BIOB111 - Tutorial activity for Session 25 General topics for week 14 Session 25 The metabolism of proteins Students are asked to draw the concept map showing all details of protein metabolism 1 Instructions: Use the following link to check your understanding about protein metabolism http://wwwwileycom/college/fob/quiz/quiz20/20-8html (Link verified 8 October 2015) Use this link to check your understanding of deamination: http://nutritionjbpubcom/resources/animationscfm?id=18&debug=0 (Verified 8 October 2015 Matching 1Peptide bond hydrolysis (a) Degradation of amino acids in the liver, usually produces glutamate and a new α-keto acid 2 Transaminase (b) Inactive form of an enzyme that is activated by stomach HCl 3 Oxidative Deamination (c) Exogenous (dietary) and endogenous protein is catabolized then some of it used for anabolism of protein, DNA and other nitrogen-containing compounds 4 Pepsinogen (d) Removes the amino group as an ammonium ion from glutamate 5 protein turnover (e) gastric pepsin and duodenal trypsin & chymotrypsin Then answer the following questions: 2 Protein turnover is important because a) Enzymes and structural proteins are regularly broken down and re-made so that they are often being replaced by new amino acids from our diet or other amino acids in the blood b) Once anabolized, proteins in the body never need to be replaced c) Unless the protein molecule is turned over on its side, it might only get damaged on one side Last Updated on 6-Feb-14 Page 1 of 5
3 Transamination generally involves a) α-ketoglutarate being converted to glutamate at the same time as another amino acid is converted to its related α-ketoacid b) glutamate being converted to α-ketoglutarate and ammonium ion c) Both of the above metabolic pathways are part of transamination of amino acids 4 Urea cycle occurs in: a) Cytoplasm b) Mitochondria c) Both cytoplasm and mitochondria d) In lysosomes 5 Glucogenic amino acids a) Provide carbon atoms for acetyl Co A production b) Provide carbon atoms for glucose production c) Both of the above 6 Ketogenic amino acids a) Provide carbon for acetyl Co A and acetoacetyl Co A production b) Provide carbon atoms for glucose production c) Both of the above 7 Oxidative deamination generally involves a) α-ketoglutarate being converted to glutamate at the same time as another amino acid is converted to its related α-ketoacid b) glutamate being converted to α-ketoglutarate and ammonium ion c) Both of the above metabolic pathways are oxidative deamination of amino acids 8 Describe the digestion of protein Your answer should include the enzymes and the bonds hydrolysed 9 A 5 year old female child was referred for incidentally detected hyperammonaemia 2 years previously Her plasma ammonia level at that time was 110 μmol/l(reference range 10-50 μmol/l) The patient had projectile vomiting and convulsions She was found to have a mild defect in ornithine transcarbamylase an important enzyme in the urea cycle a) Describe how ammonium ion is formed in the liver b) Describe the urea cycle in terms of: Its primary function in the body Where it occurs in the body Last Updated on 6-Feb-14 Page 2 of 5
The reactions involved and where energy in the form of ATP is used Its clinical importance c) Why would a person on a high protein diet be instructed to drink large quantities of water? 10 a) What is PKU? b) How is PKU treated / managed? (http://wwwdnalcorg/view/15963-what-is-phenylketonuria-html (Link verified 8 October 2015) 11 Describe briefly how the carbon skeleton is used up in the body after the break down of an amino acid 12 Differentiate between glucogenic and ketogenic amino acids Give an example for each 13 What is the end product of protein catabolism? 14 Why is ammonia toxic and how does the body try to eliminate it? Use the following link to find out about how ammonia affects the system Revision Questions Lipid metabolism 15 How are stored fats mobilized for oxidation? 16 Where and how are fatty acids activated prior to ß oxidation? How many ATP equivalents are used? Last Updated on 6-Feb-14 Page 3 of 5
17 How are fatty acyl-coas transported to the site of ß oxidation? Where is the site of oxidation? Explain the process What is produced during one cycle of ß oxidation? 18 How many reduced coenzymes are produced per cycle 19 How many cycles are needed to completely metabolise palmitate and Stearate? 20 What is the net yield of ATP from palmitate and Stearate? 21 Miss Belinda is 18 years old Her body weight is 100 kg and her height 155 cm She decided to change her diet and switch to high protein and low carbohydrate diet in order to reduce her weight On urine examination, her urine was found to have ketone bodies a) Describe the mechanism of ketone bodies formation in the above case b) Name the three ketone bodies c) Under what other conditions does ketogenesis occur? Explain 22 Describe the synthesis of fatty acid (its location and the important enzyme and coenzyme involved in the process) 23 Discuss the hydrolysis of triglycerides by lipase enzymes in the lumen and wall of the small intestine and in the adipocytes 24 How are triglycerides transported in the portal circulation? 25 How is cholesterol transported in the systemic circulation? Revision Questions Protein metabolism 26 What are the proteolytic enzymes required for digestion of protein and in which organ of the gastrointestinal tract are these enzymes made / active? Last Updated on 6-Feb-14 Page 4 of 5
27 Explain transamination and oxidative deamination 28 Which of the following statements concerning the compound urea is incorrect? a It is a white solid in the pure state b It is very soluble in water c It gives urine its odor and color 29 Which of the following compounds is a urea cycle intermediate? a carbamoyl phosphate b aspartate c ornithine Last Updated on 6-Feb-14 Page 5 of 5