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biology 0610printed 161 · PDF 161

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printed 161 · PDF 161

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161 Urea is made from excess proteins and amino acids Amino acids travel to the liver through the hepatic portal vein. The required amino acids are allowed to travel throughout the body through blood. The excessive amino acids are broken down into 2 parts with help of enzymes: one that contains energy and the nitrogen part The energy part is stored for future use as carbohydrates. The Nitrogen part is turned into urea. The removal of nitrogen from the amino acids to form urea is known as deamination. Pathway of Urine in the kidney Blood flows into the kidneys through the renal artery. The renal artery is divided into small capillaries known as glomeruli. Blood is filtered as it passes through glomeruli. Small molecules (the filtrate) such as urea,glucose,ions and water pass through it whereas large molecules don't. As the filtrate move into the nephrons, some of it such as urea and excessive water and ions are needed to be lost from body On the other hand glucose and some amount of water is needed for the body so they are taken back into blood. This process is known as reabsorption At the end the final liquid coming out of nephron consists of urea, excessive water and excessive ions. More concentrated urine the darker its color is so the color of urine is a good indication of how well the body is hydrated. Homeostasis Keeping the internal environment of the body constant is known as homeostasis. Blood Glucose Concentration It is controlled by hormones, secreted by pancreas In the pancreas a group of cells called islets secrete these hormones. The 2 hormones are insulin and glucagon If the blood glucose concentration increases the islet cells detect this change. They secrete insulin which travels in blood to the liver. The liver, identifying the insulin, converts the glucose in the blood stream into a large complex known as glycogen. On the other hand, if there is less concentration of glucose in the blood, glucagon is released. Now the liver breaks down its store of glycogen and balances the glucose in the blood. Set point is the normal value or range of values for a particular parameter.