chapter 6 cells. 6.1 & 6.2 microscopy & types of cells
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Chapter 6 Cells
6.1 & 6.2Microscopy & Types of Cells
History-Microscopes first used by Renaissance
scientists
-Technology progression developed as cell study developed
-1665: Robert Hooke used a microscope to see dead cells
-1674: Leeuwenhoek created lenses through which he could see living cells
-Light Microscope: Light is passed through the specimen and then through the glass lenses, that refract the light so the image is magnified
-Magnification: The ratio of an object’s image size to its real size
-Resolution: A measure of the clarity of the image
-Contrast: Accentuation of differences in parts of the specimen
-Electron Microscope: Focuses a beam of electrons onto specimen instead of light
-Cell Ultrastructure: Cellular anatomy revealed by EM
-Scanning Electron Microscope(SEM): Used to study the topography of a specimen, creates 3-D images
-Transmission Electron Microscope(TEM): Used to study the internal ultrastructure of cells, uses electromagnets to bend the paths of the electrons
Cell Fractionation-Cell fractionation takes cells apart, separates the major
organelles and other structures from one another-A centrifuge is used to spin the cells in order to
separate their components, applying more than 1 million times the force of gravity
-Cell fractionation allows researchers to prepare certain cell components in bulk
Eukaryotic Cells
Store DNA in nucleus, bound by a double membrane
Internal membranes divide the cell into compartments that
facilitate specific metabolic functions
(organelles)
Larger than prokaryotic cells—can carry out more cellular functions
Surrounded by a phospholipid bilayer
Prokaryotic Cells-Smaller and less complex
than eukaryotic cells
Nucleoid: A dense region of DNA in a prokaryotic cell
DNA is NOT contained in a
nucleus. Instead, it floats in the
cytoplasm
Plant and Animal Cells-Both have most of the same organelles
-Cytoplasm: A semifluid, jellylike substance that contains the organelles and other components of the cell
Plant Cells-Cell Wall-Chloroplasts: Perform photosynthesis-Plasmodesmata: Channels through cell walls that connect the cytoplasms of the adjacent cells-Central Vacuole: Used for storage, breakdown of waste, hydrolysis of macromolecules
Animal Cells-Lysosomes: Digestive organelle where macromolecules are hydrolyzed.-Centrosomes: region where the cell’s microtubules are initiated.-Flagella: locomotion organelle within an extension of the plasma membrane.
-Plasma Membrane: The membrane that encloses the cell, present in both animal and plant cells.
ANIMAL
PLANT
Review 6.1 & 6.2
• Cell Tutorial• Cells
Fig. 6-210 m
1 m
0.1 m
1 cm
1 mm
100 µm
10 µm
1 µm
100 nm
10 nm
1 nm
0.1 nm Atoms
Small molecules
Lipids
Proteins
Ribosomes
Viruses
Smallest bacteria
Mitochondrion
Nucleus
Most bacteria
Most plant and animal cells
Frog egg
Chicken egg
Length of some nerve and muscle cells
Human height
Un
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Lig
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mic
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Ele
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Fig. 6-5a
Homogenization
Homogenate
Differential centrifugation
Tissuecells
TECHNIQUE
The Nucleus• The nucleus contains most of
the genes in the eukaryotic cell• The nuclear envelope encloses
the nucleus & separates the nucleus from the cytoplasm– The envelope consists of a
double membrane– Pore complexes: each pore
on nuclear envelope is ringed by protein particles
• Nuclear side of envelope lined by nuclear lamina– consists of netlike array of
protein filaments that maintains shape of nucleus
The Nucleus DNA & associated proteins are
organized into cellular structures called chromosomes
Each chromosome made up of chromatinChromatin is the complex of
DNA & proteins that makes up a eukaryotic chromosome
Exists in dispersed form as a mass of long, thin fibers when cell is not dividing (not visible)
Fibers coil up/condense when cell prepares to divide
Each eukaryotic species has a characteristic # of chromosomes
The NucleusA prominent & specialized structure
within the non-dividing nucleus is the nucleolusAppears as mass of densely stained
granules & fibers adjoining part of the chromatin
In the nucleolus: ribosomal RNA (rRNA) is
synthesized from instructions in the DNA
Proteins imported from the cytoplasm are assembled with rRNA into large & small ribosomal subunits
Subunits exit nucleus though nuclear pores where the large & small subunits assemble into a ribosome
RibosomesRibosomes are complexes of
rRNA & protein moleculesfunction as site of protein
synthesis in cytoplasmBuild proteins in 2
cytoplasmic localesFree & bound ribosomes are
identical structurally & can alternate between rolesFree ribosomes are
suspended in the cytosolBound ribosomes are
attached to outside of the endoplasmic reticulum or nuclear envelope
Endomembrane SystemThe endomembrane
system is a collection of membranes inside/around the eukaryotic cellIncludes smooth &
rough endoplasmic reticulum, Golgi apparatus, lysosomes, & vacuoles
The various membranes are not identical in structure
The Endoplasmic ReticulumThe endoplasmic reticulum
consists of membranous tubules & internal, fluid-filled spaces called cisternae
Manufactures membranes & performs many other biosynthetic functions
2 regions that differ in structure & function
Smooth endoplasmic reticulum (sER): so named because it has no ribosomes on the outer surface
Rough endoplasmic reticulum (rER): has ribosomes on the outer surface
Smooth Endoplasmic Reticulum
Rich in enzymes that synthesize lipidsInclude oils, phospholipids, steroids
sER in liver helps detoxify poisons & drugsFrequent use of drugs leads to proliferation
of sER in liver cells increases tolerancesER in muscle cells store calcium ions
sER pumps calcium ions from cytosol & stores them in cisternal space
Rough Endoplasmic ReticulumAbundant in cells that secrete
proteinsAs polypeptides are
synthesized on ribosomes on rER, they are threaded into cisternal space through pores formed by protein complexes in rER membrane
Glycoproteins, proteins to which carbhydratesare attached, are the most secretory polupeptides
rER is also a membrane factoryMembrane-bound proteins
are synthesized directly into membrane
Enzymes in rER also synthesize phospholipids
Golgi ApparatusThe golgi apparatus is the
“shipping & receiving” center of the cellTransport vesicles from the
ER travel to the Golgi for modification of their contents
The Golgi consists of flattened membranous sacs called cisternae2 sides of the Golgi
Cis side: located near ER; receives material by fusing with transport vesicles from ER
Trans side: away from ER; buds of vesicles that travel to other sites
Golgi ApparatusDuring the vesicles’ transit from cis to trans,
the ER products are modifiedThe Golgi also manufactures its own
macromolecules like pectinAlso sorts & packages materials into transport
vesiclesMolecular identification tags are added to
products to help in sortingProducts tagged with identifiers like phosphate
groups identifies the product’s final destination
QuestionsWhat does the nucleolus do?Describe the 2 types of ribosomes. What are
their similarities and their differences?What are the structural and functional
differences between smooth endoplasmic reticulum and rough endoplasmic reticulum?
Describe the roles of transport vesicles.What does the Golgi Apparatus do when the
transport vesicles reach them?
Review Golgi
Organelles
Lysosomes, Vacuoles, Mitochondria, Chloroplasts,
and Peroxisomes
-Sac of hydrolytic enzymes in animal cells used to digest macromolecules-Acids inside membrane neutralize in cytosol
-Large amounts cause autodigestion-Created from Golgi Apparatus-3D molecules prevent dissolving of membrane-Phagocytosis--Food Vacuoles
- Products used as nutrients--Macrophages-Autophagy
-Renew cell-Tay-Sachs Disease
-Lysosome Indigestion
-Food Vacuoles-Contractile Vacuoles
-Filled with water used to balance ion concentration
-Plant Vacuoles-Perform Hydrolysis-Central Vacuole
-Cell Sap-Proteins, ions, pigments,
poisons,-Disposal Site
-Take up large percentage of cell
-Site for Cellular Respiration-Use oxygen to convert sugars and fats to ATP-Nearly all living Protists, Eukaryotes, and Fungi have Mitochondria-Cristae
-Folds used for maximum productivity
-Matrix-Enzymes used to catalyze
Cellular Respiration
-Plastids-Store starches
and Pigments-Photosynthesis
-Produce sugar-Thylakoid-Granum-Stroma
-Contains DNA, enzymes, and ribosomes
MITOCHONDRIA CHLOROPLASTS
Cellular Respiration Cristae Double-layer membrane Matrix Surface Area Plants, Animals, Fungi,
Protists, Eukarya Sugar
Photosynthesis Thylakoids/Grana Double-layer membrane Stroma Ribosomes in
membrane Surface Area Plants Sunlight
-Metabolic, membrane-bound organelle
-Contains enzymes that transfer Hydrogen to produce Hydrogen Peroxide as a by-product (Oxidation)-Break down fatty acids for Mitochondria-Detoxify alcohol-Use enzymes to break down Hydrogen Peroxide
-Sectioned off-Glyoxosomes
-Fat-storing tissues in plants-Enzymes to convert fatty acids to sugar in seeds-Take nutrients from cytosol
6.4 Method lysosomes use to renew the cell Disease associated with defective lysosomes Another thing that uses Phagocytosis 3 of the 5 things offered by cell sap Biggest vacuole and why
6.5 Where ATP synthesis takes place What type of organelle is a Chloroplast? 2 similarities and 2 differences of Mitochondria and
Chloroplasts 2 functions of Peroxisomes Function of Glyoxosomes
Cell Wall (plants only)-Protects Cell Plasma membrane-Controls what enters/leaves Nucleus- Control center Vacuole-Storage Mitochondria- Generates energy Chloroplast (plants only)-Converts into Energy Lysosomes-Digestion/ Sanitation Peroxisomes Ribosomes-Makes proteins Smooth ER-Detoxifies Rough ER-Transports Golgi-Sorts & packages
Cell Wall-plants only
• Protects structure
Plasma membrane
• Controls what enters/leaves
Nucleus
• Control center
Vacuole
• Storage
Mitochondria
• Generates energy
Chloroplast
• Plants only• Converts Sun into Energy
Lysosomes
• Digestion/ Sanitation• Recycle
Peroxisomes
• Break down fatty acids
Ribosomes
• Makes proteins
Smooth ER
• Detoxifies
Rough ER
• Transports
Golgi
• Sorts & packages
Cytoskeleton: a network of fibers extending throughout the cytoplasm.
Organize structures Organize activities Three molecular
structures:◦ Microtubules◦ Microfilaments◦ Intermediate filaments
Mechanical support Maintain shape Certain movements require (Motor
Proteins) Manipulates plasma membrane to make
food vacuoles, and other phagocytic vesicles
Regulates biochemical activities in response to mechanical stimulation
Microtubules: hollow rods measuring 25 nm in diameter and 200 nm in length.
Consists of two subunits:◦ Alpha tubulin◦ Beta tubulin
Shape and support Tracks for organelles equipped with motor
proteins to move
Centrisomes: Microtubules grow out from this, a region that is often located near the nucleus and is considered a “microtubule-organizing center.”
Centrioles: Within the centrosome, a pair of centrioles, each composed of nine sets of triplet microtubules arranged in a ring
Cilia: many microtubule containing extensions that project from some cells
Flagella: a microtubule containing extensions that project from some cells
Movement Also act as signal-receiving antenna for cell Core of microtubules sheathed in extension
of the plasma membrane
Basal Body: structurally very similar to centriole, anchors the flagellum
Dyniens: large motor proteins, each composed of several polypeptides.◦ Responsible for bending movements of organelle
Microfilaments: or (actin filamints) built from molecules of actin, a globular protein.
Twisted double chan of actin subunits Microfilaments can form structural networks Bear tension in the cell Helps support cell shape Cortex: outer cytoplasmic layer of a cell,
semisolid consistency of a gel, in contrast with more fluid state of interior cytoplasm.
◦ Specialized for transporting materials across plasma membrane (intestinal cells, etc.)
◦ Myosin: protein, acts as a microfilament-based motor protein by means of projections that “walk” along the actin filaments.
◦ Pseudopodia: (Greek words pseudes: false, pod: foot) cellular extensions, extend and contract through the reversible assembly of actin subunits
◦ Cytoplasmic streaming: a circular flow of cytoplasm within cells, speeds the distribution of materials within the cell
Intermediate Filaments: specialized for bearing tension, diverse class of cytoskeletal elements. Constructed from different molecular subunits belonging to family of proteins Microtubules and microfilaments are consistent in
diameter and composition, whereas these are not More permanent fixtures of cells Make up nuclear lamina that lines the
interior of nuclear envelope
What is the definition of a cytoskeleton?
What are the three molecular structures of a cytoskeleton?
What are two functions of the cytoskeleton? What are required for certain specific kinetic
functions of the membrane? What are the two subunits of microtubules?
Cytoskeleton
Section 6.6
Structure and Function
• What is it’s Structure?– Fibers Extending in the cytoplasm – Molecular Structures: Microtubules,
Microfilaments, and Intermediate Filaments
• What is it’s Function?– Organizes structures & activities of the Cell– Gives Mechanical Support to the cell
Roles Of CytoSkeleton
Support And Motility
• Important in Animals (Lack Cell Wall!!)
• Motility (Movement) of A Cell– Requires Cytoskeleton +
Motor Proteins– Motor Proteins Bend Cilia
and Flagella by Gripping Microtubules
– Transportation System For Organelles And Vesicles (Monorail)
http://www.traffic.dk/image_uploads/vissues/big_cytoskeletoncover.jpg
Components Of Cytoskeleton
Microtubules• Hollow Rods Constructed From a protein called Tubulin• Thickest Of the Three• Shape and Support the Cell• In Animals, Grows out of Centrosome, function as compression
resisting girders of the cytoskeleton• In Eukaryotes, Beats• Flagella and cilia-propel it through water
•Microtubules •Microfilaments •Intermediate Filaments •http://academic.brooklyn.cuny.edu/biology/bio4fv/page/
cytoseleton1005.JPG
Components of the Cytoskeleton
• Solid rods, built from Acting-Globular Protein (A.K.A: Acting Filaments)
• Structure Role is to bear tension a pulling Force• Gives the Outer Cytoplasmic layer of a cell called
the Cortex, the semisolid consistency of a gel• Arranged Parallel with a thousand others along
the length of a muscle cell with thicker filaments made of Myosin a protein
• Actin and Myosin Contracting is pseudopodia(Amoeba), also cytoplasm streaming ( a circular Flow)
Microfilaments
http://www.cartage.org.lb/en/themes/sciences/Zoology/AnimalPhysiology/Anatomy/AnimalCellStructure/Microfilaments/
microfilament.jpg
Components of the CytoskeletonIntermediate Filaments
• Specialize in bearing tension– Like that of Microfilaments
• Especially important in reinforcing the shape of cells
• After a cell dies they still stand
http://teachernotes.paramus.k12.nj.us/Nolan/2005-2006/index.2.jpg
Questions • Micro Filaments are made of what Globular protein?
• What are Motor Proteins Used For?
• Which is the thickest of the three components?
• What is the Role of a Cytoskeleton?
• Whats the Singular of flagella and Cillia?
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