Category: Biology Second Paper Lecture Sheet

The cells in the mucosa layer of the stomach that secrete digestive juices are called gastric glands. There are three types of gastric glands. Fundic gland, cardiac gland and pyloric gland. 500-1000 ml of gastric juice is secreted from the stomach every time we eat. Gastric glands are:
(i) Peptic or chief cells: pepsinogen, renin, gelatinase, lipase etc. are secreted from peptic or chief cells.
(ii) Parietal or oxyntic cells: Parietal or oxyntic cells secrete intrinsic factor and HCl.
(iii) Mucous Glands: Mucin is secreted from mucous glands.
(iv) G-cells or Gastrin cells: G-cells secrete gastrin juice.
(v) Gastric gland: Gastric gland secretes gastrin juice.
(vi) Argentaphin cells: It secretes hormones and absorbs vitamin B12. It releases serotonin.
(vii) Mucous Cell or Goblet Cell: It secretes mucus.

Gastric juice
The juice secreted from G-cells, peptic cells, goblet cells, parietal cells, mucous cells etc. of stomach is called gastric juice. Deficiency of vitamin E12 in gastric juice is called pernicious anemia.

Three stages of gastric juice secretion
1. Cephalic stage: This stage begins before the food enters the stomach. At this stage, 20 percent of gastric juice is secreted.
2. Gastric phase: The gastric phase is the time when food settles in the stomach. At this stage, 70 percent of gastric juice is secreted for digestion.
3. Intestinal Phase: When food enters the small intestine from the stomach, the intestinal phase begins. At this stage very little amount of gastric juice is secreted.

Constituents of gastric juice
(i) Water: Gastric juice contains 99.45% water.
(ii) Organic components: Gastric juice contains pepsin, renin, lipase, mucin, intrinsic factor etc.
(iii) Inorganic components: Gastric juice contains sodium chloride, potassium chloride, calcium chloride, calcium phosphate, magnesium phosphate etc.

1. Hormone secretion: Pancreatic islets of Langerhans consist of a cluster of 100,000 cells.
(i) Alpha cells: 20% of human islets are alpha cells. It secretes glucagon hormone and increases blood glucose levels.
(ii) Beta cells: 50-70% of human islets are beta cells. It secretes the hormone insulin and lowers blood glucose levels. Lack of this hormone causes diabetes mellitus.
(iii) Delta cells: 10% of human islets are delta cells. It secretes the hormone somatostatin which regulates the secretion of alpha and beta cells.
(iv) Gamma cells: It secretes pancreatic polypeptide.
2. Enzyme secretion: Amylase, trypsin and lipase are secreted from this gland. Besides, chymotrypsin, collagenase, erepsin, elastase, phospholipase, esterase, carboxypeptidase, aminopeptidase, dipeptidase, tripeptidase etc. are secreted from this gland.
3. Salt secretion: Bicarbonate salt is secreted from this gland. It removes stomach discomfort.
4. Water balance: It regulates water balance in the body.
5. Acid-base balance: It maintains acid-base balance in the body.

(i) Water: Pancreatic juice contains 98% water.
(ii) Organic components: Pancreatic juice contains proteolytic, amylolytic, lipolytic, mucin, lipase, maltase, sucrase, lactase, trypsin, chymotrypsin, trypsin-inhibitor, nuclease etc.
(iii) Inorganic components: Pancreatic juice contains sodium, potassium, magnesium, calcium, zinc, sulphate, phosphate etc.

Pancreas is a mixed gland. It looks like a leaf or a cylinder or a drum or a pepper. This gland consists of three parts. Head, body and tail. In cellular structure it consists of two parts. Duct part or acinus and duct part or islets of Langerhans. Its length is 20 cm and width is 5 cm. Small ducts emerge from the pancreatic gland. These ducts join together to form the Wirsang duct. The Wirsang duct then enters the duodenum through the ampulla of Vater. Pancreas is divided into several segments called lobules. Between the lobules there are clusters of cells called islets of Langerhans. Islets of Langerhans are composed of about 1 million cells. It contains four types of cells. Alpha, Beta, Gamma and Delta. The pancreas secretes 500-1200 ml of juice every 24 hours. It is colorless, alkaline and liquid. Its pH is 7.5-8.5.

1. Hepatitis: Inflammation of the liver is called hepatitis. Jaundice is caused by the hepatitis virus.
2. Hepatic encephalopathy: Hepatic encephalopathy occurs if the liver fails to remove toxins from the blood. People go into coma or die from this disease.
3. Hepatomegaly: Abnormally enlarged liver is called hepatomegaly.
4. Bud-Kyari: When a cyst occurs in the hepatic vein that supplies blood to the liver, it is called Bud-Kyari.
5. Biliary cirrhosis: Biliary cirrhosis is an autoimmune disease of the liver.

1. Protein metabolism
(i) Production of plasma proteins: Liver cells produce plasma proteins such as albumin, globulin, fibrinogen, prothrombin, transferrin, seroplasmin, photoprotein etc. from amino acids.
(ii) Hormone synthesis: Liver synthesizes angiotensinogen hormone. This hormone increases blood pressure.
(iii) De-amination: Liver breaks down excess and unused amino acids by de-amination process to convert keto acids and amine radicals.
2. Carbohydrate metabolism
(i) Glycogenesis: The process in which glycogen is produced from glucose is called glycogenesis. The liver regulates blood glucose levels. Hexose sugars including galactose, fructose are stored as glycogen.
(ii) Glycogenolysis: In this process glucose is produced by breaking down glycogen stored in the liver. This process is influenced by the hormones epinephrine and glucagon.
(iii) Glyconeogenesis: The biochemical process by which glucose is produced from non-saccharides is called glyconeogenesis. When the level of glucose in the body is too low, glucose is produced from non-saccharides such as amino acid, lactic acid, pyruvic acid, glyceryl etc.
(iv) Lipogenesis: In this process the liver converts excess glucose into triglycerides. The triglycerides produced are stored as fat in the cells. Triglycerides are one of the main causes of heart disease and stroke.
3. Lipid metabolism
(i) Fatty acids are broken down in the liver to produce ATP. ATP is used in muscle expansion and relaxation.
(ii) Liver synthesizes lipoproteins. Lipoproteins regulate the movement of fatty acids, cholesterol and triglycerides into cells.
(iii) Liver stores cholesterol. Cholesterol produces gallstones called sodium glycocholate and sodium taurocholate.
(iv) Ketones are produced by oxidation of fatty acids and glycerol in the liver.
(v) Sodium glycocholate and sodium tyrocholate break down astringent food into tiny granules like soap suds. This process is called emulsification.
(vi) Phospholipids, glycolipids, lipoproteins, cholesterol etc. are analyzed under the influence of liver juice.
(vii) Glucose is produced from stored fat in the absence of sugar.
4. Nucleic acid metabolism: Purine and pyrimidine nucleotides are analyzed with the help of liver cells. Purines are broken down to form uric acid and pyrimidines to form urea.
5. Breakdown of Hormones: Liver juice regulates the process of breaking down all kinds of hormones. Hormones like estrogen, cortical, testosterone etc. are released with sulfuric acid. Testosterone and androsterone hormones are rapidly destroyed and hormones such as insulin, glucagon, estrogen, progesterone, adrenal, thyroxine etc. are destroyed slowly.
6. Protection of the body: The kaffer cells of the liver protect the body by eating bacteria and other microbes in the process of phagocytosis.
7. Production of Red Blood Cells: Liver cells of babies produce red blood cells. Again, this removes almost dead red blood cells.
8. Bilirubin formation: breaks down hemoglobin in the blood to produce heme and globin. The green colored biliverdin is produced from the frozen part. Later, biliverdin forms yellow colored bilirubin. Excess bilirubin in the body causes jaundice and the skin turns yellow.
9. Detoxification: Liver cells destroy and remove harmful substances from the body through oxidation, oxidation and analysis. Excess drugs are removed from the body.
10. Preparation of Urea: Urea is produced from amino acids by deamination process under the influence of liver juice.
11. Blood protein production: Blood albumin, globulin etc. proteins are produced in the liver.
12. Blood coagulation: Fibrinogen and prothrombin are produced by liver cell activity. Fibrinogen and prothrombin help in blood clotting.
13. Enzyme production: Liver produces catalase enzyme. Catalase enzyme breaks down hydrogen peroxide to produce sodium and oxygen. It destroys the body’s toxic substances.
14. Heat energy production: Heat energy is generated by oxidation of triglycerides and fatty acids in the liver.
15. Synthesis of blood components: Liver produces blood clotting factors, imine factors and platelet-forming vitreous.
16. Cholesterol Production: Cholesterol is produced in the liver by eating fatty foods. Cholesterol causes heart attack and stroke.
17. Transamination: In the transamination process, the nitrogenous part of an amino acid is replaced by a sugar to produce a new amino acid.
18. Keeping blood free of bacteria: Kaffir cells destroy blood bacteria. Blood is free of bacteria.

About 500 types of biochemical functions are completed in the liver. Therefore liver is called organic laboratory
Storage role of liver
1. Glycogen storage: When blood glucose levels are high, insulin produced by the islets of Langhans stores the excess glucose as glycogen. About 100 grams of glycogen are stored in the liver. Glycogen is changed back to glucose as needed by the body.
2. Fat storage: All the sugars that are not used in the human body and are not stored as glycogen, the liver cells convert them into fat and store them.
3. Vitamin storage: Liver cells store vitamins A, D, E and K in the human body. It also stores some amount of nicotinic acid (B12) and folic acid.
4. Blood storage: Although the ducts of the liver carry blood, they also act as reservoirs for storing a large amount of blood. The liver stores about 1500 cubic cm of blood.
5. Bile secretion and storage: Liver cells secrete and store bile. The liver secretes 400-800 ml of bile per day.
6. Iron storage: Hemoglobin in blood contains heme and globin. Heme contains iron called ferritin. Liver ferritin stores iron.
7. Mineral salt storage: The liver stores minerals such as zinc, copper, cobalt, molybdenum, ions, potassium etc. in the human body. The liver ion produces new red blood cells in the bone marrow.

Metabolic role of the liver
1. Protein metabolism
(i) Production of plasma proteins: Liver cells produce plasma proteins such as albumin, globulin, fibrinogen, prothrombin, transferrin, seroplasmin, photoprotein etc. from amino acids.
(ii) Hormone synthesis: Liver synthesizes angiotensinogen hormone. This hormone increases blood pressure.
(iii) De-amination: Liver breaks down excess and unused amino acids by de-amination process to convert keto acids and amine radicals.
2. Carbohydrate metabolism
(i) Glycogenesis: The process in which glycogen is produced from glucose is called glycogenesis. The liver regulates blood glucose levels. Hexose sugars including galactose, fructose are stored as glycogen.
(ii) Glycogenolysis: In this process glucose is produced by breaking down glycogen stored in the liver. This process is influenced by the hormones epinephrine and glucagon.
(iii) Glyconeogenesis: The biochemical process by which glucose is produced from non-saccharides is called glyconeogenesis. When the level of glucose in the body is too low, glucose is produced from non-saccharides such as amino acid, lactic acid, pyruvic acid, glyceryl etc.
(iv) Lipogenesis: In this process the liver converts excess glucose into triglycerides. The triglycerides produced are stored as fat in the cells. Triglycerides are one of the main causes of heart disease and stroke.
3. Lipid metabolism
(i) Fatty acids are broken down in the liver to produce ATP. ATP is used in muscle expansion and relaxation.
(ii) Liver synthesizes lipoproteins. Lipoproteins regulate the movement of fatty acids, cholesterol and triglycerides into cells.
(iii) Liver stores cholesterol. Cholesterol produces gallstones called sodium glycocholate and sodium taurocholate.
(iv) Ketones are produced by oxidation of fatty acids and glycerol in the liver.
(v) Sodium glycocholate and sodium tyrocholate break down astringent food into tiny granules like soap suds. This process is called emulsification.
(vi) Phospholipids, glycolipids, lipoproteins, cholesterol etc. are analyzed under the influence of liver juice.
(vii) Glucose is produced from stored fat in the absence of sugar.
4. Nucleic acid metabolism: Purine and pyrimidine nucleotides are analyzed with the help of liver cells. Purines are broken down to form uric acid and pyrimidines to form urea.
5. Breakdown of Hormones: Liver juice regulates the process of breaking down all kinds of hormones. Hormones like estrogen, cortical, testosterone etc. are released with sulfuric acid. Testosterone and androsterone hormones are rapidly destroyed and hormones such as insulin, glucagon, estrogen, progesterone, adrenal, thyroxine etc. are destroyed slowly.
6. Protection of the body: The kaffer cells of the liver protect the body by eating bacteria and other microbes in the process of phagocytosis.
7. Production of Red Blood Cells: Liver cells of babies produce red blood cells. Again, this removes almost dead red blood cells.
8. Bilirubin formation: breaks down hemoglobin in the blood to produce heme and globin. The green colored biliverdin is produced from the frozen part. Later, biliverdin forms yellow colored bilirubin. Excess bilirubin in the body causes jaundice and the skin turns yellow.
9. Detoxification: Liver cells destroy and remove harmful substances from the body through oxidation, oxidation and analysis. Excess drugs are removed from the body.
10. Preparation of Urea: Urea is produced from amino acids by deamination process under the influence of liver juice.
11. Blood protein production: Blood albumin, globulin etc. proteins are produced in the liver.
12. Blood coagulation: Fibrinogen and prothrombin are produced by liver cell activity. Fibrinogen and prothrombin help in blood clotting.
13. Enzyme production: Liver produces catalase enzyme. Catalase enzyme breaks down hydrogen peroxide to produce sodium and oxygen. It destroys the body’s toxic substances.
14. Heat energy production: Heat energy is generated by oxidation of triglycerides and fatty acids in the liver.
15. Synthesis of blood components: Liver produces blood clotting factors, imine factors and platelet-forming vitreous.
16. Cholesterol Production: Cholesterol is produced in the liver by eating fatty foods. Cholesterol causes heart attack and stroke.
17. Transamination: In the transamination process, the nitrogenous part of an amino acid is replaced by a sugar to produce a new amino acid.
18. Keeping blood free of bacteria: Kaffir cells destroy blood bacteria. Blood is free of bacteria.

1. Glycogen storage: When blood glucose levels are high, insulin produced by the islets of Langhans stores the excess glucose as glycogen. About 100 grams of glycogen are stored in the liver. Glycogen is changed back to glucose as needed by the body.
2. Fat storage: All the sugars that are not used in the human body and are not stored as glycogen, the liver cells convert them into fat and store them.
3. Vitamin storage: Liver cells store vitamins A, D, E and K in the human body. It also stores some amount of nicotinic acid (B12) and folic acid.
4. Blood storage: Although the ducts of the liver carry blood, they also act as reservoirs for storing a large amount of blood. The liver stores about 1500 cubic cm of blood.
5. Bile secretion and storage: Liver cells secrete and store bile. The liver secretes 400-800 ml of bile per day.
6. Iron storage: Hemoglobin in blood contains heme and globin. Heme contains iron called ferritin. Liver ferritin stores iron.
7. Mineral salt storage: The liver stores minerals such as zinc, copper, cobalt, molybdenum, ions, potassium etc. in the human body. The liver ion produces new red blood cells in the bone marrow.

The juice secreted from the liver is called pitta or pittrasa. It is a dark green to yellowish liquid. It has a pH of 7.5-8.6 and a bitter taste.
The components of bile are:
1. Water: Bile contains 97-98% water.
2. Bile Salts: Bile contains 6% bile salts. Bile salts are sodium taurocholate, sodium glycocholate etc.
3. Bile pigments: Bile contains 3% bile pigments. Bile pigments are bilirubin and biliverdin.
4. Fat: Bile contains 0.82% fat.
5. Inorganic salts: Bile contains 0.8% inorganic salts. Inorganic salts are sodium, potassium and calcium.
6. Cholesterol: Bile contains 0.38% cholesterol.
Bile
The juice secreted from the liver is called pitta or pittrasa. It is a dark green to yellowish liquid. It has a pH of 7.5-8.6 and a bitter taste.

The liver appears bifurcated externally as it is covered by a falciform membrane. The liver is divided into four distinct lobes. Right lobe, left lobe, caudate and quadrate lobe. The right segment is the largest, the left segment is the smallest. The right lobe is six times larger than the left lobe. The caudate and quadrate segments are square-like. The liver is covered by a membrane called Gison’s capsule. This membrane divides the liver into lobules or segments. Liver cells are arranged in each lobule like the spokes of a wheel. The space between adjacent lobules is called sinusoid. Between each lobule is a central vein. The right and left hepatic ducts together form the common hepatic/hepatic duct. The common hepatic duct joins with the common bile duct to form the common bile duct. The common bile duct enters the duodenum through the ampulla of Vater.