3. Rank from most polar to least polar. Provide reasoning. Triglycerols, fat aci

Question

3. Rank from most polar to least polar. Provide reasoning. Triglycerols, fat acids, cholestero estradiol, phosphoglycerides 4. Assuming that cells are spheres, compare three cells with diameters of 2 m, 10 m and 20 m. Calculate the surface area to volume ratio for all three cells. Based on your calculations, rank these in order (lowesst SA/V ratio first). Which cell is most suited for rapid exchange of material with the extracellular environment? For a sphere: V = 4/3 r, and A = 4r 5. A transmembrane protein has 1000 amino acids. The fifth amino acid is found on the external surface of the cell membrane. It interacts with the aqueous environment outside the cell. Amino acids 25 and 205 are covalently bonded to each other and are required to give the protein its three-dimensional shape. Amino acid 554 is found on the outer surface of the protein, but it is deep in the interior of the membrane. Amino acid 979 is found on the external surface of the protein, where t forms a weak ionic bond with a chloride ion. Can you identify each of the numbered amino acids by structural group and name there may be more than one specific amino acid possible in some cases. ? Please note that

Explanation / Answer

Fatty acids is most polar and tryglycerols are least polar. The order from most to least polar is fatty acids,cholestreol,estradiol,phosphoglycerides,tryglycerols.

Triacylglycerols are nonpolar hydrophobic molecules that can be stored in specialized nonaqueous cellular compartments.

Fatty acids are chain-like molecules that are important components of several types of lipids. The illustrations below show two different fatty acid molecules. Each has a characteristic carboxyl group (the -COOH) attached to a chain of carbons with hydrogen atoms attached to the carbon chain. Two things are noteworthy. First, the hydrocarbon chain is very non-polar and therefore doesn't dissolve in water very well. However, hydrocarbon chains do associate with each other readily. Second, note that the unsaturated fatty acid has two hydrogens removed, and this allows formation of a double bond, i.e., a stronger bond between two of the carbon atoms. Note also that the double bond tends to produce a bend or a kink in the fatty acid. The illustration to the right shows two other common fatty acids: stearic acid, which is a straight 18 carbon chain with no double bonds, and oleic acid, which is an 18 carbon chain with a single double bond, which cause a bend in the carbon chain.

Cholesterol

Cholesterol is also an important component of animal membranes (plant membranes have a similar, but distinct 'sterol' in their membranes). It is a lipid, because it is composed almost entirely of carbon and hydrogen, but it is different from fatty acids, fats and phospholipids in that it is arranged in a series of rings. The rings consist of 5 or 6 carbon atoms bonded together. The carbon atoms at the apices of the hexagonal and pentagonal rings have hydrogen atoms attached to them. The ring-like structures are fairly rigid, but there is also a hydrocarbon tail, which is somewhat flexible. The entire structure is somewhat reminiscent of a fancy kite with a tail.Cholesterol is very non-polar, except for the hydroxyl group attached to the first ring. Consequently, in an animal cell membrane the polar hydroxyl group sticks into the aqueous environment (either extracellular water or intracellular water), and the rest of the cholesterol molecule, which is non-polar, is found among the non-polar fatty acid tails of the phospholipids.The image below depicts a section of a cell membrane with water outside and inside. The polar head groups of the phospholipids are represented in red, and their non-polar fatty acid tails are shown as zig-zag lines extending from the polar head group. As we we see in greater detail, cell membranes consist of a bilayer of phospholipids with other molecules inserted into the bilayer. This illustration shows five cholesterol molecules (the black structures with four conjoined rings) inserted into the lipid bilayer. Most of the cholesterol molecule in non-polar and therefore associations with the non-polar fatty acid tails of the phospholipids. However, the hydroxyl group (-OH) on cholesterol carries a negative charge and therefore associates with the polar environment of water either inside the cell or outside.

A nonpolar molecule (ie. a fatty acid) will not dissolve in a polarsubstance (ie. water), and vice versa. As such, thirdly, lipids are insoluble in water (apolar molecule due to the high electronegative OH bond difference), for nonpolarmolecules are insoluble in polar molecules.

Triacylglycerols, also known as triglycerides, are the simplest lipids formed by fatty acids.Triacylglycerols are nonpolar, hydrophobic, and insoluble in water. This is due to the ester linked bond between the polar hydroxyls of glycerol and the polar carboxylates of the fatty acids.

Triglycerides

A fat molecule is a type of lipid that consists of three fatty acid molecules connected to a 3 carbon glycerol backbone, as shown on the right. The three fatty acids can be different from one another. Since the hydrocarbon chains are very non-polar, fats do no dissolve in water; instead, fat molecules tend to coalesce with one another. Since a fat molecule has 3 fatty acids connected to a glycerol molecule, they are also called trigylcerides.

Estradiol: Polar (but very slightly so!). Most bonds are CH (non polar), but the few polar ones make the molecule very slightly polar. this molecule is not soluble in water Because it is only very slightly polar, and the largest part of the molecule is indeed non polar. Water is very polar. Remember like disolves like.

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