Lab Report Name Section 1 Cell

Lab Reportname Section 1cell

Lab Report Name: ____________________ Section: ___________________ 1 Cell Membrane Transport Exercise 1 - Diffusion through an Artificial Membrane Data Table 1- Changes during Dialysis Color Before Dialysis After Dialysis Solution in Plastic Cup Solution in Dialysis Bag Data Table 2- Benedict’s test Results Color of Solution Before Heating After Heating IKI solution in 16 oz cup Solution in Dialysis Bag Distilled water Questions: What is the purpose of this exercise? What is being tested? What color change was observed in the dialysis tubing? What does that change indicate? Was there a color change in the water surrounding the tubing? If so, explain. What color change was observed in the water from the 16 oz cup containing the IKI used after heating? What does that change indicate? What does the Benedict’s reagent detect? What does the IKI solution detect? In what way is a cell membrane similar to the model cell made of dialysis tubing? Is the transport mechanism in the model cell passive or active, and why? Exercise 2 – Data Table 3: Diffusion of KMnO4 at Various Temperatures Questions: How does temperature affect the rate of diffusion? State a general hypothesis to cover how temperature affects rate of diffusion. Exercise 3 - Tonicity and Diffusion: Data Table 4- Potato Dimensions Potato Before Osmosis (L x W)cm After Osmosis (L x W) cm Tonicity: Hypertonic, Isotonic or Hypotonic Distilled water 10% Sodium Chloride Questions: What is the condition of each potato strip after soaking in the test tubes for an hour? Which one is limp and which one is crisp? How would you explain the difference in the conditions of the potato strips using the concept of tonicity? What was the tonicity of the fresh water solution with respect to the potato cells? What was the tonicity of the salt water solution with respect to the potato cells? How do the changes in the conditions of the potato strips relate to the wilting of plants? How does keeping vegetables cool slow them from wilting?

Paper For Above instruction

The primary purpose of this laboratory exercise is to explore and understand the principles of cell membrane transport, specifically diffusion and osmosis, through various experimental models. This investigation aims to demonstrate how molecules move across cell membranes via passive processes driven by concentration gradients, and how environmental factors influence these mechanisms.

In Exercise 1, an artificial membrane simulation through dialysis tubing is used to study the diffusion of various molecules, including iodine (IKI), Benedict’s reagent, and other solutes. The experiment observes the movement of these molecules pre and post- dialysis, noting color changes that indicate successful diffusions. For example, iodine reacts with starch to produce a blue-black coloration, signaling its diffusion into the dialysis bag, while Benedict’s reagent detects reducing sugars like glucose and fructose, turning from blue to green, yellow, or brick red upon heating, indicating the presence of sugars in the solution.

The observed change in the dialysis tubing typically involves a color change, such as the solution inside turning blue-black or green, which shows molecules like iodine or sugars have permeated the membrane. If the water surrounding the dialysis bag also changes color or clarity, it further confirms the diffusion process. These observations reflect the semi-permeable nature of the dialysis membrane, akin to a cell membrane, which allows certain molecules to diffuse passively based on size and solubility. The transport mechanism in this model is passive, relying solely on concentration gradients without requiring cellular energy, which closely parallels passive diffusion in biological membranes.

Exercise 2 investigates the rate of diffusion of potassium permanganate (KMnO4) at various temperatures. Typically, increased temperature accelerates molecular movement, thereby increasing the rate of diffusion. The hypothesis is that higher temperatures result in faster diffusion due to increased kinetic energy of molecules. This relationship can be explained by the kinetic molecular theory, which predicts that as temperature rises, molecules move more rapidly, reducing the time it takes for them to diffuse across a membrane or medium.

Exercise 3 focuses on osmosis and tonicity by measuring changes in potato dimension before and after soaking in distilled water and saltwater solutions. The initial length and width of potato strips provide a baseline, and their post-osmosis dimensions reveal whether water moves into or out of the cells. In distilled water, potatoes tend to swell and become more turgid, indicating a hypotonic environment relative to the cell sap, while in saltwater, they typically become limp, showing a hypertonic condition that causes water loss from the cells. These physical changes illustrate osmosis, which is the movement of water from areas of higher to lower water potential.

The condition of the potato strips—crisp or limp—can be directly associated with the tonicity of the surrounding solution. The distilled water environment, being hypotonic, causes water to enter the cells, making the tissue firm and crisp. Conversely, the saltwater environment is hypertonic, drawing water out and resulting in a limp, wilted appearance. This concept is fundamental in understanding plant physiology and cellular homeostasis, where maintaining proper tonicity is essential for cell function and survival. Similarly, in food preservation, keeping vegetables cool slows cellular metabolic processes and reduces water loss, thus delaying wilting and spoilage.

Overall, these experiments highlight the significance of membrane permeability, molecular motion, and environmental interactions in biological systems. They demonstrate that passive transport mechanisms are vital for maintaining cellular homeostasis, and environmental factors like temperature and tonicity profoundly influence these processes. Understanding these principles is essential for fields ranging from cell biology and physiology to agriculture and food science.

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