Alcohol (Post-Midterm) Flashcards
What are the properties of alcohol?
Alcohol is ethyl alcohol or ethanol, known for its lipophilic nature. It is not considered a nutrient, but it has a high caloric value.
How is alcohol absorbed in the gastrointestinal (GI) tract?
Ethanol in the GI tract occurs in its free form, which means no digestion is required for its absorption. Ethanol can be directly absorbed through diffusion in the gastric mucosa and small intestine.
What are the metabolic pathways responsible for the degradation of ethanol?
Alcohol dehydrogenase (ADH) pathway, and microsomal ethanol oxidizing system (MEOS)
What is the alcohol dehydraogenase pathway?
The main pathway for ethanol degradation is the alcohol dehydrogenase (ADH) pathway. In this pathway, ethanol is converted to acetaldehyde, which is then further metabolized to acetate.
What is the microsomal ethanol oxidizing system
Another pathway is the microsomal ethanol oxidizing system (MEOS) that occurs in the smooth endoplasmic reticulum. MEOS is responsible for the oxidation of ethanol along with other substances like fatty acids and drugs.
How does alcohol consumption impact the caloric value?
Alcohol has a high caloric value of 7.1 kcal/gram. While it is not considered a nutrient, it contributes to the overall energy intake. The metabolizable energy, which is the energy the body uses after excretion, depends on the amount of alcohol intake.
What are the potential effects of chronic, high alcohol consumption?
Chronic, high alcohol consumption can lead to various metabolic alterations and clinical symptoms. These include fatty liver, liver cirrhosis, liver cancer, lactic acidosis, metabolic tolerance, overweight, weight loss, and even fetal alcohol syndrome.
Alcohol digestion
Alcohol does not require digestion in the GI tract. It is directly absorbed through the gastric mucosa and small intestine, leading to its rapid uptake.
What is the main site of ethanol degradation in the body?
The liver is the most important site for ethanol degradation. Approximately 90% of absorbed ethanol is metabolized in hepatocytes in the liver.
How is ethanol metabolized in the liver?
Ethanol is metabolized in the liver through the alcohol dehydrogenase (ADH) pathway. It is converted to acetaldehyde, which is further broken down to acetate.
What happens to ethanol that is not metabolized in the liver?
Ethanol that is not metabolized in the liver can be excreted through the lungs (breathing) and the kidneys (urine). In some cases, it may also be excreted through sweat.
What is the role of the alcohol dehydrogenase (ADH) pathway in ethanol metabolism?
The alcohol dehydrogenase (ADH) pathway is the main pathway for ethanol metabolism. It converts ethanol to acetaldehyde, which is a toxic substance that can cause various adverse effects.
What is the significance of the Km value of alcohol dehydrogenase (ADH)?
The Km value represents the substrate concentration at which an enzyme works at half its maximum velocity. For alcohol dehydrogenase, a Km value of 5mg/dL means that at an intracellular ethanol concentration of 5mg/dL, the enzyme works at half its maximum velocity.
What happens when the intracellular ethanol concentration exceeds the Km value of alcohol dehydrogenase (ADH)?
When the intracellular ethanol concentration exceeds the Km value of alcohol dehydrogenase, the enzyme becomes saturated with the substrate (ethanol). This leads to maximum velocity of ethanol degradation and depletion of NAD+ due to high ADH activity.
What is the alternate pathway for ethanol metabolism?
The alternate pathway for ethanol metabolism is the microsomal ethanol oxidizing system (MEOS), which occurs in the smooth endoplasmic reticulum. MEOS is responsible for oxidizing ethanol along with other substances like fatty acids and drugs.
