OSMOSISMFEC2 Group 5:

Baldomero

Dela Rosa

Navarro

Yumol

INTRODUCTION

Osmosis Osmosis is the diffusion of a solvent from a

region of lower solute concentration (higher free water concentration) to a region of higher solute concentration (lower free water concentration).

In living systems, the solvent is water. In cells, osmosis occurs as water crosses the

phospolipid bilayer through specialized channels for water movement called aquaporins.

OSMOTIC PRESSURE

A hydrostatic pressure caused by a difference in the amounts of solutes between solutions that are separated by a semi-permeable membrane.

The region with a higher free water concentration (or lower solute concentration) has a lower osmotic pressure while the region with the lower free water concentration (or higher solute concentration) has a higher osmotic pressure.

OSMOTIC PRESSURE

Osmotic pressure causes the height of the water in the region with the higher solute concentration to rise, due to movement of water from the region with lower solute concentration to the region of high solute concentration.

The rising of the water will stop once the osmotic pressure in both regions is equal.

MATERIALS AND METHODS

Five mL of thirty percent sucrose solution was placed in a small test tube.

The mouth of the test tube was covered with longganisa skin using a rubber band.

The weight of the test tube was recorded

The test tube was then carefully inverted and the level of the liquid inside the test tube was marked.

The test tube was immersed with its sealed mouth oriented downwards in a beaker containing thirty mL of distilled water.

The test tube was positioned vertically and with the mouth not touching the bottom of the beaker

The tube was left immersed for two hours.

The level of water inside the tube was recorded and the test tube was weighed.

SET-UP

Photo courtesy of Amelyn Gan

Figure 1.0 Set-up of Osmosis

RESULTS

Figure 2.0a Test Tube Before Immersing in

Beaker

Figure 2.0b Test Tube After

Immersing in Beaker

BeforeWeight: 22.75 gWater Level: 3.0 cm

AfterWeight: 23.0 gWater Level: 3.2 cm

The water level inside the test tube rose by 0.2 cm and the weight increased by 0.25 grams after being immersed in the beaker for two hours.

Observation:

The water level rose slowly during the first few minutes but stopped rising altogether after some time.

DISCUSSION

The water level rose inside the test tube because the water from the beaker crossed the membrane into the test tube.

Water, whose concentration is higher in the beaker, diffused into the test tube where its effective concentration is lower because of the presence of dissolved solutes. In osmosis, only water diffuses and not the solutes.

DISCUSSION FOR THE OBSERVATION

The weight of the water inside the test tube became heavier and sufficient enough to stop further changes in fluid levels through diffusion of water, thereby making the osmotic pressure between the two regions equal.

Although the water level inside the test tube has stopped rising, water molecules continue to pass through the semi-permeable membrane in both directions, with as many molecules crossing from one side of the membrane into the other and vice versa.

DISCUSSION FOR THE OBSERVATION

Therefore, after being immersed for few hours, the water level in the test tube eventually stopped rise because there is no difference in osmotic pressure and the amount of solute between the two regions.

Osmosis in Red Blood Cells

MATERIALS AND METHODS

Three microscope slides were labelled A, B, and C.

Three drops of blood were extracted from a willing volunteer by pricking his or her finger with sterile lancet.

A drop of blood was placed on each of the slides, along with a drop of NaCl – which had different concentrations on each.

0.07 M, 0.15 M, and 0.30 M of NaCl solution were mixed with the blood on slides A, B, and C respectively.

The blood cells and the NaCl solution were mixed thoroughly and smeared evenly on the surface of the slides.

The slides were focused at 400x using three different microscopes.

The diameter of the cells were measured constantly every five minutes for about an hour.

Changes were observed.

Results

Figure 3.0a Red blood cells before adding a drop of 0.07 M NaCl solution

Figure 3.0b Red blood cells after adding a drop of 0.07 M NaCl solution

Figure 4.0a Red blood cells before adding a drop of 0.15 M NaCl solution

Figure 4.0bRed blood cells after adding a drop of 0.15 M NaCl solution

Figure 5.0a Red blood cells before adding a drop of 0.30 M NaCl solution

Figure 5.0b Red blood cells after adding a drop of 0.30 M NaCl solution

Result: The blood cells in slide A which are mixed with 0.07M salt solution have larger sizes compared to the cells in other slides.

Time(min) NaCl concentration(

M)

Cell size (µm)

0.07 0.15 0.30

5 10 10 7.5

10 7.5 7.5 7.5

15 7.5 5 5

20 7.5 5 5

25 7.5 5 5

30 7.5 5 2.5

35 7.5 5 2.5

40 7.5 5 2.5

45 7.5 5 2.5

50 7.5 5 2.5

55 7.5 5 2.5

Table 1.0 Size of Red Blood Cells in Different Concentrations of NaCl

FIGURE 5.0 LINE GRAPH SHOWING THE RELATIONSHIP OF MOLAR CONCENTRATIONS AND RED BLOOD CELL SIZE

5 10 15 20 25 30 35 40 45 50 550

2

4

6

8

10

12

Series1Series2Series3

Time (min)

Cell Size (µm)

0.07M

0.15M

0.30M

Discussion

• Theoretically, the cells will swell and at extreme conditions some cells will burst. •The swelling of the cells occurs when the surrounding fluid inside the cell has greater osmotic pressure or the pressure created against the cell membrane by the movement of water during osmosis than that of the surrounding fluid or simply when the solution is hypotonic. .

• The cells in slide B which are mixed with 0.15M salt solution maintained size that is at the middle of the sizes of cells in slides A and C. • Theoretically, cells in an isotonic solution will just maintain their original size since the osmotic pressure is the same inside and outside the cells therefore allowing no net entrance or exit of water.• The cells in slide C shrunk after placed in 0.30M salt solution. This is because the salt solution is hypertonic to the cells that means the solution has greater osmotic pressure. The greater the osmotic pressure of an environment the greater its tendency to take in water to equilibrate the water content.

Hemolysis - breaking open of red blood cells, resulting to the release of hemoglobin to the surrounding fluid ; possible when blood cells are exposed to a hypotonic solution

Crenation - the contraction of the cell (due to the decrease of the cytoplasm’s volume) when placed in a hypertonic solution, because of the loss of water via osmosis.