How A Membrane Affect An Element Rate Of Diffusion And Which Elements Can Not Penetrate Through The Membrane

Phospholipids make up most of the cell membrane, in a phospholipid bilayer. Phospholipid molecules form two layers, with the hydrophilic (water loving) head facing the extracellular fluid and the cytosol (intracellular) fluid, and the hydrophobic (not water loving) tails facing one another. The cell membrane is constructed in such a way that it is semipermeable, and allows oxygen, CO2 and lipid soluble molecules through easily, while other molecules like glucose, amino acids, water, and ions cannot pass through quite as easily. That is the meaning behind the chant “some things can pass, others cannot!”.

This experiment gave a visual understanding of osmosis and diffusion. The first experiment proved that solutes would move down a concentration gradient if permeable to the selective membrane. The second experiment proved different solute concentrations affect the movement of water, depending on the solute concentration inside the cell. The purpose of this lab was to look for different solutes that can cross an artificial membrane and to observe the effect of different concentrations of sucrose on the mass of a potato cell. Results for Part One suggested that the molecular weight of albumin and starch was too large to

Repeated Trials: In procedure one, we tested diffusion on different sized cell models (gelatin with various volume and surface area wise). In procedure two, we tested cell models in different internal environments and similar external environments to find the effects on rate of osmosis. In procedure three, we used potato cells in different concentrated sucrose environments to test the effects on water potential on cells and osmosis.

However one beaker received 100 mL of Deionized water with a molarity of 0.0. Afterwards a cork borer was pushed through the potato and was twisted back and forth. Once the borer was filled it was removed from the potato. Pushing the potato cylinder out of the borer, this this step was repeated six more times in order to get seven undamaged potato cylinders. Using a sharp razor blade, the potato cylinders were both cut to a uniform length of about 5cm, and were removed of their potato skins. The potato pieces were also cut in half to give the cells a greater surface area in which it was easier to absorb the solution. After the cylinders were weighed on a balance and the data was recorded in Table 4. Using the razor blade each potato was cut lengthwise into two long halves. Then the potato pieces were transferred to the water beaker and the time they were submerged was recorded. This step was repeated for all potato cylinders in which the pieces were placed in solutions 0.1 to 0.6 M. The potatoes were incubated for ninety minutes. At the end of the incubation period the time was recorded. Then the potato piece was removed form the first sample. Next potato pieces were weighed the and the final weight was recorded in Table 4. This procedure was repeated until all samples had been weighed and recorded in the chronological order they were initially placed in the test solution. Afterwards the table was completed by recording the

The cell membrane consists of eight distinctive parts that each have their own unique structure and function. The phospholipid bilayer is an integral part of the cell membrane because it is the external layer of the cell membrane and composes the barriers that isolate the internal cell components and organelles from the extracellular environment. It is composed of a series of phospholipids that have a hydrophobic region and a hydrophilic region. These regions are composed of the hydrophilic heads and the hydrophobic tails of the phospholipids, this organization of the polar heads and nonpolar tails allows the heads of the cell to form hydrogen bonds with water molecules while the tails are able to avoid water. The phospholipid bilayer also has many important functions within the cell, it gives the cell shape, provides protection, and it is selectively permeable which allows it to only let very specific molecules pass through its surface. The phospholipid bilayer is an important structure because it prevents harmful and unwanted molecules from entering the cell and isolates organelles which helps to maintain the internal environmental homeostasis of the cell.

In order to assimilate diffusion through a permeable membrane potassium permanganate and methylene blue were used in experiment. The objective was to compare the rates at which the liquid compound of different molecular weight diffused through agar. This was achieved by obtaining agar in a petri dish with two wells to hold the liquid compounds. The rate was measured by time and diameter distance diffused. This process was observed for 60 minutes at 15 minute intervals.

Introduction: Cell membranes contain many different types of molecules which have different roles in the overall structure of the membrane. Phospholipids form a bilayer, which is the basic structure of the membrane. Their non-polar tails form a barrier to most water soluble substances. Membrane proteins serves as channels for transport of metabolites, some act as enzymes or carriers, while some are receptors. Lastly carbohydrate molecules of the membrane are relatively short-chain polysaccharides, which has multiple functions, for example, cell-cell recognition and acting as receptor sites for chemical signals.

Introduction: The biological membranes are composed of phospholipid bilayers, each phospholipid with hydrophilic heads and hydrophobic tails, and proteins. This arrangement of the proteins and lipids produces a selectively permeable membrane. Many kinds of molecules surround or are contained within

is something that lets some things in and some things out of the cell. It is an outer cover for the cell. If the cell membrane was non existences the cell would spill all over the place. Its function is to protect the integrity of the interior of the cell by allowing certain substances into the cell, while keeping other substances out. It is composed of a thin, double-layered sheet of lipids, around the Cell and is a protective membrane layer around every Cell.

More specifically for the experiment we will need four deshelled eggs, four beakers and distilled water with a certain percentage of sucrose, a timer, and a scale to weigh the eggs. Using the process of osmosis, we will determine the weight of the eggs after being soaked in the solution. The four beakers each had distilled water in them with sucrose but all contained different amounts. One beaker contained 0% sucrose. The other beakers contained 10%, 40%, and an “unknown” amount of sucrose. Before placing the eggs into the solution, we are to weigh each egg separately to the nearest 0.1g and record this in table. Once that step has been completed, we then place one egg in each of the beakers separately that was marked with the amounts of sucrose. At fifteen-minute intervals, remove the deshelled egg from the water inside the beaker and wipe off all the excess water. After that process has been completed, we will weigh each egg separately to see if they have gained or lost their mass/weight. Once each egg has been weighed accurately, the recorded data is placed in the table provided. This step goes on for an hour. The deshelled eggs in this experiment will increase in mass in the different types of distilled water. This lab session provided the class with the evidence that diffusion and osmosis occurs within the different types of solutions.

The experiment showed the flow of substances through the membrane. The pores in the membrane must be small enough to let water, glucose, and IKI to move freely but not enough to let starch pass through.

Biological membranes must be semi-permeable to allow the passage of substances in and out of the cell. The semi-permeability allows the passage of substances such as proteins, nutrients, and more to be regulated. Only substances of a particular size can go into the cell and only these certain small substances will be allowed to exit the cell.

All cells have a cell membrane. The structure of membranes is formed from a double layer of phospholipids with proteins floating in it. The proteins are embedded on the surface and inside or bridge the double layers of phospholipids. This structure is called a mosaic model. The main function of cell membranes is to provide protection and support for the cell and they also control what enter and exit the cell to maintain internal balance, called homeostasis. There are two types of a membrane protein: integral proteins and peripheral proteins. The integral membrane proteins are

Cell membrane is a selective boundary composed of a unique phospholipid bi-layer structure consisting of lipids, proteins and carbohydrates. This structure regulates the import and export to maintain homeostasis condition inside the cell. (Knox et al., 2014) The plasma membrane is referred as a fluid mosaic which also has selective permeability. The permeability of the membrane can be varied depending on the external conditions. (Mitchel, 2015)

In performing the proper experimentation, we poured some of the methylene blue substrate in a piece of paper, for ease transport towards the agar plates. We performed it cautiously by not inhaling it, for it is a form of powder. We carefully place the substrate at the center of the agar plates, to ensure that is that there is enough space for diffusion to take place. After the moment we placed the substrate, we carefully placed a transparent ruler under the plate to measure the diameter of the substrate in 0 minutes. We carefully note the time, having a 15-minute interval and record the changes in the diameter of the substrate. We continued it, until we have an hour observation.