Q.16 Describe hemoglobin role in the transport of oxygen. (2011)
Ans. Transport of O2: -
Water has poor solubility for O2. Hence blood plasma is a poor carrier of this gas. That is why the R.B.Cs. of blood are specialized to carry oxygen. About 97% of the O2 transported by blood is actually carried by the hemoglobin of R. B.Cs. Hemoglobin is a complex hemeprotein, which forms oxyhemoglobin.
Hb4 (hemoglobin) + 4O2 --> Hb(O2)4
Oxyhemoglobin
The remaining 3% of O2 transported by blood is found dissolved in its plasma. Since O2 is highly soluble in lipids, some of it is presumably transported as bound with the cell membrane of R.B.Cs.
Since the blood drained from lungs includes not only the oxygenated blood but also some deoxygenated blood that has supplied its O2 to those parts of lungs in which gaseous exchange does not occurs, the po2 of this blood is actually about 95 to 97 mmng instead of 104 mmng. At this po2, the hemoglobin of blood is about 97% saturated with O2. After receiving this blood from the lungs, the heart pumps it into the arteries which carries it to all part of the body, while flowing through the capillary neturoks in various tissues, this blood supplied O2 to all cells in exchange of CO2. This gaseous exchange between arterial blood and body cell is called internal respiration. It obviously occurs through the medium of tissue or intestinal fluid.
The po2 in tissue fluids of different tissues considerably varies according to the metabolic rates of concerned cells, but it averages only about 40 mmng. whereas the po2 in the arterial blood supplying the tissues 95 mmng.
CO2 continuously forms in all cells as a waste product of catabolism. Since however the CO2 diffuses about 20 times faster than O2, soon as the PCO2 rises in the cells, CO2 diffuses out from the cells into the tissue fluid and then into the capillary blood. Its pco2 in tissue fluid is about 45 and 46 mmng. The arterial blood entering into the tissue has a pco2 of 40 mmng. By the time the blood leaves the tissues as deoxygenarated, verious blood, its pco2 obviously becomes 45 to 46 mmng.
Q.17. Write an account of the intestinal digestion of food and its hormonal control. (2012)
Related Questions -
Q. Describe the physiology of digestion in human. (2014)
Ans. Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones.
When food enters the mouth, its digestion starts by the action of mastication, a form of mechanical digestion, and the contact of saliva. Saliva, which is secreted by the salivary glands, contains salivary amylase, an enzyme which starts the digestion of starch in the food. After undergoing mastication and starch digestion, the food will now be in the form of a small, round mass, called a bolus. It will then travel down the esophagus and into the stomach by the action of peristalsis. Gastric juice in the stomach starts protein digestion. Gastric juice mainly contains hydrochloric acid and pepsin. As these two chemicals may damage the stomach wall, mucus is secreted by the stomach, providing a slimy layer that acts as a shield against the damaging effects of the chemicals. At the same time protein digestion is occurring, mechanical mixing occurs by peristalsis, which are waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes. After some time (typically an hour or two in humans, 4–6 hours in dogs, somewhat shorter duration in house cats), the resulting thick liquid is called chyme. When the pyloric sphincter valve opens, chyme enters the duodenum where it mixes with digestive enzymes from the pancreas, and then passes through the small intestine, in which digestion continues. When the chyme is fully digested, it is absorbed into the blood. 95% of absorption of nutrients occurs in the small intestine. Water and minerals are reabsorbed back into the blood in the colon (large intestine). Some vitamins, such as biotin and vitamin K (K2MK7) produced by bacteria in the colon are also absorbed into the blood in the colon. Waste material is eliminated during defecation.
Digestive hormones: -
Action of the major digestive hormones
There are at least five hormones that aid and regulate the digestive system in mammals. There are variations across the vertebrates, as for instance in birds. Arrangements are complex and additional details are regularly discovered. For instance, more connections to metabolic control (largely the glucose-insulin system) have been uncovered in recent years.
· Gastrin - is in the stomach and stimulates the gastric glands to secrete pepsinogen (an inactive form of the enzyme pepsin) and hydrochloric acid. Secretion of gastrin is stimulated by food arriving in stomach. The secretion is inhibited by low pH .
· Secretin - is in the duodenum and signals the secretion of sodium bicarbonate in the pancreas and it stimulates the bile secretion in the liver. This hormone responds to the acidity of the chyme.
· Cholecystokinin (CCK) - is in the duodenum and stimulates the release of digestive enzymes in the pancreas and stimulates the emptying of bile in the gall bladder. This hormone is secreted in response to fat in chyme.
· Gastric inhibitory peptide (GIP) - is in the duodenum and decreases the stomach churning in turn slowing the emptying in the stomach. Another function is to induce insulin secretion.
· Motilin - is in the duodenum and increases the migrating myoelectric complex component of gastrointestinal motility and stimulates the production of pepsin.
Q.18. What are the respiratory pigments? Decribe briefly the transport of gasses. (2012, 15)
Other Related Questions -
Q. Write short note on respiratory pigments. (2018)
Ans. A respiratory pigment is a molecule, such as hemoglobin in humans, that increases the oxygen-carrying capacity of the blood. The four most common invertebrate respiratory pigments are hemoglobin, haemocyanin, haemerythrin and chlorocruorin. Hemoglobin is bright red when oxygenated, and dark red(purplish) when deoxygenated, oxygenated haemocyanin is blue in color, deoxygenated is almost colorless. Oxygenated chlorocruorin turns from green to red where oxygenated haemerythrin is a violet to pink colour, and colorless when deoxygenated. All vertebrates use the hemoglobin respiratory pigment.
Respiration (physiology) -
In physiology, respiration (often confused with breathing) is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction. This is in contrast to the biochemical definition of respiration, which refers to cellular respiration: the metabolic process by which an organism obtains energy by reacting oxygen with glucose to give water, carbon dioxide and ATP (energy). Although physiologic respiration is necessary to sustain cellular respiration and thus life in animals, the processes are distinct: cellular respiration takes place in individual cells of the organism, while physiologic respiration concerns the bulk flow and transport of metabolites between the organism and the external environment.
In unicellular organisms, simple diffusion is sufficient for gas exchange: every cell is constantly bathed in the external environment, with only a short distance for gases to flow across.
In plants oxygen is produced in photosynthesis but most oxygen used in plant respiration enters passively by diffusion or through structural openings such as lenticels.
Complex multicellular animals such as humans have a much greater distance between the environment and their innermost cells, thus, a respiratory system is needed for effective gas exchange. The respiratory system works in concert with a circulatory system to carry gases to and from the tissues.
In air-breathing vertebrates such as humans, respiration of oxygen includes four stages:
· Ventilation, moving of the ambient air into and out of the alveoli of the lungs.
· Pulmonary gas exchange, exchange of gases between the alveoli and the pulmonary capillaries.
· Gas transport, movement of gases within the pulmonary capillaries through the circulation to the peripheral capillaries in the organs, and then a movement of gases back to the lungs along the same circulatory route.