Bio Study Guide Test 3 Microscopy two primary considerations in microscopy magnification object image object s true size resolution minimum distance between two points such that the points can still be distinguished from each other Types of Microscopy brightfield unstained light shined through specimen brightfield stained light through a stained specimen phase contrast used to examine living cells in culture amplifies variation in density differential interference contrast fluorescence molecules tagged with fluorescent dyes confocal lasers used to observe fluorescent stains scanning electron microscopy the surface of whole cells or large molecules are coated with gold and an electron bean excites surface electrons The pattern translates to a video screen transmission electron microscopy cells stained with heavy metals and an electromagnetically controlled electron beam encounters variation in density Cell fractionation cells are ground or gently homogenized cell extract goes through a series of centrifugation steps nuclei and cell debris mitochondria and chloroplasts microsomes pieces of plasma membranes ribosomes proteins and or organelles are subjected to further biochemical analysis Prokaryotic cell Cells require a high surface to volume ratio in order to insure an efficient exchange of materials across the cell membrane Plasma membrane of eukaryotic and prokaryotic cells is composed of a phospholipid bilayer and transmembrane proteins that communicate between the cytoplasm and extracellular environment cytoplasm area between the nucleus and plasma membrane cytosol semi fluid substance within the plasma membrane that suspends organelles Animal cells have lysosomes centrioles and flagella some plant have this in sperm Plant cells have chloroplasts central vacuole and tonoplasts cell wall and plasmodesmata Nucleus contains a nucleolus that contains rRNA and is responsible for ribosome assembly nuclear envelope inner and outer membrane nuclear pores scattered with chromatin DNA and histones Ribosome large and small subunit ribosomal RNA and ribosomal proteins Site of protein synthesis Free ribosomes synthesize proteins that are used in the cytosol Bound ribosomes synthesize proteins that are either membrane bound or secreted Ribosome numbers vary depending on cell type Endoplasmic Reticulum Rough ER site of synthesis of secreted proteins polypeptide chain grows from ribosome into the lumen of the rough ER proteins fold into the native shape and can be modified with carbohydrate chains glycoproteins secreted proteins are transported in vesicles that bud from the transitional ER transitional ER site of synthesis of membrane phospholipids Smooth ER lipid synthesis phospholipids and steroids responsible for the detoxification of drugs and toxins in liver the enzymes add hydroxide groups to drugs increase their solubility and allow the drugs to be flushed from the body Drugs induce smooth ER synthesis leading to drug resistance Site of cellular Calcium ion storage Golgi Site of further protein and phospholipid modification Amino acid sequences within the newly synthesized mature proteins provide the protein s intracellular address which the Golgi recognize and transport accordingly Lysosome Vacuole Mitochondria Microtubule Microfilaments membranous sac of hydrolytic enzymes to break down macromolecules enzymes and lysosomal membranes are synthesized in the rough ER and completed in the Golgi phagocytosis lysosome digesting food Damaged organelles are broken down and the monomeric subunits of macromolecules are recycled by the cell Autophagy lysosome breaking down damaged organelle membrane bound regions that carry out a variety of functions depending on the cell adipocytes lipid molecules protists contractile vacuole Site of ATP generation from glucose and lipids Contains inner and outer membrane mitochondrial DNA mitochondria matrix cristae Matrix contains free ribosomes Hollow tubes whose wall consists of 13 columns of tubulin molecules subunits are alpha tubulin and beta tubulin responsible for maintaining cell shape cell motility chromosome and organelle movements Two intertwined strands of actin actin subunits responsible for maintaining cell shape changes in cell shape muscle contraction cytoplasmic streaming cell motility cell division Intermediate filaments Fibrous proteins supercoiled into thicker cables Subunits are keratins keratin forms an alpha helix and then a two chain coiled coil two alpha helixes wrapped around each other and a protofilament forms from two staggered anti parallel arrangement from disulfide bonds between adjacent coiled coils which forms a protofibril 16 32 polypeptides arranged in cross section responsible for maintaining cell shape anchoring the nucleus and certain other organelles and the formation of the nuclear lamina ATP powered motor protein traveling up the microtubule of the cytoskeleton with ATP receptor for motor protein Kinesin Whipping motion of the flagella and cilia