35. Which one of the following statements relating to lipids and membranes is correct?
(A) Triacylglycerols are the major component of most cell membranes.
(B) Clusters of cholesterol molecules are generally used to provide ion channels.
(C) Na⁺ and K⁺ ions readily diffuse through the lipid bilayer.
(D) Both saturated and unsaturated fatty acyl groups are used in typical phospholipids.
(E) All phospholipids incorporate a glycerol unit as part of their structure.

31. Which one of the following statements relating to proteins is correct? (A) All proteins have quaternary structure. (B) Histidine is often found at the active site of globular proteins. (C) The primary structure of a protein describes the amino acid composition, but not the amino acid sequence. (D) Both alpha-helix and beta-sheet segments occur as secondary structural elements in all proteins. (E) When proteins are denatured, they can never be reconstituted back to a functional state.

32. The Type II glycogen disease (Pompe’s disease) is lack of _______. (A) glucose-6-phosphatase (B) glucose-1-phosphatase (C) lysosomal alpha-1 to 4- and 1 to 6- glucosidase (acid maltase) (D) debranching enzyme (E) branching enzyme

33. Severe combined immunodeficiency disease (SCID) is caused by deficiency of_______ . (A) adenosine deaminase (B) thymidine kinase (C) xanthine oxidase (D) DNA ligase (E) hypoxanthine-guanine phosphoribosyltransferase

34. Which one of the following statements about natural fatty acids is correct? (A) Molecules with odd and even numbers of carbon atoms are equally common. (B) All of the natural fatty acids are unsaturated. (C) Fatty acids provide a useful source of intermediates for gluconeogenesis. (D) Oxidation of fatty acids can lead to the production of ketone bodies. (E) The natural unsaturated fatty acids most commonly have their double bonds in trans geometry.

36. Which one of the following statements about cholesterol is correct? (A) The complete oxidation of cholesterol to CO2 and H2O occurs in the liver as an energy source. (B) Cholesterol esters are an important component of the outer monolayer of lipoproteins. (C) Some cholesterol synthesis occurs in the liver but most takes place in other tissues. (D) Beta-hydroxy-beta-methylglutaryl-CoA is generated from three molecules of acetyl-CoA and is an intermediate in cholesterol biosynthesis. (E) Cholesterol is an important precursor for the production of the various prostaglandins, important in a broad range of physiological roles. 

37. Which of the following enzymes in liver is/are activated as a result of an elevated insulin level after a meal? (A) cAMP-dependent protein kinase and adenylate cyclase (B) Fructose 1,6 bisphosphate (FBPase-1) (C) Glycogen phosphorylase, phosphokinase (D) Glycogen synthase, phosphofructo-kinase-1 (PFK-1), and pyruvate kinase (E) Phosphoenolpyruvate carboxykinase (PEPCK)

38. Oncogenes that have tyrosine kinase activity_______ . (A) probably correspond to protooncogenes that are growth factor receptors (B) probably correspond to protooncogenes that are polypeptide growth factors (C) are probably Gs proteins (D) are probably Gi proteins (E) are probably DNA binding proteins

39. Correct statements regarding arachidonic acid include all of the following except_______ . (A) it is a precursor of thromboxane A2 (B) it activates lipoxygenase (C) it is a 20-carbon fatty acid with three double bonds (D) it can be derived from linoleic acid (E) it is esterified to the sn-2 position of glycerophospholipids

40. The cost in high-energy phosphate bonds for the formation of 1 mol of glucose from lactate is_______ . (A) 8 mol of ATP (B) 6 mol of ATP (C) 4 mol of ATP (D) 2 mol of ATP (E) none of the above

41. In the sequence of reactions that convert lactate to glucose in cells capable of gluconeogenesis, three reactions are used to bypass enzymes of the glycolytic pathway in which glucose is converted to lactate. All of the following enzymes fall into this category except_______ . (A) pyruvate carboxylase (B) pyruvate dehydrogenase (C) phosohoenolpyruvate carboxykinase (D) fructose 1,6-diphosphatase (E) glucose 6-phosphatase