Cell Biology of Disease The cell biology of Parkinson sdisease
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Transcript of Http:// Biology Review Cell Biology.
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Biology ReviewCell Biology
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Much of the text material is from, “Essential Biology with Physiology” by Neil A. Campbell, Jane B. Reece, and Eric J. Simon
(2004 and 2008). I don’t claim authorship. Other sources were also used and are noted.
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Outline
• Cell theory• Microscopy• Cells and their components
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Cell Theory
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Cell Theory
• Cells were first described in 1665 by the British scientist, Robert Hooke, from microscopic examination of thin slices of cork from Mediterranean oak trees.
• Over the next two centuries, cells have been found in all organisms that were examined.
• The accumulation of evidence led to cell theory: all organisms are com-posed of cells.
• Cell theory was later expanded to encompass observations that all cells arise from previously existing cells—that is, cells do not spontaneously form.
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Cellular Structure of Cork
http://farm1.static.flickr.com
Robert Hooke’s drawing.
http://www.isa.utl.pt
http://cache.eb.com
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Microscopy
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Microscopic World of Cells
• Each and every cell in a living organism is intricate and extremely complex.
• The most elaborate machine, if it were reduced to the size of a cell, would seem simple in comparison.
• Cells must be very small for materials to to move in and out to meet their metabolic needs.
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Microscopic World of Cells (continued)
• Organisms are single-cellular (bacteria, archaea, and some pro-tista) or multi-cellular (other protista, fungi, plants, and animals).
• The human body has many trillions of cells that work cooperatively to perform their functions, which is a focus of this course on human physiology.
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Light Microscope
• The light microscope was invented during the Renaissance, about 400 years ago.
• Visible light passes through a specimen—the lens enlarges the image and projects it onto the human eye, film camera, or electronic sensing device.
• Modern light microscopes have compound lenses to reduce chromatic (color) aberration and spherical aberration to improve the quality of the viewed image.
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Light Microscope (continued)
http
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A modern lab and classroom version.
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Magnification and Resolving Power
• Two key aspects of microscopes are their magnification and resolving power.
• Magnification is the increase in an object’s apparent size compared to its actual size.
• Resolving power is the ability to show two or more objects as distinct entities.
• Due to limitations in resolving power (about 0.2 m), the maximum useful magnification of a light microscope ranges between X400 and X1000.
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Red blood cells and a stained white blood cell.
http
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Light Micrograph
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Another Light Micrograph
Coronal cross section of a rat brain under low magnification (about X10).
http://www.emsdiasum.com
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Electron Microscope
• Electron microscopes use beams of electrons rather than light to access the very small world.
• Resolving power is much higher than for light microscopes, allowing for much higher useful magnifications.
• Electron micrographs can be produced at magnifications of X100,000 or higher.
• The study of cells advanced rapidly when electron microscopes were developed in the 1950s.
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Electron Microscope (continued)
http
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An electron microscopy laboratory.
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Types of Electron Microscopes
• Scanning electron microscopes are used to study the surfaces of cells.
• Transmission electron microscopes are used to explore the inter-nal structures of cells.
• Electron microscopes are used with prepared (dead) specimens, while light microscopes are suited for either live or prepared speci-mens.
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Electron Micrograph
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A collection of pollens.
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Another Electron Micrograph
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Escherichia coli (E. coli).
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Cells and Their Components
http://www.steve.gb.com
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Prokaryotic and Eukaryotic Cells
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Eukaryotic cellPlants, animals, and fungi
(animal cell shown)
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Prokaryotic cellBacteria and archaea
(bacterium shown)
Not to scale: A prokaryotic cell is about 1000 times smaller in volume
than a eukaryotic cell.
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Cell Comparisons
• Prokaryotic cells first appeared about 3.5 billion years ago; eukary-otic cells appeared about 1.8 billion years later.
• Eukaryotic cells are much larger—they are about ten times the dia-meter of prokaryotic cells and their volume is even greater (by about a thousand times).
• The DNA in eukaryotic cells is in the nucleus surrounded by a mem-brane, while the DNA in prokaryotic cells is in an unenclosed central region.
• The two cell types use different processes for the replication of their DNA.
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Cell Comparisons (continued)
• Eukaryotic cells have several types of membrane enclosed organ-elles with specialized functions, while prokaryotic cells have many fewer.
• Eukaryotic cells use aerobic respiration and anaerobic respiration for chemical energy production, while prokaryotic cells only use an-aerobic respiration.
Organelle = a compartment within a cell that has a specialized function, for example, ribosome, lysosome, Golgi apparatus, or
mitochondrion. (http://sis.nlm.nih.gov/enviro/iupacglossary/glossaryo.html)
Most of these membrane-enclosed organelles, as we will discuss, are unique to eukaryotic cells.
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A Few Animal Cell Types
1. Blood
2. Purkinje (cerebellum)
Images 1 and 2, http://upload.wikimedia.orgImage 3, http://www.proteinpower.comImage 4, http://focus.harvard.edu
3. Adipose
4. Intestinal
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Components of Eukaryotic Cells
Component Animal cell Plant cell
Plasma membrane x xNucleus x xChromosomes x xCytoplasm x x �Ribosomes x xEndoplasmic reticulum x xGolgi apparatus x xLysosomes x RareMitochondria x xCytoskeleton x xVacuoles and vesicles x xFlagella and cilia x RareCentrioles x xCell wall -- xChloroplasts -- xCentral vacuole -- x
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Plasma Membrane
• A plasma membrane separates the intracellular space in a cell from its surrounding extracellular space.
• The plasma membrane defines the cell boundary.
• The membrane is a double layer (bilayer) of phospholipid molecules.
Computer generated graphichttp://www.sci-design.com
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Plasma Membrane (continued)
• The glycerol heads with their attached phosphate group orient toward the fluids in the intracellular and extracellular spaces because they are hydrophilic.
• The two lipid tails attached to the glycerol molecule orient inward since they are hydrophobic.
• Phospholipid membranes can be self-organizing due to their hydrophilic and hydrophobic properties.
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Plasma Membrane (continued)
• Receptors and other protein molecules are embedded in the plasma membrane.
• The plasma membrane is not a static structure of molecules fixed in place.
• Phospholipids and most proteins are drift about in the plane of the membrane, much like icebergs floating in the high-latitude oceans.
• The plasma membrane of a cell is often described as a fluid mosaic.
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Selective Permeability, Membrane Transport
• The plasma membrane and membranes that enclose organelles are selectively permeable.
• The membranes allow some substances to pass while blocking others.
• Some substances can diffuse across the plasma membrane including O2, CO2, and some nutrients.
• The passage of other substances requires transport proteins in the plasma membrane.
• Glucose, a major source for cellular energy, is attached to a transport protein to enter cells.
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Nucleus
• The nucleus of a cell contains the genetic code of life in the form of DNA.
• The nucleus is enclosed in a double membrane known as the nuclear envelope—it is similar in molecular structure to the cell’s plasma mem-brane.
• Pores in the nuclear envelope permit the passage of material between the nucleus and cytoplasm (specifically, messenger RNA and compon-ents of ribosomes).
Electron micrographhttp:.//www.science.org.au
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Nucleus (continued)
• DNA molecules and proteins in the nucleus form long fibers called chromatin.
• Each fiber makes-up one chromosome—humans usually have 46 chromosomes in the somatic cells of their bodies.
• A ball-like mass in the nucleus, called the nucleolus, produces the components of ribosomes.
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Cytoplasm
• The cytoplasm is the region between the cell’s plasma membrane and its nucleus.
• It contains organelles suspended in a fluid known as cytosol.
• Each type of organelle performs specific functions, as we will discuss.
• Most organelles in eukaryotic cells have their own phospholipid mem-branes.
Electron micrographhttp://www.danforthcenter.org
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Ribosomes
• Ribosomes are found in the cytoplasm, and often in close proximity to the cell nucleus.
• These organelles synthesize the polypeptides that make up proteins from amino acids.
Computer generated graphichttp://rna.ucsc.edu
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Ribosomes (continued)
• The genetic information of DNA is transferred via messenger RNA (mRNA) to the ribosomes to provide instructions for the synthesis of polypeptides that form proteins.
• Some ribosomes synthesize proteins for use in the cytoplasm or plasma membrane.
• Other ribosomes make proteins for secretion by the cell for use by other cells.
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Endoplasmic Reticulum
• The endoplasmic reticulum (ER) produces many types of biological molecules.
• ER is made-up of an elaborate system of tubes and sacs in the cyto-plasm.
• The two types of endoplasmic reticulum are rough ER and smooth ER.
Electron micrographhttp://www.bu.edu
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Rough ER
• Rough ER has the appearance of roughness due to the ribosomes that stud its surface.
• Rough ER produces proteins for the plasma membranes of cells and organelles, and for secretion by the cell.
• Cells that secrete substantial amounts of proteins, such as salivary glands of the mouth, are rich in rough ER.
• Products are sent to other locations in the cell in membrane covered packages called transport vesicles—the vesicles bud and separate from the ER.
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Smooth ER
• Smooth ER lacks the ribosomes that stud the surface of rough ER.
• One function is the synthesis of steroids in the testes, ovaries, and adrenal glands.
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Smooth ER (continued)
• Smooth ER in liver cells (known as hepatocytes) produce enzymes to detoxify drugs and poisons in the blood.
• The amount of smooth ER increases (up-regulates) with exposure to certain drugs.
• The body increases its tolerance to the drug, which requires higher dosages to achieve the same physiological effect.
• One hallmark of addiction is increased drug tolerance (along with a psychological component).
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Golgi Apparatus
• The Golgi apparatus works with the endoplasmic reticulum to refine, store, and distribute molecules synthesized by the cell.
• Products synthesized in the ER reach the Golgi apparatus via trans-port vesicles.
• Enzymes in the Golgi apparatus modify many of the products synthe-sized by the ER.
Electron micrographhttp://www.bu.edu
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Golgi Apparatus (continued)
• The Golgi apparatus is named for its discoverer, Camillo Golgi.
• It works with the ER to refine, store, and distribute chemical products.
• The Golgi apparatus tags proteins with addresses of their destinations within the cell.
• Vesicles that bud from the Golgi apparatus distribute products to other organelles.
• Other products are distributed to the plasma membrane for secretion by the cell.
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Lysosomes
• Lysosomes are membrane-enclosed sacs of enzymes for digestion to prevent self destruction of the cell.
• Enzymes in the lysosomes breakdown macromolecules including pro-teins, glycogen, fats, and nucleic acids.
• Molecules from this process nourish the cell.
Electron micrographhttp://biology.unm.edu
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Lysosomes (continued)
• Other lysosomes function as recycling centers by engulfing and digest-ing damaged organelles and making some of these molecules available for the synthesis of new organelles.
• Lysosomes in white blood cells ingest bacteria—their enzymes destroy bacterial cell walls.
• Another type of lysosome destroys the webbing that joins the fingers in human embryos.
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Mitochondria
• Mitochondria perform cellular respiration to harvest chemical energy for cellular work.
• The processes, known as the Krebs or citric acid cycle and the elec-tron transport chain, are aerobic since as require a continuing supply of oxygen molecules.
• Sugars and other types of food molecules are converted to a form of energy known as ATP.
Electron micrographhttp://is2.okcupid.com
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Mitochondria (continued)
• The inner membrane of a mitochondrion contains enzymes and other molecules for cellular respiration.
• The membrane has many folds to increase its surface area and maxi-mize ATP output.
• Mitochondria may have been invaders in the earliest eukaryotic cells.
• Now, a symbiotic relationship exists between mitochondria and eukary-otic cells.
Mitochondria—plural; mitochondrion—singular.Symbiotic = an interaction between dissimilar organisms,
especially when they benefit each other.
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Mitochondria (continued)
• Mitochondrial DNA is passed through maternal lineage from mother to daughter.
• The DNA maintains remarkable stability from generation to generation.
• These aspects enable mitochondrial DNA to be used in tracing popula-tion groups 10,000 years or more back in time as they have migrated.
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Cytoskeleton
• Microtubules of several different types of proteins form a network of fibers known as the cytoskeleton.
• The cytoskeleton is found in the cytoplasm.
• It provides structural support for a cell and a means for specialized movements.
Color enhanced electron micrographhttp://www.bcsb.org
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Cytoskeleton (continued)
• Microtubules also hold the organelles in place in the cytoplasm and guide the movement of vesicles.
• Other microtubules guide the movement of individual chromosomes when cells divide.
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Cytoskeleton (continued)
• Unlike a bony skeleton, a cytoskeleton can be rapidly dismantled in one location of the cell to reform in a new location.
• This process occurs through the removal and replacement of its pro-tein units.
• It contributes to the crawling motion of single-cell amoeba and move-ment of white blood cells.
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Vacuoles and Vesicles
• Vacuoles and vesicles are membrane enclosed sacs that bud from a cell’s plasma membrane, endoplasmic reticulum, and Golgi appar-atus.
• They differ in their functions—for example, vacuoles in the plasma membrane of a cell engulf food molecules for transportation to the lysosomes.
Electron micrographhttp://www.pharmacology.com
In neurons, vacuoles known as synaptic vesicles store neurotransmitters to com-municate with other neurons, muscles,
and glands.
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Flagella
• Some eukaryotic cells have appendages and specialized microtub-ules that enable movement.
• Flagella (singular, flagellum) propel cells by an undulating, whip-like motion.
• Flagella usually occur singly—for example, in sperm that must travel the length of the female reproductive tract to fertilize an egg released by an ovary.
Human sperm, Electron micrographhttp://www2.sunysuffolck.edu
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Cilia
• Cilia, which are usually shorter and more numerous than flagella, pro-duce motion through rhythmic back-and-forth movements (think of the rows of oars on an ancient galley ship).
• Cilia of cells in the oviducts (fallopian tubes) can sweep a fertilized egg along the reproductive path for implantation in the uterus.
http://www.gibinquirer.net Electron micrographhttp://www.talbotcentral.ucr.edu
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Cilia (continued)
• Tobacco smoke can damage or destroy the cilia in the bronchial tubes, which interferes with the body’s normal means for removing pollutants from the lungs.
• Smoker’s cough is the body’s compensatory attempt to cleanse the respiratory system.
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Extracellular Matrix
• Most animal cells secrete a thick, sticky substance known as the extracellular matrix.
• It helps hold cells together in tissues, and provides protective and supportive functions.
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Cell Junctions
• The cells in many animal tissues are often connected by cell junctions.
• Tight junctions bind cells to form a leak-proof sheet of tissue such as in the small intestine and large intestine to prevent fluids from leaking into the abdominal cavity.
• Anchoring junctions bind cells together while allowing some molecules to pass among the spaces between them.
• Communicating junctions have channels that permit water and other small molecules to flow among neighboring cells.
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Centrioles
• Centrioles are can-shaped structures of microtubules in the cyto-plasm that support cell division.
• We will cover their functions when we discuss mitosis and meiosis in the next lecture.
Computer generated graphichttp://www.sparkleberrysprings.com