The following exercises are available in this section
Why does an adult require so much protein in the diet?
By the end of this exercise you should be able to:
- Explain what is meant by nitrogen balance and the conditions under which balance may be negative or positive
- Explain how studies of nitrogen balance can be used to estimate protein requirements
- Explain what is meant by the half-life of a protein, and why different proteins have very different rates of turnover
- Explain what is means by essential and non-essential amino acids, and describe how requirements for essential amino acids can be determined
- Describe and explain the cycling between positive nitrogen balance in the fed state and negative nitrogen balance in the fasting state
- Explain why an adult has a continual need for a dietary intake of protein
- Explain how a high-protein diet may be beneficial for weight reduction
Transamination and deamination of amino acids
By the end of this exercise you should be able to:
- Describe the reaction of transamination and the role of pyridoxal phosphate as the prosthteic group of transaminases
- Describe the reactions involved in overall deamination of various amino acids linked to glutamate dehydrogenase and aspartate transaminase
- Explain how the keto-acids of essential amino acids can be used in treating patients in renal failure
- Expain how red blood cell transaminases can be used to assess vitamin B6 nutritional status
Urea synthesis in the liver, and potentially fatal hyperammonaemia in a child
By the end of this exercise you should be able to:
- Explain the catalytic effect of adding arginine, and other metabolites on the rate of urea synthesis from ammonium in liver, and describe the pathway of urea synthesis
- Describe the main pathways of ammonium formation in liver and its incorporation into urea
- Explain the importance of N-acetylglutamate in urea synthesis
- Explain how supplements of arginine are beneficial in the treatment of hyperammonaemia associated with argininosuccinic aciduria
- Describe the enterohepatic circulation of urea
An unconscious child with hyperammonaemia and keto-acidosis
By the end of this exercise you should be able to:
- Describe the metabolism of propionyl CoA
- Describe the function of carnitine in muscle metabolism
- Explain the importance of N-acetylglutamate for ammonia metabolism
Gout and hyperuricaemia - and anti-cancer drugs
By the end of this exercise you should be able to:
- Describe the synthesis and catabolism of purines
- Describe in outline the renal handling of uric acid
- Explain why inhibition of xanthine oxidase is effective for the treatment of gout
- Explain how folic acid antimetabolites, glutamine analogues and mercaptopurine act to inhibit purine synthesis and are effective anti-cancer agents
- Describe the regulation of purine synthesis and the importance of PRPP amidotransferase and the availability of phosphoribosyl pyrophosphate
- Describe the process of purine salvage and explain the consequences of partial or more or less complete lack of hypoxanthine-guanine phosphoribosyltransferase
A severe sunburn-like rash and unusual urinary metabolites
By the end of this exercise you should be able to:
- Describe and explain the group specific nature of amino acid transport across cell membranes
- Explain how small peptides are absorbed from the small intestine
- Describe in outline the synthesis of NAD from tryptophan