Question

can someone please answer question C :) a Why is the process of cytoplasmic streaming important in a large cell such as Nitella? b How do the inhibitors cytochalasin and oryzalin work? c If you were to repeat the experiment with an inhibitor and the DMSO control and the DMSO slowed streaming to the same rate as the inhibitor what would your conclusion be?

(The experiment was an investigation into the role of the cytoskeleton and calcium ion channels in cytoplasmismic streaming. For the question relating to question C, it was an exercise to determine whether actin filaments and/or microtubules are involved in cytoplasmic streaming in nitella. "The inhibitor solutions that you have been supplied should be of sufficient concentration to disrupt microfilaments (cytochalasin) or microtubules (oryzalin). You have 3 ml of a 10mM solution of oryzalin and 3 ml of a 15mM solution of cytochalasin D. Due to poor solubility in water the inhibitors were initially made up as stock solutions in DMSO (a commonly used solvent in the lab). Unfortunately DMSO can be toxic to cells and can affect membrane permeability. You have a solution of DMSO that has a concentration of DMSO that is the same as the maximum concentration that the cells were exposed to in the inhibitor solutions (0.15% v/v). This solution should form the basis of a control experiment."

Answer 1

1. Cytoplasmic streaming refers to the flow of molecules in the cytoplasm. Generally, cytoplasmic streaming takes place in large cells like Nitella, which have a diameter more than 0.1 mm. This is attributed to the fact that with an increase in cell size, the rate of diffusion decreases in these cells, so cytoplasmic streaming is necessary for improving the movement of nutrients within the cells.
2. Action of Cytochalasins: They are a group of chemicals that are excreted by different fungi and are known inhibitors of cell movement. They bind to the plus end of the microfilaments and block the polymerisation of the actin molecules, which can inhibit the cell movement, phagocytosis, microfilament-based vesicular and organelle trafficking and also the production of lamellipodia and microspikes. (Ref: http://www.sciencedirect.com/ science/article/pii/B9780123704580500086) ​​​​​​​Action of oryzalin; Oryzalin is a dinitroaniline herbicide which causes a depolymerisation of the plant microtubules.
3. With Regards to Question c; if the application of DMSO and the inhibitor affect the cytoplasmic streaming at the same rate, it indicates that DMSO is not a suitable solvent for the experiment. This was due to the fact that the use of DMSO alone affects the cytoplasmic streaming and the actual effect of the inhibitor is either masked or the inhibitor shows no additional effect on the cytoplasmic streaming.