EXCESS AMINO ACIDS, NITROGNEOUS WASTE AND THE KIDNEYS ESSAY Describe what happens to excess AMINO ACIDS present in the intestine of the human body after consuming a meal rich in PROTEIN and how the resulting NITROGENOUS WASTE is sent to and removed from the body by the KIDNEYS. Facts: 17 marks Synthesis: 3 marks DEALING WITH EXCESS AMINO ACIDS The amino acids are absorbed into the villi and transported by the capillary network into the hepatic portal vein which takes it to the liver where excess amino acids are de-aminated to form carbohydrate and urea REMOVAL OF THE NITROGENOUS WASTE The urea is send via the hepatic vein to the heart and via the renal artery to the kidneys. The urea enters the glomerulus of the Bowmans capsule from where it passes into the capsular space of the Bowmans capsule. Here it becomes part of the glomerular filtrate. As the filtrate moves through the renal tubule more urea may be added to it from the second capillary network at the distal tubule by tubular excretion. The accumulated urea then passes into the collecting tubules and into the pelvis of the kidney where it forms part of urine. The urine is then sent to the bladder via the ureters from where it is passed to the exterior via the urethra LIFE SCIENCE – GRADE 11 ESSAY - CELLULAR RESPIRATION AND GAS EXCHANGE – 20 Marks Describe The Phase Of Cellular Respiration That Releases Carbon Dioxide And How This Gas Is Then Taken To The Lungs And Released Into The Atmosphere RELEASE OF C02 FROM KREBS CYCLE C02 is released during the Krebs cycle of cellular respiration Which occurs only if oxygen is present The pyruvic acid produced during glycolysis enters the mitochondrion where it is used in a cyclic series of reactions Energised hydrogen atoms and C02 are released during these reactions any (4) TRANSPORT OF C02 THE LUNGS As it is produced from cellular respiration the C02 concentration in the cells increase This creates a concentration gradient with the blood C02 diffuses into the blood It is transported in the blood in three ways: 1. Dissolved in the plasma 2. Combined with haemoglobin to form carbhaemoglobin 3. Combined with water to form bicarbonate ions The blood reaching the lungs accumulate C02 from other cells along the way Creating a concentration gradient with the air in the lungs C02 diffuses through the squamous epithelium of the alveolus into the lung any (8) RELEASE OF C02 FROM THE LUNGS The C02 is then exhaled from the lungs During exhalation the diaphragm relaxes and becomes arched. The length of the thoracic cavity (i.e. top to bottom distance) is decreased The external intercostal muscles relax and the rib cage is lowered This causes the side-to side and back-to-front distance of the thoracic cavity to decrease The total volume of the thoracic cavity decreases and pressure on the lung (interpleural pressure) increases Air rich in carbon dioxide is forced out of the lungs LIFE SCIENCE - GRADE 11 any (5) Content (17) Synthesis (3) Total (20)
Posted on: Wed, 17 Sep 2014 13:22:44 +0000
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