biochem ch 19

The brain requires a constant input of glucose. The metabolic activity of which organ(s) is/are necessary to maintain the concentration of glucose required by the brain when dietary glucose is low?

Adipose tissue, kidney, liver

How do the effects of leptin and insulin signaling on anorexigenic and orexigenic neurons compare?

Both activate anorexigenic neurons and inhibit activation of orexigenic neurons.

How does ephedrine work to stimulate weight loss?

Fatty acid oxidation is increased

Insulin signals for an increase in glucose uptake in both skeletal muscle and adipose tissue. Which of the following correctly describes how these organs use this glucose?

Glucose in muscle cells is completely oxidized or stored as glycogen, depending on the ATP demand. In adipose tissue, glucose is used to synthesize fatty acids and glycerol.

Individuals who develop type 2 diabetes are often overweight or obese (i.e., exhibit hyperlipidemia), although there is no correlation between weight and the development of type 1 diabetes. Why does obesity contribute to the development of type 2 diabetes?

Hyperlipidemia reduces adiponectin release from adipose tissue.

Patients with type 1 diabetes must inject insulin up to several times a day and monitor their carbohydrate intake to regulate their blood glucose level. The amount of insulin injected is based on the carbohydrate content of the diet and so must be adjusted accordingly; otherwise, hypoglycemia will result. Which of the following explain(s) why injecting too much insulin before a meal results in hypoglycemia?

Increased glucose uptake, Increased glycogen storage, Decreased glucose synthesis

Pancreatic β cells release insulin from intracellular vesicles. This release is regulated in part by the activity of glucokinase. How would insulin release be affected if pancreatic β cells were mutated to express hexokinase rather than glucokinase?

Insulin release from pancreatic β cells would be constant if hexokinase was expressed rather than glucokinase, and expression of insulin would not be affected by changes in the serum glucose.

Genetic studies with OB and DB mice identified leptin as a possible regulator of obesity. Which observations in humans indicated that the relationship between leptin and obesity in mice could not be used as a model to study obesity in humans?

Leptin levels are elevated in obese humans and leptin receptor mutations are rare.

Terri and Ronise are both runners. Terri is a short-distance runner for the university track team and competes primarily in 100-meter and 200-meter sprints. Ronise competes in local 10K races and has even completed a half-marathon. Terri notices that Ronise brings glucose gels with her on her longer training runs. Terri asks Ronise if the glucose gels could give her a boost if she ate one halfway through her 200-meter sprint. What should Ronise tell her?

No, ingesting a glucose gel during a 200-meter sprint will not provide useful fuel, and may even decrease the efficiency of ATP synthesis.

Elevated levels of free fatty acids and elevated levels of TNF-α can both result in a decrease in sensitivity to insulin. What do the mechanisms of both have in common?

Serine phosphorylation on the insulin receptor substrate protein

More ATP per carbon is produced from oxidation of fatty acids as compared to glucose. However, fatty acids are used primarily to provide fuel for ATP synthesis during long periods of exercise. Why can't fatty acids be used to fuel short, intense periods of exercise?

Short, intense periods of exercise do not provide sufficient time for oxidative phosphorylation to occur.

Which of the following reactions or pathways is/are activated by insulin signalling in the liver but are not affected in the muscle under the same conditions?

Synthesis of glucose-6-phosphate, Synthesis of malonyl-CoA

Insulin-stimulated glucose uptake and utilization by skeletal muscle and liver cells results in a reduction in the blood glucose level. Which organ is primarily responsible for the decrease in serum glucose, and why?

The skeletal muscle is responsible for the majority of glucose uptake, as the total mass of skeletal muscle is greater than the mass of liver cells.

Peroxisome proliferator-activated receptor (PPAR) nuclear receptor agonists represent an attractive class of protein targets for the development of pharmaceutical drugs for treating human metabolic disease. These drugs can be used to treat high cholesterol and type 2 diabetes. PPARα activation is known to induce expression of HDL-specific proteins, leading to an increase in HDL concentration and reverse cholesterol transport. PPARα activation also inhibits sterol response element binding protein-2 (SREBP2), a transcripton factor that activates synthesis of HMG-CoA reductase and the LDL receptor.

Yes, treatment with PPARα-specific agonists affects cholesterol transport and uptake as well as synthesis, whereas statins affect synthesis only.

Process that would disrupt the regulation of metabolic homeostasis

insulin release from the pancreas, glucagon release from the pancreas, somatostatin release from the pancreas, PPAR nuclear receptor activation