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Biochemistry > Chapter 4 Biomolecules In water > Flashcards

Chapter 4 Biomolecules In water Flashcards

0
Q

Water is a bent molecule because

A 
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

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1
Q

Water is polar because

A

Oxygen is more electronegative then hydrogen which is why the molecule is polar

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2
Q

One unique feature of water is that

A 
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             H
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3
Q

The positive hydrogen can interact with a non-bonding pair of electrons on atoms such as

A

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

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4
Q

In hydrogen bonding the alcohol -OH will

A

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

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5
Q

Hydrogen bonding in ice

A

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

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6
Q

Hydrogen bonding between the hydroxyl group of an alcohol and water looks like what

A 
R
  \
   O
    l
   H
    :
   O
  /   \
H    H
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7
Q

What does H bonding between the carbonyl group of a Ketone and water look like

A 
R1    R2
  \     /
    C
     ll
    O
     :
    H
     l
    O
      \
       H
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8
Q

Example of hydrogen bonding between peptide groups in polypeptides

A 
H      R
        l       l
       N      C
\    /   \    / H \    /
  \/       \/         \/
            C
             ll
            O
             :
            H
             l
            N
/\  H    /    \  / \
    C          C
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9
Q

What does a strong hydrogen bond look like

A 
R
          l
         O
          l
         H
          :    ↕️
         O
\     //
- P
/
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10
Q

What does a weaker hydrogen bond look like

A 
R
              l
             O
              l
             H
            .
           .
         .
        O
      //
\
- P
/
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11
Q

Water solubility versus fat solubility has mostly to do with what

A

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
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12
Q

How does water dissolved electrolytes

A

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

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13
Q

Hydronium ions give up a

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-

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14
Q

Water has which chemical property

A

It is very polar

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15
Q

Water tends to stick to other water molecules the primary reason for this is due to which attractive force

A

Hydrogen bonds

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16
Q

The hydrogens of water will mostly hydrogen bond to the non-bonding electron pairs of which atoms

A

Oxygen
Nitrogen
Fluorine

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17
Q

Which of the following functional groups increase the water solubility of a molecule

A

Alcohol
Carboxylate
Amine
Ammonium

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18
Q

What is a hydronium ion

A

Water with an extra H+

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19
Q

What is the formula for the equilibrium of water

A

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

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20
Q

What is the constant for Keq

A

1.8x10^-16

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21
Q

Kw= Keq x [H2O]

⬇️

A

Kw= (1.8x10^-16)x [55.5M]
(It is the sum) Kw=1.0x10^-14
(Sum of) [H+] [OH-]= 1.0x10^-14

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22
Q

At neutral pH what does the equation look like

A

[H+]=[OH-]= 1.0x10^-7

-log[H+]=-log[OH-]= -log(10^-7)

pH=pOH=7

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23
Q

What is the formula for all other pHs besides water

A

[H+][OH-]= 1.0x10^-14

-log[H+]+ -log[OH-]= -log(10^-14)

pH+pOH=14

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24
Q

How can you calculate the pH if you already know what the pOH is

A

14-pOH=pH

And if you know what the pH then I know how to find the pOH

14-pH= pOH

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25
Q

What is the pH of a neutral solution

A

7

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26
Q

What is the pH of a solution that has a pOH of 6

A

8

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27
Q

What is the formula for weak acids and bases

A

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

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28
Q

The pH of a solution when an acid is half to dissociated is the

A

pKa

29
Q

What is pH?

A

pH=-log[H+]

pOH=-log[OH-]

pH+pOH=14

30
Q

What is the pH if something is basic

A

Greater than 7

31
Q

What is the pH if something is acidic

A

Less than 7

32
Q

A solution has a pH of 4.1 is this considered acidic or basic

A

Acidic

33
Q

What is the Henderson -hasselback equation

A

pH= pKa+ log [A]/[HA]

H+ is hydrogen ion concentration
A conjugate base of acid
HA undissociated acid
p= substitute -log

34
Q

How do you make a .1M pH 5 acetate buffer?

A
  1. 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]

  1. 10^(.24)=1.74
  2. 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

35
Q

Most buffers work best when

A

Within 1 pH unit of it pKa

36
Q

Why is sodium phosphate monobasic considered an acid relative to sodium phosphate dibasic?

A

The monobasic has one more titratable H ion

37
Q

What is the pH of a neutral solution

A

7

38
Q

A solution has a pOH of 5 what is the pH

A

9

39
Q

If a solution has a pH of 9.8 is this considered to be an acidic or basic solution

A

Basic

40
Q

The pH of a solution when an acid is half dissociated is

A

pKa

41
Q

Most buffers work best

A

Within 1 pH unit of its pKa

42
Q

Sodium phosphate dibasic is a—— compared to sodium phosphate monobasic

A

Base relative to the other compound

43
Q

Sodium phosphate monobasic is —–compared to sodium phosphate dibasic

A

Acid relative to the other compound

44
Q

Definition of diffusion

A

Movement of molecules along a concentration gradient

High to low

45
Q

Define osmosis

A

Diffusion of small molecules like (water sodium potassium chlorine phosphate sugar urea) across a semi permeable membrane

46
Q

Define osmotic pressure

A

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

47
Q

Define oncotic pressure

A

Osmotic pressure exerted by the plasma proteins

48
Q

Define osmolarity

A

Number of molecules of osmotically active molecules per liter of solvent

49
Q

Define osmolality

A

Number of moles of osmotically active molecules per kilogram of solvent

50
Q

Body fluid osmolality is maintained at

A

285-300 mOsm H2O

51
Q

Osmolarity is independent of the type of

A

Solute in a solution

52
Q

Both electrolytes and electrolytes contribute to

A

Osmolarity

53
Q

Osmolarity is independent of the type of

A

Ions in a solution

54
Q

Both cations and and anions contribute to

A

Osmolarity

55
Q

Osmolarity of a nonelectrolyte is

A

1xM where M is the molar concentration of the nonelectrolyte

56
Q

Osmolarity of an electrolyte is

A

nxM where n= number of ions in the electrolyte and M= molar concentration of the electrolyte

57
Q

Osmolarity of a 1M glucose

A

1 OsM

58
Q

Osmolarity of 1 M sodium chloride

A

2 OsM

59
Q

Osmolarity of 1M calcium chloride

A

3 OsM

60
Q

Osmolarity of 1M sodium phosphate tribasic

A

4 OsM

61
Q

What would happen if you placed a membrane in water with a high concentration of salt in the tube membrane?

A

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

62
Q

What is the osmolarity if the number of solutes on the inside are equal to the outside

A

Isotonic

63
Q

What is the osmolarity it the number of solute is higher inside the cell then outside the cell

A

Hypotonic

64
Q

What is osmolarity if the number of solute is higher outside the cell than inside the cell

A

Hypertonic

This could cause the cell to crenate

65
Q

What is the gas law equation

A

PV=nRT

66
Q

What is the equation if we rearrange the gas law for osmolarity

A

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

67
Q

Isotonic Celine is .9% sodium chloride if you are asked to make the solution how would you do it?

A

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

68
Q

What is the osmolarity of isotonic sodium chloride

A

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

69
Q

To make an isotonic solution of NaCl what that is .32 OsM what molarity of NaCl would you need to make?

A

.32/2= .16

70
Q

To make a isotonic magnesium chloride solution .30 OsM what molarity of magnesium chloride would you need to make?

A

.30/3= .1M

Biochemistry (18 decks)

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