Osmosis Lab report BIO 102L PDF

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Botany Lab Report with Analysis Questions and Answers...

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Republic of the Philippines BATANGAS STATE UNIVERSITY Gov. Pablo Borbon Campus II Alangilan, Batangas City COLLEGE OF ARTS AND SCIENCES Biology Department

LABORATORY REPORT Osmosis in Plant Cells

Date: October 2020 Course/Block: BS BIOLOGY/1103

Direction: Find an experiment on You Tube (or on any other platform, site) about osmosis in plant cells, potatoes in tap water and in distilled water. Describe the process starting with materials and procedure. Then record the data and the result of the experiment. In one box, draw the potato in tap water and in another box, the potato in distilled water. Finally, write a conclusion about the experiment. Fill out the table below (or design your table as it may apply) Specimen

Potato slices Potato slices Questions 1. 2. 3.

Osmotic changes in… Tap water Distilled water

Initial length (cm)

Final length (cm)

Initial weight (g)

Final weight (g)

Initial texture

Final texture

I.

Introduction

Human blood, at 0.9% salt concentration, is a little less salty than seawater, which has a salt concentration of about 35 parts per thousand (3.5%). If we take seawater as an example of a solution, the salt is called the solute (the particles that are dissolved) and the water is the solvent (the liquid that dissolves the particles). Osmosis is the movement of a solvent across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. The water (the solvent) can move across the membrane but the dissolved solutes (the sodium and chloride ions that form salt) cannot. In such situations, water will move across the membrane to balance the concentration of the solutes on both sides. Cells tend to lose water (their solvent) in hypertonic environments (where there are more solutes outside than inside the cell) and gain water in hypotonic environments (where there are fewer solutes outside than inside the cell). When solute concentrations are the same on both sides of the cell, there is no net water movement, and the cell is said to be in an isotonic environment. In this lab we will test samples of potato tissue to see how much water they absorb or release in salt solutions of varying concentrations. This gives us an indirect way to measure the osmotic concentration within living cells, (Osmosis Lab). Osmosis is the movement of solvent particles e.g. water along its concentration gradient - from high to low concentration - via a semi-permeable membrane. In this experiment the semipermeable membrane is the cell (surface) membrane, (Brilliant Biology). I predict that if the potato cylinders would be put in a sucrose/salt concentration where the water potential is higher than the water potential of the potato, the mass od the potato will increase, and if it has similar water potential, there will be no change in mass. II.

Objectives

The aim of this experiment is to experiment the effect of changing the concentration of sucrose or salt on the rate of osmosis in cylinders of potatoes. III. • • • • • • • IV.

Materials 3 Potato strips (5 x 1 x 1) cm (or potato cylinders/cores of equal length e.g. 5 cm diameter, made with a cork borer) 2 Petri dishes with equal volumes of solutions A and B; A = sucrose or salt solution (hypertonic solution); B = distilled water (hypotonic solution) 1 empty petri dish (control) paper towels Stop watch or timing device beam balance ruler Procedure • • • • • •

Observe each strip by feeling it, noting whether it is turgid or flaccid. Record this. Weigh and measure each potato strip, recording the initial mass and length Place a strip in each petri dish, taking care not to mix the strips. Start the timer. Remove the strips after 15 minutes and dab on tissue. Weigh each strip and measure each potato strip, recording the final mass and length. Observe each strip by feeling it, noting whether it is turgid or flaccid. Record this.

• •

V.

Perform % difference calculations for the mass and length using the formula: (final - initial) x 100% / initial

Observation

Potatoes when immersed in a more concentrated solution (soft/ flaccid) and lower concentrated solution (turgid) [left to right].

Strips in water • •

•

Description - Turgid Mass - The increase in mass of the potato strip in water is due to the movement of water molecules into the plant cells via osmosis. Water molecules in the petri dish are at a higher concentration than water molecules in the cytoplasm of cells and so move along their concentration gradient into the cells. As more water molecules are present in cells - and water has mass - the final mass of the potato strip will be greater than the first. Length - the decrease in length is also due to the movement of water molecules via osmosis. More water molecules occupy more space - volume - and push against the cell membrane and the proximate cellulose cell wall. The push of the water molecules results in expansion in all dimensions, including length. The expansion is limited - and regulated by the cellulose cell is inelastic. The push/force acting upon the surface area of the rigid cell produces turgor pressure (recall pressure is force acting per unit area), and hence strips are turgid.

Strips in Salt Solution • •

Description - Flaccid Mass - the decrease in the mass of the potato strip is due to the movement of water molecules outside of the plant cells. Water molecules in the cytoplasm are at a higher concentration than in the salt solution in the petri dish and so move along their concentration gradient out of the cells. Water molecules have mass and so the decreased number of water molecules results in decreased mass.

•

VI.

Length - the decrease in the number of water molecules results in loss of volume. The turgor pressure exerted by the water molecules against the cell membrane and consequently the cellulose cell wall is less. The cell may even shrink if the turgor pressure diminishes further.

Analysis

1. Why did some potato samples gain water and others lose water? Because some are hypotonic and others are hypertonic and because of the movement of water molecules into the plant cells via osmosis; the more concentrated the solution the lighter the potato was at the end. 2. What happens to a cell's water when the exterior liquid is saltier than its interior? A living cell submerged in a saltier solution would come under concentration gradient of the salt, it could lose water and absorb salt due to its lower salt concentration. In the process, it could try to establish an equilibrium but lose homeostasis. That might lead to shrinkage of the cell and eventually death by apoptosis (cell suicide), Naina, (2017) 3. What happens to water outside the cell when the interior is saltier than its surroundings? If there is more salt in a cell than outside it, the water will move through the membrane into the cell, causing it to increase in size, swelling up as the water fills the cell in its imperative to combine with the salt. 4. When a cell gains water, what happens to its size and weight? When a cell gains water it becomes much bigger and heavier which could possibly lead to its explosion. 5. When a cell loses water, what happens to its size and weight? As a cell loses water, it does too lose weight and it shrinks in size. It might eventually end with it shriveling and dying out.

VII.

Conclusion

The purpose of this lab was to test osmosis through two mediums. Although the results contained error the initial hypothesis remains true. The degree to which osmosis occurs is directly related to the molarity of the substances involved. Water molecules transfer through permeable membranes until both sides are equal, this means that the hypotonic to hypertonic flow is directly proportional to the mass increase. VIII.

References

Bibliography Biology Lab Notebook. (n.d.). Retrieved from LAb Report 1- Osmosis: https://sites.google.com/a/newtech.coppellisd.com/emma-s-biology-lab-notebook/labreports/lab-report-1 Brilliant Biology. (n.d.). Retrieved from brialliantbiologystudent.weebly.com: http://brilliantbiologystudent.weebly.com/osmosis.html Lobo, T. (2018, April 26). Sciencing. Retrieved from sciencing.com: https://sciencing.com/scienceexperiments-osmosis-potato-8360195.html Naina. (2017, September 15). Wyzant. Retrieved from Wyzant Ask an Expert: https://www.wyzant.com/resources/answers/396267/what_happens_to_a_cell_39_s_water_w hen_the_exterior_liquid_is_saltier_than_it_39_s_exterior#:~:text=A%20living%20cell%20subme rged%20in,to%20its%20lower%20salt%20concentration.&text=That%20might%20lead%20to%2 Osmosis Lab. (n.d.). Retrieved from jan.ucc.nau.edu Osmosis Lab: http://jan.ucc.nau.edu/lrm22/lessons/osmosis/osmosis.html Zaki, A. (2012, January 12). Slideshare. Retrieved from slideshare.net: https://www.slideshare.net/XAB00DX/osmosis-lab-report...