There is a Glu at site 55 of protein A. You wish to investigate whether this ami

Question

There is a Glu at site 55 of protein A. You wish to investigate whether this amino acid is important for activity. This can be done by introducing point mutations of the amino acid at position 55 that is of a different classification, the greater the difference in classification the more detrimental to activity. Which of the following would you expect to have the greatest decrease in activity if the Glu at site 55 is changed to: (choose the one best answer) a) Val b) Arg c) Gly d) Ala e) Gln Which of the following would be expected to be most soluble in water? Choose the one best answer a) CH_3CH_2CH_2CH_2CH_3 b) CH_3CH_2CH_2CH_2CHOH c) H_2NCH_2CH_2CH_2CH_3 d) HOOCCH_2CH_2COOH e) CH_3CH_2CH_2CH_2CHO Osmotic pressure occurs because of the transfer of _____ across a semi-permeable membrane, while dialysis involves the transfer of _____ across a semi-permeable membrane. (choose one best answer) a) solute, solvent b) solvent, solute c) solute, solute d) solvent, solvent Transmembrane proteins completely span the lipid bilayer with the polar portions on the exterior and interior (cytoplasm side) of the protein and nonpolar portions embedded within the interior of the lipid bilayer. Which of the following sequences would be most expected within the interior of the lipid bilayer? Choose the one best answer. a) Gln-Thr-Tyr b) Val-Leu-Pro c) Cys-Leu-Pro d) Met-Val-Ser e) Arg-Val-Phe

Explanation / Answer

Answer 11)

i) Like Dissolves Like is the governing principle behind solubility or Insolubility of given solute in given Solvent.

ii) Water is highly polar solvent and hence polar compounds only dissolve in water. As polarity of compound increases it's solubility does so.

iii) There are 2 more factors which additioally affect the solubility of given compound in water like solvent viz.

a) Hydrogen Bonding : As stregth and extent (i.e. # of H-bonds per molecule) Hydrogen bonding increases, solubility of compound increases.

b) Complete or Partial Ionization of solute in solvent : If solute/compound have tendeency of ionization in given solvent there is more solubility in solvent.

Of the give choices HOOC-CH2-CH2-COOH has both these contributing factors.

-COOH carboxylic group shows 2 H-bonds- 1 through -OH and other through C=O. and also is slightly ionizable group which increases polarity and hence solubility in water.

Answer option : (d) HOOCCH2CH2COOH,

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Answer 12)

Osmotic pressure occurs becausee of transfer of SOLVENT accross seemipermeable membrane, while dialysis involve transfer of SOLUTE accross semipermeable membrane.

Explanation : Osmosis takes place in beween two solutions with unequal concentration. After osmosis two solutions attains same concentration i.e. become Isotonic.

In osmosis, solvent molecules from comparitively dilute (low conceentrration) solution migrates accross semi perrmeable membrane to concentrated solution.

Decrease in solvent molecues in dilute one makes it concentrated and increase of solvent molecules in concentrated one makes it dilute till isotonic state is achieved.

While in Dialysis, solute particle from concentrated solution migrates to dilute solution.

Answer option : (b) Solvent, solute.

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