Liver and Integration of Metabolism

Question 1

The liver plays an important role in the metabolism of drugs and xenobiotics. Describe how the liver metabolizes drugs and xenobiotics to ensure they will be excreted in the urine

Answer 1

In order for the kidney to eliminate drugs and xenobiotics, the compounds must be made hydrophilic. There is a two phase reaction that takes place in the liver to convert drugs to their hydrophilic form.

Question 2

Identify the enzyme complex responsible for the oxidation reactions in phase I metabolism of drugs and xenobiotics

Answer 2

Phase 1: The introduction of OH or COOH groups, usually through the oxidation of the parent compound. The enzymes responsible for this are present a an enzyme complex of

NADPH-cytochrome P450 reductase and hemoproteins

aka cytochrome p450

Question 3

The liver plays an important role in the metabolism of carbohydrates. Identify the major pathways of carbohydrate metabolism that are active in the liver

Answer 3

Glycolysis, glycogenolysis, gluconeogenesis, glycogenesis

Question 4

Compare the rates of glycogen synthesis and degradation following a period of feeding.

Answer 4

Glycogen synthesis&raquo_space; glycogen degradation following a period of feeding

Question 5

Describe insulin’s role in regulating hepatic glycogen metabolism and gluconeogensis

Answer 5

Insulin, released when glucose levels are high, stimulates the storage or glucose as glycogen in the liver

Question 6

Describe glucagon’s role in regulating hepatic glycogen metabolism and gluconeogenesis

Answer 6

Glucagon, released when blood glucose levels drop, stimulates gluconeogenesis

Question 7

Explain the impact of hepatic liver disease on blood glucose levels.

Answer 7

When the liver is damaged, it can not properly regulate blood glucose levels. This leads to hypoglycemia during times of fasting

Question 8

The liver plays an important role in the metabolism of lipids. Review the role of the liver in lipid metabolism

Answer 8

The liver is responsible for the beta oxidation

Question 9

Identify the plasma lipoproteins that are synthesized and/or metabolized in the liver

Answer 9

VLDL and HDL are synthesized in the liver

Chylomicron remnants are sent to the liver to deliver CE
IDL and LDL delivers cholesterol to the liver and other cells

Question 10

The liver produces most of the circulating plasma proteins. Explain why liver disease and long term starvation can result in generalized edema.

Answer 10

Not producing enough proteins in the blood/not enough albumin.

This leads to high hydrostatic pressure (and low oncotic pressure) so fluid leaks out into the interstitium.

Cirrhosis –> portal hypertension –> ascites.

Question 11

Identify at least four protein that are synthesized predominantly in the liver.

Answer 11

Plasma proteins: albumin

Clotting factors: fibrinogen, prothrombin, transferrin

Question 12

Where is urea produced?

Answer 12

The liver

Question 13

What happens when the liver can no longer process amino groups into urea?

Answer 13

Hyperammonemia –> brain damage

Question 14

WHat is the role of the liver in the handling of amino acids

Answer 14

The liver plays an important role in the synthesis and inter-conversion of amino acids.

Question 15

What type of vitamins are stored in the liver?

Answer 15

Fat soluble vitamins

Question 16

What metals are stored in the liver?

Answer 16

Iron and copper.

The liver is important in the storage and hemostasis of iron and copper.

Question 17

What is another name for vitamin A?

Answer 17

Retinol

Question 18

What is the major role of the liver in vitamin D handling

Answer 18

Although the major vitamin D stores are in the adipose and skeletal muscle, some is stored in the liver.

The liver is responsible for the initial activation of D3; it converts this form to 25-hydroxycholecalciferol and synthesizes the vitamin D binding protein

Question 19

How does the liver affect thyroid hormones?

Answer 19

Conversion from T4 to T3 (functional form)