Most proteins (do or don't) pass through the plasma membrane? Explain?
Substances that dissolve in (lipids or water) can more readily pass across the plasma membrane. Explain
Ions can cross the plasma membrane more easily if they have the (same or opposite) charge as the membrane. Explain.
Plasma membranes have special molecules that help to transport substances across the membranes. These molecules are named what?
Most proteins do not pass through the plasma membrane.
Explanation: The plasma membrane is selectively permeable, which means it allows only certain substances to pass through while restricting others. Small molecules, such as water and gases, can pass freely through the plasma membrane due to their small size and their ability to dissolve in lipids or water. However, larger molecules such as proteins generally do not pass through the plasma membrane because they are too big.
Substances that dissolve in lipids can more readily pass across the plasma membrane.
Explanation: The plasma membrane is primarily composed of a lipid bilayer, which consists of phospholipids that have both hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails. Substances that are hydrophobic or can dissolve in lipids, such as fatty acids or fat-soluble vitamins, can pass more readily through the plasma membrane. This is because they can easily move through the hydrophobic core of the lipid bilayer.
Ions can cross the plasma membrane more easily if they have the same charge as the membrane.
Explanation: Ions are charged particles that can either be positive (cation) or negative (anion). The plasma membrane is electrically polarized, meaning it has an uneven distribution of electrical charges on either side of the membrane. It has a negative charge on the inside and a positive charge on the outside (in most cases). Ions with the same charge as the membrane, such as positive ions in the case of a positive membrane potential, can cross the plasma membrane more easily because they are attracted to the opposite charges.
Plasma membranes have special molecules that help to transport substances across the membranes. These molecules are named transport proteins.
Explanation: Transport proteins are integral membrane proteins that are involved in the selective transport of specific substances across the plasma membrane. They can either allow passive diffusion of molecules along their concentration gradient (facilitated diffusion) or actively transport molecules against their concentration gradient (active transport). These transport proteins play a crucial role in regulating the movement of substances across the plasma membrane and ensuring that the right molecules enter and exit the cell.