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2021-05-14

What kind of molecules can move easily through the membrane?

What kind of molecules can move easily through the membrane?

Small nonpolar molecules, such as O2 and CO2, are soluble in the lipid bilayer and therefore can readily cross cell membranes. Small uncharged polar molecules, such as H2O, also can diffuse through membranes, but larger uncharged polar molecules, such as glucose, cannot.

Why can’t proteins pass through plasma membranes?

The plasma membrane is selectively permeable; hydrophobic molecules and small polar molecules can diffuse through the lipid layer, but ions and large polar molecules cannot. Integral membrane proteins enable ions and large polar molecules to pass through the membrane by passive or active transport.

How do molecules get across the plasma membrane?

The simplest mechanism by which molecules can cross the plasma membrane is passive diffusion. During passive diffusion, a molecule simply dissolves in the phospholipid bilayer, diffuses across it, and then dissolves in the aqueous solution at the other side of the membrane.

Why do molecules move across the cell membrane in both directions?

Because diffusion depends upon random particle movements, substances diffuse across membranes without requiring the cell to use energy. Even when equilibrium is reached, particles of a solution will continue to move across the membrane in both directions.

Do molecules stop moving when diffusion stops?

Diffusion stops when the concentration of the substance is equal in both areas. This does not mean that the molecules of substance are not moving any more, just that there is no overall movement in one direction. Molecules of substance are moving equally in both directions.

How do large molecules move across the cell membrane through facilitated diffusion?

In facilitated diffusion, molecules diffuse across the plasma membrane with assistance from membrane proteins, such as channels and carriers. A concentration gradient exists for these molecules, so they have the potential to diffuse into (or out of) the cell by moving down it.

What are two differences between facilitated diffusion and active transport?

Active transport uses carrier proteins. Energy is used to change the shape of the carrier protein. Facilitated diffusion uses both gated channel proteins and carrier proteins in transport. Active transport is used to transport molecules against their concentration gradient

What is the main difference between active transport and facilitated diffusion?

Active transport is an active process meaning it requires the use of ATP, whereas facilitated diffusion is a passive process meaning it does not need ATP.To carry out the process active transport only requires carrier proteins; facilitated diffusion on the other hand involves protein channels or carriers.

What is the major difference between passive diffusion and facilitated diffusion?

Simple diffusion is a passive transport as thus, doesn’t require any energy. Facilitated diffusion is also a passive transport mechanism that doesn’t require any energy, but some facilitated diffusion processes can be active. The speed of simple diffusion is relatively low

What is an example of a protein pump?

– a kind of protein that is capable of pumping out compounds that could pose a threat to the cell. An example is AcrB, a bacterial protein complex that repels a wide range of antibiotics through its ability to capture and pump out a spectrum of structurally diverse compounds.