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Cell Function and Structure (viewing cells (Brightfield (unstained…
Cell Function and Structure
viewing cells
Brightfield (unstained specimen)
light passes through the specimen making it difficult to view unless the specimen is pigmented or stained
Brightfield (stained specimen)
visabiltiy increases with staining with dyes requiring killing cells
phase-contrast
amplifies variations and density to enhance visuality in unstained cells . useful in examining live cells that are unpigmented cells
Differential interference contrast (nomarski)
as in phase-contrast microscopy, optical modifications are used to exaggerate differences in density appearing almost 3-D
confocal
eliminates out of focus light to increase the sharpness in the image and a 3-D image is created
Deconvolution
process uses deconvolution software to reconstruct an image to increase its sharpness
super-resolution
uses super-resolution technique lights up individual fluorescent molecules
scanning electron microscopy (SEM)
takes micrographs with scanning electron microscope to show a 3-D image of the surface of a specimen.
Transmission electron microscopy
takes cross sectional images.
cell fractionation
homogenization
homogenate
centrifugation
centrifuged at 1,000g/ 10 min
produces pellets rich in nuclei and cellular debris
first run poured into second tube centrifuged at 20,000g produces rich in mitochondria (and chloroplasts if cells are from a plant)
second run poured into third tube centrifuged at 80,000g/60 min that produces pellets rich in microsomes (pieces of plasma membrane and cells' internal membranes)
third run poured into a fourth tube and centrifuged at 150,000g for 3 hours producing pellets rich in ribosomes
Geometric relationships between surfaces area and volume
total surface area [sum of the surface areas (height x width) of all box sides x number of boxes]
Total volume [height x width x length x number of boxes]
Surface-to-volume (S-to-V) ratio [surface area divided volume]
organelle structure
eukaryotic
nucleus
nuclear envelope
nucleolus
chromatin
plasma membrane encloses the cell
hydrophilic region
inner cell and outer cell (outer cell includes carbohydrates side chains)
integrins, membrane proteins with two subunit, bind to the ECM on the outside and to associated proteins attached to microfilaments on the inside. this linkage can transmit signals between the cells environments and its interior and can result in changes in cell behavior
hydrophobic region
includes proteins and phospholipids
collagen fibers are embedded in a web of proteoglycan complexes
fibronectin attaches the ECM to integrins embedded in the plasma membrane
a proteoglycan complex consist of hundreds of proteoglycan molecules attached noncovalently to a single long polysaccharide molecule
ribosomes (small brown dots): complexes that make proteins; free in cytosol or bound to rough ER or nuclear envelope
golgi apparatus: organelle active in synthesis, modification, sorting and secretion of cell products
lysosome: digestive organelle where macromolecules are hydrolyzed
mitochondrion: organelle where cellular respiratoin occures and most ATP is generated
peroxisome: organelle with various specialized metabolic functions; produces hydrogen peroxide as a by-product and then converts it to water
microvilli: projections that increase the cell's surface area
microtubules
intermediate filaments
microfilaments
cytoskeleton: reinforces cells shape; functions in cell movemmetn; components are made of protein.
centrosome: region where the cells microtubules are initiated; contains a pari of centrioles
flagellum: motility structure present in some animal cells, composed of a cluster of microtubules within and extension of the plasma membrane
endoplasmic reticulum (ER): network of membranous sacs and tubes; active in membrane synthesis and other synthetic and metabolic processes; has rough(ribosome-studded)and smooth regions
prokaryotic
no nucleus (instead has a nucleoid that contains cells DNA yet not inclosed by a membrane)
fimbriae attachment structures on the surface of some prokaryotes
ribosomes: complexes that synthesize proteins
plasma membrane
cell wall: rigid structure outside the plasma membrane
glycocalyx: outer coating of many prokaryotes, consisting of a capsule or a slime layer
flagella: locomotion organelles of some prokaryotes
diffusion
the diffusion is how the molecules pass through membrane
Osmosis
the diffusion of free water across cell membranes and the balances of water between the cell and its environment are crucial to organisms