which require high levels of water transport such as the kidney, salivary glands, (lacrimal) tear glands andother epithelial cells. Can you think of a reason why aquaporins are so important in these tissues?Althoughaquaporins can be ubiquitous in certain locations, the actual aquaporin present may vary by tissue/organ.The most common aquaporin in called aquaporin 1 (AQP1). AQP1 is found in the kidney and forms ahomotetramer protein across the cellular membranes within this organ. “Homotetramer” means that it iscomposed of four, identical simpler molecules. Water molecules are attracted to these pores. However, rather than moving through the centralhomotetramer central channel, water molecules move through one of the four individual channels formed bythe four monomer subunits. These channels are very tiny, with a diameter of only 3 Å (3 Å: 1 Å = 1 x 10-10 m).This further increases the specific of aquaporins because many molecules are much larger than this (note:water molecules are only 2.8 Å). Pre-Lab Questions1.A concentration gradient affects the direction that solutes diffusion. Describe how molecules move withrespect to the concentration. 2.How does size affect the rate of diffusion? The bigger the item the slower the rate of diffusion3.Does polarity affect the rate of diffusion? Explain your answer. Polarity does affect the rate of diffusionbecause if attracted then it allows osmosis to happen better while if they do not attract it will not allowosmosis to happen readily.
Diffusion and Osmosis 104 4.Draw a picture of a cell in a isotonic, hypotonic, and hypertonic states. 5.What is the water potential of an open beaker containing pure water? 6.Why don’t red blood cells swell or shrink in blood? 7.How do osmotic power plants work? 8.Research the structures that protect plant and animal cells from damage resulting from osmotic pressure.Write a few paragraphs explaining what they are, how they work, and where they are located. Experiment 1: Diffusion through a LiquidIn this experiment, you will observe the effect that different molecular weights have on the ability of dye totravel through a viscous medium. 1 60 mL Corn Syrup Bottle Red and Blue Dye Solutions (Blue molecular weight = 793 g/mole; Red molecular weight = 496 g/mole) (1) 9 cm Petri Dish (top & bottom halves) Ruler Stopwatch Tape Procedure1.Use tape to secure one half (either the bottom or the top half is fine) of the petri dish over a ruler. Makesure that you can read the measurement markings on the ruler through the petri dish. The dish should bepositioned with the open end of the dish facing upwards. 2.Carefully fill the half of the petri dish with corn syrup until the entire surface is covered. 3.Place a single drop of blue dye in the middle of the corn syrup. Note the position where the dye fell byreading the location of the outside edge of the dye on ruler.
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- Fall '19