CHAPTER 4 A Tour of the Cell: History, Tools, Parts and Function
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings History Cells couldn’t be discovered until the microscope was invented Anton von Leeuwenhoek 1673 Simple Microscopes Basically a hand lens Looked at water, poop, muscle tissue, bacteria, mold, bees, lice
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings History Robert Hooke – 1665 – Cork cells First to use the word ‘cell’ to describe the boxes he saw in cork, a plant
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The accumulation of scientific evidence led to the cell theory. –All living things are composed of cells. –All cells are formed from previously existing cells.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The compound microscope
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The compound microscope Resolving power –Is the ability of an optical instrument to show two objects as being separate. Magnification –Is an increase in the specimen’s apparent size.
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Magnification Total Magnification is: ocular lens x the objective –10x X 4x = 40 times magnified –The object should look 40x larger than normal Field of view – the size of the area you can see Which picture has a larger field of view?
Figure 4.3
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The electron microscope (EM) uses a beam of electrons. –It has a higher resolving power than the light microscope. The electron microscope can magnify up to 100,000X. –Such power reveals the diverse parts within a cell.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The scanning electron microscope (SEM) is used to study the detailed architecture of the surface of a cell.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The transmission electron microscope (TEM) is useful for exploring the internal structure of a cell.
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Cells are different Can be big, little, flat, round A nerve cell can be 2 meters long!
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The Two Major Categories of Cells The countless cells on earth fall into two categories: –Prokaryotic cells –Eukaryotic cells
Figure 4.4
The Plasma Membrane: A Fluid Mosaic of Lipids and Proteins The membranes of cells are composed mostly of: –Lipids –Proteins The lipids belong to a special category called phospholipids. Phospholipids form a two-layered membrane, the phospholipid bilayer. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Figure 4.7b
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Membrane phospholipids and proteins can drift about in the plane of the membrane. This behavior leads to the description of a membrane as a fluid mosaic: –Molecules can move freely within the membrane. –A diversity of proteins exists within the membrane.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Cell Surfaces Most cells secrete materials for coats of one kind or another –That are external to the plasma membrane. These extracellular coats help protect and support cells –And facilitate interactions between cellular neighbors in tissues.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Plant cells have cell walls, –Which help protect the cells, maintain their shape, and keep the cells from absorbing too much water. Animal cells have an extracellular matrix, –Which helps hold cells together in tissues and protects and supports them.
The Nucleus and Ribosomes: Genetic Control of the Cell The nucleus controls the cell –Genes in the nucleus (DNA) store information necessary to produce proteins. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Structure and Function of the Nucleus The nucleus is bordered by a double membrane called the nuclear envelope. –It contains chromatin. –It contains a nucleolus. Ribosomes are responsible for protein synthesis. –Made in the nucleolus
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings How DNA Controls the Cell DNA controls the cell by transferring its coded information into RNA. –The information in the RNA is used to make proteins.
The Endomembrane System: Manufacturing and Distributing Cellular Products Many of the membranous organelles in the cell belong to the endomembrane system. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Rough ER The “roughness” of the rough ER is due to ribosomes that stud the outside of the ER membrane. The functions of the rough ER include: –Producing proteins to be sent out of the cell –Producing new membrane lipids
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings After the rough ER synthesizes a molecule, it packages the molecule into transport vesicles.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Smooth ER The smooth ER lacks the surface ribosomes of RER –produces lipids, including steroids –detoxifies poisons
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Golgi Apparatus The Golgi apparatus –Works in partnership with the ER. –Refines, stores, and distributes ( SHIPS OUT ) the chemical products of cells.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Lysosomes A lysosome is a membrane-enclosed sac. –It contains digestive enzymes. –The enzymes break down macromolecules from the food you eat. Break down old organelles
Figure 4.13a
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Vacuoles Vacuoles are membranous sacs. –Two types are the contractile vacuoles of protists and the central vacuoles of plants. Paramecium Vacuole
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chloroplasts Chloroplasts are the sites of photosynthesis, the conversion of light energy to chemical energy.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Mitochondria Mitochondria are the sites of cellular respiration, which involves the production of ATP from food molecules.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Mitochondria and chloroplasts share another feature unique among eukaryotic organelles. –T–They contain their own DNA. The existence of separate “mini-genomes” is believed to be evidence that –M–Mitochondria and chloroplasts evolved from free-living prokaryotes in the distant past.
Cytoskeleton: Microtubules and Microfilaments functions of the cytoskeleton –Both structure and movement Skeleton and muscles –Protect cell from breaking –Help move organelles into place –Organize DNA for cell division
Figure 4.18a
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Cilia and Flagella Cilia and flagella are motile appendages.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Flagella propel the cell in a whiplike motion. Cilia move in a coordinated back-and-forth motion. Paramecium Cilia Cilia and Flagella
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Some cilia or flagella extend from nonmoving cells. –The human windpipe is lined with cilia.