As noted earlier, the first step in glycolysis, which occurs within cells, is phosphorylation of glucose to glucose 6-phosphate. Why does this step prevent passive diffusion of glucose back out of the cell?

What is the basic difference between simple diffusion and facilitated diffusion across a cell membrane?

When a vegetable oil is converted to a soft margarine, a nonnatural product is synthesized. What is this product?

Why are glycerophospholipids, rather than triacylglycerols, found in cell membranes?

Arrange the following three triglycerides in order of increasing melting point: Tristearin, tripalmitin, and tripalmitolein

One of the constituents of the carnauba wax used in floor and furniture polish is an ester of a $\mathrm{C}_{32}$ straight-chain alcohol with a $\mathrm{C}_{20}$ straight-chain carboxylic acid. Draw the structure of this ester.

Where in a liver cell do the following pathways occur? (a) Glycolysis (b) Gluconeogenesis (c) Glycogenesis (d) Glycogenolysis

Name the anabolic pathway for making glucose.

Which of the following statements about enzyme catalysis is true? F. The enzyme molecule is used only once. G. The reactant binds to an active site on the enzyme. H. The enzyme must be denatured before it can participate in a reaction. I. Reaction energy must be supplied to cause the enzyme to form the proper shape.

Review the 10 steps in glycolysis and then answer the following questions: (a) Which steps involve phosphorylation? (b) Which step is an oxidation? (c) Which step is a dehydration?

Define a biochemical pathway. How are the steps in a biochemical pathway controlled? What are three ways in which enzymes are regulated?

Under which physiological condition is the following pathway the predominant one? (a) glycolysis (b) gluconeogenesis

. What conditions promote glycogenesis, glycogenolysis, and gluconeogenesis?

Outline the conditions that direct pyruvate toward the following: (a) Entry into the citric acid cycle (b) Conversion to ethanol and $\mathrm{CO}_2$ (c) Conversion to lactate (d) Glucose synthesis (gluconeogenesis) In what tissues or organisms is each pathway present?