6 - A Tour of the Cell

6 - A Tour of the Cell - 6: A Tour of the Cell 11:25...

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Unformatted text preview: 6: A Tour of the Cell 11:25 Overview: The Importance of Cells All organisms are made of cells Everything an organism does occurs fundamentally at the cellular level o Cooperation of cellular skeleton o Interaction of organisms with environment 6.1: To study cells, biologists use microscopes and the tools of biochemistry Microscopy o Wavelengths of radiation affect clarity Shorter the better o Important Parameters Magnification: the ratio of an objects image size to its real size Resolution: the clarity of the image Min distance 2 points can be separated & still be distinguished as 2 points o Light microscopes (LMs): visible light Resolution limit: 200 nm (0.2 m) small bacterium Magnification limit: 1000x Cannot see organelles Advantages: living cells o Electron microscopes (EMs): focuses a beam of electrons thru the specimen/onto its surface Resolution limit: 2 nm (theoretically:0.002 nm) Cell ultrastructure: a cells anatomy as revealed by an electron microscope Advantages: detail Disadvantage: kills cells Scanning electron microscope (SEM) Surface Coated w/ thin gold Beam excites electrons on surface device translates pattern of electrons into an electronic signal to screen 3D image Transmission electron microscope (TEM) Internal ultrastructure Specimen stained w/ atoms of heavy metals Attach to certain cellular structures Enhance electron density Electromagnets = lenses o Cytology (study of cell structure) o Biochemistry (the study of the molecules & chemical processes [metabolism] of cells) Isolating Organelles by Cell Fractionation o Cell Fractionation has goal to take cells apart & separate the major organelles from one another o Instruments Blender Homogenization (breaking up cells) Centrifuge: fractionates cells by spinning test tubes holding mixtures of disrupted cells at various speeds Resulting force separates cell components by size & density Ultracentrifuge: can spin as fast as 130,000 revolutions per minute & apply forces 1 million force of gravity Most powerful o Can study cells composition and functions in bulks 6.2: Eukaryotic cells have internal membranes General Background o Prokaryotes = Bacteria + Archaea o Eukaryotes = Protists + Fungi + Animals + Plants Comparing Prokaryotic & Eukaryotic Cells o Things in Common Plasma Membrane Cytosol: a semi fluid substance Chromosomes: carrying genes as DNA Ribosomes: tiny organelles that make proteins according to instructions from the genes o Differences Chromosome location Prokaryotes: no nucleus...
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6 - A Tour of the Cell - 6: A Tour of the Cell 11:25...

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