren’t broken down build up occurs death by age 5 Pompe’s disease glycogen builds up
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Vacuoles are membranous sacs Vacuoles –Two types are the contractile vacuoles of protists and the central vacuoles of plants Figure 4.15 Contractile vacuoles Central vacuole (a) Contractile vacuoles in a protist(b) Central vacuole in a plant cell
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings A review of the endomembrane system
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Cells require a constant energy supply to do all the work of life CHLOROPLASTS AND MITOCHONDRIA: ENERGY CONVERSION
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Chloroplasts are the sites of photosynthesis, the conversion of light energy to chemical energy CHLOROPLASTS Figure 4.17 Inner and outer membranes of envelope Space between membranes Stroma (fluid in chloroplast) Granum
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Chloroplasts Double membrane Grana – Stacks of thylakoids Hollow disks Sunlight energy is coverted to chemical energy Stroma- fluid filling chloroplast Contains some DNA
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Mitochondria are the sites of cellular respiration, which involves the production of ATP from food molecules Mitochondria Figure 4.18 Outer membrane Inner membrane Cristae Matrix Space between membranes
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Mitochondria Double membrane –Big bag stuffed into smaller bag –Folds of inner bag called cristae Matrix -space inside inner bag Contains some DNA
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The cytoskeleton is an infrastructure of the cell consisting of a network of fibers –Microfilaments - small threads –Intermediate filaments - ropelike –Microtubules - small tubes THE CYTOSKELETON: CELL SHAPE AND MOVEMENT
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings One function of the cytoskeleton Maintaining Cell Shape –Provide mechanical support to the cell and maintain its shape
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Figure4.9x
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The cytoskeleton can change the shape of a cell –This allows cells like amoebae to move
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Cilia and flagella are motile appendages Cilia and Flagella
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Flagella propel the cell in a whiplike motion Cilia move in a coordinated back-and- forth motion Figure 4.20A, B
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Some cilia or flagella extend from nonmoving cells –The human windpipe is lined with cilia –Smoking damages the cilia
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Cilia and Flagella Same structure and function arrangement of microtubules Wrapped in plasma membrane
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Mechanism of Movement Dynein arms use ATP for energy to ‘walk’ up adjoining microtubule, causing them to bend
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Most cells secrete materials that are external to the plasma membrane This extra cellular matrix –Regulates –Protects –Supports CELL SURFACES: PROTECTION, SUPPORT, AND CELL-CELL INTERACTIONS
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Plant cells are encased by cell walls Plant Cell Walls and Cell Junctions Figure 4.21 –These provide support for the plant cells Walls of two adjacent plant cells Vacuole Plasmodesmata (channels between cells)
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Animal cells lack cell walls Animal Cell Surfaces and Cell Junctions –They secrete a sticky covering called the extracellular matrix –This layer helps hold cells together
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Animal cells connect by various types of junctions –Tight junctions - leakproof –Adhering junctions - hold cells together but allows movement between of materials between cells –Communicating junctions - like plasmodesmata
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Figure 4.22 Extracellular matrix (a) Tight junctions (b) Anchoring junctions (c) Communicating junctions Plasma membranes of adjacent cells Extracellular matrix
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings