Membrane Transport and Body Fluid Compartments

Electrical and concentration gradients.

Passive diffusion occurs without energy input, while active transport requires energy to move solutes against their gradient.

The sodium-potassium pump (Na+/K+ ATPase) is a classic example of primary active transport.

<p>290 mOsm.</p> Signup and view all the answers

<p>Aquaporins facilitate the passive diffusion of water molecules across the lipid bilayer.</p> Signup and view all the answers

<p>Secondary active transport utilizes the energy from primary active transport to move other substances against their gradient.</p> Signup and view all the answers

<p>It requires a concentration gradient.</p> Signup and view all the answers

<p>Facilitated diffusion uses specialized carrier proteins for transport.</p> Signup and view all the answers

<p>Active transport requires energy to move molecules against their concentration gradient.</p> Signup and view all the answers

<p>Endocytosis is the invagination of the membrane to encase a molecule in a vesicle.</p> Signup and view all the answers

<p>A solute moves down its electrical and/or chemical gradient.</p> Signup and view all the answers

<p>Non-coupled transport means solute movement is independent of other solutes or chemical reactions.</p> Signup and view all the answers

<p>The solute's lipophilicity determines its ability to cross the membrane.</p> Signup and view all the answers

<p>A concentration gradient drives the movement of solutes during passive and facilitated diffusion.</p> Signup and view all the answers

<p>Simple passive diffusion due to its high lipid solubility.</p> Signup and view all the answers

<p>The pKa determines the proportion of ionised versus un-ionised forms, influencing the drug's ability to permeate the membrane.</p> Signup and view all the answers

<p>It diffuses as a high percentage of un-ionised in the stomach but becomes mostly ionised in the plasma.</p> Signup and view all the answers

<p>They exist in both ionised and un-ionised forms, affecting their absorption and distribution.</p> Signup and view all the answers

<p>pH influences the ionisation state, thereby affecting drug permeability and absorption in different compartments.</p> Signup and view all the answers

<p>It restricts the passage of many drugs, requiring specific characteristics for effective transport.</p> Signup and view all the answers

<p>They facilitate the active transport and diffusion of nutrients and drugs across intestinal membranes.</p> Signup and view all the answers

<p>It refers to the phenomenon where drugs become trapped in different compartments due to changes in their ionisation based on pH.</p> Signup and view all the answers

<p>ATP hydrolysis provides the energy necessary to move a solute against its electrochemical gradient.</p> Signup and view all the answers

<p>Initially, the transporter has a high affinity for Na+ and a low affinity for K+.</p> Signup and view all the answers

<p>Phosphorylation transforms the enzyme, altering its affinity for sodium and potassium ions, which is crucial for the transport cycle.</p> Signup and view all the answers

<p>Secondary active transport utilizes the energy from the Na+ gradient to facilitate the movement of sugars and amino acids against their gradients.</p> Signup and view all the answers

<p>The phosphoenzyme undergoes a transition that reduces its affinity for ADP and alters its affinities for Na+ and K+.</p> Signup and view all the answers

<p>Ouabain sensitivity suggests that hydrolysis of the aspartyl-phosphate bond is critical for enzyme activity and ion transport.</p> Signup and view all the answers

<p>The final step is the return of the pump to its native enzyme form, completing the transport cycle.</p> Signup and view all the answers

<p>The Na+/K+ pump can operate in at least five modes due to the reversibility of several steps in the reaction cycle.</p> Signup and view all the answers

<p>Secondary active transport mediated by SGLT1.</p> Signup and view all the answers

<p>Fructose is absorbed by facilitated diffusion mediated by GLUT5.</p> Signup and view all the answers

<p>GLUT2 mediates the exit of all monosaccharides from the intestinal cells into the bloodstream via facilitated diffusion.</p> Signup and view all the answers

<p>A substrate must be a hexose in the D-conformation or one that can form a pyranose ring.</p> Signup and view all the answers

<p>Primary active transport.</p> Signup and view all the answers

<p>The Na+/K+ ATPase pump maintains the electrochemical gradients of Na+ and K+ across the membrane.</p> Signup and view all the answers

<p>Hydrophilic, polar molecules can enter through specialized carrier proteins.</p> Signup and view all the answers

<p>Primary active transport, like the Na+/K+ ATPase, establishes concentration gradients necessary for secondary active transport.</p> Signup and view all the answers

<p>P-glycoprotein acts as a multidrug transmembrane transporter responsible for drug resistance by actively transporting drugs out of cells.</p> Signup and view all the answers

<p>The liver uses P-glycoprotein to transport drugs into bile, facilitating their elimination from the body.</p> Signup and view all the answers

<p>The kidneys utilize P-glycoprotein to pump drugs into the urine for excretion.</p> Signup and view all the answers

<p>Na+/glucose absorption is primarily facilitated through secondary active transport mechanisms known as cotransport.</p> Signup and view all the answers

<p>The negative transepithelial potential drives the parallel absorption of chloride ions in the intestines.</p> Signup and view all the answers

<p>Na+/H+ exchange in the jejunum occurs at the apical and basolateral membranes, contributing to Na+ movement and intracellular pH regulation.</p> Signup and view all the answers

<p>NHE1 acts as a 'cellular pH housekeeper' and regulates intracellular pH but does not contribute to transepithelial Na+ movement.</p> Signup and view all the answers

<p>In the placenta, P-glycoprotein transports drugs back into maternal blood, reducing fetal exposure to potentially harmful substances.</p> Signup and view all the answers