Chapter 36 Plants

Biology, 7th Edition (Book & CD-ROM)

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Chapter 36 Transport in Vascular Plants I. Physical forces A. Three types of transportation 1. Transport of water and solutes by individual cells (root hairs) 2. Short-distance transport of substances from cell to cell at the levels of tissues and organs a. Like loading of sugar from leaves into the sieve tubes of the phloem 3. Long distance transport within xylem and phloem throughout the whole plant B. Transport Overview 1. Roots absorb water and dissolve minerals from soil 2. Water and minerals are transported upwards from roots to shoots as xylem sap 3. Transpiration (loss of water from leaves) creates a force within leaves that pulls xylem sap upward 4. Leaves take in carbon dioxide and expel oxygen. The carbon dioxide is used for photosynthesis, and the oxygen is used in cellular respiration 5. Sugars are produced by photosynthesis 6. Sugars transported as phloem sap to roots and other parts of the plant 7. Roots exchange gases with air spaces, taking in oxygen and discharging carbon dioxide. Oxygen breaks down sugar. C. Selective Permeability 1. Passive transport- diffusion across a membrane down the concentration gradient 2. Active transport- the pumping of solutes across the membrane against the concentration gradient; requires energy in the form of ATP 3. Transport protein- bind to a solute on one side of the membrane and release it on the other side a. Other proteins provide selective channels, where they only bind to certain substances D. Proton Pumps 1. Proton pump- uses energy from ATP to pump hydrogen ions out of the cell a. Active transport b. Results in a higher hydrogen ion gradient outside the cell than inside c. It’s a form of potential energy i The hydrogens will naturally flow down later on, and the flow can be harnessed to do work 2. Membrane potential- separation of opposite charges across a membrane a. Proton pumping results in the inside of the cell to be more negative b. Charge separation is a form of potential energy (membrane potential) i Will be used to drive the transport of many different solutes Contributes to the uptake of K + by root cells 3. Contransport- a transport protein couples the downhill passage of one solute to the uphill passage of another
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a. Basically taking two solutes at a time, one down the concentration gradient and the other up its concentration gradient, but they’re both going the same way 4. Chemiosmosis- where one process creates something (ex: ATP), and another process uses it up so that you’re back to normal a. When H + is channeled across by the proton pumps, it uses up energy. But then it will naturally diffuse down the concentration gradient and give off energy E. Effects of Differences in Water Potential 1. Osmosis- the passive transport of water across a membrane 2. Water will travel by osmosis from an area of low solute concentration to an area with high solute concentration 3. In plant cells there is a cell wall, which adds another factor: physical pressure a. Combined effects of solute concentration and physical pressure = water
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Chapter 36 Plants - Chapter 36 Transport in Vascular Plants...

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