The cells lining the small intestine have projections into the lumen of the intestine. These projections, combined with the highly folded layering of cells lining the lumen, function to
A) facilitate countercurrent exchange.
B) decrease the reabsorption of water.
C) slow the nerve impulses that trigger peristalsis.
D) increase the surface area for nutrient absorption.
E) increase the rate of peristalsis.
D
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It is summer, and you are excited about going to your local amusement park, and specifically about riding the new roller coaster that was just built. You imagine waiting at the top of the stairs for the roller coaster to pull into the station, climbing into the car, strapping yourself into the seatbelt, and pulling down the harness. You can imagine the cars slowly chugging up to the top of the
first hill, coming down on the other side, and the excitement you expect to feel as you go along for the ride. Of all of the things that you have imagined, which is an example of potential energy? A. Waiting at the top of the stairs for the roller coaster to pull into the station B. Climbing into the car C. Pulling down the harness D. The roller coaster car going up the first hill
Microscopic fossils are also called microfossils
A. These minerals are needed as cofactors for enzymes needed in photosynthesis. B. These minerals are needed as cofactors for enzymes needed in cellular respiration. C. These skeletons allow for more complex reactions to take place inside the cell. D. These skeletons probably afforded them protection from being eaten. E. These minerals are necessary to maintain genome integrity.
Which scenario is an example of positive feedback?
a. When oxygen levels are low, the kidneys secrete erythropoietin, which stimulates the proliferation and differentiation of red blood cells until oxygen demands are met. b. As blood pressure increases, specialized neurons relay the change to the brainstem, which in turn, decreases the contractility of the heart and leads to vasodilation, thereby decreasing blood pressure. c. After an injury, chemicals released at the site of injury will activate platelets, which will in turn activate additional platelets, and so on, until the clot has formed and the injury is no longer bleeding. d. When stress levels are high, the hypothalamus secretes corticotropin-releasing hormone (CRH), which in turn stimulates the secretion of adrenocorticotropic hormone (ACTH), which then triggers the release of cortisol. Increased cortisol levels then inhibit the release of CRH and ACTH. e. After eating, when glucose levels are high, insulin levels increase, leading to an increase in glycogen and fat synthesis to remove excess glucose from circulation.
Cyclic AMP is degraded by __________.
A) phosphodiesterase B) adenylate cyclase C) G proteins D) AMP E) protein kinase