Question

A2. A scientist has a beaker of water. She adds 10 ml of sunflower oil into the beaker of water and stirs it. The water becomes cloudy, then gradually clears as an oily layer forms on the surface. The structure of sunflower oil is shown below: o O What is happening here? Why does the oil behave this way in the solvent water? Draw diagrams of chemical structures and use thermodynamic terms and equations to help explain your answer. (10 marks) A3. A drug company accidentally mixes up some bottles of ATP with some bottles of the benzoyl ATP compound shown below. Scientist Dan uses this benzoyl ATP in a RNA synthesis experiment, believing it to be ATP. What do you think will happen in Dan's experiment? Explain your answer with reference to the structure of the benzoyl ATP. O-P-O-P-O-P-O он

BIOCHEMISTRY

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Answer 1

Oils are triglycerides or the esters of three fatty acids linked to glycerol. Sunflower oil is actually a mixture of polyunsaturated fatty acid, linoleic acid, and monounsaturated fatty acid, oleic acid and small quantities of saturated fatty acid Palmitic acid and stearic acid. The molecules in oils like sunflower oil have long hydrophobic carbon of 16 -18 carbon atoms with polar group “esters” on one of its end, but these groups do not influence solubility in the water when compared to the O-H group of water and alcohols.

When sunflower oil is added to the beaker containing water and stirred, the water gets cloudy for some time but eventually clears and oil forms a layer on the water surface. This happens because oil has a lesser density in comparison to water. Oil does not get mixed with the solvent water as the water is polar, the molecules are more attracted towards each other than to the molecules of oil. Oil has hydrophobic fatty acyl chains esterified with a moiety of glycerol hence it is non-polar and gets separated as a distinct layer when mixed with polar solvent water. This separation of oil and water mixture into two separate layers is called Hydrophobic effect. It is an observed ability of non-polar substances to get aggregated and separated from water molecules.

Thermodynamic factors that give rise to the hydrophobic effect:

Free energy of mixing non-polar compounds like oils in water includes enthalpy change, entropy change, and temperature.

AH-TAS

At room temperature, the enthalpy of transfer is negligible, however, entropy is negative. Water has the tendency to form ordered cages called clathrates around the molecules of oil that are non-polar that decreases entropy.

That is,$\Delta S<0$

According to Gibbs energy formula,

AH-TAS

The small value of $\Delta H$ and large value of $\Delta S$ makes the value of $\Delta G$  positive. This positive value of $\Delta G$ indicates that the reaction of mixing polar and non-polar compounds is non-spontaneous.

0 0 0 hydrophobic or non polar molecule (oil) cage formed of water molecules by hydrogen bonds.