BOT 331 Exam 2 Questions With Verified Answers

List two essential mineral elements. For each, state a function and a deficiency symptom. -reduced growth, woody stems, and purple leaf pigment from anthocyanins. Another nutrient is phosphorus. Phosphorus deficiency causes reduced growth and slender stems, and dark green leaves with necrotic spots. A gardener observes symptoms on their tomato plants of chlorosis in between leaf veins on older leaves before younger leaves. The gardener and horticulture experts agree that the plant has a Magnesium deficiency. The gardener adds the proper amount of Magnesium to the soil. However, a month later, new sets of older leaves still show the symptoms. The horticulture experts then suggest that the gardener should check the soil pH. Explain why the experts suggested checking the soil pH. - Answer Acidic soils can cause cation exchange, which means the protons replace other cations that are absorbed to the surface of negatively charged soil particles. Although cation exchange could make Magnesium more available to the roots, if the soil is routinely watered, then the Magensium may be leaching out of the soil. Acidic soils can also cause mineral ions to precipitate, in which case the Magnesium would not be dissolved in water anymore, and would be less available for uptake by the roots. Nitrate requires active transport into a plant cell. A researcher observes that nitrate uptake stops shortly after the plant cell runs out of ATP. The researcher discovers the protein involved and determines that the protein does not bind nor hydrolyze ATP. Explain how nitrate uptake stops when the plant cell runs out of ATP. - Answer Active transport can be either primary or secondary. If primary, then the transport protein couples the binding and hydrolysis of ATP to moving the molecule across the membrane. If secondary, then the transport protein uses the proton motive force: the protein couples moving the molecule across the membrane to the favorable 'downhill' flow of protons across the membrane. The proton motive force is generated by the H+-ATPase, which does primary active transport of protons across the membrane. When ATP runs out, then the H+-ATPase pump stops moving protons across the membrane and the proton motive force gets used up quickly. So active transport of nitrate must be secondary and stops once there is no proton motive force. Imagine a cell with a plasma membrane permeable to K+ but not Cl-. At the start of the experiment there is 10 milliMolar (mM) KCl outside and 100 mM KCl inside. Explain your answers. a. At equilibrium will the concentration of K+ be equal on both sides of the membrane? b. At equilibrium will the bulk solution on the outside have a net negative charge? c. At equilibrium, will the inside surface of the plasma membrane be positive or negative? - Answer 1) No. As soon as K+ crosses the membrane, leaving Cl- at the membrane's outer surface, the separation of charge results in a membrane potential that prevents further net flow of K+ into the cell. So only a small amount of K+ enters the cell, and the potassium remains near the membrane's inner surface, being attracted to the excess negative charges at the outer surface. 2) No. The bulk solution remains electroneutral. The only separation of charge is across the