Experiment 3. The role of serum albumin in the transport of fatty acids in the blood.

The blood always contains a certain amount of nonesterified (free) higher fatty acids that appear in the enzymatic cleavage of nutrition lipids and lipids from the body fat depots by lipase. Higher fatty acids, insoluble in water, are transported in plasma mainly as complexes with albumins. An albumin molecule contains a cavity formed by hydrophobic amino acid radicals. The hydrocarbon chain of fatty acids may be placed in this cavity (see Fig).

Fig. Transport of fatty acids by blood serum albumin

Pure 0,5 ml of sodium oleate solution in two test tubes. Add 1,5 ml of blood serum to the first test tube and the same amount of water to the second one. Then add the hydrochloric acid solution drop by drop to the second test tube until the first signs of higher fatty acid residue are observed. Repeat the procedure with the first test tube. Describe and explain the observed phenomena.

Test Questions

1. Dietary lipids are poorly soluble in water. How do lipolytic enzymes cope with them?

2. Clinical symptoms of steatorrhea are characterized by an excess of lipids in the feces, mostly due to two reasons: a) lack of bile acids secretion; b) lack of the pancreatic gland secretion. Why do these reasons lead to the appearance of lipids in the feces?

3. Explain why patients with decreased secretion of pancreatic bicarbonates suffer from steatorrhea even when the secretion of lipase and colipase is normal.

Laboratory work 2. Phospholipids. Cholesterol

Experiment 1. Extraction of phosphatides from brain tissue.

Put 5 g of brain tissue dried out with gypsum into a flask and add 10 ml of alcohol. Attach a reflux condenser and place for 15-20 minutes in preheated to 70⁰C water bath. Shake from time to time. If a significant amount of the alcohol is evaporated, add some more. At the end of the extraction cool the flask and filter the extract.

Experiment 2. Qualitative reaction of lecithin with cadmium chloride.

Add 1 ml of saturated alcoholic solution of cadmium chloride to 2 ml of alcoholic solution of lecithin (experiment 1). A white flocculent precipitate of the complex compound of lecithin with cadmium chloride is observed. Cholesterol and vegetable oil solutions do not give this reaction.

Experiment 3. Extraction of cholesterol from the brain tissue.

Put 3 g of brain tissue dried out with gypsum into a clean dry test tube and add 6 ml of chloroform alcohol. Shake for 10 minutes. Filter the extract into a dry tube.

Date: 2016-04-22; view: 840