Chapter 4 Biomolecules In water Flashcards
Water is a bent molecule because
Since the two bonds to hydrogen plus the two pairs of non-bonding electrons form a near tetrahedral (4 available bonds)
..
H-O: (:are paired and non bonding)
l
H
If we look at the oxygen and hydrogen only it’s going to be a bent molecule
Water is polar because
Oxygen is more electronegative then hydrogen which is why the molecule is polar
One unique feature of water is that
The hydrogen ion of one water can hydrogen bond to the unpaired electrons of another oxygen to form bonds between waters
.. ..
H-O: ⬅️ H-O:
l l
H HThe positive hydrogen can interact with a non-bonding pair of electrons on atoms such as
Oxygen, nitrogen, and fluorine
H+acceptor
\ / \ // \ / \ / \ / \ /
C N O C O N
ll : : ll : :
O H H O H H
: l l : l l
H O O H N N
l l l l l l
O N
l l
H+donor
Ketone, amine, ether, aldehyde,alcohol, other amines
In hydrogen bonding the alcohol -OH will
The alcohol will bond hydrogen to most other oxygen that will have non-bonding electrons they also want to bond to nitrogen that has extra electrons
Hydrogen bonding in ice
Both liquid and solid water forms large numbers of hydrogen bonds with each other
It forms a crystalline structure and this is the case of ice
Hydrogen bonding between the hydroxyl group of an alcohol and water looks like what
R
\
O
l
H
:
O
/ \
H HWhat does H bonding between the carbonyl group of a Ketone and water look like
R1 R2
\ /
C
ll
O
:
H
l
O
\
HExample of hydrogen bonding between peptide groups in polypeptides
H R
l l
N C
\ / \ / H \ /
\/ \/ \/
C
ll
O
:
H
l
N
/\ H / \ / \
C CWhat does a strong hydrogen bond look like
R
l
O
l
H
: ↕️
O
\ //
- P
/What does a weaker hydrogen bond look like
R
l
O
l
H
.
.
.
O
//
\
- P
/Water solubility versus fat solubility has mostly to do with what
Water solubility versus fat solubility has mostly to do with the amount of polar and nonpolar groups on the molecule
If you see aliphatic hydrocarbons (carbons form open chains) those are not water-soluble and the more there are in the molecule the less water-soluble that module is.
Polar groups make it more soluble like alcohol (-OH), ammonium a (NH3),
carboxylates (R--C--OH)
ll
.. O
Amines (R--N--H)
l
R
How does water dissolved electrolytes
Water dissolves electrolytes by forming a hydration shell around both positive and negative ions
H H H
\ \ / H
O O /
/ Na+ O
H \
O H
/ \
H H
The water dissolve the salt because the N+ ions will bind them selves up with the O- side of water and hide the H+ side of water will find themselves up with the Cl- and form salvation sell around each of ions
Hydronium ions give up a
Hydronium ions give up a proton (H3O+) so the H+ bounces around until H2O accepts a proton and becomes a hydronium ion
Protons can bounce around in a solution
O- unpaired electrons hydrogen bond to the H+ of the other water
2H20 ↔️ H3O+ + OH-
Water has which chemical property
It is very polar
Water tends to stick to other water molecules the primary reason for this is due to which attractive force
Hydrogen bonds
The hydrogens of water will mostly hydrogen bond to the non-bonding electron pairs of which atoms
Oxygen
Nitrogen
Fluorine
Which of the following functional groups increase the water solubility of a molecule
Alcohol
Carboxylate
Amine
Ammonium
What is a hydronium ion
Water with an extra H+
What is the formula for the equilibrium of water
H2O ↔️H+ + OH-
Keq(Constant) = [H+] [OH-] ➗[H2O] ⬇️ [H2O]x Keq = [H+] [OH-] ⬇️ Kw= [H+] [OH-] (stands for) ⬇️ Kw= Keqx [H2O]
Water concentration is extremely high compared to H+ or OH- or any other solute so we move it over to the other side of the equation
What is the constant for Keq
1.8x10^-16
Kw= Keq x [H2O]
⬇️
Kw= (1.8x10^-16)x [55.5M]
(It is the sum) Kw=1.0x10^-14
(Sum of) [H+] [OH-]= 1.0x10^-14
At neutral pH what does the equation look like
[H+]=[OH-]= 1.0x10^-7
-log[H+]=-log[OH-]= -log(10^-7)
pH=pOH=7
What is the formula for all other pHs besides water
[H+][OH-]= 1.0x10^-14
-log[H+]+ -log[OH-]= -log(10^-14)
pH+pOH=14
How can you calculate the pH if you already know what the pOH is
14-pOH=pH
And if you know what the pH then I know how to find the pOH
14-pH= pOH
What is the pH of a neutral solution
7
What is the pH of a solution that has a pOH of 6
8
What is the formula for weak acids and bases
pH=pKa + log1(if equal to each other)
pH(how acidic solution is)= pKa(how acidic an H atom in a molecule is)
If equal to each other log1=0
The pH of a solution when an acid is half to dissociated is the
pKa
What is pH?
pH=-log[H+]
pOH=-log[OH-]
pH+pOH=14
What is the pH if something is basic
Greater than 7
What is the pH if something is acidic
Less than 7
A solution has a pH of 4.1 is this considered acidic or basic
Acidic
What is the Henderson -hasselback equation
pH= pKa+ log [A]/[HA]
H+ is hydrogen ion concentration
A conjugate base of acid
HA undissociated acid
p= substitute -log
How do you make a .1M pH 5 acetate buffer?
- Calculate the MW of acetic acid and for sodium acetate (C2H4O2) + (C2H3O2Na)= [HA] 60 + [A]82
2.pKa= 4.76 pH=5
pH=pKa+log [A]/[HA]
5=(4.76) +log [A]/[HA]
5-4.76=log [A]/[HA]
.24=log [A]/[HA]
- 10^(.24)=1.74
- 74= [A]/[HA]
4. 1.74 [HA]= [A] [HA]+ 1.74[HA] =0.1M [HA]= 0.1M/2.74 2.74 [HA]= 0.1 M [HA]= 0.1/2.74 [HA]=0.036M (acetic acid) [0.036]+[A]=0.1 [A]=0.1M -0.036M=0.064M(sodium acetate)
Grams:
[A]=0.064mol/L x 82g/mol = 5.24g/L
[HA]=0.036mol/L x 60g/mol=2.16g/l
Most buffers work best when
Within 1 pH unit of it pKa
Why is sodium phosphate monobasic considered an acid relative to sodium phosphate dibasic?
The monobasic has one more titratable H ion
What is the pH of a neutral solution
7
A solution has a pOH of 5 what is the pH
9
If a solution has a pH of 9.8 is this considered to be an acidic or basic solution
Basic
The pH of a solution when an acid is half dissociated is
pKa
Most buffers work best
Within 1 pH unit of its pKa
Sodium phosphate dibasic is a—— compared to sodium phosphate monobasic
Base relative to the other compound
Sodium phosphate monobasic is —–compared to sodium phosphate dibasic
Acid relative to the other compound
Definition of diffusion
Movement of molecules along a concentration gradient
High to low
Define osmosis
Diffusion of small molecules like (water sodium potassium chlorine phosphate sugar urea) across a semi permeable membrane
Define osmotic pressure
Pressure that must be applied to a solution to prevent the inward flow of water across a semi permeable membrane
How much pressure solute is putting on the membrane
Define oncotic pressure
Osmotic pressure exerted by the plasma proteins
Define osmolarity
Number of molecules of osmotically active molecules per liter of solvent
Define osmolality
Number of moles of osmotically active molecules per kilogram of solvent
Body fluid osmolality is maintained at
285-300 mOsm H2O
Osmolarity is independent of the type of
Solute in a solution
Both electrolytes and electrolytes contribute to
Osmolarity
Osmolarity is independent of the type of
Ions in a solution
Both cations and and anions contribute to
Osmolarity
Osmolarity of a nonelectrolyte is
1xM where M is the molar concentration of the nonelectrolyte
Osmolarity of an electrolyte is
nxM where n= number of ions in the electrolyte and M= molar concentration of the electrolyte
Osmolarity of a 1M glucose
1 OsM
Osmolarity of 1 M sodium chloride
2 OsM
Osmolarity of 1M calcium chloride
3 OsM
Osmolarity of 1M sodium phosphate tribasic
4 OsM
What would happen if you placed a membrane in water with a high concentration of salt in the tube membrane?
The amount of pressure it would take to push that water back across the membrane would be equal to the osmotic pressure exerted by solutes in the tube
What is the osmolarity if the number of solutes on the inside are equal to the outside
Isotonic
What is the osmolarity it the number of solute is higher inside the cell then outside the cell
Hypotonic
What is osmolarity if the number of solute is higher outside the cell than inside the cell
Hypertonic
This could cause the cell to crenate
What is the gas law equation
PV=nRT
What is the equation if we rearrange the gas law for osmolarity
II=RT (ic(ions in conc.)+ ic+ ic….)
Isotonic is .32OsM
C= concentration of each substance
I= The number of ions or solutes
-ex: sucrose= i=1, NaCl= i=2, CaCl2=3
Isotonic Celine is .9% sodium chloride if you are asked to make the solution how would you do it?
Since percent means per 100 you add 0.9 g of sodium chloride to each 100 mL of water this would be the same as 9 g of NaCl into 1 L of water
9g=1000mL of water
What is the osmolarity of isotonic sodium chloride
Since my osmolarity is equal to iC where i= number of ions or molecules per formula mass and c= the molarity of the formula, calculation would be as follows
MW of NaCl= 58.5g/mol
(9g/L)/ (58.5g/mol)=.152mol/L
NaCl has i=2
.153mol/L x2= .306 OsM
To make an isotonic solution of NaCl what that is .32 OsM what molarity of NaCl would you need to make?
.32/2= .16
To make a isotonic magnesium chloride solution .30 OsM what molarity of magnesium chloride would you need to make?
.30/3= .1M
