Biology : Cell Membrane Transport

If the solution in the left beaker contained both urea and albumin, which membrane(s) could you choose to selectively remove the urea from the solution in the left beaker? How would you carry out this experiment?

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!”.

Explain the effect that increasing the Na+ Cl- concentration has on osmotic pressure and why it has this effect. How well did the results compare with your prediction?

The purpose of these experiments is to examine the driving force behind the movement of substances across a selective or semiperpeable plasma membrane. Experiment simulations examine substances that move passively through a semipermeable membrane, and those that require active transport. Those that move passively through the membrane will do so in these simulations by facilitated diffusion and filtration. The plasma membrane’s structure is composed in such a way that it can discriminate as to which substances can pass into the cell. This enables nutrients to enter the cell, while keeping unwanted substances out. Active

A major determinant of diffusion in a biological system is membrane permeability. Small, uncharged molecules pass through cellular membranes easily, while most and/or charged molecules cannot pass through the membrane. The movement of water across a selectively permeable membrane, like the plasma membrane

What happens to the urea concentration in the left beaker (the patient)? It mixes with the water to balance out the structure.

Water diffuses across the membrane from the region of lower solute concentration (higher free water concentration) to that of higher solute concentration (lower free water concentration) until the solute concentrations on both sides of the membrane are equal. The diffusion of free water across a selectively permeable membrane, whether artificial or cellular, is called osmosis. The movement of water across cell membranes and the balance of water between the cell and its environment are crucial to organisms. ("Diffusion And Osmosis - Difference And Comparison | Diffen"). A semi-permeable membrane known as the cell membrane surrounds the living cells of both plants and animals. Both solute concentration and membrane permeability are

The structure of the phospholipid bilayer is a 2-layer arrangement. Basically, the phospholipid bilayer has 2 ends. One end is hydrophilic (attracted to water); therefore, the opposite end is hydrophobic and repels water. The hydrophilic ends face outwards and the hydrophobic ends face inwards. This experiment enables researchers to investigate how the cell membrane selectively chooses what cells to enter the cell through osmosis and diffusion. Within osmosis, it’s a process of what substance passes and exits the semipermeable membrane into a higher concentration to equal the outside and the inside. Unlike osmosis, diffusion is the movement of molecules transporting from a high concentration to

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 this lab, neutral red was used as a pH indicator. The color changes from yellow to red in a basic solution to an acidic solution. The neutral red dye was applied to Saccharomyces Cerevisiae. When the S. Cerevisiae cells come in contact with the neutral red dye, the dye gets to the cell by crossing the cell membrane. The cell membrane is the outer surface of the cell that functions as a barrier. The outside of the cell membrane is made of lipid and membrane proteins (Hardin, 2012). It is selectively permeable, which means only select ions and molecules can pass through it by transport. Membrane transport can be actively or passively moving a substance from side of the membrane to another (Hardin, 2012). Passive transport does not require energy to move molecules across the cell membrane. Diffusion is a form of passive transport that moves molecules across the membrane from an area of higher concentration to an area of lower concentration. Osmosis, diffusion, and facilitated diffusion are all examples of passive transport. Active transport requires energy to move molecules across the membrane from areas of lower concentration to higher concentration. It requires energy because it pushes sodium ions (Na+) and potassium ions (K+) (Hardin, 2012). When the dye entered the cell, it also showed its location. Sodium azide (Na+N3-) is a metabolic inhibitor that blocks the flow of electrons along

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)

The diffusion across a cell membrane is a process of passive and spontaneous net movement of small lipophilic molecules. The molecules move from a high concentration to a low concentrated region along the concentration gradient. The result being a point of equilibrium, this is where a random molecular motion continues but there is no longer any net movement. However, there are things that can affect the rate of diffusion, these being temperature, surface area, concentration, size of the molecule, permeability, diffusion distance and concentration difference. Osmosis is a type of diffusion as it is the movement of water molecules through a semipermeable membrane into a region of higher solute concentration. Equilibrium is reached when the solute concentration is equal on both sides. Water potential is measured in kiloPascals, it is the measuring of the concentration of free water molecules that are able to diffuse compared to pure water, which is 0 kilopascals. It is a measure of the tendency of free water molecules to diffuse from one place to another. The result being, the more free water molecules, the higher the Water Potential. However, Water potential is affected by two factors: pressure and the amount of solute.

Cells are always in motion, energy of motion known as kinetic energy. This kinetic energy causes the membranes in motion to bump into each other, causing the membranes to move in another direction – a direction from a higher concentration of the solution to a lower one. Membranes moving around leads to diffusion and osmosis. Diffusion is the random movement of molecules from an area of higher concentration to an area of lower concentration, until they are equally distributed (Mader & Windelspecht, 2012, p. 50). Cells have a plasma membrane that separates the internal cell from the exterior environment. The plasma membrane is selectively permeable which allows certain solvents to pass through

All cells contain membranes that are selectively permeable, allowing certain things to pass into and leave out of the cell. The process in which molecules of a substance move from an area of high concentration to areas of low concentration is called Diffusion. Whereas Osmosis is the process in which water crosses membranes from regions of high water concentration to areas with low water concentration. While molecules in diffusion move down a concentration gradient, molecules during osmosis both move down a concentration gradient as well as across it. Both diffusion, and osmosis are types of passive transport, which do not require help.

In the human body, there are many processes happening all while one's day is going on. One process is homeostasis, which is the steady-state physiological condition of the body (Postlethwait, Hopson, 2009, p. 8). For homeostasis to occur, cells rely on the cell membranes to control what substances go into or out of the cell through passive or active transport. Passive transport is the movement of substances across a cell membrane without the use of energy by the cell. In passive transport the easiest way to move substances is through diffusion. It occurs when the solute is in a high to low concentration in the solution, and due to kinetic energy the solute will move until a state of equilibrium exists (Postlethwait, Hopson, 2009, p. 97). Another way to move substances through the cell membrane is through osmosis.