Biology Module 2 Cell Biology Reminder of the tenets of cell theory Cells are the fundamental units of life All living things are made of cells All cells come from pre existing cells Compare and Contrast Prokaryotes and Eukaryotes Both eukaryotic cells and prokaryotic cells have DNA ribosomes and cytoplasm Eukaryotic cells have a nucleus and organelles while prokaryotic cells do not Organelles are membrane bound structures within cells that are important for compartmentalizing and regulating traffic Studying cells Light Microscopy Limit of resolution 200nm Used to see general size and shape of cells and large organelles DAPI is used to see the nucleus and binds to the minor groove of DNA and fluoresces Specifically binds a particular portion of a specific protein polysaccharide Limit of resolution 200nm Fluorescence microscopy Used to see specific cell components Epifluoresence blurry D2 1 Confocal fluorescence clearer D2 2 Electron microscopy Used to see subcellular structures and surfaces in more detail Practical limit of resolution 2 3 nm Can be used to see protein polymers D2 3 Transmission microscopy up to 250 000x Used to closely see one unit D2 4 Scanning electron microscopy up to 50 000x Used to see several units D2 5 Crystallography Used to solve 3 D structures of proteins and nucleic acids D2 6 Differential centrifugation Used to separate cell components D2 7 Density gradient centrifugation D2 8 Subcellular Structure The actin cytoskeleton A cell is kinda like a pool with a floating octopus Filamentous proteins Microfilaments small diameter polymer made of actin Microtubules large diameter made of alpha and beta proteins Intermediate filaments intermediate diameter comprised of various proteins Cytoskeletal filaments are long chains made up of repeating protein subints Protein monomer D2 9 Protein heterodimer D2 10 Microfilament subunits are called actin monomers Globular and filamentous actin Globular individual subunits form filamentous actin Actin filaments are asymmetric have polarity Actin forms different types of bundles that help to shape the cell Contractile bundle stress fiber D2 11 Cell cortex gel like network D2 12 Filopodium tight parallel bundle D2 13 Dynamic actin filaments extend and retract Filopodia as they polymerize and depolymerize Actin filaments support relatively stable microvilli that help to increase surface area of a cell and also look like Top Thrill Dragster and Kingda Ka D2 14 and D2 15 Dynamic actin filaments extend lamellipodia protrusion gel like network bundle to facilitate cell Myosins are motor proteins that use the energy from ATP hydrolysis to travel along actin crawling D2 16 Allows direction movement and coordinated contraction Some myosins can carry cargo Allows directional transport of substances across the cell Myosin can move organelles and cytoplasm in plants cytoplasmic streaming Actin filaments can form antiparallel bundles that allow contraction similarly to myosin Filamentous myosin myosin II effects contraction of antiparallel actin filaments Muscle cells Electron microscopy Cytokinesis in all animal cells D2 17 Long chains Rope like structure Intermediate filaments provide the cell with tensile strength Many bonds forming such as hydrogen bonds which are weak but the sum is strong 2 proteins dimer Intermediate filaments are less dynamic than actin which grows and shrinks very quickly Immunofluorescence is used to study Ifs Ifs are vital for cell cell interactions Desmosomes Hold shit together in areas where the tissues are exposed to high mechanical forces such as the skin Cell striatum interactions and the heart D2 18 Hemidesmosomes D2 19 Structure Nuclear Lamins Located in the nucleus Gives the nucleus shape and anchors chromosomes Progeria is a mutation in the nuclear lamins If subunits are antiparallel heterotetramer then there is no directionality and the ends are identical to one another Microtubules Alpha and beta tubulin heterodimers Chain of 13 forms hollow rigid unbranched tubes unlike actin D2 20 Microtubules give cells shape resist particularly compression force and form a structural framework for organelles organization They form a radial network similar to roads into out of a city Originate at the Microtubule Organizing Center MTOC D2 21 Unlike Intermediate Filaments microtubules are asymmetric and have polarity Contain motor proteins which are important for directional transport Alpha end is positive Beta end is negative Kinesin is positive Dynein is negative D2 22 energy D2 23 D2 24 Kinesin and Dynein control the coloration in fish and amphibians by carrying pigment granules Microtubules form the mitotic spindle where the chromosomes align Not static will gain and lose subunits Motors walk along the microtubule where every step hydrolyzes ATP into ADP and Phosphate for Cancer cells can be targeted using microtubules Microtubules form the core of cilia located in fallopian tubes for example and eukaryotic flagella only sperm cells 9 and 2 arrangement of microtubules in cilia and flagella known as the axonem Cilia and flagella movement is powered by motor proteins Dynein hydrolyses ATP Transcribe info encoded by DNA into mRNA Translate info encoded by mRNA into protein Fold and modify protein Steps in protein synthesis Deliver protein to its proper place within or outside of the cell The nucleus Functions DNA Replication Transcription mRNA processing The nuclear envelope has a double membrane and is selectively permeable Ribosome assembly Protection Role Nucleotides mRNA and ribosomes All incoming and outgoing traffic goes through nuclear pores aqueous Large proteins only get in if they have a series of amino acids NLS Small molecules can diffuse through pores Ribosomes are assembled in the nucleolus and are machines for protein synthesis Cytosolic Mitochondrial nuclear proteins are translated by free ribosomes Endomembrane and secreted proteins are translated by ribosomes bound to the Rough ER The Endomembrane System The ER is contiguous with the nuclear envelope An RER signal sequence steers ribosomes translating endomembrane system and secreted proteins to the ER Proteins are folded and glycosylated in the RER lumen Chaperone proteins monitor folding Adding sugars to protein is call glycosylation The RER is in charge of quality control Proteosome degrades missed folded protons The golgi receives membrane bound packages of proteins vesicles from the RER Proteins exiting the golgi apparatus are addressed