Biochem 1: Water, pH, buffers

Question 1

water structure and special properties

Answer 1

• polar molecule
• forms hydrogen bonds
• tetrahedral shape

Question 2

bonds each water molecule can be involved with

Answer 2

• 4 hydrogen bonds

- 2 as a donor, 2 as acceptor

Question 3

what is important about hydrogen bonding

Answer 3

even though hydrogen bonds are weaker than covalent bonds, they have a significant effect on the physical properties of hydrogen-bonded compounds

Question 4

hydrophilic interactions

Answer 4

“water-loving”

• a polar molecule that interacts with water
• interact through weak attractions of hydrogen bonds

Question 5

hydrophobic interactions

Answer 5

“water-fearing”

• a nonpolar molecule that aggregates with other non polar molecules
• hydrocarbon molecules

Question 6

an aqueous solution

Answer 6

solvent is water

-most biochemical reactions occur in aqueous solutions

Question 7

solvent properties in water

hydrophobic

Answer 7

tend to not dissolve in water

Question 8

solvent properties in water

hydrophilic

Answer 8

tend to dissolve in water

Question 9

amphipathic

Answer 9

has characteristics of both properties

-molecules that contain one or more hydrophobic and one or more hydrophilic regions

Question 10

amphipathic molecules interactions

Answer 10

-both polar and non polar character
-interaction between non polar molecules is very weak
(Called van der Waals interactions)

Question 11

when some substances dissolve in water, they release

Answer 11

protons

-these H+ molecules can interact with other molecules and change their properties

Question 12

what is a micelle

Answer 12

a spherical arrangement of organic molecules in water solution clustered so that

• their hydrophobic parts are buried inside the sphere
• their hydrophilic parts are on the surface of the sphere and in contact with the water environment

Question 13

an acid:

Answer 13

releases hydrogen ions (H+) when dissolved in solution

Question 14

a base:

Answer 14

accepts hydrogen ions (H+) when dissolved in solution

Question 15

strong acid/base

Answer 15

fully ionizes in water

Question 16

weak acid

Answer 16

not all the acid molecules dissociate into ions

Question 17

weak base

Answer 17

can accept a H+ ion

Question 18

acid-base reactions may be _____

Answer 18

reversible

Question 19

ionization of strong acids and bases is

Answer 19

irreversible

Question 20

ionization of weak acids and bases is

Answer 20

somewhat reversible

Question 21

water acts as both a

Answer 21

weak acid and a weak base

Question 22

water has a tendency to

Answer 22

ionize

Question 23

what is Ka

Answer 23

numerical measure for acid strength, the acid dissociation constant

Question 24

the higher the value of the Ka, the ____ the acid

Answer 24

stronger

Question 25

in biochemistry, most of the acids encountered are

Answer 25

weak acids (Ka well below 1)

Question 26

the lower the value of pKa, the ____ the acid

Answer 26

stronger

Question 27

pH is the measure of

Answer 27

hydrogen ion concentration

the negative logarithm of the molar concentration of H+ ions

Question 28

H+ concentration of pure water is

Answer 28

10^-7 M

Question 29

lower pH numbers mean

Answer 29

higher H+ concentration or greater acidity

Question 30

what can pH influence

Answer 30

the rate of biological reactions and can change the 3 dimensional structure of biological molecules, which impacts function

Question 31

Henderson-Hasselbalch equation connects

Answer 31

Ka to pH of a solution containing both acid and base

using HA, weak acid and A-, conjugate base ratio

Question 32

in Henderson-Hasselbalch,

pH < pKa means

Answer 32

weak acid predominates

Question 33

in Henderson-Hasselbalch,

pH > pKa means

Answer 33

conjugate base predominates

Question 34

titration is

Answer 34

an experiment in which measured amounts of acid (or base) are added to measured amounts of base (or acid)

Question 35

buffer

Answer 35

a solution whose pH resists change upon addition of acid or base
(consists of a weak acid and its conjugate base)
-helps maintain stable pH

Question 36

hyper-ventilation can results in increased blood pH, resulting in

Answer 36

respiratory alkalosis

Question 37

hypo-ventilation can result in decreased blood pH, resulting in

Answer 37

respiratory acidosis