Active and Passive Transport of Molecules Through Plasma Membrane

The movement of molecules have two forms of transport through the plasma membrane: active transport and passive transport. Active processes require energy, such as ATP, in order for the molecules to be transported. In active transport, the cell administers ATP.i Within passive processes no energy is required and changes n pressure and concentration are the driving forces. Processes such as simple diffusion, facilitated diffusion, osmosis, and filtration are characterized as passive transport, while solute pumps are a form of active transport. Each of these form of transports occur in the cells of all living organisms and are essential to life.

The process of diffusion occurs in and out of a cell when molecules travel from areas of higher concentration to region of lower concentration, and this variation in concentration is described as a concentration gradient. i In order for locomotion to occur, the molecules use its kinetic energy and constant motion. The barrier of the cell is its plasma membrane, which allows the passage of molecules through the pores if they are small enough. i The plasma membrane has a phospholipid bilayer which separates the inside (the cytoplasm) and the outside (extracellular fluid and lipid-soluble solutes) of the cell. The fact that the plasma membrane monitors the passage of molecules based on size and solubility constitutes it as semi-permeable.

Diffusion can be categorized as either simple diffusion or facilitated diffusion. A similarity between simple and facilitated diffusion is that they are both passive processes and travel from areas of higher concentration to region of lower concentration. Simple diffusion only takes place through a phospholipid bilayer and occurs only for non-polar and small...

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...es in the human body to fight off cancer cells and microorganisms that could potentially be harmful to the body.

Knowing that simple diffusion is a passive process, I hypothesized the larger the MWCO (Molecular Weight Cut Off), the more solutes will pass through the semi-permeable membrane. For Activity 2, I hypothesized that by accumulating more transport proteins, the rate of solute transport heightens. I speculated in Activity 3 that the concentration gradient and osmotic pressure are related; as the concentration gradient increased, so did the osmotic pressure. As for Activity 4 that pertains to filtration, I hypothesized as the pore size or pressure enlarges, the filtration rate speeds up. Due to the fact that active transport requires ATP, for Activity 5 I speculated that as the concentration of ATP rises, it will allow active transport to happen more often.