Ch. 2 - Water, pH, acids, bases, buffers

Question 1

Water can serve as both

Answer 1

Hydrogen bond donor and acceptor

Question 2

Hydrogen bonds are strong dipole-dipole interactions that arise between

Answer 2

A covalently bonded hydrogen and lone pair of electrons

Typically N or O

Question 3

H bonds are strongest when the bonded molecules allow for _____ bonding patterns

Answer 3

Linear

Question 4

Up to ___ H bonds per water molecule

Answer 4

Four

Question 5

Hydrogen bonding in water is

Answer 5

Cooperative

Question 6

Hydrogen bonds between neighboring molecules are

Answer 6

Weak relativize to the H-O covalent bonds

Question 7

Importance of hydrogen bonds

Answer 7

Structure and function of proteins, DNA, polysaccharides

Bonding of substrates to enzymes

Binding of hormones to receptors

Matching of mRNA to tRNA

Question 8

“Significance of H bond is greater than any more other structural feature”

Answer 8

Linus Pauling

Question 9

Hexagonal I’ve contains _____ hydrogen bonds

Ps. Also low entropy bc organized lattice

Answer 9

Maximal

Question 10

Water bound to ____ is essential for their function

Answer 10

Proteins

Question 11

Water is a _____ solvent for charges and polar substances

Ex)
Amino acids and peptides
Small alcohols
Carbohydrates

Answer 11

Good

Question 12

Water is a _____ solvent for non polar substances

Ex)
No polar gases
Aromatic moieties
Aliphatic chains

Answer 12

Poor

Question 13

Noncovalent interactions do ____ involve sharing a pair of electrons

Answer 13

Not

Question 14

Electrostatic interactions between PERMANENTLY charged species, or between the ion and permanent dipole

Answer 14

Ionic interactions

Question 15

Electrostatic interactions between uncharged but POLAR molecules

Answer 15

Dipole interactions

Question 16

Van der waals interactions

Answer 16

Weak interactions between all atoms

Attractive (dispersion)

Repulsive (steric)

Question 17

Hydrophobic effect

Answer 17

Complex phenomenon associated with the ordering of water molecules around non polar substances

Question 18

Attractive force
Which depends on the polarizability (very weak)
Dominates at longer distances

Answer 18

London dispersion

Question 19

Repulsive force
Which depends on the size of atoms
Dominates at very short distances

Answer 19

Steric Repulsion

Question 20

Determines steric complementarity.
Stabilizes biological macro molecules. (Stacking in DNA)
Facilitates binding off polarizable ligands.

Answer 20

Van der Waals Interactions

Question 21

Refers to the association of non polar molecules or components of molecules in the aqueous solution

Answer 21

The hydrophobic effect

Question 22

Hydrophobic effect is main factors behind

Answer 22

Protein folding
Protein-protein Association
Formation of lipid micelles
Binding of steroid hormones to their receptors

Question 23

Hydrophobic affect does ___ arise solely because of attractive direct force between two non polar molecules

Answer 23

Not

Question 24

Water surrounding non polar solutes has _____ entropy

Answer 24

Lower

Question 25

Non polar portions of the amphipathic molecule aggregate so that ______ water molecules are ordered

Answer 25

Fewer

Question 26

With high enough concentration of amphipathic molecules, complete aggregation into _____ is possible

Answer 26

Micelles

Question 27

All hydrophobic groups are sequestered from water; ordered shell of H2O molecules is minimized and entropy is further increased.

Answer 27

Micelles

Question 28

Hydrophobic effect favors ____ binding

Answer 28

Ligand

Question 29

Binging sites in enzymes and receptors are often ______

Answer 29

Hydrophobic

(These sites can bind hydrophobic substrates and ligands, such as steroid hormones, which displace water and increase entropy of the system)

Question 30

Diffusion requires:

Answer 30

1. Concentration gradient

2. Method to get across the membrane

Question 31

Substance passes directly through membrane

Answer 31

Simple diffusion

Question 32

Substance requires a protein to cross membrane

Answer 32

Facilitated diffusion

Question 33

Do not depend on the nature of the solute, just the concentration

Ex) bp, mp, and osmolarity

Answer 33

Colligative properties

Question 34

Depend on the chemical nature of the solute

Ex( viscosity, surface tension, taste, color

Answer 34

Noncolligative properties

Question 35

Cytoplasm of cells have _____ osmotic pressure dye to dissolved solutes

Answer 35

High