BCEM 393 UPDATED ACTUAL Exam Questions and CORRECT Answers
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Course
BCEM 393
Institution
BCEM 393
BCEM 393 UPDATED ACTUAL Exam
Questions and CORRECT Answers
Hydrogen bonds - CORRECT ANSWER- Partial charges on hydrogen atoms interact
with lone pairs
Hydrophobic interactions - CORRECT ANSWER- Release of ordered water on non-polar
surfaces, often called entropy driven and only occur in aqu...
BCEM 393 UPDATED ACTUAL Exam
Questions and CORRECT Answers
Hydrogen bonds - CORRECT ANSWER✔✔- Partial charges on hydrogen atoms interact
with lone pairs
Hydrophobic interactions - CORRECT ANSWER✔✔- Release of ordered water on non-polar
surfaces, often called entropy driven and only occur in aqueous solution
Ionic interactions - CORRECT ANSWER✔✔- Positive charges interact with negative
charges, water molecules around the charges weakens them
Dipole-dipole interactions - CORRECT ANSWER✔✔- Dipole on one molecules interacts
with a dipole of another molecule, they align in opposite directions, weaker when water is
present
Van der Waals interactions - CORRECT ANSWER✔✔- Caused by temporary dipoles from
shifting e- clouds on two molecules, occur between any types of molecules
Can two ethanol molecules have a hydrophobic interaction with each other in solution? -
CORRECT ANSWER✔✔- Yes because they have non-polar ch3 groups
Why does adding salt to a solution increase the strength of hydrophobic interactions? -
CORRECT ANSWER✔✔- It interacts with free H2O molecules
What sign is logP if a molecules is hydrophilic? (In bottom layer) - CORRECT
ANSWER✔✔- Negative
What amino acids absorb light at 280nm? - CORRECT ANSWER✔✔- Tryptophan and
tyrosine
What is blood buffered by? - CORRECT ANSWER✔✔- Carbonic acid
, Hyperventilation - CORRECT ANSWER✔✔- Less CO2 gas, equilibria shift to the left
absorbing H+ which causes the bloods pH to increase
What is the inside of cells buffered by? - CORRECT ANSWER✔✔- Phosphate, H2PO4
(pka=6.86)
What must a buffer contain? - CORRECT ANSWER✔✔- A weak acid and its conjugate base
3 ways to make buffers - CORRECT ANSWER✔✔- 1. Add both HA and A- to water
2. Add HA to water and titrate with OH- to desired pH
3. Add B to water and titrate with H+ to desired pH
pH < pka - CORRECT ANSWER✔✔- Equilibrium is more to the left; [A-] < [HA]
Can most phosphoglycerolipids help to buffer pH in the cell? - CORRECT ANSWER✔✔-
No because the buffer region does not include 7.2
Isoelectric point - CORRECT ANSWER✔✔- pH at which a molecule has zero net charge
(mostly zwitterion), to calculate the pI average the two pka values on either side of the
zwitterion
PKU (phenylketonuria) - CORRECT ANSWER✔✔- A genetic disorder in which the
enzymatic activity of phenylalanine hydroxylase is lacking (can't make phenylalanine)
Glycine (G) - CORRECT ANSWER✔✔- Not hydrophobic or hydrophilic, small, not chiral
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