Why do the large molecules stay on their own side of the membrane?
Why are they assuming the large molecules will stay on their own side of the membrane? The membrane is semipermeable, so the membrane only allows some molecules through and not others. In this case, it doesn’t allow the large molecules through.
Why can iodine pass through a membrane?
The Dialysis tubing provides a semi-permeable membrane. Only allowing smaller molecules to pass through it. Iodine molecules are small enough to pass freely through the membrane, however starch molecules are complex and too large to pass through the membrane. Thus iodine diffused into the tube with the starch.
Why do only certain molecules diffuse across the cell membrane?
The difference in the concentrations of the molecules in the two areas is called the concentration gradient. The kinetic energy of the molecules results in random motion, causing diffusion. The inside of the plasma membrane is hydrophobic, so certain molecules cannot easily pass through the membrane.
How do large molecules move across the cell membrane?
It is possible for large molecules to enter a cell by a process called endocytosis, where a small piece of the cell membrane wraps around the particle and is brought into the cell. If the particle is solid, endocytosis is also called phagocytosis. If fluid droplets are taken in, the processes is called pinocytosis.
Is carrier proteins active or passive?
Unlike channel proteins which only transport substances through membranes passively, carrier proteins can transport ions and molecules either passively through facilitated diffusion, or via secondary active transport.
What Happens When carrier proteins are saturated?
When the carrier is saturated (that is, when all solute-binding sites are occupied), the rate of transport is maximal. This rate, referred to as Vmax, is characteristic of the specific carrier and reflects the rate with which the carrier can flip between its two conformational states.
What is the role of carrier proteins in facilitated diffusion?
Carrier proteins can change their shape to move a target molecule from one side of the membrane to the other. The carrier proteins involved in facilitated diffusion simply provide hydrophilic molecules with a way to move down an existing concentration gradient (rather than acting as pumps).
Which substance requires a protein carrier in order to cross a membrane?
118 Cards in this Set
|hypotonic solution is one whose concentration is…||less than that inside the cell|
|Name substances that require a protein carrier to cross the cell membrane||water, glucose, sodium ion, an amino acid|
|What substance fails to cross cell membranes under any circumstances?||DNA|
Why do molecules need a carrier protein to move across a membrane?
Carrier proteins bind and carry the molecules across the cell membrane. These proteins bind a molecule on one side of the membrane, change shape as they carry the molecule across the membrane, and deposit the molecule on the other side of the membrane.
Which molecules need facilitated diffusion to move across the plasma membrane?
Facilitated diffusion therefore allows polar and charged molecules, such as carbohydrates, amino acids, nucleosides, and ions, to cross the plasma membrane. Two classes of proteins that mediate facilitated diffusion are generally distinguished: carrier proteins and channel proteins.