LAB REPORT 4 [ Biology] - EXPERIMENT 4: TRANSPORT ACROSS MEMBRANESBy using potato strips and blood as PDF

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EXPERIMENT 4: TRANSPORT ACROSS MEMBRANES
By using potato strips and blood as materials. This lab report consists of objectives, introduction, apparatus & materials, discussion, and conclusion....

Description

BIOLOGY 1 SCI 1034 EXPERIMENT 4: TRANSPORT ACROSS MEMBRANES NAME

NUR FARISHA ADLIN BINTI MOHD SHAHRIN NOOR DIYANA AZZARIESHA BINTI MOHMAD KHAIR NUR AYUNI BINTI NAZLIN NOR AQILAH BINTI ZAIBUDIN IFFAH IRDINA BINTI NORIZAN

COLLEGE ID

KMK2101090 KMK2101074 KMK2101087 KMK2101077 KMK2101203

PROGRAMME

FIS-YTP

CLASS TUTORIAL

FB

TEACHER/LECTURE NAME

IYLIA’ SYAHMI BINTI SAHURI

DATE SUBMIT

18.10.2021

OBJECTIVES

1. To demonstrate how matter moves from one area to another through the membrane in the living system. 2. To study the effect of varying solutions (hypotonic, isotonic & hypertonic) on plant and animal cells. 3. To determine the sucrose concentration which is isotonic to potato cells. 4. To determine the osmotic pressure of potato cells in the atmospheric unit. 5. To determine the concentration of sodium chloride that is isotonic to red blood cells.

INTRODUCTION

Semipermeable membranes are termed selectively permeable membranes or partially permeable membranes, allowing certain molecules or ions to pass through by diffusion. Osmosis is the movement of water through a semipermeable membrane according to the concentration gradient of water across the membrane, which is inversely proportional to the concentration of solutes. The semipermeable membrane limits the diffusion of solutes in the water. Not surprisingly, the aquaporin proteins that facilitate water movement play a large role in osmosis, most prominently in red blood cells and the membranes of kidney tubules. Three terms hypotonic, isotonic, and hypertonic are used to relate the osmolarity of a cell to the osmolarity of the extracellular fluid that contains the cells. In a hypotonic situation, the extracellular fluid has lower osmolarity than the fluid inside the cell, and water enters the cell. (In living systems, the point of reference is always the cytoplasm, so the prefix hypo- means that the extracellular fluid has a lower concentration of solutes, or a lower osmolarity, than the cell cytoplasm. ) It also means that the extracellular fluid has a higher concentration of water in the solution than does the cell. In this situation, water will follow its concentration gradient and enter the cell, causing the cell to expand and burst for an animal cell which is a condition named lysis or hemolysis. For plant cells, they will expand but the increase in size is restricted by the cell wall, turgid. As for a hypertonic solution, the prefix hyper- refers to the extracellular fluid having a higher osmolarity than the cell’s cytoplasm; therefore, the fluid contains less water (lower water potential) than the cell does. Because the cell has a relatively higher concentration of water (high water potential), water will leave the cell, and the cell will shrink. The shrinking of a plant cell is named plasmolysis while the shrinking of an animal cell is called crenation. In an isotonic solution, the extracellular fluid has the same osmolarity as the cell. If the osmolarity of the cell matches that of the extracellular fluid, there will be no net movement of water into or out of the cell, although water will still move in and out.

APPARATUS AND MATERIALS

Experiment 4.1: Osmotic pressure of potato cells

APPARATUS

Boiling tube Beaker Cork borer Electronic balance Forceps Measuring cylinder (25 ml) Petri dish Pipette (10 ml)

MATERIALS

Distilled water Filter paper Fresh potato tuber Graph paper Labeling paper Razorblade Ruler Sucrose solution Tile

4.2: Haemolysis

APPARATUS

6 test tubes Pipette 10ml Glass rod Compound Microscope Slides Coverslips Sterilized Lancet Cotton Dropper

MATERIALS

40ml of 1% NaCl solution Distilled Water Ethanol Oil Immersion

PROCEDURES

Exercise 4.1: Osmotic pressure of potato cells

1. 20ml of sucrose solution with different molarities was prepared in boiling tubes using the dilution method. The molarities required were 0.1M, 0.2M, 0.3M, 0.4M, and 0.5M. The volume of sucrose solution (1M) and the distilled water used in preparing the sucrose solutions were recorded in Table 4.1. 2. 15 pieces of potato strips were prepared using a cork borer, 3 replicates were needed for each concentration. The length of each strip was 4 cm. 3. 3 potato strips were taken for every concentration and their average weight was recorded in a table. 4. All potato strips were put into the boiling tubes containing different sucrose concentrations. 5. After 30 minutes, the three strips were removed from the boiling tube, wiped, and immediately their average weight was recorded. 6. A graph for the changes in weight of the potato strips against the molarities of the sucrose solutions was drawn, based on the results. 7. The sucrose concentration which is isotonic to potato cells was determined from the graph obtained in step 6. 8. Based on the values given in Table 4.2, a standard graph of osmotic pressure against the molarity of sucrose solution was drawn. 9. From the graph obtained in step 8, the osmotic pressure of potato cells in the atmospheric unit (atm) was determined.

Exercise 4.2: Haemolysis

1. 6 test tubes from A to F were labeled. 2. NaCl solution of different concentrations was prepared from the stock solution of 1% NaCl solution as shown in the table below.

Concentration

of 1.0

0.8

0.6

0.4

0.2

0

8

6

4

2

0

2

4

6

8

10

10

10

10

10

10

NaCl (%) Volume of 1% NaCl 1.0 (ml) Volume of distilled 0 water (ml) Total volume (ml)

10

3. Hands were cleaned using ethanol. A sterilized lancet was used to prick one of the fingers. The lancet was disposed of. 4. 2 drops of blood were added to each test tube. 5. Each tube was shaken and left for 5 minutes. 6. The color of the solution in each tube was examined. 7. A drop of the solution was transferred onto a slide 8. A coverslip was placed onto the slide and examined under 100x magnification. 9. The observation was recorded in a table

OBSERVATION

Table 4.1.1: Average weight of potato strips Molarity of

Initial Weight of Potato Strip (g)

Sucrose Solutions (M)

1st

2nd

3rd

Average

0.1

1.78

1.94

1.86

1.86

0.2

1.94

1.94

1.94

1.94

0.3

1.93

1.89

1.78

1.87

0.4

1.78

1.84

1.83

1.82

0.5

1.84

1.81

1.75

1.80

Table 4.1.2 Changes in weight of potato strips Final Weight of Potato Strip (g) Molarity of

Initial Weight of Potato Strip (g)

Sucrose Solutions (M) Initial

Final

Change

0.1

1.86

1.99

+0.13

0.2

1.94

1.99

+0.05

0.3

1.87

1.85

-0.02

0.4

1.82

1.75

-0.07

0.5

1.80

1.64

-0.16

GRAPH 4.1

Table 4.2 Values for constructing a standard graph MOLARITY (M)

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

OSMOTIC PRESSURE (atm)

1.3

2.6

4.0

5.3

6.7

8.1

9.6

11.1

12.6

14.3

16.0

GRAPH TABLE NaCl 4.2

Exercise 4.2: Haemolysis

Test tube A

Test tube C

Test tube D

Test tube E

Test tube F

Test Tube

The concentration of NaCl (%)

Colour of Solution

Appearance of Erythrocytes

A

1.0

Cloudy

Crenated

B

0.8

Cloudy

Swollen

C

0.6

Cloudy

Haemolysed

D

0.4

Cloudy

Haemolysed

E

0.2

Clear

Haemolysed

F

0

Clear

Haemolysed

DISCUSSION Exercise 4.1: Osmotic pressure of potato cells In graph 4.1, when the molarity of the sucrose solution increases the changes in weight of potato strips decrease because when the molarities of sucrose solution increase, the concentration of solute decreases as the water molecule is lower compared to the sucrose molecule. The water molecule moves from high water potential to low water potential across the plasma membrane down the concentration gradient. When the molarities of sucrose solution are 0.1 M, the changes in weight of potato is positive, +0.13 gram means there is an increase in mass of potato. Potatoes are hypertonic to the sucrose solution because potatoes have a lower concentration of solute while sucrose solution has a high concentration of solute. So, the water molecule will move from the sucrose solution to the potato. When the molarities of sucrose solution are 0.28 M, there is no change, 0 gram in weight of potato strip. The solution is said to be isotonic to the potato strip meaning that the concentration of solute in the potato and the sucrose solution is the same. So, no net flow of water molecules. When the molarities of sucrose solution is 0.5 M, the changes in weight of potato strip giving negative value, -0.16 gram means that the weight of potato is decreasing. The potato is said to be hypotonic to the sucrose solution. So, the water molecule will move out of the potato to the sucrose solution. So the size and mass of the potato will be decreasing and the final mass of the potato strip will be smaller.

The molarity of sucrose solution affects the osmotic pressure of potato cells. From graph 4.2, when the molarity of sucrose solution increases, the osmotic pressure increases. This means the molarity of sucrose solution is directly proportional to the osmotic pressure. This can be shown when the molarity of the solution is 0.1 M, the osmotic pressure is 2.6 atm. When the molarity of the solution is 0.5 M, the osmotic pressure is 16.0 atm. Osmotic pressure is defined as the measure of the tendency of a solution to take in a pure solvent by osmosis. The osmotic pressure of the potato cells based on the graph obtained is 8.0 atm.

Exercise 4.2: Haemolysis In experiment 4.2, the effect of different concentrations of NaCl solutions on erythrocytes was observed through different colours of solutions produced. Also, the appearance of erythrocytes was examined under the microscope. When the concentration of NaCl solutions is the highest, the concentration of water in the solution is the lowest. This means that the solution is hypertonic to the erythrocyte. The water is transported out from the cell because solute concentration inside the cell is lower. This will explain the crenated and shrunk appearance of the erythrocytes under the microscope. If the concentration of NaCl solutions is the lowest, the concentration of water in the solution is the highest. The solution is said to be hypotonic to the erythrocytes. The water is transported into the cell because the solute concentration inside the cell is higher. This will explain the swollen appearance of the erythrocytes when examined under the microscope. In a hypotonic solution, the erythrocytes gain water rapidly by osmosis until it bursts, this situation is known to be haemolysis. However, If the concentration of solute in both NaCl solution and in the erythrocyte is the same, both of them are said to be isotonic to each other. The colour of the solution in test tubes E and F were clear due to the bursting of erythrocytes as water moves rapidly into the cells through osmosis. Once the erythrocytes rupture, it loses its haemoglobin and becomes transparent and nearly invisible under the microscope. Hypertonic solutions lose water through osmosis, causing cells to shrink and become crenated in appearance, yet solutions remain cloudy. This can be seen in the color of the solution in test tube A. As the concentration of hypotonic salt solutions decreases, the solution becomes less cloudy as seen in test tubes B, C, and D.

QUESTIONS

1. Does the erythrocyte become hemolyzed if the solution is clear? How do you explain this situation? Yes, the clear solution shows that all the cells have haemolysed. When the erythrocyte is placed in a hypotonic solution, water will diffuse into the cell by osmosis. The cell will swell and burst, releasing its intracellular components such as protein, carbohydrate, and hemoglobin. This will form a transparent red solution.

2. What is the concentration of NaCl for hemolysis to occur? Briefly explain the event likely to occur? Any NaCl solution that has a NaCl concentration significantly less than 0.85% is considered hypotonic, when red blood cells are placed in a sufficiently strong hypotonic fluid, there is an uncontrolled net inward osmosis, resulting in the continuous uncontrolled swelling of the cells. Depending on how hypotonic the fluid is, a certain percentage of the cells will swell until they break open, a process known as hemolysis (the lysis of red blood cells).

3. Erythrocytes can show various forms of haemolysis in hypotonic solutions. Give evidence to support the given statement by comparing your result with your friend’s result. In a hypotonic environment (e.g. 0.4% NaCl or distilled water), an influx of water occurs: the cells swell, the integrity of their membranes is disrupted, allowing the escape of their hemoglobin (hemolysis) which dissolves in the external medium. As seen in the results, the colour of solutions in test tube D is cloudy and the appearance of erythrocytes is hemolyzed. The hemolyzed appearance of erythrocytes and cloudy solutions mean an unusually large number of reticulocytes (immature erythrocytes), or atypically small, round cells were observed indicating hemolysis does occur in a hypotonic solution when examined under the microscope. While, based on the other group’s result, the colour of solutions in test tube D is clear and the appearance of erythrocytes is nowhere to be seen under the microscope. This means that water moves into the cells causing the

erythrocytes to swell and become larger and more spherical. Eventually, the erythrocytes will rupture and lose all contents and colour, making them very difficult to see when examined under the microscope. This is another form of haemolysis that occurs in hypotonic solutions. By comparing with other results, it is shown that erythrocytes can show various forms of haemolysis in hypotonic solutions.

CONCLUSIONS

In conclusion, all of the objectives stated above are achieved. This experiment shows how matter moves from one area to another through the membrane in the living system. Water molecules move from regions of higher concentration to regions of lower concentration until equilibrium is achieved. Different concentration of solution gives different effects on the potato cells. Students can observe the changes in the weight of the potato cells in experiment 4.1 before and after the experiment due to the movement of water molecules depending on what is the concentration of solutions either hypotonic, isotonic, or hypertonic. The sucrose solution that is said to be isotonic to the potato cells based on the graph obtained is 0.28M. Next, because each person's red blood cell component is distinct, the concentration of sodium chloride that is isotonic to red blood cells could not be calculated. The precautionary step is that the potato strips must be the same size which is 4 cm each so that each one has the same surface area. In addition, the blood used in experiment 4.2 must come from the same person because each individual's red blood cell component is different so the results will be more accurate if only one person’s blood is used. Lastly, the experiment should be repeated to acquire more accurate results.

REFERENCES 1. Courses.lumenlearning.com. 2021. Transport Across Membranes | Boundless Anatomy and Physiology. [online] Available at: [Accessed 15 October 2021]. (Transport Across Membranes | Boundless Anatomy and Physiology, 2021) 2. Guevara, M., & Vollrath, M. (n.d.). Red cell fragility - Osmotic hemolysis. The McGill Physiology

Virtual

Laboratory.

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October

17,

2021,

from

https://www.medicine.mcgill.ca/physio/vlab/bloodlab/eryfrag1_n.htm 3.

Davidson, M. (n.d.). Galleries | Hemolytic Anemia at 20x Magnification. Nikon’s microscopy. Retrieved October 17, 2021, from https://www.microscopyu.com/galleryimages/hemolytic-anemia-at-20x-magnification

4. Inspi, S. (2016, June 3). Red blood cells under the microscope, hypo and hypertonic solutions

[Video].

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