1. A Few Review Questions…

2. Question 1 Say that your cells have met all of their ATP needs. If you eat glucose in excess of your cells’ ATP needs, what is/are the fates of this glucose, in order of priority?

3. Answer: Question 1 If your cells have met all of their energy needs, the glucose will not go through ATP production (glycolysis -> citric acid cycle -> ETC). Instead… The first thing that will happen is glycogen formation -- storage of this energy supply in liver and muscle cells. But the glycogen tanks are also limited in size. When the glycogen “tanks” get full, the excess glucose gets synthesized into fatty acids. The first step of this pathway involves glycolysis, but only to form acetyl- CoA, involved in fatty acid formation.

4. Question 2 Protein monomers and lipid monomers are both absorbed into the bloodstream from the small intestine. The method by which each molecule type travels through the blood to the cells is different, however. Explain why this is, and how the above molecule types are transported through the bloodstream.

5. Answer: Question 2 Amino acids are zwitterionic at neutral pH and therefore water soluble -- once they are absorbed across the small intestine lining, they can be transported through the water-based blood. However, lipids are nonpolar. They have to be attached to a protein, forming a lipoprotein (specifically in the digestive system, a special lipoprotein called a chylomicron is formed) which is then polar enough to be transported through the bloodstream.

6. Question 3 Explain what is involved in designing primers for PCR. (or, as it’s often referred to, “PCRing up a gene”)

7. Answer: Question 3 Decide what the boundaries/ends will be of the region you wish to amplify. Each primer will be a short nucleotide sequence (typically 12-15 NT -- you don’t need to know this) that will bind to your template DNA. –The 5’->3’ orientation of each primer should be such that new nucleotides get added moving in toward the center of your gene after the two strands have been separated. In a real-life situation, you’d consider re-annealing temperature (which is dependent on %AT vs. %GC) as well…

8. Question 4 You just ate a big, yummy dinner. Describe what is happening to your blood glucose levels and hormones released by the pancreas. (YES, we are assuming that you are not diabetic, and we are assuming that your meal was reasonably balanced in terms of carbs/proteins/fats!)

9. Answer: Question 4 Big meal… blood glucose levels are high. If you are normal (well… metabolically so), your pancreas is releasing insulin. This will allow the glucose to enter your cells for processing in whatever capacity it decides is proper for the cell’s current metabolic and energy needs.

10. Question 5 Some of the proteolytic (protein-digesting) enzymes are produced by glands found in the lining of the stomach. However, they are produced as zymogens and not active until they make contact with HCl inside the cavity of the stomach. Why do you think this form of regulation is used by these particular proteolytic enzymes?

11. Answer: Question 5 The walls of the stomach contain structural proteins. If the enzymes were produced from their glands already in an active form, they would digest the stomach lining. Since they are produced in an inactive form, they will not digest the stomach lining upon release, and they will not start “doing their business” until they make contact with HCl, which cleaves off the inactive part of the zymogen.