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Lesson 30. BIOCHEMISTRY OF NUTRITION AND DIGESTION

Questions to study.

1. Main stages of metabolism.

2. Characteristics of digestion stage.

3. Chemical composition of the saliva, gastric and pancreatic juices, bile and intestinal juice, and their role in digestion.

4. Pathological components of gastric juice, changes in gastric juice acidity in gastrointestinal diseases.

Assignment for self-instruction

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Task

Guidelines for performing the task

1

2

3

1

Study the main stages of metabolism

1. Describe the main stages of metabolism.

2. Charicterize digestion as first phase of metabolism

2

Study chemical composition of digestive juices

1. Write down the daily amount, pH, organic and inorganic components, proteins and enzymes contained in:

a) saliva;

b) gastric juice;

c) pancreatic juice;

d) intestinal juice;

e) bile

3

Study pathological components of gastric juice

1. List the pathological components of gastric juice.

2. Draw and fill in the table:

Pathological component

Disease with which this pathological component is associated

Blood Bile acids Lactic acid Volatile fatty acids

Ending of the table

1

2

3

4

Study the types

of gastric juice acidity

1. Write down normal values of total acidity, free and bound hydrochloric acid in gastric juice.

2. List biological functions of HCl in gastric juice.

3. Describe the mechanism of production of HCl.

4. Define the terms hyperchlorhydria, hypochlorhydria, achlorhydria, achylia.

5. Draw and fill in the table:

Disease

Total acidity

Free HCl

Reference level Hyperacidic gastritis Peptic ulcer of stomach Stomach cancer Achylic gastritis

5

Study the main components of human food

1. Write down the daily requirement for proteins for a healthy adult.

2. Write down chemical formulas of essential amino acids.

3. Define in writing the term nitrogen balance and types of its imbalance.

4. Describe the manifestations and causes of Kwashiorkor.

5. Write down the main dietary carbohydrates.

6. Write down the daily requirement for carbohydrates and lipids.

7. Write down structural formulas of essential polyunsaturated fatty acids (PUFA) and list their functions in the human body

6

Study the role of mineral components and vitamins in the diet

1. What does the term macroelements mean? Give examples.

2. What does the term microelements mean? Give examples.

3. Name diseases associated with deficiency of iron, copper, calcium, fluorine, iodine ions in the diet.

4. What are vitamins? Write down their classification

Main features of digestive juices

Index

Saliva

Gastric juice

Pancreatic juice

Bile

Intestinal juice

Daily volume

0.5-2.0 l

2.0-2.5 l

1.5-2.0 l

0.5-1.2 l

1.2-1.5 l

рН

6.0-7.4

1.0-2.5

7.8-9.0

7.3-8.0

7.1-7.5

Dry residue

0.5-0.6%

0.6-1.0%

1.2-1.6%

2.5%

1.4-1.6%

Ending of the table

Index

Saliva

Gastric juice

Pancreatic

Bile

Intestinal juice

juice

Main mineral components

К+, Na+, Са2+, Mg2+, Сu2+, Fe3+

Сl-, НСОз-, F-, SO42-, I-, РO43-, CNS-

НСl - up to 0.6%, Na+,

К+, Са2+, Mg2+, Сl-, НСОз-, РO43-, SO42-

К+, Na+, Са2+, НСОз-, Сl-

Na+, К+, Са2+,

Mg2+, НСОз-, Сl-, F-, SO42-,

РO43-

Na+, К+, Са2+, Сl-, РO43- НСОз-

Main

organic

compounds

Urea

Ammonia Amino acids Monosaccha-rides

Creatinine Syalic acid, etc.

Urea

Ammonia Uric acid Polypeptides Amino acids Syalic acid, etc.

Urea

Ammonia Amino acids Creatinine

Bile acids Bile pigments Cholesterol Lecithin Fatty acids Urea, etc.

Urea

Lactic acid Amino acids Creatinine

Mucus proteins

Mucin

Group-specific proteins

Gastro-muco-proteins

Mucin

Mucin

Mucin

Main enzymes

α-amylase

α-glucosidase

Lysozyme

Pepsin

Gastrixin

Chymosin

Trypsin

Chymotrypsin

Elastase

Carboxy-pepti-

dases A and B

α-amylase

Lipase

Phospholipase A

RNAase

DNAase

Alkaline

phosphatase

Catalase

α-amylase

α-glucosidase

ß- glucosidase

ß-galactosidase

Amylo-1,6-glyco-

sidase

Lipase

Phospholipases

В, С, D

Cholesterol

esterase

Enterokinase

Aminopeptidases

Phosphatases

Nucleases

Nucleotidases etc.

Library-research paper 1. Digestive hormones.

LABORATORY WORK

1. Determination of gastric juice acidity

Total acidity, total hydrochloric acid, free and bound hydrochloric acid is determined for characteristics of gastric juice acidity. Total acidity is the sum of all acidic compounds present in gastric juice: free hydrochloric acid, acidic phosphates, organic acids, etc.

Total acidity of gastric juice is expressed in ml of 0.1 N sodium hydroxide used for neutralization of 1000 ml of gastric juice in the presence of phe-nolphthalein (the interval of pH for color change is 8.2-10.0; at pH below 8.2 phenolphthalein is colorless, at pH above 10 it is crimson).

According to Boas-Ewald breakfast test for adults, normal total acidity is in the range 40-60 mmol/l, for newborns - 2.8 mmol/l, for four-week-old babies - 1 year, four-month-old babies - 20 mmol/l.

The content of free hydrochloric acid in gastric juice is expressed in ml of 0.1 N sodium hydroxide used for neutralization of 1000 ml of gastric juice in the presence of dimethylaminoazobenzene (pH interval for color change is 2.3-4.0; at pH below 2.3 the indicator is pink-red, at pH above 4.0 it is yellow). Free hydrochloric acid is completely neutralized at pH 3; and dimeth-ylaminoazobenzene changes from pink-red to orange. Weak acids, e.g. lactic acid or acid phosphates and associated hydrochloric acid are present in solution in undissociated form at pH 2.3-4.2 and do not react with base.

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