[MOD2LEC] Acids And Bases, Organic Chemistry

Acid

A hydrogen-containing substance that releases H⁺ in detectable amounts in water

Acids are proton donors

Base

A molecule or ion that absorbs H⁺ in detectable amounts in solution

Bases are proton acceptors, which can also release OH^- to bond with H⁺ to form water

pH

The relative concentration of hydrogen ions in solution

Acids range from a pH of 0 - 6.99

Neutral is pH 7, due to equal amounts of H⁺ and OH^-

Bases range from a pH of 7.01 - 14

pH of Acids

Weak acids 5 - 6.99

Mild acids 3 - 4

Strong acids 0 - 2

The lower the pH of an acid, the more H⁺ it will contain and less OH^- it will contain

pH of Bases

Weak bases 7.01 - 9

Mild bases 10 - 11

Strong bases 12 - 14

The higher the pH of a base, the more OH^- it will contain and less H⁺ it will contain

What is the difference between a strong acid and a weak acid?

A strong acid ionizes freely, giving up most of its H⁺ and thus changing the pH

A weak acid ionizes few H⁺ and therefore there is little to no change in pH

What is the difference between a strong base and a weak base?

A strong base has a tendency to bind H⁺ in solution

A weak base has less tendency to bind H⁺ in solution

Why is acid-base balance one of the most important aspects of homeostasis?

Because metabolism depends on the function of enzymes (proteins). These enzymes are very sensitive to pH levels, and slight deviations from a normal pH can denature and negatively affect the function of these enzymes

The normal pH level of blood and tissue fluids is around 7.35 to 7.45

Buffer

A substance that resists pH changes by converting a:

strong acid into a weak acid

OR

strong base into a weak base

Physiological buffer

A system (respiratory, urinary systems) that stabilizes pH by controlling the body’s output of acids, bases, or carbon dioxide

• Out of all buffer systems, the urinary system buffers the largest amount of acids or bases

Chemical buffer

A substance that binds or takes up H⁺ and removes it from solution as its concentration begins to rise

OR

A substance that releases H⁺ into solution as its concentration falls

What are the three major chemical buffer systems of the body?

• Bicarbonate buffer system - involves carbonic acid and is common in the blood. Occurs by adding water to carbon dioxide and then disassociates into bicarbonate

• Phosphate buffer system - binds H⁺ to raise pH OR releases H⁺ to lower the pH

• Protein buffer system - the most concentrated buffer out of all three buffer systems. It accounts for 75% of all chemical buffering ability of body fluids. The most important protein for this system is albumin

Bicarbonate buffer system (lungs and kidneys)

A buffer system that involves carbonic acid and is common in the blood

• Forms by the hydration (adding H₂0) to CO₂ and then disassociates into bicarbonate

• Is a reversible reaction

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When occurring left to right: carbonic acid acts as a weak acid and releases H⁺

When occurring from right to left, carbonic acid acts as a weak base and binds H⁺

Why does the bicarbonate buffer system work well in the body?

Bicarbonate buffers are more concentrated than any other extracellular buffers

• The lungs and kidneys constantly remove CO₂ and purposefully prevent an equilibrium from being reached, keeping the reaction moving from right to left and neutralizing more H⁺

Phosphate buffer system

Phosphoric acid can release H⁺ to lower the pH

OR

Phosphate can bind with H⁺ to raise the pH

Phosphoric acid will release H⁺ because it is an acid

Protein buffer system

A buffer that works due to certain side groups

• Carboxyl (-COOH) side groups release H⁺ when pH rises, therefore lowering the pH

• Amino (-NH²) side groups bind H⁺ and raises the pH towards normal

Albumin is the most important blood protein in the protein buffer system

The protein buffer system accounts for 75% of all chemical buffering ability

Organic compounds

Compounds and molecules unique to living organisms

• Usually not soluble in water

• Decompose easily

• Contain carbon bonded to hydrogen atoms and frequently other atoms

The four categories of organic compounds include, carbohydrates, lipids, proteins, and nucleic acids

Inorganic compounds

Compounds that NEVER have carbon atoms bonded to hydrogen

• Usually contain ionic bonds

• Usually soluble in water

• Usually resist decomposition

What are the differences between organic and inorganic compounds?

Organic compounds are typically not soluble in water, and decompose easily. They contain carbon bonded to hydrogen atoms and frequently other atoms

Inorganic compounds are usually soluble in water, typically contain ionic bonds, and never contain carbon bonded to hydrogen atoms

Hydrocarbons

Organic molecules containing only C and H

Saturated hydrocarbons

Only single bonds are present between carbons

Unsaturated hydrocarbons

At least one double covalent bond is present in the molecule