The impermeability of cell plasma membranes is a major barrier to using drugs to kill tumor cells or affect cells transgenically. CPPs are peptides that were discovered to have the ability to transport themselves (and even attached cargo) into cells.
How are the membrane components oriented? A. the hydrophobic heads are oriented towards the outside of the cell and the hydrophilic tails are oriented towards the inside of the cell. B. the hydrophilic heads are oriented towards the outside and the inside of the cell and the hydrophobic tails are oriented towards each other.
A. aquaporins - move water through the membrane by active transport B. carrier protein - nonspecific and will allow material to pass directly through C. channel protein - allow passage of material through the hydrophilic pore
The carrier protein has a reduced affinity for Na+ B. ATP is hydrolyzed by a protein carrier C. Carrier protein binds to 3 Na+ D. Phosphate group is removed and K+ is attached E. Shape change increases the carrier's affnity for K+ ions C. Carrier protein binds to 3 Na+
Thus, gases (such as O2 and CO2), hydrophobic molecules (such as benzene), and small polar but uncharged molecules (such as H2O and ethanol) are able to diffuse across the plasma membrane.
Passive osmosis and diffusion Some substances (small molecules, ions) such as carbon dioxide (CO2) and oxygen (O2), can move across the plasma membrane by diffusion, which is a passive transport process.
Water, carbon dioxide, and oxygen are among the few simple molecules that can cross the cell membrane by diffusion (or a type of diffusion known as osmosis ). Diffusion is one principle method of movement of substances within cells, as well as the method for essential small molecules to cross the cell membrane.
Small, non-polar gasses easily move through the plasma membrane because they are hydrophobic. Steroid molecules can pass more easily through the plasma membrane than a disaccharide. Ions and other charged molecules cannot diffuse through the membrane without the aid of a carrier protein or channel protein.
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.
Bio quiz 3QuestionAnswerwhich of the following molecules would most likely require a transport protein to cross the plasma membrane of a red blood cell?C6H12O636 more rows
Explanation: Molecules move across the plasma/cell membrane through diffusion. If they are not small enough, they have to broken down by other substances, such as enzymes, which are biological catalysts. If they are small enough, usually, the easiest way for them to move is through diffusion.
Charged molecules, such as ions, are unable to diffuse through a phospholipid bilayer regardless of size; even H+ ions cannot cross a lipid bilayer by free diffusion.