Basic BiochemistryCHE 242

MTWR 11:00 am – 1:30 pm

Julian Hall 216

Dr. Jon A. Friesen

Office: 318 Science Laboratory Buildingphone: (43)8-7850

email: jfriese@ilstu.eduOffice Hours: TWR 1:30 p.m. – 2:30 p.m.

What Do Biochemists Study?

The periodic table of the elementsFigure 1.1

The periodic table of the elementsFigure 1.1

Bulk elements97%

The periodic table of the elementsFigure 1.1

Essential ions

The periodic table of the elementsFigure 1.1

Trace elements

Organic compounds in biochemistryFigure 1.2

Functional groups in biochemistryFigure 1.2

Linkages in biochemical compoundsFigure 1.2

Types of molecules in biochemistry1. ProteinsAre composed of twenty different kinds of monomeric units, the amino acids.

2. Polysaccharides (sugar)Are constructed of monomeric units called monosaccharides. Also called carbohydrates.

3. Nucleic acids (DNA and RNA)Are synthesized from monomeric units called nucleotides.

4. Lipids (Fat)Water insoluble molecule containing fatty acids.Used for membrane structure and energy storage.

Energy Flow

Page 14

Prokaryotic CellsFigure 1.14

Eukaryotic CellsFigure 1.15

Water, Water Everywhere

Water is a Polar Molecule

Figure 2.1

Polarity of Small Molecules

Figure 2.2

Hydrogen Bonding Between Two Water Molecules

Figure 2.3

Water Can Form Up To Four Hydrogen Bonds

Figure 2.4

Water Molecules Form a Hexagonal Lattice in IceFigure 2.5

Sodium Chloride (NaCl) crystal

Figure 2.6

Ionic and PolarSubstances Dissolve

in Water

Example:Dissolution of

Sodium Chloride in water

Figure 2.6

Glucose, a sugar, contains polar groups, and is soluble in water

Nonpolar substances are relatively insoluble in water

Noncovalent interactions in biomolecules

1. Charge-Charge Interactions

2. Hydrogen Bonds

3. Van der Waals Forces

4. Hydrophobic Interactions

Hydrogen bonding isa common noncovalent

interaction betweenbiomolecules

Figure 2.10

Hydrogen bonding between bases in DNA

Figure 2.11

Van der Waals forces are weak noncovalent forces between atoms

Figure 2.12

Amphipathic molecules,such as detergents,

have both a polar anda nonpolar end.

Detergents can form monolayers at the air-water interface

Figure 2.9

Detergents can form micelles in aqueous solution

Figure 2.9

Ionization of Water

Water has a slight tendency to ionize

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Strong acids completely dissociate in water.

Example: Hydrochloric acid (HCl)

Weak acids dissociate in water with a characteristicacid dissociation constant (Ka).

Example: Acetic acid, present in vinegar

Relationship between pH and pKa

Titration of acetic acid with aqueous baseFigure 2.17

Titration of phosphoric acid,

a polyproticacid, with

aqueous base

Figure 2.19

12345678910

1. Write the equilibrium reaction for the ionization of the weak acid.

2. What is the chemical structure of the conjugate base?

3. What is the pH of a solution containing equal amounts of theweak acid and the conjugate base?

4. What is the pH of a solution containing 10 times more weak acidthan conjugate base?

5. What is the ratio of conjugate base to weak acid at pH = 7?

1. Write the equilibrium reaction for the ionization of the weak acid.

2. What is the chemical structure of the conjugate base?

1. Write the equilibrium reaction for the ionization of the weak acid.

2. What is the chemical structure of the conjugate base?

3. What is the pH of a solution containing equal amounts of theweak acid and the conjugate base?

CH3COO-

CH3COOH4.8

14.8

4.8 0

1. Write the equilibrium reaction for the ionization of the weak acid.

2. What is the chemical structure of the conjugate base?

3. What is the pH of a solution containing equal amounts of theweak acid and the conjugate base?

CH3COO-

CH3COOH4.8

14.8

4.8 0

4. What is the pH of a solution containing 10 times more weak acidthan conjugate base?

CH3COO-

CH3COOH4.8

0.14.8

4.8 (-1)

3.8

5. What is the ratio of conjugate base to weak acid at pH = 7?

CH3COO-

CH3COOH4.87

2.2CH3COO-

CH3COOH

102.2 CH3COO-

CH3COOH

CH3COO-

CH3COOH158

Titration of acetic acid with aqueous baseFigure 2.17

Titration of acetic acid with aqueous baseFigure 2.17

Buffering Region1 pH unit from pKa

Maintenance of Blood pHin Humans

CO2 – Bicarbonate Buffer System

Carbon dioxide – carbonic acid – bicarbonate buffer systemmaintains blood pH at 7.4

Figure 2.20

Regulation ofblood pH

in mammals

Figure 2.21

Why is the CO2 – bicarbonate buffer system used in the human body?

1. The raw materials (CO2 and H2O) for the production of carbonic acid (H2CO3) are readily available.

2. The lungs and kidneys can easily adjust to ratio alterationsbetween carbonic acid (H2CO3) and the conjugate basebicarbonate (HCO3

-).

Role of the lungs and kidneys inregulation of physiological pH

LungsControl the supply of H2CO3 in the blood by controlling theamount of CO2 exhaled.When the blood level of HCO3

- decreases, the breathing rate isincreased, increasing amount of CO2 expelled, decreasing H2CO3.If H2CO3 (CO2) increases it is called respiratory acidosis. If H2CO3 (CO2) decreases it is called respiratory alkalosis.

KidneysControl the concentration of HCO3

-. If HCO3- is too high it is called

metabolic alkalosis. If HCO3- is too low, it is called metabolic alkalosis.

Blood Concentrations

Ratio of HCO3- : H2CO3 = 10 : 1 This results in pH = 7.4

HCO3- = 24 - 27 mEq/L (mM)

H2CO3 = 1.20 - 1.35 mEq/L (mM)

Clinicians often monitor blood pH, HCO3- and CO2 concentrations.

Non-graded Homework:Use Henderson-Hasselbalch equation to convince yourselfthis makes sense.

Problem #11 at the end of the chapter.