Chapter 2-water, weak bonds, generation of order out of chaos

Question 1

Define Brownian Motion

Answer 1

random movement of molecules (in a fluid/gas) powered by thermal energy

Question 2

How is water polar, but uncharged?

Answer 2

Electronegative because:
Hydrogen bonds bear partial positive charge
Oxygen bonds bear partial negative charge
Uncharged because:
total charge on molecule is zero

Question 3

Why are weak bonds important in biochemistry

Answer 3

many weak bonds allow for highly specific yet transient interactions

Question 4

What are the common weak bonds in biochem & how does water affect these bonds?

Answer 4

ionic bonds & hydrogen bonds: water disrupts

van der waals: most common between hydrophobic groups & water strengthens these bonds through hydrophobic effect

Question 5

What effect does freezing water and heating water do to hydrogen bonded water molecules?

Answer 5

freezing water: reduces motion of water and allows formation of more hydrogen bonds
heating water: fewer hydrogen bonds are allowed to form

Question 6

What would the effect of an organic solvent on electrostatic interactions?

Answer 6

the interactions would be stronger in an organic solvent because there would be no competition from the solvent for the components of the reaction

Question 7

What is an electronegative atom and why are they important in biochem?

Answer 7

electronegative atom has a high affinity for atoms

polarity when bonded to hydrogen atom allows formation of hydrogen bonds

Question 8

Define the hydrophobic effect

Answer 8

tendency of nonpolar molecules to interact with one another in the presence of water.
interaction is powered by increase in entropy of water molecules when nonpolar molecules are removed from watery environment

Question 9

How does the second law of thermodynamics allow for the formation of biochemical order?

Answer 9

2nd law: states entropy of system and surroundings always increases in spontaneous process
when hydrophobic molecules are isolated away from water the entropy of water increases
the isolation, called hydrophobic effect leads to formation of biochem structures

Question 10

What is the relation between the pKa of an acid and the strength of the acid?

Answer 10

lower the pKa, greater the Ka.

greater the Ka, stronger the acid