The Cell : Transport Mechanisms And Cell Permeability

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?

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?

Essentially, the nucleus is vital for the cell’s survival. The nucleus controls and gives instructions to all organelles and inhabitants of the cell(Doc. 2). It is a dense, ball shaped configuration that contains the DNA of the cell.

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

This is an individual study investigating the process of diffusion, osmosis and active transport. To start you should know that substances are moving in and out of cells of your body all the time. To understand and make sense of the cells of your body, you need to know about the process of diffusion, osmosis and active transport.

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

The Transport of Substances Across the Plasma Membrane The plasma membrane or, the cell surface membrane, is made almost entirely of protein and lipid. The plasma membrane controls the movement of substances into and out of a cell. It is partially permeable so some substances cross more easily than others.

Breaking down an organism leads scientists to identify cells. A group of cells create tissues, tissues combined are organs, and organs and their functions make up systems. Basically, cells make up living organisms. There are 2 kinds of cells: Prokaryotic and Eukaryotic. Within a prokaryotic, it doesn’t contain a DNA bounded nucleus; however, a eukaryotic cell does. Though the prokaryotic cell differs from a eukaryotic cell, they share a cell membrane. The cell membrane is composed of a phospholipid bilayer and proteins, which makes it selectively permeable. It is located outside of the cytoplasm and controls the movement of substances in and out of the cell. Its basic function is to protect the cell from its surroundings by selecting what can enter and exit the cell.

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.

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.

The cytoplasm is the area between the nucleus and the cell membrane. The cytoplasm contains many important structures. This area is basically the main place where you will find structures that help the cells stay alive.

Cellular transport refers to materials moving across the membrane. Transport also deals with how the materials move into and out of the cell. Passive and active transport are the two main types of transport. In our daily lives, we can link transport to many different functions that occur in our bodies. I have chosen three things to relate transport to: sodium and potassium transport to kidney function and dialysis, calcium transport to muscular dystrophy, iron transport to Parkinson's disease.

In order for cells and organisms to “live” they need to perform certain tasks such as produce energy through respiration, send messages, maintenance and reproduction. To enable the cell to do so, it contains within small structures called organelles, each organelle is different and carries out a specific function.

Test results concerning the permeability of cell membranes found that temperature stress effected the function of cell membranes. The test exhibited that cell membrane function is altered at temperature extremes relative to room temperature or 23°C. The test results found that the further the temperature was from room temperature the higher the betacyanin concentration was in the water meaning that the betacyanin escaped the cell membrane indicating a change in its functionality from the control; the control being the test done at room temperature (23°C) and resulting in an average colorimeter reading of 0.0098 units of optical density (see figure 1). All other temperatures resulted in a higher average reading for absorbance of betacyanin, meaning that more betacyanin was released from the cells.

Only uncharged, small, polar molecules, (such as water) and hydrophobic molecules, (such as oxygen, carbon dioxide) and lipid-soluble molecules (such as hydrocarbons) can freely pass across the membrane. All ions and large polar molecules (such as glucose) are not permeable to the membrane.