The Effect of Ph on the Rate of Osmosis Using a Glucose Solution

The Effect of pH on the Rate of Osmosis Using a Glucose Solution

Melissa Werderitch Biology 157 11/6/06

Introduction

In a journal article written by Florian Lang, osmosis is essentially explained as the flow of water from one area to another that are separated by a selectively permeable membrane to equalize concentrations of particles in the two locations (Lang, 1997). Osmosis is able to maintain osmotic pressure and regulate a cell's volume.

In a hypotonic () or hypertonic () environment, a cell may be liable to gain or lose water. Osmotic pressure is known as the amount of force needed to prevent the flow of water through a membrane. Osmotic pressure allows a cell to prevent itself from shrinking or swelling and possibly bursting. However, it is necessary in some cases to perform these actions to prevent the opposite from occurring, that can also be known as stabilizing the osmotic pressure of the cell (Lang, 1997). Studies have shown that ions of sodium, potassium, hydrogen, and chloride have been most successful in controlling cell volume by exposing environments surrounding a cell to the ions.

It necessary to study what effects the previously mentioned ions would have on another substance or solute dissolved in water. Osmoregulation is the regulation of water and ion concentrations in a cell (Driscoll). Animals must regulate there water intake, and they do so by performing this process. Animals like fish and insects have an isotonic environment, and they use a chemical called trimethylamine oxide to maintain this balance. However, larger water animals or vertebrates in a saltwater area are in more of a hypotonic environment, and are exposed to a large amount of ions including Na+ and Cl-, therefore they must absorb more water to equalize the concentrations of these ions. This process is usually performed by the kidneys. Freshwater fish are in a hypertonic environment, so they maintain their balance by secreting water through urine. Other animals like ticks and mites have the ability to absorb water vapor by secreting high concentrations of substances, usually a KCl solution (Driscoll).

For this experiment, the topic to focus on is the kidneys' production of urine and the ability to control pH. There is a bicarbonate ion, HCO3-, which serves as a buffer for the body. Urine is slightly acidic and aids in maintaining the balance of the bicarbonate. This is done through things called A-type cells and B-type cells, in which the A cells secrete acid and the B cells secrete bases that determine the uptake of the bicarbonate into the bloodstream. It is also done through the absorption of H+ ions by the lumen, which is the interior of a vessel within the body, such as the small central space in an artery or vein, or any of their relating vessels through which blood flows (Driscoll).

In this experiment, the effect of pH on osmosis will be explored using a glucose solution instead of plain water. It is predicted that the rate of osmosis will increase as pH fluctuates because pH affects osmosis. If the rate of osmosis is affected by pH, then by creating a basic and acidic environment surrounding the glucose solution, the rate of osmosis will increase or decrease within the two boundaries.

Problem

Does pH affect the rate of Osmosis?

Materials and Methods

NaOH solution

HCl solution

Glucose Solution

9 250mL beakers

9 Dialysis sacs

pH paper

18 rubberbands

Balance/scale

Pipette for glucose solution

Distilled water

Separate the beakers into 3 different groups. Each will serve as one trial. Number the trials 1, 2, and 3 and label the beakers within the trial as #1, #2, and #3. Fill all sets of beakers of #1 with 200mL of distilled water and 50mL of 1.0 HCl solution or until a pH of 4 is reached. Fill all sets of beakers of #3 with 240mL of distilled water and approximately 15 drops of NaOH, or until a pH of 11 is reached. Fill one of the remaining beakers with distilled water, and use this to soften the dialysis sacs by placing them in there for about 10 seconds. Open the sacs, and twist off and seal one side of the sac to prevent anything from leaking through. Using the pipette, fill all 9 dialysis sacs with 10mL of the glucose solution. Twist off and seal the open side of the sacs to prevent the solution from leaking, and make sure there are no air bubbles present in the sealed sac. Empty the beaker, clean it, and fill that beaker, as well as the 2 remaining with distilled water. Take the mass of the initial sacs and record. Arrange the beakers according to trials, making sure to include one basic solution, one distilled water, and one acidic solution in each. Drop the sacs into the solutions and let settle for one hour. After one hour, remove the sacs and dry them. Take the final mass of the sacs and determine whether water was gained or lost during the experiment.

Results

All