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Chapter 10

BIOL 4309 Chapter Notes - Chapter 10: Isopropyl Alcohol, Carbon Dioxide, Psychoactive Drug

Course Code
BIOL 4309
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Chapter 10 Alcohol
Overdrinking causes physical effects:
- Loss of coordination and judgement
- Enhanced sexuality
- Memory loss and stupor
- Increased hostility and aggression
- Potential for unpleasant side effects
- The worst: its chronic use that damages the individual, his family, and society
Many people don’t consider alcohol as a drug, like caffeine, it’s the most commonly used psychoactive drug
and is the most abused drug.
- Alcoholism have the same features of drug addiction and its symptoms such as drug dependence
Psychopharmacology of alcohol
Alcohol comes in three forms, though similar structures, they have different uses:
1) Methyl alcohol
2) Ethyl alcohol
3) Isopropyl alcohol
Methyl alcohol (wood alcohol)
- Has a simple chemical structure but is highly toxic if consumed
- The metabolites of methyl alcohol include formic acid and formaldehyde
- Drinking this causes: blindness, coma, and death
- Commonly used as: fuel, antifreeze, and an industrial solvent (industrial alcohol)
Ethyl alcohol (ethanol)
- Used as a beverage
- Has only two C atoms, a complement of hydrogens, plus the -OH group
Isopropyl alcohol
- Has a small molecular side chain that changes its characteristics and makes it most useful as: rubbing
alcohol or disinfectant
- Its dangerous to consume
Where does ethanol come from?
- Its produced by fermentation a process that occurs naturally when yeast cells in the air fall on a
product containing sugar (such as honey, fruit, sugar cane, or grains like rye, corn, etc.)
Fermentation reaction:
C6H12O6 -> 2C2H5OH+2CO2
Sugar ethanol carbonic gas

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Note: - Alcohol is high in calories providing heat/energy when metabolized.
- There’s no nutritional value with those calories, alcohol doesn’t provide proteins, vitamins, or minerals
that are a necessary component of a normal diet
SO, individuals who chronically consume large quantities of alcohol in lieu of food suffer from inadequate
nutrition (like thiamine deficiency), leading to health problems like severe brain damage
Pharmacokinetics of alcohol determine its bioavailability
- It provides a way to measure how much alcohol is freely available to enter the brain from the blood,
in order to evaluate the effects of alcohol in the CNS
Ethanol is unique because:
- Alcohol is a small simple molecule that cannot be ionized, but is highly water soluble and moderately
lipid soluble
- Its easily absorbed from the GI tract and diffuses throughout the body, which readily enters most
tissues including the brain
- The rate of absorption, distribution, and clearance of alcohol contribute to the highly variable blood
levels that occur following ingestion of a fixed amount of the drug
- Behavioral effects are described based on blood alcohol concentration (BAC), rather than the amount
In general, it takes a BAC of 0.04% (40 mg of alcohol per 100 ml of blood) to produce measurable behavioral
- One 12 oz. can of beer, one 4 oz. glass of wine, a cocktail with 1.25 oz. of spirits, or a 12 oz wine cooler
will raise blood levels by the equivalent amount.
Absorption & Distribution
Where is it absorbed?
- After being taken orally, absorption will occur from the GI tract: about 10% in the stomach and 90%
from the small intestine
How is it absorbed?
- Alcohol moves across the membrane barriers by passive diffusion from higher concentration on one
side of the GI tract to lower concentration on the other (blood)
- The more alcohol you drink in a short period of time or the more you drink in an undiluted form -> the
more rapid the movement from the stomach and intestine to blood -> producing a higher BAC

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- The presence of food in the stomach SLOWS absorption because it delays the movement into the small
intestine through the pyloric sphincter (a muscle that regulates the movement of material from the
stomach to the intestine)
Gender differences in absorption:
- This occurs because of the certain enzymes (such as alcohol dehydrogenase) present in gastric fluid
are 60% more active in men than in women
- Body size and gender differences also play a part in the distribution of alcohol and in the magnitude
of its effect.
o The same amt. of alcohol is much more concentrated in the average woman compared to a
man because:
Women’s fluid volume is much smaller due to their size
Women have a higher fat-to-water ratio
- Also, alcohol readily passes the placental barrier, so alcohol consumed by a pregnant woman will be
delivered immediately to her fetus, producing potentially damaging effects to the developing infant
- Approximately 95% of alcohol that reaches the general circulation is metabolized by the liver before
being excreted as CO2 and H20 in urine. The remaining 5% (not metabolized) is evaporated through
the lungs and can be measured in a person’s breath using a breathalyzer, providing a means to
calculate alcohol levels
Rate of alcohol metabolism: varies from one person to the other. The average rate is 1-1.5 oz. (12-18ml) of 80
proof alcohol per hour
- Since the metabolic rate is constant for an individual, if the rate of consumption is faster than the rate
of metabolism, alcohol accumulates in the body resulting in intoxication
Several enzyme pathways in the liver are capable of oxidizing alcohol.
One pathway includes:
Step 1) alcohol dehydrogenase - converts alcohol to acetaldehyde ( a potentially toxic intermediate)
Step 2) Acetaldehyde is rapidly modified further by acetaldehyde dehydrogenase (ALDH) to form -> acetic
Step 3) further oxidation yields carbon dioxide, water, and energy
Note: ALDH activity becomes critical for finally degrading alcohol to be detoxicated
- ALDH exists in several genetically determined forms with varying activities:
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