BIOL 1070 Lecture Notes - Lecture 11: Wood Frog, Ice Crystals, Tonicity

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crimsondog239

9 Dec 2016

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Let"s rst explore some strategies that are employed by ectotherms to deal with freezing either to avoid it or to promote it in a controlled manner. In order to understand some of the challenges posed by freezing, it is important to be clear on the concepts of osmosis and osmotic pressure. Osmosis is the passive movement of water across a membrane from a solution of low solute concentration to a solution of high solute concentration. Osmosis occurs from a solution with lower osmotic pressure to one with higher osmotic pressure. The terms hypertonic , isotonic , and hypotonic describe the effect that solutions have on cells. Hypertonic solutions cause cells to shrink, whereas hypotonic solutions swell cells. When tissues are exposed to temperatures below freezing, ice crystals form in the extracellular uid and they reduce the amount of free water outside the cell, which creates an increase in osmotic pressure.

Related Questions

A hypertonic solution has a higher level of solutes so the water moves out of the cells to the surroundings

A hypotonic solution has a higher level of solutes so the water moves out of the cells to the surroundings

The salt and water solution in the potato is a hypotonic solution

Osmosis is the movement of large molecules across a membrane which require embedded proteins

The plain water in this experiment is the solvent and the salt is the solute.

Passive transport requires no energy and the molecules move with the concentration gradient or from high concentration to low concentration

Active transport required no energy and the molecules move with the concentration gradient or from high concentration to low concentration.

The water on the inside of the potato with the salt molecules is an isotonic solution the same as the solution on the outside of the potato.

Water will not move by simple diffusion (osmosis) into or out of cells it requires energy or protein transporters

The solution of salt water in the potato has a lower concentration of water molecules so the water on the outside should move into the cells

1. In lecture, we described a simple osmotic pressure gradient when discussing osmosis. For question #1, describe the simple osmotic pressure gradient, in terms of osmotic pressure, that exists across the red blood cell plasma membrane when red blood cells are suspended in a severely hypotonic solution, such as a 0.2% NaCl solution. Use scientific terminology.

2. We mentioned in class that biological systems are always in a state of osmotic equilibrium due to a combination of solute diffusion in some cases and osmosis in others. In this experiment, when you add the red blood cells to a severely hypotonic solution, what substances are moving across the red blood cell plasma membrane to achieve osmotic equilibrium, Na+ and Cl- or water? Explain why based on your understanding of the permeability characteristics of biological membrane. Always use scientific language.

CAN QUESTIONS 1 AND 2 BE ANSWERED DIRECTLY AND ADEQUATLEY PLEASE.

HERE IS AN INTRO TO THE LAB EXPERIMENT

Intro:

We have known for a very long time that the mammalian red blood cell plasma membrane is very permeable to water. Even the introductory biology student understands that if you put mammalian red blood cells in water, they will rapidly swell and break open (hemolyze) due to the rapid osmosis of water into the cell. The experimental question we are asking in today's lab experiment is "Is the high water permability of mammalian red blood cell plasma membrane due solely to the lipid bilayer, or are there water channels present in the membrane?"

Experimental Design:

It has been shown by several investigators that water movement through water channels can be blocked by the known K+ channel blocker, tetraethylammonium chloride (TEAC). Brooks, Regan and Yool (2000) showed that TEAC reduces the water permeability of human water channels expressed in the plasma membranes of frog ocytes. After preincubation of the oocytes for 15 min with 100 microM TEAC, the water permeability of frog oocyte plasma membrane containing human water channels was reduced 20 to 40%. The investigators concluded that treatment of cells with TEAC can be useful in determining the presence of aquaporins in membranes.The specific objective of today's experiment is to uncover the presence of water channels in mammalian red blood cell plasma membrane by determining the effect of tetraethylammonium chloride on the water permeability of mammalian RBC plasma membrane.

True or False: The solution of salt water inside of the hollowpotato has a lower concentration of water molecules so the water onthe outside of the potato should move into the potato cells. Or thewater molecules inside of the grape or pea will move to the outsidewhere there are fewer water molecules and more salt.

True or False: The water on the inside of the potato with thesalt molecules is an isotonic solution the same as the solution onthe outside of the potato.

True or False: Water will not move by simple diffusion (osmosis)into or out of cells it requires energy or proteintransporters.

T or F The salt and water solution inside of the hollow potatois a hypotonic solution.

T or F: Osmosis is the movement of large molecules across a semipermeable membrane which require embedded proteins.

T or F The plain water in this experiment is the solvent and thesalt is the solute.

T or F Active transport requires no energy and the moleculesmove with the concentration gradient from low concentration to ahigh concentration.

T/F Passive transport requires no energy and the molecules movewith the concentration gradient or from high concentration to lowconcentration

T/F A hypotonic solution has a higher level of solutes so thewater moves out of the cells to the surroundings.

T/F A hypertonic solution has a higher level of solutes so thewater moves out of the cells to the surroundings.

Why does a slug die when you put salt on her/him? (Think aboutwhat happened in this lab) :

A. The salt on the outside of the slug causes the water frominside of the cells to move out of the cells. The dehydration ofthe slug causes death

B. The slug does not die but becomes enlarged from the movementof water into the slug cells caused by a hypertonic solution

C. The salt and moisture on the outside of the slug cause anisotonic state and the water leaves the slug quickly byosmosis.

D. Sigh. The poor slug, sacrificed for science by many youngnature lovers around the world. Obviously this happens as theoutside solution is hypotonic and the inside of the slug's cellsare hypertonic. Energy is used for active transport leading toosmosis.

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BIOL 1070 Lecture Notes - Lecture 11: Wood Frog, Ice Crystals, Tonicity

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