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Bioc 460 > 1. Water > Flashcards

1. Water Flashcards

1
Q

What characteristic of water made life evolve in it?

A

protection from UV light
high heat of vaporization

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2
Q

What type of environment do chemical reactions occur in?

A

aqueous

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3
Q

What is a critical determinant of the structure and function of proteins, nucleic acids, and membranes?

A

water

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4
Q

What is the octet rule?

A

four electron pairs around an oxygen atom in water

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5
Q

What is the structure of a water molecule?

A

two electron pairs covalently link two hydrogen atoms to a central oxygen atom and two pairs remain nonbonding

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6
Q

What molecular shape is water?

A

distorted tetrahedron

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7
Q

What is the electronegativity of the two hydrogen atoms in a water molecule?

A

positive dipole moment

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8
Q

What is the electronegativity of the two nonbonding pairs in a water molecule?

A

negative dipole moment

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9
Q

Define a hydrogen bond

A

electrostatic attraction between the oxygen atom of one water molecule and the hydrogen of another

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10
Q

When is the hydrogen bond the strongest?

A

when the bonded molecules allow for linear bonding patterns

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11
Q

Can water serve as a H donor or acceptor?

A

yes, both

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12
Q

How do water molecules interact with each other?

A

through hydrogen bonding

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13
Q

What properties does hydrogen bonding give water?

A

high boiling and melting point, large surface tension

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14
Q

What are the properties of hexagonal ice?

A

organized lattice and low entropy

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15
Q

Why is ice less dense than water?

A

hexagonal ice has maximal hydrogen bonds which forces the water molecules into equidistant arrangement

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16
Q

What is the max amount of hydrogen bonds able to be formed per molecule?

A

four

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17
Q

What are the four reasons H bonds are important?

A
  1. source of unique properties of water
  2. structure and function of proteins, DNA, and polysaccharides
  3. binding of substrates to enzymes and hormones to receptors
  4. matching of mRNA and tRNA
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18
Q

Water is a good solvent for what type of substances?

A

charged and polar

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19
Q

Water is a poor solvent for what type of substances?

A

nonpolar

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20
Q

What type of situation do hydrogen bonds readily form between?

A

electronegative atom and a hydrogen atom covalently bonded to another electronegative atom

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21
Q

What is a polar molecule?

A

negative on one side and positive on the other

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22
Q

What is a nonpolar molecule?

A

contains no polar charges

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23
Q

Will nonpolar gases be soluble in water?

A

no

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24
Q

Define noncovalent interactions

A

don’t involve sharing a pair of electrons

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25
Q

What are the four types of noncovalent interactions?

A

ionic
dipole
van der waals
hydrophobic effect

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26
Q

Define ionic interactions

A

electrostatic attraction between oppositely charged ions

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27
Q

Define dipole interactions

A

electrostatic interactions between uncharged but polar molecules

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28
Q

Define Van der Waals interactions

A

weak interactions between all atoms

29
Q

Define hydrophobic effect

A

ordering of water molecules around nonpolar substances

30
Q

What is the strongest noncovalent interaction?

A

ionic

31
Q

What does it mean when ions are hydrated?

A

water molecules cluster about the ions

32
Q

What effect do nonpolar compounds have on hydrogen bonding among water molecules?

A

increase enthalpy and decrease entropy

33
Q

Is the free energy change for dissolving a nonpolar solute in water favorable or unfavorable?

A

unfavorable

34
Q

How are the factors in the free energy change affected by dissolving a nonpolar solute in water?

A

Delta H will be positive
Delta S will be negative
Delta G will be positive

35
Q

What shape does water form when interacting with nonpolar solute molecules?

A

cage like shell around each nonpolar solute molecule

36
Q

What has to happen in order to dissolve salts?

A

break the ionic interactions

37
Q

What happens to the ions when salt is dissolved?

A

they are hydrated

38
Q

Are polar molecules hydrophilic or hydrophobic?

A

hydrophilic

39
Q

Are nonpolar molecules hydrophilic or hydrophobic?

A

hydrophobic

40
Q

What is an amphipathic molecule?

A

has polar and nonpolar areas

41
Q

How does the hydrophobic effect work?

A

nonpolar portions of amphipathic molecules gather inward and polar portions are exposed

42
Q

Why do amphipathic molecules follow the hydrophobic effect?

A

to form an energetically favorable statae

43
Q

What effect do enzymes and receptors follow?

A

hydrophobic effect

44
Q

What happens to the water when enzymes and receptors bind following the hydrophobic effect?

A

they displace the water

45
Q

What are the two portions of Van der Waals interactions?

A

attractive and repulsive forces

46
Q

How do attractive Van der Waals forces work?

A

at longer distances, depend on size of polarizability

47
Q

How do repulsive Van der Waals forces work?

A

at very short distances, depends on size of atoms

48
Q

What are the two reasons for using Van der Waals interactions?

A

they occur between any two atoms near each other and together they are strong

49
Q

What do noncovalent interactions dictate?

A

macromolecular structure that affects function

50
Q

What are colligative properties of water?

A

properties that depend on the concentration of the solute

51
Q

What are three examples of colligative properties?

A

boiling point, melting point, and osmolarity

52
Q

What are noncolligative properties?

A

properties that depend on the chemical nature of the solute

53
Q

What are four examples of noncolligative properties?

A

viscosity, surface tension, taste, color

54
Q

Colligative and noncolligative properties depend on what?

A

solutes

55
Q

What produces osmotic pressure?

A

movement of water from higher to lower concentration

56
Q

What is osmotic pressure?

A

force necessary to resist water movement

57
Q

What is the van’t Hoff equation?

A

icRT

58
Q

What is the van’t hoff factor?

A

measure of the extent to which the solution dissociates into 2+ ionic species

59
Q

What is the van’t hoff factor for non-ionizing solutes?

A

1

60
Q

What is the van’t hoff factor for solutes that dissocite into two ions?

A

2

61
Q

What three things does osmotic pressure depend on?

A

van’t hoff factor, solute’s molar concentration, R and T

62
Q

Define osmosis

A

water movement across a semipermeable membrane driven by differences in osmotic pressure

63
Q

Define isotonic

A

equal amount of solutes inside and outside of cell

64
Q

What direction is the water moving in an isotonic solution?

A

no water movement

65
Q

Define hypertonic

A

higher concentration outside of cell

66
Q

What is the water movement of a hypertonic solution?

A

water moves out of cell

67
Q

Define hypotonic

A

higher concentration of solute inside the cell

68
Q

What is the water movement in a hypotonic solution?

A

water moves into cell

Bioc 460 (6 decks)

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