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(Types/Functions of microscopes (Electron Microscope (EM) - are used to…
Types/Functions of microscopes
used to visualize cells
Light Microscope (LM) - visible light is passed through a specimen and then through glass lenses
Lenses refract (bend) the light so that the image is magnified
Three important parameters of microscopy
Magnification
Resolution
Contrast
Light Microscopes can magnify effectively to about 1,000 times
The Resolution of Standard light microscopy is too low to study organelles
Electron Microscope (EM) - are used to study sub-cellular structures
Scanning electron microscope
Focus a beam of electrons onto the surface of a specimen
Transmission electron microscopes
Focus a beam of electrons through a specimen
TEMs are used mainly to study the internal structure of cells
Recent advances in light microscopy are cell labeling, confocal microscopy (better 3D), and super-resolution microscopy
Cell Fractionation
Takes cells apart and separates the major organelles from one another
Centrifuges fractionate cells into their component parts
enables scientists to determine the functions of organelles
Eukaryotic cell's membranes
Prokaryotic vs Eukaryotic
Eukaryotic
DNA in a nucleus that is bounded by a double membrane
Membrane-bound organelles
Cytoplasm in the region between the plasma membrane and nucleus
Eukaryotic cells are generally much larger
Prokaryotic
DNA in
nucleoid
No membrane bound organelles
Cytoplasm, bound by the plasma membrane
No nucleus
Plasma Membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste
Intternal membranes that divide the cell into compartments--the organelles
the basic fabric of biological membranes is the double layer of phospholipids
Metabolic requirements set upper limits on cell size
Surface area to volume ratio of a cell is critical
As a cell increases in size, it's volume grows proportionately more than it's surface area
Genetic instructions in Eukaryotes
Nucleus
contains most of the cell's genes and is usually the most conspicuous organelle
nuclear envelope separates it from the cytoplasm
double membrane (each membrane consists of a lipid bilayer)
Nuclear Lamina lines the envelope and maintains nucleus shape
Chromosomes, made of chromatins
chromatin condenses to form discrete chromosomes as a cell prepares to divide
Nucleolus is located within the nucleus and is the site of ribosomal RNA synthesis
Ribosomes
Comp;exes made of ribosomal RNA and protein
carry out protein synthesis in two areas
outside of the endoplasmic reticulum or nuclear envelope (Bound)
Cytosol (Free)
Endomembrane
components
Endoplasmic reticulum
acciunts for more than half of total membrane
Smooth ER
lacks ribosomes
Synthesizes lipids
Metabolizes carbs
Detoxifies drugs and poisons
Stores calcium ions
Rough ER
sruface studded with ribosomes
ribosomes separate glycoproteins (proteins covalently bonded to carbs)
Distributes transport vesicles (proteins surrounded by membranes)
membrane factory for the cell
Golgi apparatus
flattened membranous sacs called cisternae
modifies products of the ER
Makes ceratins macromolecules
sorts/packages materials into transport vesicles
Lysosomes
membranous sac of hydrolytic enzymes that digest macromolecule
lysosomal enzymes work best in the acidic environment inside the lysosome
made by rough ER--transferred to the Golgi apparatus
Phagocytosis - cell engulfing another to form a food vacuole
Autophagy - enzymes recycle cell organelles/macromolecules
Vacuoles
plasma membrane
Nuclear envelope
all connected by vesicles
Surface area vs Volume Ratio
Membrane Protein Functions
Diffusion/Osmosis/Tonicity
Active Transport