Question

Lipoprotein lipase A. is an intracellular enzyme. B. is stimulated by cAMP-mediated phosphorylation. C. functions to mobilize stored triacylglycerols from adipose tissue. D. is stimulated by one of the apoproteins present in VLDL. E. produces free fatty acids and a monoacylglycerol.

Short answer

A. It is an intracellular enzyme. B. It is stimulated by cAMP-mediated phosphorylation. C. It mobilizes stored triacylglycerols from adipose tissue. D. It is stimulated by one of the apoproteins present in VLDL. E. It does not produce free fatty acids and a monoacylglycerol. Answer: D. Lipoprotein lipase is stimulated by one of the apoproteins present in VLDL.

Step-by-step solution

Analyze each option

To determine the correct answer, let's analyze each option individually. A. Lipoprotein lipase is an extracellular enzyme, not an intracellular enzyme. It is primarily found on the surface of capillary endothelial cells. B. Lipoprotein lipase is not stimulated by cAMP-mediated phosphorylation. It is stimulated by insulin. C. Lipoprotein lipase does not mobilize stored triacylglycerols from adipose tissue. It is responsible for hydrolyzing triacylglycerols in circulating lipoproteins, such as chylomicrons and VLDL, to release free fatty acids and monoacylglycerols. D. Lipoprotein lipase is stimulated by apoprotein C-II, which is present in VLDL and chylomicrons. When bound to a lipoprotein, apoprotein C-II activates lipoprotein lipase and facilitates the hydrolysis of triacylglycerols. E. Lipoprotein lipase indeed produces free fatty acids and a monoacylglycerol as it hydrolyzes triacylglycerols in circulating lipoproteins.

Identify the correct answer

Based on our analysis, we can conclude that the correct answer is: D. Lipoprotein lipase is stimulated by one of the apoproteins present in VLDL.

Key concepts

Biochemistry Education

Biochemistry is the study of the chemical processes and substances which occur within living organisms. Biochemistry education focuses on imparting knowledge about the biomolecular components that drive cellular activities, including enzymes, lipids, DNA, RNA, and their interactions.

Lipoprotein lipase (LPL) is a critical enzyme taught within the realm of lipid metabolism, a core topic in biochemistry courses. Understanding how LPL functions is essential for grasping its role in health and disease. Educators employ various methods, from visual aids to interactive models, to ensure students learn how LPL interacts with lipoproteins in our body, offering a thorough insight into its biological significance. An example would be analyzing the function of LPL in the context of varying nutritional states or in pathological conditions like hyperlipidemia.

Enzyme Function

Enzymes are catalysts that accelerate biochemical reactions in the body without being consumed in the process. The function of enzymes, like lipoprotein lipase, is a pivotal concept in biochemistry which explains how these biological molecules influence various physiological processes.

LPL serves as an excellent example to illustrate enzyme specificity and regulation. Located on the surface of endothelial cells lining the blood vessels, LPL specifically hydrolyzes the triacylglycerols (fats) in lipoproteins into free fatty acids and monoacylglycerol. This action is crucial for the lipid metabolism as it allows the released fatty acids to be absorbed by adjacent tissues, such as muscle and adipose tissue. Activation of LPL by apoprotein C-II (as mentioned in the exercise solution) and its regulation by insulin and nutritional state are key regulatory mechanisms that emphasize the fine-tuned control our body exerts over enzyme function.

Lipid Metabolism

Lipid metabolism involves the synthesis and degradation of lipids in cells and is vital for maintaining energy homeostasis in the body. The role of lipoprotein lipase in lipid metabolism is central to the understanding of how the body processes dietary fats as well as how fats are stored and mobilized.

LPL plays the initial step in the catabolism of circulating chylomicrons and Very Low-Density Lipoproteins (VLDL), which transport triacylglycerols from the gut and liver, respectively, to peripheral tissues. The free fatty acids produced by the action of LPL can be either used immediately as a source of energy or can be re-esterified and stored in adipose tissue for future use. Therefore, through its hydrolytic activity, lipoprotein lipase directly influences the level of circulating lipids and plays a key role in energy balance and lipid storage, which is critical to maintaining proper health.