Question

Scenario for Questions 8-13 For the remaining questions, you will be living in the world of Star Wars, the epic space opera originally envisioned by George Lucas. In this scenario - you are involved in a research group studying the cellular processes of various groups in this amazing world. Of course, you also have to have time traveled for this scenario – so be careful and don’t mess anything up that might destroy your present!

Question 10 Another research group is studying membranes in a species known as Ortolans, which resemble small blue elephants. They are renowned for their ability to play the saxophone (see Return of the Jedi), and you are interested (really) if their membrane structure has anything to do with that ability. We discussed membrane function and protein localization, but didn’t spend time on membrane lipids. You may need to review some cell biology text (including the fluid mosaic model) to address parts of this question. Ortolan membranes are made of phospholipids, but unlike humans, which have fatty acid tails averaging 16 carbons, Ortolan membranes lipids contain chains of approximately 12 carbons.

(A) Predict the properties of the lipid bilayer that might result from this change. What methodology would you use to test these properties. Explain expected results, briefly. Ortolan membranes and human membranes were compared and found to be very similar in permeability to most molecules. In these experiments, researchers reconstitute functional membrane spheres in vitro. The spheres are placed in different complex solutions (Biologically relevant concentrations of sodium, chloride, potassium, calcium, etc. ions) and solute movement is assessed to determine membrane permeability. However, one noticeable exception was identified – Ca2+. Specifically, they found that at equilibrium, Ca2+ concentration across human cell membranes is hugely asymmetric, but is equal on both sides of the membranes from Ortolans.

(B) Describe differences between the membranes of the two cells could explain these differences in calcium equilibrium?

Answer 1

Lipids are insoluble in water and have large regions of their surface composed of hydrocarbons with very few polar groups. Their aversion to water is responsible for the hydrophobic effect that drives membrane stability. Membrane lipids are ‘amphipathic’, with a polar end anchoring the lipid to the aqueous interface and a long hydrophobic segment that forms the oily membrane interior. In human cells there are over 1,000 major lipid species and countless minor lipids. There have been several attempts to classify lipids, the most recent being a lipidomics-based system by Fahy et al. from 2005. The most important lipid component of membranes is fatty acids. A fatty acid is a mono-carboxylic acid with a long (normally 14–24 carbons), un-branched, hydrophobic tail which may be either saturated or unsaturated (usually 0–6 cis non-conjugated double bonds). Fatty acids are the basic building blocks of complex membrane lipids and so are largely responsible for membrane structure, fluidity, and function.

Their are several methods to detect fluid mosaic model and composition of lipidbilyar and theirorientation as To achieve quantitative in situ imaging of various lipids, we developed a ratiometric analysis using fluorescence biosensors, each of which is composed of an engineered lipid-binding protein and a covalently attached solvatochromic fluorophore. To cover a wide range of lipid concentration, lipid-binding proteins are engineered to have variable dynamic ranges. These tunable sensors allow robust and sensitive in situ quantitative lipid imaging in mammalian cells, providing new insight into the spatiotemporal dynamics and fluctuation of key signaling lipids. The sensor strategy is also applicable to in situ quantification of multiple cellular lipids or a single lipid in the opposing leaflets of cell membranes.

as in the above question the human have fatty acid tails averaging 16 carbons, Ortolan membranes lipids contain chains of approximately 12 carbons.means it saturated fatty acid chain and their is fluidity and permiability of the mambrane is higher than human so in this membrane all ions and other componants are easy permit and transportation will be easy than human cell membrane so the Ca2+ concentarion has their differ in human and the given scenario so their equilibrium comcentration also differ in both condition as the carbon chain length is having low no of carbon this will happan in case of Ortolans