1Transport of ions and metabolites:1. How do plants take up, distribute, & sort nutrients in organs and in cells?2. How do plants deal with excess ions and toxic metals?3. What controls guard cell movement?Changes in ion levels and water movement4. Form of communicationTRANSPORTHow are essential mineral nutrients taken up and distributed in the plant?Concepts1. p-lipid bilayer is a remarkable barrier2. Proteins catalyze transport of nutrients and metabolites just as enzymes catalyze chemical reactions. There are 3 main classes of transport proteins.Channels,PumpsCarriers3. Transport can be active or passive.Passive and active transport of ions result in electric potential difference across membranes4. Major Transport Proteins in Plantsa. H+ pumping ATPases are the major ion pumps in plants b. Active transport of many nutrients and metabolites depend on H+-coupled co-transport. Energy from H+ gradient is used to drive uphill movement of other nutrients.c. Channels allow rapid, passive transport of ions and metabolites. d. Water is transported via WATER CHANNELS or AQUAPORINS in membranes that conduct large volumes of water rapidly.Taiz. P-lipid is a remarkable barrier to ions6-7. Proteins catalyze transport. Channel, carrier pumpActiveFig. 2-17 Taiz. Protein catalyze transport just like enzymes catalyze chemical reactions. Specific, fast23. Transport can be active or passive.•Passive transport is movement downan electrochemical gradient.•Active transport is movement againstan electrochemical gradient.What is an electrochemical gradient? Δμ = conc gradient + electrical gradientChemical gradientElectrical gradient: unequal distribution of charges across a membrane.Passive or active transport of ions result in electric potential difference across membranes.••How do you know if an ion is moving uphill or downhill?Nernst equation•It predicts passive ion distribution for a given electrical potential.Diffusion of uncharged species depend only on the concentration gradient.Diffusion of charged species is dependent on the concentration and the electrical gradient.At equilibrium, the conc gradient of an ion between two compartments is balanced by the electrical gradient.6-2. Taiz. A diffusion potential develops when + & - ions diffuse across a membrane at different rates.More K+Pump potential is generated when there is an active ion pump.H+K+Pump potentialDiffusion potentialATPProton transport is a major determinant of the membrane potential.What is the driving force for uphill movement?ATP and a H+electrochemical