BSC 2011 Lecture 15: Osmolarity

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amberhare518

4 Sep 2019

School

University of Florida

Department

Biology - Biological Sciences

Course

BSC 2011

Professor

Ellen C Davis

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Osmolarity

ECF in body is like sea water with sodium and chloride ions

Osmoregulation: process by which the body regulates solute concentrations and balances the

gain and loss of water.

Osmosis: the basic mechanism of osmoregulation (water diffusion)

- Osmosis is a subcategory of diffusion that is specific to water

Water moves from…

- Water: high to low concentrations

- Solute: low to high concentration

Active transport: needs a form of energy to move that solute (low to high)

- There is no such thing as an active water transport. It is always passive by osmosis and

always in the direction of higher Osmolarity.

- Water can only move passively across membranes down its osmotic gradient (meaning?)

o Animals have no way to actively transfer water against the osmotic gradient

Water will always move across a semi-permeable membrane, from the hypo-osmotic solution

(low solute) to the hyper-osmotic solution (high solute).

- In animals, water can either diffuse through the lipid bilayer or move through special

water channels called aquaporins that speed up the movement of water

Osmolarity: measure of the amount of osmotically active particles present per volume of

solution

- Purpose: quantify a solution’s tendency to gain or lose water by osmosis when placed

next to another solution and separated by a semi permeable membrane (assuming it is

permeable to water but not solutes)

The osmolarity depends on the number of

solutes not the type of solute

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Document Summary

Ecf in body is like sea water with sodium and chloride ions. Osmoregulation: process by which the body regulates solute concentrations and balances the gain and loss of water. Osmosis: the basic mechanism of osmoregulation (water diffusion) Osmosis is a subcategory of diffusion that is specific to water. Active transport: needs a form of energy to move that solute (low to high) There is no such thing as an active water transport. It is always passive by osmosis and always in the direction of higher osmolarity. Water can only move passively across membranes down its osmotic gradient (meaning?: animals have no way to actively transfer water against the osmotic gradient. Water will always move across a semi-permeable membrane, from the hypo-osmotic solution (low solute) to the hyper-osmotic solution (high solute). In animals, water can either diffuse through the lipid bilayer or move through special water channels called aquaporins that speed up the movement of water.

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. predict the direction of water movement based on differences in solute concentrations. Use the terms osmotic pressure, hypotonic, isotonic, and hypertonic
2. Why do membranes have to be selectively permeable?

3. What determines whether a particular substance can diffuse (simple or facilitated) through a membrane?

4. What mechanisms drive molecules across membranes? Use the terms concentration gradient, (facilitated) diffusion and active transport.
5. Which parts of the plasma membrane proteins do you expect to be hydrophobic or hydrophilic? Justify your answer.
concise and short answers pls

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.

BSC 2011 Lecture 15: Osmolarity

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