A Study Of The Regulation Of Body Fluids Biology Essay

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The spread of particles through random motion from regions of higher concentration to regions of lower concentration is called diffusion. When two solutions of different solute concentration are separated by a semi-permeable membrane, which is permeable to the solvent molecules but not the bigger solution molecules the solvent moves along the concentration gradient through the membrane. In living systems the solvent is water, which moves from a region of high water concentration to low water concentration. This effect is called Osmosis. It is shown in an experimental environment applying a visking tube and sugar solution. In this example the visking tube demonstrates a selectively permeable membrane and the dyed sugar solution as a solution of high solute concentration.

Method: As per schedule

Results:

After about 20 minutes the dyed sugar solution climbed up slowly in the capillary tube.

Later on the solution reached the top and ran down the outside of the tube. By the end of the lab the water, which had been clear for the whole experiment, changed its colur into a light orange.

Discussion:

The Experiment showed, as explained in the introdution, that osmosis took place.

Water molecules moved from a region with a lower solute concentration to a region of a higher solute concentration. The increase of the volume of solution lead to pressure inside the tubing. The dyed sugar solution had to climb up the capillary tubing which was attached to the viscing tubing to equal out the pressure, as the volume increased.

The clear water in the baker confirmed that no sugar solution moved through the visking tubing into the water. Therefore the visking tubing worked as a semi permeable membrane.

The change of the colour of the water at the end of the lab, was the result of some drops of the dyed sugar sulution, dropping out of the top of the capillary tube into the baker.

Osmosis is very important in biological systems. Most of the biological membranes are semi permeable. 2/3 of the water in our body is found inside cells, 1/3 is outside the cells.

The force behind the water movement is called the osmotic pressure. „The osmotic pressure of a solution is proportional to the concentration of the solute particles that cannot cross the membrane. The higher the solute concentration, the higher the solution's osmotic pressure."

(Totora & Derrickson) Measuring the pressure that has to be applied to the solution of higher concentration, to prevent osmosis is a way to find the value of the osmotic pressure.

The osmotic pressure equals zero, when the concentration is balanced by enough solvent moving through the membrane and osmosis stops. Once the osmotic pressure is zero, there are still some random movements of molecules through the membrane because of their kinetic energy. Osmotic movements require no directed energy. Therefore the movements are called passive movements of molecules.

In the human body this reglatory system is needed to maintain the right concentrarion of solute and water intracellular and extracellular.

If this system is disturbed, conditions as Cerebral oedema can occur. Cerebral oedema is an overflow assemblage of water in the intracellular and/or extracellular spaces of the brain.

Mennitol, an osmotic diuretic can be used to treat this life-theretening condition.

Osmotic diuretics are substances who have high molecular weight and inhibit reabsorption of water and sodium. They get filtered in the kidney but the kidney can't resorb them. Because of this the water is osmotically held back in the tubular system of the Kidney and exerted

with the urine, thus reduces the hydrostatic pressure in the vascular system.

Malte Fröhlich

Student No: 10/091

Group: E

Experiment Two

Titel: A demonstration of the effect of buffers and Acid-base solutions affecting change of pH in experiment

Introduction:

Buffers are very important copounds that resist pH changes when acid or alkali are added.

They are not reactive and they try to bring reactions to their optimum pH level. Buffers are essential beacause if the pH goes out of range Enzymes stop working.

Part A aims at the realization about the pH value in certain acid-base relations of Acetic acid and Sodium acetate. The difference between pH measured with a pH meter and calculated with Henderson-Hasselbach equation will be evaluated.

Part B showes the influence of buffers in change of pH in an experimental enviroment to understand their regulatory.

Method: As per schedule

Results:

Part A

Flask

1

2

3

4

5

Vol. acetic acid (ml)

40

30

25

20

10

Molecul concentration (mol/dm³)

0.08

0.06

0.05

0.04

0.02

Vol. sodium acetate (ml)

10

20

25

30

40

Molecular concentration (mol/dm³)

0,02

0.04

0.05

0.06

0.08

Figure 1: The concentration and Volume of acid and sodium in each flask.

Flask

1

2

3

4

5

pH meter

3.85.

4.35

4.57

4.79

5.19

Henderson-Hesselbach equation

4.09

4.52

4.70

4.87

5.30

Difference in Data

0.24

0.17

0.35

0.08

0.11Figure 2: The Value of pH measured and calculated. Incl. Difference between calculations and measurements. The calculated pH value's using the formula: pH=pKa+log10((base)(acid)) with a pKa value of 4.7

Results:

Part B

Beaker

Drops required to colour water

Colour change

- destilled water (10ml)

- 2 drops methyl orange

indicator

1

Pink/Red

- 0.1 mol/dm³ acetic acid (1ml)

- 0.1 mol/dm³ sodium acetate (1ml)

- destilled water (8ml)

- two drops of methyl orange indicator

16

Pink/Red

Beaker

Drops required to colour water

Colour change

- destilled water (8ml)

- 2 drops phenolphthalein indicator

1

Purple

- 0.1 mol/dm³ acetic acid (1ml)

- 0.1 mol/dm³ sodiumm acetate (1ml)

- destilled water (8ml)

- Two drops of phenolphthalein indicator

15

Purple

Discussion:

In part A of the experiment, there was a mixture of a weak acid and a weak base in different proportions. The base was sodium acetate and the acid was acetic acid. The result is explained as follows. A mixture which contains more volume of the acid than sodium with the same concentration, has a lower pH value. The pH value raised when the volume of the added base was higher. pH values are determined by the activity of oxonium in the water.

If there is more oxonium there is a lower pH value.

Acids submit their hydrogen ions H+ to the water which connects to oxonium H30+ with water. Bases bind oxonium itself or built hydroxyl ions, which bind oxonium. That lowers the active oxonium concenntration which leads to a higher pH value.

The Henderson- Hesselbach equation confirmed that the measurements compared with the calculation were quite accurate.

pH=pKa+log10((base)(acid))

Some resons that the results didn't match could be inaccuracy of the experiment.

The pH meter wasn't too accurate, or it hasen't been cleaned properly. Furthermore the constant pKa used to determine the strenght of the acid in the calculation, is an approximation. Another problem could have been that the solutions weren't exactly

0.1 mol/dm³ or the solutions didn't mix probperly.

In part B of the experiment, the working and effectiveness of buffers has been shown.

Beaker 1 and Beaker 2 just contained 10ml destilled water and two different indicator

(methyl orange in Beaker 1 and phenolphthalein in Beaker 2). After just one drop of 0.1M HCl into Beaker 1 the colour changed into pink. The same happened to beaker 2 after adding 1 drop of 0.1M NaOH. Destilled water wasn't a good buffer at all. The pH value changed immediately after a small amount of acid or base was added.

Beaker 3 and 4 sodium acetate and acetic acid were added as a buffer to destilled water and the indicators. It took 15-16 times more drops of each 0.1NaOH and 0.1HCL to change the solution due to the colour of the indicator.

In Beaker 3 the following reaction occurred:

Na+(aq)+CH3COO-(aq)+CH3COOH(aq)+Cl-(aq)+H+(aq)→

Na+(aq) + Cl-(aq) + CH3COOH(aq)

In Beaker 4 the following reaction occurred:

2Na+(ap) + CH3COO-(ap) + CH3COOH(ap) + OH-(ap) → 2Na+ + H2O(l) + 2CH3COO-

In Beaker 3 a part of the acetate reacts with the hydrogen ions and produces more acetic acid.

The pH value raises. In Beaker 4, the buffer transforms OH- into H2O by taking H+ from the acetic acid. Na+ ions accept in solution the spare electron from acetate CH3C00-.

As a result, the acetate is now a base and can take up hydrogen - ion H+.

In aqueous solution the acetic acid dissolves completly to CH3COO- and H+.

In the human body protein buffer system or carbonic acid-bicarbonate buffer system act in intracellular fluid and blood plasma, to prevent it from pH changes. They are essential to maintain the ideal pH level arround 7.35 in the blood. If the blood pH level would raise or drop by 2 points in either directions, Enzymes would stop working and the electrical chemistry in the body would change. This would cause death.

The most common buffer in intracellular fluid and blood plasma is the protein buffer system. Hemoglobin contains at least one carboxyl and amino group (-COOH and -NH2). They are the functional components of the protein buffer. When pH raises the free carboxyl group acts like an acid by releasing H+ to react with OH- to form water. The other end acts as a base by combining with H+ when pH drops. (Tortora & Derrickson Volume 2).

Malte Fröhlich

Student No: 10/091

Group: E

Experiment Three:

Titel: The effect of Tonicity on Red Blood Cells observed in an experimental environment using three solutions of different saline concentration.

Introduction:

Red Blood Cells (Erythrocytes) are blood cells which deliver O2 to body cells trough the blood flow. The Protein Heamoglobin inside the Erythrocytes and the iron atom which is bound to heme carry the oxygen from the lungs to the body capillaries. (Physiology book Ext year)

Red Blood Cells maintain their donut shape and volume in an isotonic solution because there is no water movement into or out of the cell. An example would be 0.9% NaCl solution. „normal (physiological) saline solution." (Tortora & Derrickson Volume 1)

The Expetiment shows how the nutral state of Erythrocyts can be affected by changing the concentration of the extracellular fluid. (using saline solution)

Method: As per schedule

Figure 3: Erythrocytes under the influence of saline solution in percent of concentration, where A has 0.9%, B 0.45% and C 1.8%.

(http://www.bcscience.com/bc8/images/0_quiz_blood_cells.jpg)

Results:

The results of the experiment were quite good. We took blood of a subject and mixed it with 0.9%, 0.45% and 1.8% saline solution. Most of the red blood cells under the microscope matched with the picture of figure 3.

Discussion:

In the experiment 3, osmosis as seen in experiment 1 took place. The saline solution which represented extracellular fluid in the human body, showed what effect different concentrations in the body could have on Erythrocytes. The various saline concentrations lead to different sizes and shapes of the red blood cells.

The solution with the lowest concentration of 0.45% increased the size and shape of the red blood cells and even made some burst. This state is called Hypotonic. The concentration gradient between the intracellular fluid and saline solution lead too the inner of the Erythrocyte, the concentration of the saline solution was lower than the one of the particles in the cell. If there is too much water going inside the cell, it can be demaged and split or burst. This is called Hemolysis.

The red blood cells which were treated with 0.9% saline solution, had the normal typical donut shape of a red blood cell, they did not change in shape or volume. There was no net movement of water in or outside the cell and the concentrations were balanced ( osmotic pressure equals zero as explained on page 3). A solution where a cell maintains its shape and volume, without any osmotic effects is called isotonic (Tortora & Derrickson Volume 1).

The cells in 1.8% saline solution looked small and very shrunk. This time the disbalance went into the other direction. The pressure from the inside of the cell with low concentration of solutes to the extracellular space with higher concentration of solutes. In this case the solution is called hypertonic. The water moves out of the cell quicker than into the cell.

When the cell gets thinner or smaller this is called cranation. High blood pressure and sensation of thirst is the result of a high concentration of solutes in the blood.

Isotonic saline solution concentration of 0.9%NaCl is used in hospitals, because it does not harm cells. It is used to clean catheter after dialysis to prevent from thrombosis within the catheter. (Nowack Birk Weinreich) Further more patients can be put on a 0.9%NaCl drip because of the disability to drink. The solution can equal out a dehydration and does not harm the body.

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