Alcohol
March 2015
Yeast and Alcohol
For thousands of years, people have used a fungus called baker’s yeast,
Saccharomyces cerevisiae, to ferment ethanol (drinking alcohol) and bake bread. The
bubbles in champagne, for example, owe to the activity of this yeast. When yeast are
causing bread dough to rise, do they also make alcohol?
Fermentation
When glucose is broken down by
glycolysis, the electron carrier NAD+ is
converted into NADH. This NADH can
be used in the electron transport chain
to make ATP if oxygen is available.
But what about when there’s no free
oxygen available? In that case, the
organism needs to recycle the NADH
back to NAD+! In addition, there needs
to be a way to get rid of the pyruvate.
In yeast, this is done by making carbon
dioxide and ethanol – the bubbles and
alcohol in alcohol fermentation.
These bubbles are also what causes
bread dough to rise.
Distillation
Once yeast make enough alcohol to
raise the concentration to about 15%,
they stop fermenting; too much alcohol
would kill them. To make drinks with a
higher percentage of alcohol than that,
we use distillation. Because alcohol
evaporates more easily than water,
heating an alcoholic drink and
capturing the steam will separate it
from water.
(Note: Improper distillation carries a
risk of explosion.)
Proof and Percentage Alcohol
Concentration
As a general rule, which, if any, of the following contains the most alcohol?
A 12 oz. can of beer
A 5 oz. glass of wine
A 1.5 oz. shot of whiskey
Proof/Percentage Alcohol by Volume
Because the beer has the lowest concentration of alcohol and the whiskey has the
highest concentration of alcohol, but a single drink of whiskey is smaller than a
can of beer… all three servings have about the same total alcohol content. By and
large, an alcoholic drink is an alcoholic drink; wine is only “safer” in that people
may drink it more slowly than shots.
Alcohol content can be measured in percentage by
volume or by proof. Proof is just twice the
percentage by volume. If a drink is 50% alcohol, it
is 100 proof.
Proof is not a measure of quality. Even high proof
beverages can contain impurities that increase
hangover pain, and some can have a deceptively
mild taste, making it easy to become intoxicated
quickly without realizing the high alcohol content.
Drinking cups not specifically
meant for a given drink do not
take proof into account. Be
careful when drinking from
large cups.
Blood Alcohol Concentration (BAC)
What is the legal limit for Blood Alcohol Concentration
for driving in most U. S. states?
A)
B)
C)
D)
8% (8/100 of your blood is alcohol)
.8% (8/1000 of your blood is alcohol)
.08% (8/10,000 of your blood is alcohol)
.008% (8/100,000 of your blood is alcohol)
Assuming no problems with alcohol metabolism, how
many drinks would it take a 140-lb woman to reach
this level? What about a 220-lb man?
Blood Alcohol Concentration
Safer Drinking Habits
• Always have a designated driver at events that
involve alcohol.
• Do not drink too much at one occasion. Very
generally, binge-drinking is defined as >4 drinks
within 2 hours for men, or >3 drinks within 2 hours
for women.
• Never drink on an empty stomach; food slows down
the rate of alcohol absorption and reduces the risk
of alcohol poisoning.
• Avoid drinking games, and never drink to
unconsciousness.
What Causes Hangovers?
Which of the following play a role in hangovers?
Choose all that apply:
A)
B)
C)
D)
Dehydration
Poisonous molecules the body makes from alcohol
Poisonous molecules found with alcohol in drinks
Low blood sugar
Will coffee reduce the symptoms of a hangover?
Alcohol Metabolism
Alcohol dehydrogenase (ADH) converts ethanol into poisonous acetaldehyde, which
is 20 times more toxic than alcohol itself. This happens mostly in the liver, but also
in the stomach lining, where alcohol is absorbed.
The acetaldehyde dehydrogenase enzyme (ALDH) then converts the acetaldehyde
into relatively harmless acetate (same stuff as vinegar) in the liver.
People without a working ALDH enzyme are highly sensitive to alcohol and can
suffer brain damage quickly from alcohol consumption!
Alcohol and the Liver
Long-term alcohol consumption
damages the liver. This damage3
can take multiple forms:
Fatty liver: Buildup of fat in liver
cells. Can cause inflammation
Hepatitis: Inflammation of the
liver; can lead to jaundice and
eventually liver failure.
Cirrhosis: Scarring and hardening
of the liver. Eventually can be fatal.
Alcohol and Nutrition
Because alcohol is a form of empty
calories, it can displace healthy
foods from the diet and lead to
weight gain.
In addition, because alcohol is a
diuretic, it causes loss of watersoluble vitamins and minerals, in
particular B vitamins and zinc.
Wernicke-Korsakoff syndrome:
nerve damage, paralysis, memory
loss – brain damage.
Fetal Alcohol Syndrome
Alcohol is a teratogen – that is to say, it
can cross the placenta and cause birth
defects in a developing embryo in the
form of Fetal Alcohol Syndrome, which
can affect facial and brain development.
Some studies suggest that very modest
alcohol consumption during pregnancy (1
glass of wine a week) is harmless.
However, the Centers for Disease Control
advise caution in this – there is no
guaranteed safe amount.
Alcohol Dependency and Abuse
Destructive use of alcohol can lead to dependence. A person begins
needing more alcohol to achieve the same sensation, and suffers
withdrawal symptoms, such as nausea, insomnia, anxiety, or even
tremors and seizures when they go without drinking.
Alcohol dependency develops over time, and cannot be reversed quickly
or easily. Support groups, antiabuse drugs, and therapy can help, but
long-term abstinence from alcohol is always challenging for those who
have struggled with alcohol abuse.
Warning signs of alcohol dependency include unsuccessful efforts to cut
down on drinking, reduction in important daily activities for alcohol use,
and episodes of binge-drinking and hangovers.
Benefits of Red Wine?
Some studies suggest that phytochemicals from the skin of grapes, such as
resveratrol, found in red wine, can have healthy antioxidant effects and
reduce the risk of heart attacks.
Our text uses this to explain the French Paradox. The French Paradox is
that on average, the French eat a diet with a great deal of cholesterol and
saturated fat, yet have lower risks of heart disease than Americans. They
also drink more red wine.
Is this line of reasoning sufficient to conclude that drinking red wine is
responsible for the better health of the French? What else could be at play
here?
Given what I’ve said above, is there any way to get the benefits of
resveratrol without drinking red wine?