Chapter 2-Water: The Solvent for Biochemical Reactions

Question 1

What is the principal component of most cells?

Answer 1

water

Question 2

electronegativity

Answer 2

the tendency of an atom to attract electrons to itself (so it becomes more negative) in a chemical bond

Question 3

atoms of the same element have the same electronegativity. why?

Answer 3

because they share electrons equally in a bond

Question 4

Which pair is more electronegative? Oxygen and Nitrogen or Carbon and Hydrogen

Answer 4

Oxygen and Nitrogen

Question 5

If atoms of differing electronegativity form a bond, are the electrons shared equally?

Answer 5

No. More negative charge will be found closer to one of the atoms.

Question 6

Example: In an O-H bond, where are more the electrons located?

Answer 6

near the oxygen because it is more electronegative

Question 7

difference in electronegativity between hydrogen oxygen and hydrogen in an O-H bond gives rise to…

Answer 7

a partial positive and negative charge (S+/S-)

Question 8

Polar Bonds

Answer 8

bonds in which two atoms have an unequal share in bonding electrons, so you notice a partial positive and negative charge

Question 9

Non polar bonds

Answer 9

bonds where two atoms share electrons equally

Question 10

give an example of a non-polar bond

Answer 10

C-H bond in CH4 (methane)

Question 11

Can a bond within a molecule be polar and the molecular itself be non polar?

Answer 11

Yes. It all depends on the geometry. For example, carbon dioxide fits this criteria because of the linear nature of the O=C=O.

Question 12

What is the geometry of water?

Answer 12

bent with a bond angle of 104.3

Question 13

Dipoles

Answer 13

bonds with positive and negative ends due to an uneven distribution of electrons in bonds

Question 14

Is water polar or non polar?

Answer 14

polar

Question 15

Do polar molecules dissolve in polar compounds?

Answer 15

Yes. “Like dissolves like”

Question 16

what are the strongest type of bonds?

Answer 16

ionic and covalent

Question 17

does water have a large dipole moment?

Answer 17

yes. think: charge distribution

Question 18

salt bridges

Answer 18

an interaction that depends on the attraction of unlike charges results from attraction of two side chains that are oppositely charged and in close proximity to eachother

Question 19

ion-dipole and dipole-dipole interactions both help…

Answer 19

ionic and polar compounds dissolve in water

Question 20

ion-dipole interactions

Answer 20

ions interacting with molecules that have dipoles example: Cl- & H20

Question 21

van der waals forces

Answer 21

noncovalent associations based on the WEAK attraction of transient dipoles for one another

Question 22

how many noncovalent bonds that do not involve electrostatic interaction of a fully charged ion are in van der waals forces?

Answer 22

3

Question 23

Dipole-dipole interactions

Answer 23

occur between molecules that are dipoles, with the partial positive side attracting the partial negative side

Question 24

dipole induced dipole interactions occur by…

Answer 24

distorting electron cloud

Question 25

london dispersion force

Answer 25

an attraction between transient induced dipoles

Question 26

hydrophilic

Answer 26

water loving

Question 27

what kind of substances tend to dissolve in water?

Answer 27

ionic and polar

Question 28

are hydrocarbons polar or non polar?

Answer 28

nonpolar

Question 29

examples of hydrophilic substances

Answer 29

polar compounds (alcohols and ketones) sugars ionic compounds (KCl) amino acids phosphate esters

Question 30

examples of hydrophobic substances

Answer 30

nonpolar covalent compounds (hydrocarbons) fatty acids cholesterol

Question 31

hydrophobic

Answer 31

water-hating does not dissolve in water

Question 32

why do oil and water mixed together separate into layers?

Answer 32

has both hydrophobic (oil) and hydrophilic (water) properities

Question 33

amphipathic

Answer 33

molecule that contains an end with a polar, water-soluble group and another end with a non-polar, hydrocarbon group that is insoluble in water (aka hydrophilic and hydrophobic)

Question 34

hydrogen bonds

Answer 34

noncovalent association formed between a hydrogen atom covalently bonded to one electronegative atom and a lone pair of electrons on another electronegative atom

Question 35

hydrogen bonding occurs when hydrogen is bonded to

Answer 35

nitrogen, flourine or oxygen (FON)

Question 36

does ice or liquid water have a lower density

Answer 36

ice

Question 37

what types of bonds help stabilize DNA, RNA and proteins

Answer 37

hydrogen

Question 38

acid

Answer 38

proton (H+) donor

Question 39

base

Answer 39

proton (H+) acceptor

Question 40

acid strength

Answer 40

the tendency of an acid to dissociate to a hydrogen ion and its conjugate base (H+ and A-); amount of hydrogen ion released when a given amount of acid is dissolved in water

Question 41

acid dissociation constant

Answer 41

represented by Ka the number that characterizes the strength of an acid

Question 42

Equation for Ka

Answer 42

Ka= [H+][A-} ______ [HA]

Question 43

greater the Ka the ______ acid

Answer 43

stronger the acid

Question 44

ion product constant for water

Answer 44

represents by Kw a measure of the tendency of water to dissociate to give hydrogen ion and hydroxide ion

Question 45

equation for pH

Answer 45

pH= -log10[H+]

Question 46

what is a neutral pH

Answer 46

7

Question 47

what value is considered to be an acidic pH

Answer 47

lower than 7

Question 48

what value is considered to be an basic pH

Answer 48

higher than 7

Question 49

pKa

Answer 49

measures acid strength pka= -log10(Ka)

Question 50

the smaller the pka

Answer 50

the stronger the acid

Question 51

Henderson-Hasselbalch equation (HH eqn)

Answer 51

mathematical relationship between the pka of an acid and the pH of a solution containing the acid and its conjugate base

Question 52

HH eqn formula

Answer 52

pH= pka + log [A-]/[HA]

Question 53

titration

Answer 53

an experiment in which a measured amount of base is added to an acid

Question 54

equivalence point

Answer 54

the point in a titration where an acid is equally neutralized

Question 55

pepsin

Answer 55

found in stomach maximum activity at low pH

Question 56

lysozyme

Answer 56

maximum activity at pH of 5

Question 57

trypsin

Answer 57

most active at pH of 5

Question 58

monoprotic acids release _____ hydrogen ion and have _____ ka and ____ pka

Answer 58

1; 1; 1

Question 59

diprotic acids release _____ hydrogen ion and have _____ ka and ____ pka

Answer 59

2; 2; 2

Question 60

polyprotic acids release _____ hydrogen ion and have _____ ka and ____ pka

Answer 60

more than 2; more than 2; more than 2

Question 61

If pH of a solution is less than the pKa, what form dominates? Meaning... pH

Answer 61

protonated (H+ on)

Question 62

If pH of a solution is greater than the pKa, what form dominates? Meaning... pH\>pKa

Answer 62

deprotonated (H+ off)

Question 63

buffer

Answer 63

something that resists change

Question 64

buffer solution

Answer 64

-tends to resist change in Ph on addition of moderate amounts of strong acid or strong base -consists of a mixture of a weak acid and its CB

Question 65

Le Chatelier's Principle

Answer 65

if stress is applied to a system in equilibrium the equilibrium will shift in the direction that relieves the stress

Question 66

when the pH is higher than the pKa, the ratio of the conjugate base to form the conjugate acid form is

Answer 66

10

Question 67

when the pH is higher than the pKa, the ratio is

Answer 67

100 (see table 2.7 on page 52)

Question 68

why can a buffer maintain the pH at a relatively constant value?

Answer 68

because of the amounts of both acid and the CB (usually met at pH values at or near pKa of the acid)

Question 69

[https://www.youtube.com/watch?v=UnzycyqM0G4](https://www.youtube.com/watch?v=UnzycyqM0G4) explain the concepts.

Answer 69

* A- is unprotonated form (above 7) * HA is protonated form (below 7) * +/- 1 away 90:10 ratio * +/- 2 away 99:1 ratio

Question 70

buffering capactity

Answer 70

a measure of the amount of acid or base that can be absorbed by a given buffer solution

Question 71

how do we make a buffer?

Answer 71

add acid or base to a solution

Question 72

hemoglobin

Answer 72

oxygen carrying protein in the blood

Question 73

zwitterions

Answer 73

molecules that have both a positive and negative charge

Question 74

are zwitterions more or less likely to interfere with biochemical reactions?

Answer 74

less

Question 75

acidosis

Answer 75

blood pH drops below 7.35

Question 76

alkalosis

Answer 76

blood pH rises about 7.45

Question 77

naturally occuring phsophate and carbonate buffers help maintain physiological pH near

Answer 77

7