Which statement about LDL and HDL is true?

Which statement about LDL and HDL is true?

• A. LDL has low protein density and delivers cholesterol to peripheral tissues; HDL has high protein density and removes cholesterol from tissues
• B. LDL has high protein density and removes cholesterol; HDL has low density and delivers cholesterol
• C. Both LDL and HDL primarily deliver cholesterol to peripheral tissues
• D. HDL carries triglycerides more than cholesterol

Answer: (A)

Lipoproteins differ in density because density reflects how much protein they contain relative to lipids. LDL is relatively low in protein compared to its lipid content, so it is low density, and its main role is to deliver cholesterol to peripheral tissues via receptors on those tissues. HDL, on the other hand, has a higher protein content and is therefore high density; it scavenges excess cholesterol from tissues (including the arterial wall) and returns it to the liver in a process known as reverse cholesterol transport. So the statement that LDL is low density and delivers cholesterol to tissues, while HDL is high density and removes cholesterol from tissues, correctly describes both their densities and functions. The other choices misstate either the densities, the roles, or what each lipoprotein carries (HDL does not primarily carry triglycerides, which are carried more by VLDL and chylomicrons).

Lipoproteins differ in density because density reflects how much protein they contain relative to lipids. LDL is relatively low in protein compared to its lipid content, so it is low density, and its main role is to deliver cholesterol to peripheral tissues via receptors on those tissues. HDL, on the other hand, has a higher protein content and is therefore high density; it scavenges excess cholesterol from tissues (including the arterial wall) and returns it to the liver in a process known as reverse cholesterol transport. So the statement that LDL is low density and delivers cholesterol to tissues, while HDL is high density and removes cholesterol from tissues, correctly describes both their densities and functions. The other choices misstate either the densities, the roles, or what each lipoprotein carries (HDL does not primarily carry triglycerides, which are carried more by VLDL and chylomicrons).