ATP Powered interaction between actin and myosin is the basis for an array of cell movements cytokinesis cell moving is the process of cell division In animals this occurs by the use of actin filaments connected to the plasma membrane and arranged in ring around the cell Myosin causes the filaments to slide past one another Cytoplasmic streaming directed flow of cytosol and organelles within plant cells Actin filaments powered by myosin ex Material transport cell crawling actin filaments grow causes plasma membrane to extend and move the cell Intermediate filaments not polar each end identical not involved in movement Only play structural role ex Keratin hair skin ex nuclear lamins form dense mesh under nuclear envelope they help give the cell is shape they also anchor chromosomes they also break up and reassemble the nuclear envelope when cells divide Microtubules The largest cytoskeletal component in terms of diameter consists of two polypeptides a tublin and b tublin exist as stable protein DIMERS a tublins minus end and b tublins plus end grow faster at their plus ends MTOC microtubule organizing center plus ends grow outward plants cells have hundreds of sites where microtubules are growing most animal fungal cells have only ONE site near the nucleus In ANIMALS MTOC has distinct structure called a centrosome contains two bundles of microtubules called centrioles In function microtubules similar to actin filaments provide stability and are involved in movement Microtubules are best known for role in separating chromosomes during mitosis and meiosis kinesin converts the chemical energy in ATP into mechanical energy in form of movement the protein moves along microtubules in a directional manner toward the plus end kinesin has a head with two globular pieces a tail associated with small polypeptides and stalk that connects the head and tail Bacterial flagella are helical rods made of protein called flagellin eukaryotic flagella consist of several microtubules constructed from tubulin dimers bacterial flagella move by rotating rod like propeller eukaryotic flagella move by undulating whip back and forth eukaryotic flagella surrounded by the plasma membrane and are considered organelles bacterial flagella are not flagella much longer than cilia 9 2 structure is called the axoneme axle thread originate from basal body dynein is a motor protein like myosin and kinesin that uses ATP to undergo conformational changes These shape changes move dynein along microtubules toward the MINUS end IF the dynein arms on just one side of the axoneme are activated then the localized movement results in bending Bending of cilia or flagella causes swimming Screen clipping taken 5 4 2014 7 16 PM 18 1 To use lactose E coli must first transport the sugar into the cell Once Lactose is inside the cell the enzyme b galactosidase catalyzes a reaction that breaks down the disaccharide into glucose and galactose Lactose is an inducer small molecule that triggers transcription of a specific gene Screen clipping taken 4 30 2014 11 21 PM Screen clipping taken 4 30 2014 11 21 PM Screen clipping taken 4 30 2014 11 22 PM Screen clipping taken 4 30 2014 7 53 AM In negative control the repressor is the parking brake lactose releases the brake Screen clipping taken 4 30 2014 9 32 AM Screen clipping taken 4 30 2014 9 35 AM Screen clipping taken 4 30 2014 9 39 AM Screen clipping taken 5 4 2014 8 12 PM 18 3 Negative Control occurs when a regulatory protein called a repressor binds to DNA and shuts down transcription Positive control occurs when a regulatory protein called an activator binds to DNA and triggers transcription It turned out that the lacZ and lacY genes in E Coli are controlled by engaging or releasing a parking brake they are under negative control The lacI gene produces a repressor protein that exerts negative control over lacZ and lacY gene transcription In negative control the repressor is the parking brake lactose releases the brake Screen clipping taken 5 4 2014 8 07 PM Screen clipping taken 5 4 2014 8 03 PM Screen clipping taken 5 4 2014 7 20 PM Screen clipping taken 5 4 2014 7 22 PM Screen clipping taken 5 4 2014 7 23 PM Steps in Mitosis M phase Mitosis nuclear division and Cytokinesis condense chromosomes limit the risk of breaking them when you separate them cytoskeleton reorganizes to form mitotic spindle to send out microtubles to grab onto sister chromatids and facilitate separation nuclear envelope disappears chromosomes move to opposite poles reformation of nuclear envelope cytokinesis Mitosis Interphase two centrosomes in cells centrosomes replicate two pairs of centrioles Move from G2 into prophase the interphase microtubule array is completely disassembled Prophase rebuild microtubules into mitotic spindles poles and put one pole on each side of cell condensing chromosomes now visible in X shape Late Prophase disassemble nuclear envelope to allow newly formed microtublules to gain access to chromosomes phosphorylate nuclear envelope nuclear pores and nuclear lamina Lamin proteins broken down into dimers do not diasassemble dimers disassmble system of rope like fibers all the way to free lamins Phosphoralate proteins into free nuclear membrane vesicles of nuclear envelope Remnants of nuclear pore in cytoplasm They are not hyrdolyzed they just lose affinity for their neighbors and pieces go in different directions they do not break up remove phosphate groups to come back together cannot make eveything again b c nucleus disssembled A type Lamins and C type lamins are free floating B type lamins integrated into nuclear envelope they are bound to nuclear membrane even after phosphorylated Prometaphase the chromosomes are completely condensed nuclear envelope mostly disassembled kinetochore chromosomes move back and forth until aligned in the center called metaphase plate Kinetechore have motor proteins Microtubule Kinesin moves toward plus if you polymerize Dynein move toward minus if you depolymerize Screen clipping taken 4 28 2014 9 43 PM Metaphase breaking down proteins called cohesins to separate chromosomes Anaphase separate sister chromatids and push spindle poles away from each other extednding boundary of cell Structural regulatory and motor proteins in kinetochore Anaphase A and B happen at same time Anaphase A movement of sister chromatids to opposite poles via kinetochore microtubules plus end in kinetochore minus ends in centrosome walk to minus end using dyneins That s how