CHAPTER 4 A Tour of the Cell: History, Tools, Parts and Function.
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Transcript of CHAPTER 4 A Tour of the Cell: History, Tools, Parts and Function.
CHAPTER 4CHAPTER 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
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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
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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.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
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
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• 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.
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• The transmission electron microscope (TEM) is useful for exploring the internal structure of a cell.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Cells are different
Can be big, little, flat, round
• A nerve cell can be 2 meters long!
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
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
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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
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• After the rough ER synthesizes a molecule, it packages the molecule into transport vesicles.
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Smooth ER
• The smooth ER lacks the surface ribosomes of RER
– produces lipids, including steroids
– detoxifies poisons
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The Golgi Apparatus
• The Golgi apparatus
– Works in partnership with the ER.
– Refines, stores, and distributes ( SHIPS OUT ) the chemical products of cells.
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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
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Vacuoles
• Vacuoles are membranous sacs.
– Two types are the contractile vacuoles of protists and the central vacuoles of plants.
Paramecium Vacuole
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Chloroplasts
• Chloroplasts are the sites of photosynthesis, the conversion of light energy to chemical energy.
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Mitochondria
• Mitochondria are the sites of cellular respiration, which involves the production of ATP from food molecules.
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• Mitochondria and chloroplasts share another feature unique among eukaryotic organelles.
– They contain their own DNA.
• The existence of separate “mini-genomes” is believed to be evidence that
– Mitochondria and chloroplasts evolved from free-living prokaryotes in the distant past.
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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
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Cilia and Flagella
• Cilia and flagella are motile appendages.
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• Flagella propel the cell in a whiplike motion.
• Cilia move in a coordinated back-and-forth motion.
Paramecium Cilia
Cilia and Flagella
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• Some cilia or flagella extend from nonmoving cells.
– The human windpipe is lined with cilia.