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Lipid Metabolism and Transport Quiz
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Which molecule mainly carries free fatty acids in the bloodstream?
- A Albumin, which binds non-esterified fatty acids in the circulation You picked ✓
- B Micelles, which enclose fatty acids in a phospholipid shell You picked ✕
- C High-density lipoproteins, which remove cholesterol from tissues You picked ✕
- D Very low-density lipoproteins, which carry liver-made triglycerides You picked ✕
- E Chylomicrons, which carry dietary triglycerides You picked ✕
Correct!
Incorrect
The answer is A: Albumin, which binds non-esterified fatty acids in the circulation
Explanation
Why A is correct
See Lipids. Option A is correct. Fatty acids are hydrophobic (they repel water), so they cannot dissolve and travel freely in the watery plasma. Free fatty acids, released from fat stores when glucose is low, are therefore carried bound to albumin, the most abundant plasma protein, which acts as a soluble carrier and delivers them to tissues such as muscle and heart, where they are used for energy. Think of albumin as a taxi for free fatty acids. Fatty acids that are already joined to glycerol as triglycerides (also called triacylglycerols, three fatty acids on one glycerol) travel differently: they are packed inside lipoproteins, which are spheres with a water-friendly phospholipid shell and a fatty core. The difference to learn is therefore free fatty acids on albumin, triglycerides in lipoproteins. Glucagon, released when blood glucose is low, triggers the breakdown of fat stores and so raises the amount of free fatty acids on albumin.
- Problem: Fatty acids are hydrophobic, so they cannot travel freely in the watery plasma.
- Carrier: Free fatty acids travel bound to albumin.
- Contrast: Triglycerides travel inside lipoproteins instead.
Why the other options are incorrect
- B. Micelles, which enclose fatty acids in a phospholipid shell: Micelles help to absorb fats in the gut lumen and are not a transport system in the blood. They are not the plasma carrier of free fatty acids released from fat stores. Your answer
- C. High-density lipoproteins, which remove cholesterol from tissues: HDL carries cholesterol back to the liver and is not the carrier of free fatty acids. It would be the answer for reverse cholesterol transport. Your answer
- D. Very low-density lipoproteins, which carry liver-made triglycerides: VLDL exports triglycerides made in the liver. These are esterified fatty acids, not the free (unesterified) fatty acids released from fat stores, so VLDL is not the main carrier of free fatty acids. Your answer
- E. Chylomicrons, which carry dietary triglycerides: Chylomicrons carry dietary triglycerides, which are fatty acids already joined to glycerol, not free fatty acids. They would be the answer for transport of fat absorbed from a meal. Your answer
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More questions from this set. Start the quiz to answer them and see each explanation.
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1
Which mechanism allows long-chain fatty acids to enter the mitochondrial matrix for energy production?
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2
Which lipoprotein is mainly responsible for transporting dietary triglycerides from the intestine to the peripheral tissues?
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