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21 Cards in this Set
- Front
- Back
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Water is capable of forming this stable structure. What does it consist of and what is its function?
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Hydration shells. It consist of tightly bound and oriented wate molecules known as bound water. It helps stabilize the macromolecules (proteins, carbs, nucleic acids) it surrounds as well as preventing their recombination to form crystal structures.
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What is the most important property of water?
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It is a liquid over the range of temperatures most relevant to life.
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How does water aid in preventing localized overheating and aiding in evaporation?
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Water has high specific heat and thermal conductivity which allows it to act as a buffer to protect against overheating and it has a high heat of vaporization which promotes cooling by evaporation.
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What is cohesion and what does it cause and lead to?
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H-bonding betwen water molecules. Exceptionally high surface tension because water molecules now interact more strongly with each other than with the surrounding air. It leads to high tensile strength of water which is the maximum force a column of water can withstand without breaking.
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Explain the concept of capillary action.
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Water attracted to polar surface of the tube (adhesion) and attempts to minimize air-water interface (surface tension). These factors lead to the pull on the molecules up the tube until the weigt of the water tube equals upward force.
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What is translocation, what are two types, and what type occurs in plants?
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Movement of substances from one region to another. Active which requires ATP and Passive which does not. Passive occurs in plants, which is specifically known as bulk flow, diffusion, and occasionally a special type of diffusion, osmosis.
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What is bulk flow? What is it the predominent mechanism for?
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Concentrated movement of groups of molecules en masse, most often in response to a hydrostatic pessure gradient.(ex. water in a hose) Long distance transport of water in xylem.
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What is diffusion?
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Directed movement of molecules from a region of high concentration to ow concentration accomplished by random thermal motion. (ex. dispersal of scent in air)
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What is the average time needed for a particle to diffuse a certain distance?
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L2/D, where L equals length of distance and D equals the diffusion coefficient (larger molecules have smaller values). Thus diffusion is onyl effective within cellular dimension as a means of mass transport.
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What is osmosis? What is the differnece here from diffusion and
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A special case of diffusion through a selectively permeable membrane. In diffusion and bulk flow, substance move down a concentration gradient. In osmosis, substances can move with and against a concentration gradient.
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The total free energy gradient of water is represented by what?
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chemical gradient of water relative to a standard state and expressed in J/mol-1
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Water potential equals what?
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chemical potential of water divided by the volume of 1 mol of water, which makes it a measure of the free energy of water per unit volume
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What 3 major factors influence water potential in plants?
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Concentration, pressure, and gravity
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What will water do to minimize water potential?
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Redistribute itself
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What do solutes do to the free energy and entropy of water?
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Reduce it, increase it
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Explain how pressure effects water potential and also what are the two types of pressure and how do they come to be?
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It can either increase it or decrease it depending on the type of pressure. If its POSITIVE pressure, brough about by turgor pressure in plant cells, then it increase water potential. If it is NEGATIVE pressure, which occurs when there is pressure in the xylem, then it decreases water potential
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Osmosic in plant cells is ____ energy dependent.
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indirectly
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In the context of a plant cell, water potential is dtermined by what?
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The concentration of vacuolar solutes and the pressure exerted outward against the cell walls by the expanding protoplast.
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What is incipient plasmolysis?
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When the protoplast exerts no pressure against the cell wall, but is also not withdrawn from it.
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The difference between full turgor and incipient plasmolysis usually causes no more than a ___% differnece in cells volume. Thus, when cells take up or lose water they experience ____ differences in solute potential but ____ differneces in turgor pressure.
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10, minimal, large
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The direction of water movement is determined solely by the what?
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The value of the water potential in adjacent plant cells.
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