Class notes
Alcohol - Biochemistry
- Course
- Institution
Here are lecture notes for a biochemistry lecture on alcohol
[Show more]
Seller
Follow
lucygodbeer
Content preview
BIOCHEMISTRY – LECTURE 10 PART 1alcohol and the body
Alcohol can be part of much human and some animal culture for at least 7000
years. The cost to the NHS is said to be £3.5 billion, including 1,008,850 hospital
admissions (2012/2013) figures – admissions related to alcohol consumption is
defined as where an alcohol-related disease, injury or condition was the primary
reason for hospital admission or a secondary diagnosis. In 2012 there were 6490
deaths directly related to alcohol. Of these alcohol related deaths, the majority
(4075) died from alcoholic liver disease, the remaining deaths are from
accidents. 1 in 13 people have an alcohol problem and there are potential health
benefits of alcoholic drinks.
Absorption of alcohol by simple diffusion beings in the stomach. Alcohol
dehydrogenase is present in gastric mucosa cells, this catalyses oxidation of
ethanol to acetaldehyde and most is absorbed in the small intestine. Men have
more alcohol dehydrogenase (ADH) in their gastric mucosa, this increases the
conversion of ethanol to acetaldehyde prior to absorption. This contributes to the
typically higher tolerance to alcohol in men compared to women. As most
absorption happens in the small intestines, factors which slow gastric emptying
slow down absorption (such as a fatty meal).
There are some immediate physiological effects of ethanol:
o Vasodilation (causes blushing of the skin)
o CNS depression (from loss of inhibition to coma)
o Inhibition of antidiuretic hormones (ADH) action (increased urination).
Some research suggests inhibition of ADH secretion, other suggest alcohol
causes renal insensitivity to it.
95% of ethanol is removed by hepatic metabolism. The other 5% is excreted in
sweat, breath and urine. The first reaction occurs in the cytosol, the second
reaction mainly occurs in the mitochondria. Both generate NADH, which is fuel
for the electron transport chain.
Alcohol dehydrogenase also catalyses the oxidation of antifreeze (ethylene
glycol) to form very toxic products, including glycolaldehyde and oxalate. As it is
the products formed that causes the damage (not ethylene glycol itself),
treatment is aimed at preventing their formation. Patients who have ingested
ethylene glycol are given something that competes with alcohol dehydrogenase,
to prevent the formation of damaging metabolites from ethylene glycol. By
administering ethanol, it competes with ethylene glycol for the active site on
alcohol dehydrogenase. This gives the body more of a chance to eliminate
ethylene glycol before it can be metabolised into the toxic products.
, The cytochrome P450 are a group of >50 enzymes, all with a haem prosthetic
group. The name P450, comes from the characteristic absorption of 450nm. This
is important in alcohol metabolism when alcohol accounts for 15% of calorie
intake. Its also important for detoxification of xenobiotics (compounds foreign to
the body). This is less efficient at extracting energy from ethanol than the
alcohol dehydrogenase pathway which causes formation of reactive oxygen
species. This explains alcohol tolerance, as, unlike alcohol dehydrogenase, it is
inducible. P450 enzymes are not just there so we can drink alcohol and take
medicines. They are important in a wide range of reactions, such as the
hydroxylation of cholesterol (a step toward steroid hormone synthesis) and in the
breakdown of haemoglobin.
Unlike the constitutively expressed alcohol dehydrogenase enzyme, the P450
enzymes are inducible, more can be expressed with increased ethanol intake.
The typical reduction of molecular oxygen, to form water, and lead to the release
of superoxide, a partially reduced intermediate of the reaction. Superoxide (O 2-)
is a reactive species, capable of damaging cellular molecules, including DNA.
The blood vessels that take absorbed molecules away from the GIT link to the
liver via the hepatic portal vein. The blood from the GIT is taken to the liver
before transport to the rest of the body. This gives the liver the opportunity to
remove/metabolise absorbed molecules before they are transported to other
tissues. So, what happens in the liver?
The liver received blood from the hepatic portal vein and the hepatic
artery
These branch out and terminate at the corners of lobules
Blood from these bathe hepatocytes on their journey to the central vein
During this contact time, hepatocytes are able to perform their metabolic
functions, including the oxidation of alcohol, before the processed blood
moves into general circulation, via the central veins to the hepatic vein.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller lucygodbeer. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.09. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
70055 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now