Biochemistry Quiz: Lipid Metabolism

Lipoprotein lipase is an enzyme that plays a crucial role in breaking down triglycerides in circulating lipoproteins, allowing the release of fatty acids for various metabolic processes. It is primarily found on the luminal surface of the capillary endothelium in tissues that require high levels of fat metabolism, such as adipose tissue and lactating breast. Therefore, the statement that lipoprotein lipase is located on the luminal surface of the capillary endothelium of lactating breast is true.

Measuring plasma lipids in brain stroke patients is important because it can provide valuable information about the patient's cardiovascular health. Elevated levels of plasma lipids, such as cholesterol and triglycerides, are known risk factors for stroke and other cardiovascular diseases. By measuring these lipid levels, healthcare professionals can assess the patient's risk and make appropriate treatment decisions. Additionally, monitoring lipid levels can help evaluate the effectiveness of interventions, such as lifestyle changes or medication, in managing the patient's cardiovascular health. Therefore, it is crucial to measure plasma lipids in brain stroke patients.

The polar lipid surface layer of lipoproteins contains cholesterol. Cholesterol is a type of lipid that is essential for the structure and function of cell membranes. It plays a crucial role in maintaining the integrity and fluidity of the lipid bilayer. Lipoproteins are complexes of lipids and proteins that transport cholesterol and other lipids in the bloodstream. The polar lipid surface layer of lipoproteins contains phospholipids, which are a type of lipid, and cholesterol. Therefore, the statement is true.

The statement "Body can synthesize essential FAs" is incorrect. Essential fatty acids (EFAs) are fatty acids that cannot be synthesized by the body and must be obtained from the diet. The body can only synthesize non-essential fatty acids.

High-density lipoprotein (HDL) is commonly known as "good" cholesterol because it helps remove excess cholesterol from the bloodstream and carries it back to the liver for processing and elimination. It does not transport cholesterol to extrahepatic tissues; instead, it works to prevent the buildup of cholesterol in the arteries. Therefore, the correct answer is False.

Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone. One of the effects of hypothyroidism is an increase in LDL cholesterol levels in the blood. LDL cholesterol is often referred to as "bad" cholesterol because high levels of it can lead to the buildup of plaque in the arteries, increasing the risk of heart disease. Therefore, the statement "Hypothyroidism increases LDL cholesterol in circulation" is correct.

The statement is false because LDL cholesterol is actually considered a more important risk factor for coronary heart disease (CHD) compared to hypertriglyceridemia. LDL cholesterol is often referred to as "bad" cholesterol because high levels of it can lead to the buildup of plaque in the arteries, increasing the risk of CHD. Hypertriglyceridemia, on the other hand, refers to high levels of triglycerides in the blood and is typically considered a secondary risk factor for CHD.

Familial hypertriglyceridemia is a genetic disorder characterized by high levels of triglycerides in the blood. It is caused by mutations in genes that affect the metabolism of lipoproteins, particularly the production and clearance of apolipoprotein B (apoB) particles. These mutations can lead to impaired clearance of triglyceride-rich lipoproteins, resulting in elevated triglyceride levels. Therefore, the correct answer is False, as familial hypertriglyceridemia is not caused by hepatic overproduction of apoB, but rather by impaired clearance of triglyceride-rich lipoproteins.

Apolipoprotein E is a protein involved in the metabolism of lipoproteins. It can be found in several types of lipoproteins, including IDL (intermediate-density lipoprotein). Therefore, the statement that "Apolipoprotein E can exist in IDL" is correct.

Mobilizing lipase is activated by the decrease in glucagon and increase in insulin, not the other way around. Glucagon stimulates the breakdown of stored glycogen into glucose, while insulin promotes the storage of glucose as glycogen. When insulin levels decrease and glucagon levels increase, it signals the body to break down stored fat for energy, activating mobilizing lipase.

Remnant hyperlipoproteinemia is a condition characterized by elevated levels of triglyceride-rich lipoproteins, such as chylomicrons and very low-density lipoproteins (VLDL). It does not directly increase LDL cholesterol levels. LDL cholesterol levels are primarily affected by other factors such as genetics, diet, and lifestyle choices. Therefore, the statement that remnant hyperlipoproteinemia increases LDL cholesterol is false.

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The number of LDL-apoB receptors on the cell surface is regulated by the cholesterol pool. This means that when there is a high level of cholesterol in the body, the number of LDL-apoB receptors decreases, leading to a decrease in the uptake of LDL particles by cells. On the other hand, when the cholesterol level is low, the number of receptors increases, allowing for more LDL uptake. This regulation helps maintain cholesterol homeostasis in the body and prevents excessive accumulation of LDL particles, which can lead to health issues such as atherosclerosis.

The incorrect option is "High P/S ratio increase LDL cholesterol." This statement is incorrect because a high polyunsaturated to saturated (P/S) ratio actually decreases LDL cholesterol levels.

Tangier disease is a rare genetic disorder characterized by the absence or severe reduction of high-density lipoprotein (HDL) levels in the blood. HDL is responsible for removing cholesterol from the bloodstream and transporting it to the liver for excretion. In Tangier disease, the lack of functional HDL leads to the accumulation of cholesterol in various tissues, including the tonsils, spleen, and liver. Therefore, the statement that Tangier disease reduces HDL levels is correct.