1. vena cava. left atrium. right atrium. left ventricle. right ventricle.
Blood returning to the mammalian heart in a pulmonary vein drains first into the
vena cava.
left atrium.
right atrium.
left ventricle.
right ventricle.

2. Compared with the interstitial fluid that bathes active muscle cells, blood reaching these cells in arteries has a
higher PO2.
higher PCO2.
greater bicarbonate concentration.
lower pH.
lower osmotic pressure.

3. In negative pressure breathing, inhalation results from
forcing air from the throat down into the lungs.
contracting the diaphragm.
relaxing the muscles of the rib cage.
using muscles of the lungs to expand the alveoli.
contracting the abdominal muscles.

4. When you hold your breath, which of the following blood gas changes first leads to the urge to breathe?
rising O2
falling O2
rising CO2
falling CO2
rising CO2 and falling O2

5. Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
the citric acid cycle
the electron transport chain
glycolysis
synthesis of acetyl CoA from pyruvate
reduction of pyruvate to lactate

6. The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
oxygen.
water.
NAD+.
pyruvate.
ADP.