Science 10 – Unit CScience 10 – Unit CBIOLOGYBIOLOGY

Chapter 1 – The Chapter 1 – The MicroscopeMicroscope

C1.3 & C1.4C1.3 & C1.4Development in imaging, Development in imaging, staining, and cell researchstaining, and cell research

Cells inside the pulmonary artery of a cow

The quality of the imageThe quality of the image

Three factors affect the quality of an Three factors affect the quality of an image in microscopy:image in microscopy:– magnificationmagnification– contrastcontrast– resolutionresolution

Skin cells of a frog

MagnificationMagnification

improved with advancements in lens-improved with advancements in lens-makingmaking

light microscopes used in labs today light microscopes used in labs today can now magnify can now magnify between 1000-between 1000-2000X2000X

ContrastContrast

refers to refers to the variation of shadow and the variation of shadow and colourcolour– it is contrast that allows the human eye to it is contrast that allows the human eye to

focus on different aspects of the image focus on different aspects of the image andand to register depth to register depth

cells by themselves are mostly cells by themselves are mostly colourlesscolourlessimage quality has improved with:image quality has improved with:– new stains and staining techniquesnew stains and staining techniques– new methods of illuminating the specimennew methods of illuminating the specimen

ContrastContrast

a cell with low contrast

a cell with high

contrast

a cell with phase

contrast illumination

ResolutionResolution

the ability to the ability to distinguish between two distinguish between two structures that are very close structures that are very close togethertogether– the human eye is capable of resolving the human eye is capable of resolving

objects that are objects that are 0.1mm or larger0.1mm or larger

the higher the resolution of a the higher the resolution of a microscope, microscope, the more clearly you can the more clearly you can see the magnified imagesee the magnified imagesimilar to the resolution capabilities similar to the resolution capabilities of a digital cameraof a digital camera

ResolutionResolution

the picture on the picture on the left has low the left has low resolution, and resolution, and appears appears pixelatedpixelatedthe picture on the picture on the right has a the right has a higher resolution higher resolution and is therefore and is therefore a clearer imagea clearer image

Fluorescent microscopyFluorescent microscopyfluorescent stains called GFP (green fluorescent stains called GFP (green fluorescent protein) are introduced to fluorescent protein) are introduced to the specimenthe specimendifferent cell structures absorb stains different cell structures absorb stains in different amountsin different amountsthe specimen is subjected to UV lightthe specimen is subjected to UV lightdepending on the type of dye, the depending on the type of dye, the cell glows either cell glows either yellow, orange or yellow, orange or greengreenunlike conventional staining, unlike conventional staining, GFP GFP does not kill the cell, and allows for does not kill the cell, and allows for observation of living specimensobservation of living specimens

Brightfield microscopesBrightfield microscopes

light light passes through the specimenpasses through the specimen

fixing and staining process kills the fixing and staining process kills the specimenspecimen– you can’t view you can’t view living tissuesliving tissues

limited resoloutionlimited resoloution– you can’t get any higher resolution than you can’t get any higher resolution than

0.2µm0.2µm

Confocal technologyConfocal technology

uses lasers and computers to focus the uses lasers and computers to focus the lightlightthe later reflects off the object and back the later reflects off the object and back to the eyepieceto the eyepieceyou see you see a thin section with high resolutiona thin section with high resolutioncomputer software can be used to computer software can be used to build build up a 3D imageup a 3D imagefluorescent stains work better with fluorescent stains work better with confocal microscopes because confocal microscopes because they they eliminate the blurriness of the reflected eliminate the blurriness of the reflected lightlight

Confocal technologyConfocal technology

traditionatraditional optical l optical microscomicroscopepe

confocal confocal microscomicroscopepe

Electron microscopyElectron microscopy

uses a fine beam of electrons instead uses a fine beam of electrons instead of lightof light

the electrons pass through different the electrons pass through different materials at different rates, due to materials at different rates, due to differences in densitydifferences in density

instead of lenses, EMs use instead of lenses, EMs use magnetic magnetic fields to focus the imagefields to focus the image

Transmission Electron Transmission Electron Microscope (TEM)Microscope (TEM)

electrons electrons pass through the specimenpass through the specimen

100X better magnification and 100X better magnification and resolution than light microscoperesolution than light microscope

difficult to difficult to produce 3D imagesproduce 3D images

specimens are fixed and stained, so specimens are fixed and stained, so living specimens cannot be observedliving specimens cannot be observed

Scanning Electron Microscope Scanning Electron Microscope (SEM)(SEM)

good for observing good for observing surface features of surface features of specimensspecimens– the specimen is the specimen is fixed, and coated in goldfixed, and coated in gold– the electrons reflect off the gold and the electrons reflect off the gold and

produce a 3D imageproduce a 3D image– 2X better image quality than the TEM2X better image quality than the TEM

uses computes to uses computes to move the specimen move the specimen and view it from different anglesand view it from different anglesnew SEMs permit the use of new SEMs permit the use of live live materialmaterial

Gene mappingGene mapping

with new imaging techniques comes with new imaging techniques comes new possibilities for new possibilities for research at the research at the cellular levelcellular levelgene mappinggene mapping refers to refers to decoding of decoding of a species’ genomea species’ genome– an organism’s genome refers to all the an organism’s genome refers to all the

information contained information contained within its DNAwithin its DNA

in 2001, the Human Genome Project in 2001, the Human Genome Project published a published a complete map of the complete map of the entire human genomeentire human genome

Gene mappingGene mapping

could help us could help us understand where understand where cancer and other cancer and other diseases diseases come from and come from and how to treat them more how to treat them more effectivelyeffectivelyalso allows us to also allows us to create create new varieties of plantsnew varieties of plants– ethical arguments arise ethical arguments arise

about the dangers of about the dangers of genetically modified foodgenetically modified food

Cell communicationCell communication

cells are open systems, meaning cells are open systems, meaning they they must interact with their environment to must interact with their environment to survivesurvivehormoneshormones are chemicals produced in one are chemicals produced in one part of your body part of your body that act on a different that act on a different partpart– for example, the hormone adrenaline is for example, the hormone adrenaline is

produced in your brain, but acts all over your produced in your brain, but acts all over your body body in times of stress or excitementin times of stress or excitement

– hormones and other transmitter chemicals hormones and other transmitter chemicals form part of your cells’ communication systemform part of your cells’ communication system

Cell communicationCell communication

receptorsreceptors on the on the surface of the cells surface of the cells allow transmitters allow transmitters to attach to the cell to attach to the cell and carry out their and carry out their functionfunction– only transmittersonly transmitters

with the correct with the correct shape can dock at a shape can dock at a particular receptorparticular receptor

– similar to a similar to a lock and lock and key methodkey method

Cell communicationCell communication

certain viruses and certain viruses and bacteria can trick the bacteria can trick the cells by cells by mimicking the mimicking the shape of a harmless shape of a harmless moleculemoleculein order for your in order for your immune system to fight immune system to fight off invaders, it must first off invaders, it must first identify them, based on identify them, based on the markers on their cell the markers on their cell membranesmembranes

Cell communicationCell communication

better understanding of cell better understanding of cell communication allows scientists and communication allows scientists and research companies to:research companies to:– diagnose diseasesdiagnose diseases carried by viruses carried by viruses

and bacteriaand bacteria– diagnose diseasesdiagnose diseases of the immune of the immune

systemsystem– make make more targeted, and more effective more targeted, and more effective

medicationsmedications

HomeworkHomeworkPage 264 #1, Page 265 #10, 11Page 264 #1, Page 265 #10, 11

Complete the following table:Complete the following table:

FeatureFeature Light Light microscopemicroscope

Electron Electron microscopemicroscope

illuminationillumination

focused byfocused by

how image how image is viewedis viewed

advantagesadvantages

disadvantagdisadvantageses