There are several congenital disorders of fructose metabolism resulting from a variety of enzyme deficiencies. These patients have difficulty using fructose for a variety of reasons, of course depending on the specific deficient gene product. Fructose is regularly consumed by humans because of their omnivorous diet that includes fruits (…and other sweets). FBPase-1 deficiency is one example of a deficiency that leads to a disorder of fructose metabolism. Explain why these patients present with hypoglycemia and lactic acidosis during fasting. Which one of these will work to treat a FBPase-1 deficient patient and which one will not? Treatments: Lactose Sucrose Ribose Glycerol

Please describe four different modes of the regulation of the pentose phosphate pathway.

One of the earliest responses to cellular injury is a rapid increase in the levels of enzymes in the pentose phosphate pathway. About ten days after an injury, levels of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in heart tissue are 20 to 30 times higher than normal. However the levels of glycolytic enzymes are only 10% to 20% of normal. Explain this phenomenon.

Please describe four different modes of the regulation of the pentose phosphate pathway.

Yarrowia lipolytica(Yl) is a non-conventional yeast that diverged from baker’s yeast, Saccharomyces cerevisiae(Sc), early in evolutionary history. The regulation of glycolytic enzymes in Yl differs from that of Sc. The figures below show how PFK activity is affected by fructose-2,6-bisphosphate and phosphoenolpyruvate. Based on these data, which molecule is the major regulator of PFK activity in each species?

An individu with chronic hypoglycemia was suspected of having a defect in one of the enzymes unique to gluconeogenesis. To identify the defective enzyme, tissue samples from a normal liver were compared to samples from the patient's liver biopsy, using a biochemical assay that measures glucose production from glycerol or malate. It was found that incubation with glycerol produced normal amounts of glucose in both the control and biopsied liver samples; however, incubation with malate did not lead to glucose production in the liver biopsy, even though it did lead to glucose production in the control liver sample. Based on these observations, which of the 4 unique gluconeogenesis enzymes is most likely defective in the individual? Consider each enzyme and explain your choice, including why you ruled out enzymes that you did not choose. To answer this question, review how glycerol enters gluconeogenesis (figure 9.48) and how citrate cycle metabolites are transported in and out of the…

Describe two types of regulation of the enzyme glutamine synthetase and explain why the regulation of this enzyme is soooo complex.

In gluconeogenesis, only the carbon skeletons of amino acids, not fatty acids, are utilised. So how does fatty acid oxidation in the liver produce brain fuel? Describe the substances and routes involved.

Glucocorticoids (GC) are stress hormones that modulate glucose homeostasis. One effect is to reduce glucose uptake from the bloodstream into skeletal muscle and adipose tissue, to increase the catabolism of expendable proteins in the skeletal muscle, and to increase gluconeogenesis in the liver. Why are these metabolic adaptations important during stressful situations, like fasting/starvation? Predict how the glucocorticoid cortisol will affect blood urea concentrations.

Fatty acid biosynthesis occurs through a series of reactions involving fatty acid synthase (FAS), a polypeptide multienzyme complex. The result of this synthesis is a saturated fatty acid with up to 16 carbon atoms (palmitic acid). Longer fatty acids and unsaturated fatty acids result from modifications to fatty acids produced by FAS activity. What saturated fatty acid gives rise to myristoleic acid, CH3(CH2)3CH=CH(CH2),COOH? H₂ H₂ OH པཱལིནཊྛདྡྷིསཏྟཔཱཎཱསིངྒཱརཨིནྡྷནཾ ཀིཾསུ fatty acid + O2 + NADPH + H+ H3C H H myristoleic acid + 2 H2O + NADP+ Modufy the given molecule of myristoleic acid to show the fatty acid used to produce myristoleic acid. H₁C || Н H OH