Which statements accurately reflect the permeability of the cell membrane? Choose all that apply. The hydrophilic part of the ce
ll membrane is A, the phosphate head. The lipid tails are hydrophobic and will only allow molecules which are small and polar to pass through. Molecules that are large or charged must use a channel protein, such as D, to cross the cell membrane. Molecules using membrane proteins, such as E, for transport require energy. Charged molecules, such as K+ or Ca++ are unable to pass through the lipid bilayer because of their charge and must use a membrane protein to cross the cell membrane. C, the lipid tails, are hydrophobic and repel water.
The hydrophilic part of the cell membrane is A, the phosphate head.
Molecules that are large or charged must use a channel protein, such as D, to cross the cell membrane.
Molecules using membrane proteins, such as E, for transport require energy.
Charged molecules, such as K+ or Ca++ are unable to pass through the lipid bilayer because of their charge and must use a membrane protein to cross the cell membrane. C, the lipid tails, are hydrophobic and repel water.
Further Explanation:
Arranged in a phospholipid bilayer, the cell membrane is semi-permeable; allowing entry into the extracellular fluid or the cytoplasm which are both hydrophilic and contain large concentrations of polar water molecules or other water-soluble compounds. The hydrophilic heads of the bilayer are attracted to water while their water-repellent hydrophobic tails face towards each other- allowing small molecules of water and hydrophilic uncharged molecules to move across the membrane along the concentration gradient.
Transport proteins spanning the plasma membrane facilitate the movement of ions and other complex, polar molecules which are typically prevented from moving across the membrane.
There are two types:
Carrier proteins bind specifically bind to molecules and move them down concentration gradients. Along with using facilitated diffusion, carrier proteins also use energy in the form of ATP and modifiy solute-specific regions, that aid in regulating ion exchange (K+ and Ca2+), through the hydrophobic layer of the plasma membrane.
Channel proteins which are pores filled with water versus enabling charged molecules to diffuse across the membrane, from regions of high concentration to regions of lower concentration. This is a passive part of facilitated diffusion.
The tourniquets are tight straps around an arm or leg and tightened to stop bleeding, used to control arterial and venous blood flow. In the past, tourniquet are used to control bleeding during amputations. Now, a tourniquet is used in surgeries to block arterial blood flow following and to minimize blood loss.
