Factors Affecting Exchange of Materials Across Membrane Flashcards
How do chemical factors affect exchange across the cell membrane?
While many uncharged particles can easily diffuse across the membrane (such as ethanol), Hydrophilic, charged ions such as sodium and potassium cannot cross the hydrophobic centre of the membrane - must use channel proteins. Water is not lipid soluble, must use aquaporins.
How do physical factors affect exchange across the cell membrane?
The size and shape of molecules can have an impact. Small molecules diffuse easier. Glucose and amino acids are relatively large and use carrier proteins. Very large molecules are transported by endo/exocytosis
How does the concentration gradient affect exchange across the cell membrane?
If the concentration gradient is high, then the substance will diffuse rapidly.
How does the surface area to volume ratio affect exchange across the cell membrane?
A smaller cell, with higher SA:V has faster movement of substances, allowing optimum functioning. A lower SA:V is less efficient. Long flat cells have a higher SA:V than spherical cells with same volume.
How is a large SA:V sometimes harmful?
With high SA:V, small mammals lose heat very quickly, must eat constantly, but this is the trade off for conserving water.
How do cells and organisms maximise SA:V for metabolic processes?
They compartmentalise by forming organelles with membranes, increasing SA. Organs or cells may have folds or protrusions to maximise SA:V (villi, root hairs, intestines)
