Bio 201 1st Edition Lecture 10 Outline of Last Lecture I. Endomembrane System ContinuedA. Pulse- Chase ResultsB. SecretionC. EndocytosisOutline of Current Lecture I. Peroxisomes and Glyoxysomes II. CytoskeletonA. 3 TypesB. Determining Molecular SizeCurrent LectureI. Peroxisomes and Glyoxysomes-Our last organelle, although not exactly a part of the endomembrane system because they are not functionally contiguous therefore there is no transport between the interior of these organelles and the endomembrane system-These are difficult to distinguish between lysosomes-Peroxisomes are found in eukaryotes while glyoxysomes are found in plants -These organelles have enzymes that are important for peroxide production and enzymes that are important for elimination of damaged peroxides-Contents may crystallizeII. Cytoskeleton- Filamentous network in the cytoplasm-Exists only in eukaryotes for structural support because cells with peptidoglycan do not need support-Cells with peptidoglycan such as bacteria contain cytoskeletal like proteins but these are not the same as eukaryotic cytoskeletons-Used for maintaining cell shape and structure as well as motility-Also used for transportation of organelles, vesicles, proteins and mRNA through cell -Used for role in endocytosis as well as cell divisionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.A. 3 Types:1. Microtubules (MTs)- Largest of filaments, most abundant and highly concentrated around nucleus. -MTs are made up of tubuline heterodimer which ismade up of alpha and beta subunits which polymerize to form an entire MT. -alpha subunit is positive, where polymerization is favorable and points towards the right while Beta subunit is negative, where de-polymerization is favored -The heterodimer is polar-MTs are used for structural support and are the train tracks for transport, also used in cell division (mitosis)-3 types of MTs include cytoplasmic, axonemal, and centriolar -Cytoplasmic- tube, “singlet” (13) single tubile. Used as train track, cell shape and cell division. These are unstable and contually depolymerizing and polymerizing. Located in the cytoplasm, minus ends toward nucleus and positive end towards plasma membrane.-There is a microtubule organizing center in plants and animal, which includes a centriole made up of MTs and other proteins, nucleates new MTs, anchors minus ends of MTs and organizes mitotic assembly in dividing cells -In cytoplasmic MT, MT treadmilling occurs, this is the continuous polymerization at the positive end and depolymerization at the negative end. This happens because the affinity of GTP gets sticky binding to heterodimers (polymerization) with the addition of a catalyst the GTP turns into GDP becoming less sticky and therefore leading to depolymerization at the minus end.-Axonemal- larger, provide cilia and flagella, and are used for motility, extracellular movement of fluids, and hearing. Have a “doublet” (9+2) structure. These are stable.-Centrolar- “triplet” (9) structure, used in centrioles for nucleation of cytoplasmic MTs, also organize the mitotic spindle. These are stable.-Dynamic Instability- Occurs when MTs are in dynamic equilibrium between polymerization and depolymerization at all times. 2. Intermediate filamentous- Diverse and medium sized, oddball of cytoskeleton. Not polymers. Multimers form antiparallel to each other no polarity. Intermediate is diverse, they have different functions such as keratin. 3. Microfilamentous (actin)- Thinnest filamentous of cytoskeleton. Comprised of monomers of actin, which polymerize at the positive end and depolymerize at minus ends. Actin consists of 2 dependent strands. Responsible foramoeboid movement, endocytosis, and cytokinesis (last step of cell division). Monomer of actin is G-actin subunits. Positive =barbed end while Negative= pointed end. -In actin, ATP binds to actin monomers, actin polymers catalyze ATP hydrolysis turning into ADP, which leads to depolymerization at minus end. Similar to microtubules but ATP instead of GTP. Actin is distributed randomly in cytoplasm, motile cells have actin on plus ends pointed towards plasma membrane, which cause membrane to protrude (pseudopod or “fake foot”) when actin polymerizes. B. Determining Molecular Size- Scientist use process to figure out what the cytoskeleton is made out of and their sizes. Proteins are separated by their size. There are 5 steps to this process:1. Homogenize cells2. Isolate organelles3. Purify the protein4. Denature (unfold) the protein with 1. SDS which breaks the secondary, tertiary, and qauternary structure, which causesthe protein to become negatively charged and 2. Beta- mercaptoethanol which oxidizes disulfide bonds and lastly 3. Heat which disrupts ionic and H-bonds. 5. Add SDS- Polyacrylamide gel electrophoresis (SDS-PAGE) to get initial look at proteins to identify length of proteins. Large proteins migrate slowly while small proteins migrate faster. Cathodes at top and Anodes at