Which of the following compounds can diffuse through the lipid bilayer of a cell 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.

How do transport and channel proteins function in a plasma membrane?

Channel proteins facilitate the transport of substances across a cell membrane. They do this through the process of either facilitated diffusion or active transport depending on the concentration gradient, or the difference in the concentration of substances inside and outside the cell membrane.

What kind of bond is most important for interactions between molecules in a cell?

These bonds form when an electron is shared between two elements and are the strongest and most common form of chemical bond in living organisms. Covalent bonds form between the elements that make up the biological molecules in our cells. Unlike ionic bonds, covalent bonds do not dissociate in water.

What interactions occur during a hydrogen bond?

The hydrogen bond is an attractive interaction between a hydrogen atom from a molecule or a molecular fragment X–H in which X is more electronegative than H, and an atom or a group of atoms in the same or a different molecule, in which there is evidence of bond formation.

How do these protein and lipid molecules interact with one another within the cellular membrane?

Membrane proteins in a biological membrane are surrounded by a shell or annulus of ‘ solvent ‘ lipid molecules. These lipid molecules in general interact rather non-specifically with the protein molecules, although a few ‘hot-spots’ may be present on the protein where anionic lipids bind with high affinity.

What can pass through channel proteins?

Water molecules and ions move through channel proteins. Other ions or molecules are also carried across the cell membrane by carrier proteins. The ion or molecule binds to the active site of a carrier protein.

Are channel proteins hydrophobic or hydrophilic?

Channel proteins have hydrophilic domains exposed to the intracellular and extracellular fluids; they additionally have a hydrophilic channel through their core that provides a hydrated opening through the membrane layers.

What types of bonds will form between the hydrophilic region of the protein and water?

The hydrophilic regions of the phospholipids tend to form hydrogen bonds with water and other polar molecules on both the exterior and interior of the cell.

Are hydrophobic interactions stronger than ionic interactions?

Ionic bonds are less strong – although some are very close to covalent, whereas others are quite weak. Hydrophobic (lipophilic) and hydrophilic bonds are much weaker and hydrogen bonds are weakest. BUT… Covalent bonds are strongest.

How does hydrogen bonding affect protein structure?

(1) Hydrogen bonds contribute favorably to protein stability. (2) The contribution of hydrogen bonds to protein stability is strongly context dependent. (3) Hydrogen bonds by side chains and peptide groups make similar contributions to protein stability.

How do hydrophobic and hydrophilic interactions affect protein structure?

Hydrophobic interactions greatly contribute to the folding and shaping of a protein. The “R” group of the amino acid is either hydrophobic or hydrophilic.

Can hydrophilic substances pass through the hydrophobic membrane?

Without a channel through the hydrophobic membrane, the hydrophilic substances could not pass. The protein in the above graphic has both hydrophobic and hydrophilic portions. The exterior of the protein, the parts exposed to the environment and the cytoplasm, will be hydrophilic.

How do transmembrane proteins interact with their lipid neighbors?

Like their lipid neighbors, these transmembrane proteinsare amphipathic, having regions that are hydrophobic and regions that are hydrophilic. Their hydrophobic regions pass through the membrane and interact with the hydrophobic tails of the lipid molecules in the interior of the bilayer, where they are sequestered away from water.

How do proteins transport substances across the membrane?

There are also proteins that transport other hydrophilic substances across the membrane. These proteins, while not enzymes, are also formed by amino acid chains. As seen in the graphic below, these proteins often function by using the energy from ATP to move various substances across the membrane.