Membrane transport is essential for cellular life. As cells proceed through their life cycle, a vast amount of exchange is necessary to maintain function. Transport may involve the incorporation of biological molecules and the discharge of waste products that are necessary for normal
function.1 Membrane transport refers to the movement of particles (solute) across or through a membranous
barrier.2 These membranous barriers, in the case of the cell for example, consist of a phospholipid bilayer. The phospholipids orient themselves in such a way so that the hydrophilic (polar) heads are nearest the extracellular and intracellular mediums, and the hydrophobic
(non-polar) tails align between the two hydrophilic head groups. Membrane transport is dependent upon the permeability of the membrane, transmembrane solute concentration, and the size and charge of the solute.2 Solute particles can traverse the membrane via three
mechanisms: passive, facilitated, and active transport.1 Some of these transport mechanisms require the input of energy and use of a transmembrane protein, whereas other mechanisms do not incorporate secondary
molecules.3 Passive transport is the simplest method of transport and
is dependent upon the concentration gradient, and the size and charge of the solute.2 In passive transport, small uncharged solute particles diffuse across the membrane until both sides of the membrane have reached an equilibrium that is similar in concentration. The
direction of solute travel is indicative of the concentration of that particular particle on each side of the membrane. Figure 1. Passive diffusion of O2 and CO2 across a membrane over time 1-3. Based on the thermodynamics of the system, particles will move from an area of high concentration to an area of low concentration in order to increase the entropy of the cell. Additionally, this particle movement will occur spontaneously as the free energy (Gibbs free energy; ∆G) of the system is negative.4 Where:
Which of the following types of membrane transport mechanism is an active process?Exocytosis is a form of vesicular transport. All vesicular transport processes are active processes that require ATP.
What transport mechanisms are active?There are two types of active transport: primary active transport that uses adenosine triphosphate (ATP), and secondary active transport that uses an electrochemical gradient. Some examples of active transport include: Phagocytosis of bacteria by macrophages. Movement of calcium ions out of cardiac muscle cells.
Which membrane transport is active?Endocytosis is a pathway for internalizing solid particles ("cell eating" or phagocytosis), small molecules and ions ("cell drinking" or pinocytosis), and macromolecules. Endocytosis requires energy and is thus a form of active transport.
What are 4 types of active transport?CONTENTS. Antiport Pumps.. Symport Pumps.. Endocytosis.. Exocytosis.. |