Test Notes - Plants

Test Notes - Plants - Anatomy stems leaves and roots...

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Primary and secondary growth regions Guard cells n how they operate Gutation definition Driving forces btw xylem phloem etc – source to sink Essay maybe 5 reason why a plant is a dicot Differences between monocot and dicot If I were a water molecule how do I get from the dirt to a leaf - specific directions!! Overview of Transport Mechanisms in Plants Land plants require a transport system, because unlike their aquatic ancestors, photosynthetic plant organs have no direct access to water and minerals. Three levels of transport occur in plants: 1. Uptake and release of water and solutes by individual cells 2. Short-distance cell-to-cell transport at the level of tissues and organs 3. Long-distance transport of sap in xylem and phloem at the whole-plant level Transport at the cellular level depends on the selective permeability of membranes The plasma membrane's selective permeability controls the movement of solutes between a plant cell and the extracellular fluids. Solutes may move by passive or active transport. Passive transport occurs when a solute molecule diffuses across a membrane down a concentration gradient. Requires no direct expenditure of energy by the cell Transport proteins embedded in the membrane may increase the speed at which solutes cross. Transport proteins may facilitate diffusion by serving as carrier proteins or forming selective channels. Carrier proteins bind selectively to a solute molecule on one side of the membrane, undergo a conformational change, and release the solute molecule on the opposite side of the membrane. Selective channels are simply passageways by which selective molecules may enter and leave a cell; some gated selective channels are stimulated to open or close by environmental conditions. Active transport occurs when a solute molecule is moved across a membrane against the concentration gradient. Energy requiring process Active transport is not accomplished by the use of transport proteins, such as those involved in facilitated diffusion, but is conducted by active transporters, a special class of membrane proteins (e.g., the proton pump is an active transporter important to plants). Proton pumps play a central role in transport across plant membranes A proton pump hydrolyzes ATP and uses the energy to pump hydrogen ions (11+) out of the cell. Produces a proton gradient with a higher concentration outside of the cell Produces a membrane potential, since the inside of the plant cell is negative in relation to the outside This membrane potential and the stored energy of the proton gradient are used by the plant to transport many different molecules Potassium ions (K+) are pulled into the cells because of the electrochemical gradient. Nitrate (NO3) enters plant cells against the electrochemical gradient by in exchange for
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Test Notes - Plants - Anatomy stems leaves and roots...

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