Biology 9700 · AS & A Level · The circulatory system
The circulatory system — practice question
Cholesterol is made in the smooth endoplasmic reticulum (SER) of liver cells through a sequence of enzyme-catalysed reactions. In the SER, cholesterol and triglyceride molecules are enclosed by proteins and phospholipids, forming lipoproteins. These lipoprotein particles then move into the Golgi apparatus, where they are packaged into vesicles and carried to the blood. Fig. 4.1 is an electron micrograph of part of a liver cell showing lipoprotein particles within the Golgi apparatus.
(a)[3]
Name structure T in Fig. 4.1 and state its function in liver cells.
(b(i))[1]
Suggest why cholesterol is assembled into lipoproteins before it is released from cells into the blood.
(b(ii))[2]
Explain why body cells need to be supplied with cholesterol.
(c)[2]
Cholesterol is also loaded into vesicles by the SER and then secreted from the cell into tiny fluid-filled spaces between the liver cells. These spaces join up to form ducts that drain into the gall bladder to make bile. Suggest how cholesterol is secreted into ducts, such as the duct in Fig. 4.1.
(d)[1]
State one function of the Golgi apparatus other than packing substances into vesicles for transport.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “the mitochondrion / the outer mitochondrial membrane” …