Answer to Question #188388 in Biochemistry for Kei

Question

 

1. What would be the metabolic consequences of cells not expressing LDL receptors?

2. Vitamin D3 is derived from cholesterol. How and in which tissues does conversion occur?

3. How much energy, in the form of ATP, is obtained from b-oxidation of 1 mol of linoleic acid?

Answer 1

1. Uptake of cholesterol, mediated by the low-density lipoprotein (LDL)-receptor, plays a crucial role in lipoprotein metabolism. The LDL-receptor is responsible for the binding and subsequent cellular uptake of apolipoprotein B- and E-containing lipoproteins. Therefore, metabolism of lipoprotein will not occur for cells not expressing LDL receptors.
2. The skin is responsible for producing vitamin D. During exposure to sunlight, ultraviolet radiation penetrates into the epidermis and photolyzes provitamin D₃ to previtamin D₃. Previtamin D₃ can either isomerize to vitamin D₃ or be photolyzed to lymisterol and tachysterol. Its conversion occurs in the liver tissue.
3. 14 ATP