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Biochemistry Exam 1 Questions with Correct and Verified Answers
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Biochemistry Exam 1 Questions with Correct and Verified Answers
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Biochemistry Exam 1True/False:
The H-bonding of water causes the high heat of vaporization - Answer -True
True/False:
Rotated chiral molecules can be superimposed on its mirror image. - Answer -False!
Mirror image is a completely different molecule; non-superimposable (enantiomers)
What are mirror image stereoisomers called? - Answer -Enantiomers
Negative ∆G is an energetically (favorable/unfavorable) reaction. - Answer -favorable
--gives off energy (exergonic)
Negative ∆H mean heat is (required/released) in reaction - Answer -Heat is released (exothermic)
--+∆H: heat is needed (endothermic)
What is the measurement of how far a reaction proceeds in a net direction until equilibrium is reached
called? - Answer -equilibrium constant (Keq)
What is the most abundant and important biological molecule? - Answer -water
-Surround every biological molecule inside a cell
,What are the three types of weak interactions that can occur between molecules in aqueous solvent? -
Answer -1. hydrogen bonds
2. ionic interactions
3. hydrophobic effect
True/False:
Water has a high melting point and boiling point relative to other liquids. - Answer -True
Why does water have a higher melting point and boiling point relative to other liquids? - Answer -Water
is a perfect hydrogen bond acceptor and donor (best H-bonding molecule)
How many times can a water molecule hydrogen bond? - Answer -4 times
True/False:
Hydrogen bonding causes the high heat of vaporization seen in water. - Answer -True
True/False:
The longer the bond, the stronger the bond. - Answer -False.
The longer the bond, the weaker the bond.
What on the water molecule is partially negatively charged? What is partially positively charged? -
Answer -Negatively charged: lone pairs (x2)
Positively charged: hydrogens (x2)
True/False:
Oxygen is a hydrogen bond donor. - Answer -False.
Oxygen is a hydrogen bond acceptor. Hydrogen is the hydrogen bond donor.
True/False:
,Water is an excellent polar solvent - Answer -True
How does water shield ionic interactions by charge-dipole interactions? - Answer -Water molecules
orient dipoles around atoms to neutralize charged atoms; fully hydrated.
--The hydrogen atoms (∂+) of water associate and shield chlorine (∂-)
--The oxygen atoms (∂-) of water associate and shield sodium (∂+)
(allows dissolution in water)
True/False:
Hydrogen bonds of liquid water have high entropy - Answer -True
--constantly changing (3.4 H-bonds be water molecule when liquid)
In what water state (liquid, solid, gas) does a H-bonded network fully satisfies the H-bonding potential? -
Answer -Solid
(4 per water molecule)
In liquid water, on average, how many H-bonds are there per water molecule? - Answer -3.4
(transitory in nature; makes water denser than ice)
-some water molecules have 4 H-bonds and others have 3
Ice filled cup, if the ice is allowed to melt will the water line be the same, higher than, or lower than the
line where ice came to? - Answer -lower than
What has the stronger hydrogen bond:
Linear or bent configuration of the hydrogen bond - Answer -linear configuration
--occurs in the crystalline lattice of water
What is the effect called in which hydrophobic molecules group together and expel water? - Answer -
hydrophobic effect
, --water molecules can't H-bond across hydrophobic area, lower entropy of water; thermodynamically
unfavorable
--interfering with the structure of water
The hydrophobic effect increase/decreases the entropy of water - Answer -decreases
--water molecules order around hydrophobic molecules
(only ordered right around lipids...elsewhere it is higher entropy)
Breaking bonds requires energy, so why does ATP hydrolysis release energy? - Answer -New bonds are
formed; creates product that is more stable than reactant
(break one bond, but added two bonds)
True/False:
Ionization of water is critical for many biological molecules and determines the pH. - Answer -True
True/False:
Every time water ionizes one H+ and one OH- ion is formed. - Answer -True
What is the pH of a 0.1 M (10^-1 M) HCl? - Answer -1
Acid or base:
proton donor - Answer -acid
Acid or base:
electron acceptor - Answer -acid
Acid or base:
proton acceptor - Answer -base
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