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Cells - Structure and Function
Important Events in the Discovery of Cells
1665 - Robert Hooke looks at cork under a microscope. Calls the chambers he see "cells"1665 - 75 Anton van Leeuwenhoek, the person incorrectly given credit for the invention of themicroscope (actually, he was just damn good at making and using them, and his scopes soon becamethe standard, and history has just given him credit as the inventor of the microscope), studies organismsliving in pond water (like you did in lab). He calls them "Animalcules."1830 - German scientists Schleiden and Schawann summarize the findings of many scientists andconclude that all living organisms are made of cells. This forms the basis of the Cell Theory of Biology
The Cell Theory of Biology
All organisms are composed of cellsThe cell is the structural unit of life - units smaller than cells are not aliveCells arise by division of preexisting cells - spontaneous generation does not existCells can be cultured to produce more cells
in vitro = outside organism or cellin vivo = inside organism or cell
Properties of Cells
Cells are complex and highly organized
They contain numerous internal structuresSome are membrane bound (organelles) while others do not
Cells contain a genetic blueprint and machinery to use it
Genes are instructions for cells to create specific proteinsAll cells use the same types of information
The genetic code is universalThe machinery used for synthesis is interchangeable
However, for this to function properly, information transfer must be error freeErrors are called mutations
Cells arise from the division of other cells
Daughter cells inherit the genes from the mother cellsBinary fission - cell division in bacteriaMitosis - the genetic complement of each daughter cell is identical to the other and to the mother cell.This is asexual reproductionMeiosis - the genetic complement of each daughter cell is reduced by half and each daughter cell is
Cells http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect06.htm
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genetically unique. This is used in sexual reproductionDaughter cells inherit cytoplasm and organelles from the mother cells
Asexual - organelles from mother cellSexual - organelles predominately from one parent
In eukaryotes, the chloroplasts and mitochondria come from the egg cellThis can be used to trace the evolutionary origin of the organism
Cells acquire and utilize energy
Plant cells undergo photosynthesisconvert light energy and CO2 to chemical energy (ATP and glucose)
Most cells respirerelease energy found in organic compoundsconvert organic compounds to CO2 and O2make ATP
Cells can perform a variety of chemical reactions
Transform simple organic molecules into complex molecules (anabolism)Breakdown complex molecules to release energy (catabolism)Metabolism = all reactions performed by cells
Cells can engage in mechanical activities
Cells can moveOrganelles can moveCells can respond to stimuli
chemotaxis - movement towards chemicalsphototaxis - movement towards lighthormone responsestouch responses
Cells can regulate activities
Cells control DNA synthesis and cell divisionGene regulation - cells make specific proteins only when neededTurn on and off metabolic pathways
Cells all contain the following structures:
Plasma membrane - separates the cell from the external environmentCytoplasm - fluid-filled cell interiorNuclear material - genetic information stored as DNA
Types of Cells
Cells http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect06.htm
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Prokaryotes
Pro = before; karyon = nucleusrelatively small - 5 to 10 umlack membrane-bound organellesearliest cell type
Archaea
Originally thought to be prokaryotesrelatively small - 5 to 10 umlack membrane-bound organellesUsually live in extreme environments(thermophiles, halophiles, etc)
Eukaryotes
Eu = true; karyon = nucleuscontain membrane-bound organellesEvolved from prokaryotes byendosymbiotic association of two ormore prokaryotesInclude Protists, Fungi, Animals, andPlants
Features of Prokaryotic Cells
Capsule - outer sticky protectivelayerCell Wall - rigid structure whichhelps the bacterium maintain itsshape
this is in NO way the same asthe cell wall of a plant cell
Plasma membrane - separates the cellfrom the environmentMesosome - infolding of plasmamembrane to aid incompartmentalizationNucleoid - region where nakedDNAis foundCytoplasm
semi-fluid cell interiorno membrane-boundorganelles
Cells http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect06.htm
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location for metabolic enzymeslocation of ribosomes forprotein synthesis
Properties of Eukaryotic Cells
Features shared with Prokaryotic cellsRigid cell wall
Plant cells, some Fungi, some Protists
Cells http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect06.htm
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Animal cells lack cell wallPlasma membraneCytoplasm with ribosomesNuclear material
Cytoskeleton - flexible tubular scaffold of microfilamentsmaintains cell shape and provides supportanchors organelles & enzymes to specific regions of the cellcontractility and movement (amoeboid movement)intracellular transport - tracks for vesicle and organelle movement by motor proteins
Cytoskeleton componentsMicrofilaments
solid protein (actin) which is assembled at one end and disassembled at the other endIntermediate filaments - rope-like fibrous proteins
provide structural reinforcementanchor organelleskeep nucleus in place
Microtubules - hollow tubes of tubulin (a globular protein)maintains cell shapeanchor organellesmovement of organellestrack for motor proteins
Cilia and Flagella - involved in cellular movementcomposed of microtubulescilia - short, numerous, complexflagella - longer, fewer, less complexboth arranged in a 9+2 pattern with dynein arms projecting outward
NucleusDouble membrane with poresOuter membrane continuous with ERNuclear matrix - protein-containing fibrilar networkNucleoplasm - the fluid substance in which the solutes of the nucleus are dissolvedChromosomes - protein and DNA complexesNucleolus - involved in the synthesis and assembly of ribosomes
Endomembrane SystemEndoplasmic Reticulum - an extensive membranous network continuous with the outer nuclearmembrane.
Rough ER - has ribosomes and is involved in secreted protein synthesisSmooth ER - lacks ribosomes and is involved in membrane lipid synthesis
Golgi ApparatusFlattened vesicles in stacks which receive protein from ERForm secretory vesicles to transport proteins to different parts of the cell (vacuole,lysosome, etc) or for secretioncis face - "receiving" side of Golgi apparatustrans face - "shipping" side of Golgi apparatus
Lysosomefound only in animal cellscontain enzymes for use in the hydrolytic breakdown of macromolecules
Peroxisome
Cells http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect06.htm
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Eukaryotic organelle that degrades fatty acids and amino acidsAlso degrades the resulting hydrogen peroxide
Plant Central Vacuole - major storage space in center of plant cell with many functionsDigestive - break down of macromoleculesStorage - ions, sugars, amino acids, toxic wasteMaintain cell rigidity - high ionic concentration generates high water potential
Images of Vesicle Transport Between Endomembrane Organelles
MitochondriaFound in ALL eukaryotic cells (yes, even in plant cells)Site of aerobic respiration
sugars + O2 - - > ATP + CO2 + H2OContain DNA which codes for mitochondrial proteins, ribosomes, etc.Divide by a process similar to binary fission when cell dividesEnclosed in a double membrane system
Inner Membrane forms the Cristae (invaginations into interior region)Site of energy generation
Matrix is the soluble portion of the mitochondiraSite of carbon metabolismLocation of mDNASite of mitochondrial protein synthesis
ChloroplastsFound only in plant cellsSite of photosynthesis
conversion of solar energy to chemical energy in the form of ATP and sugarsContain DNA which codes for chloroplast proteins, ribosomes, etc.Divide when plant cell dividesEnclosed in a double membrane envelope that does not invaginate into the chloroplastThylakoid is a third internal membrane system
contains membrane-bound photosynthetic pigmentssite of photochemistry (the conversion of light energy to ATP)site of O2 generation
Stroma is soluable portion of chloroplastsite of CO2 fixationsite of sugar synthesis (carbon metabolism)location of cpDNAsite of chloroplast protein synthesis
Ribosomes Technically not an organelle, since there is no membrane, but they are prominent cellularstructures and usually lumped in with the organellesThe "factories" of the cell - involved in protein synthesisFacilitate the specific coupling of tRNA anticodons with mRNA codons during protein synthesisMay either be free or bound to ERMade up of two subunits, the large and the small subunitBoth subunits are constructed out of protein and RNA (called rRNA)The ribosomes of prokaryotes and eukaryotes vary slightly with regard to size and shape
Cells http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect06.htm
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Endosymbiotic Origin of Chloroplasts and Mitochondria
Free-living prokaryote eaten by hostGenes transferred to host nucleusSome genes retained but most lost - can no longer survive outside of hostSymbiotic relationship
photosynthetic symbiont provides sugar - degenerates to form chloroplastaerobic symbiont provides a more efficient energy generation system - degenerates to formmitochondriahost provides stable environment, nutrients, energy, and most proteins
Evidence for Endosymbiotic TheoryChloroplasts and mitochondria have DNA
does not code for all proteinssome genes in nucleusproteins imported rom cytoplasm
Organelle proteins similar to bacterial formRibosome structure and metabolic enzymes more similar to bacterial forms
Cells http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect06.htm
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