Step by Step
M
Metabolism
The liver manages carbohydrate metabolism (glycogenesis, glycogenolysis, gluconeogenesis — maintaining blood glucose), lipid metabolism (fatty acid oxidation, ketogenesis, cholesterol synthesis), and protein metabolism (deamination, transamination, and the urea cycle, which converts toxic ammonia into urea).
D
Detoxification
Cytochrome P450 enzymes in the liver metabolize drugs, alcohol, and other toxins — this is the basis of the "first-pass effect," where orally-administered drugs get partially metabolized by the liver before reaching general circulation.
BP
Bile production and blood protein synthesis
Bile (containing bile salts, cholesterol, bilirubin from hemoglobin breakdown, and lecithin) is produced by the liver and stored in the gallbladder until CCK triggers its release. The liver also synthesizes key blood proteins: albumin (which maintains oncotic pressure and transports drugs), clotting factors (several of which are vitamin K dependent), and various transport proteins.
S
Storage
The liver stores glycogen, fat-soluble vitamins (A, D, E, K), and iron (as ferritin) — acting as a metabolic reservoir for the body.
Applied Walkthrough
1
Between meals, the liver breaks down stored glycogen (glycogenolysis) to release glucose into the blood, maintaining stable blood sugar even when no food is being digested.
2
After a meal that includes alcohol, cytochrome P450 enzymes in the liver metabolize it — part of the liver's broader detoxification role, also responsible for the first-pass effect seen with many oral medications.
3
Simultaneously, the liver continues producing bile (containing bile salts and bilirubin from hemoglobin breakdown), storing it in the gallbladder for eventual release when CCK signals that fat has arrived in the duodenum.
4
In a patient with liver failure, several of these functions break down at once: reduced albumin production leads to low oncotic pressure and edema, reduced clotting factor synthesis leads to coagulopathy, and impaired ammonia processing (normally converted to urea) leads to ammonia buildup and hepatic encephalopathy.
Exam Application
Exams test whether you can name and describe all six categories of liver function, and specifically whether you can connect specific liver failure symptoms (jaundice, coagulopathy, edema, hepatic encephalopathy) back to the specific liver function that's failing.
⚠ Common Trap
The most common trap is not connecting liver failure symptoms to their specific underlying cause — for example, edema in liver failure traces specifically to reduced albumin synthesis (lowering oncotic pressure), while hepatic encephalopathy traces to impaired ammonia-to-urea conversion.
✓ Quick Self-Check
1. What does the urea cycle in the liver accomplish?
Converting toxic ammonia (NH₃) into urea, which can be safely excreted.
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2. What is the "first-pass effect"?
The partial metabolism of orally-administered drugs by the liver's cytochrome P450 enzymes before they reach general circulation.
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3. What does albumin do, and why does its deficiency cause edema?
It maintains oncotic pressure and transports drugs; low albumin reduces oncotic pressure, allowing fluid to leak out of blood vessels into tissues.
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4. What three substances does the liver store?
Glycogen, fat-soluble vitamins (A, D, E, K), and iron (as ferritin).
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5. What causes hepatic encephalopathy in liver failure?
Ammonia (NH₃) accumulation, since the liver can no longer convert it to urea efficiently.
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