Question

What are some significant determinants of the movement of molecules in and out of cells in plants?

Answer 1

Movement of molecules:

1. Osmosis is the naturally occurring net movement or diffusion of solvent molecules across a selectively permeable membrane from an area of high water potential to a region of low water potential in a manner that tends to balance the solute concentrations on the two sides.
2. In plant cells, the vacuole membrane, cell membrane, and tonoplast are all important factors of molecular movement in and out of the cell.
3. The net movement of molecules from a high-concentration area to a low-concentration area is referred to as diffusion.
4. Because of their kinetic energy, molecules in a gas, liquid, or solid are always moving.
5. Molecules are always moving and colliding with one another.
6. The cytoplasm and vacuoles are divided by the tonoplast, a single membrane.
7. They are capable of displaying all three types of molecular motion: translational, rotational, and vibratory motion.
8. Active or passive material movement through a biological membrane is possible.

Passive Transport

1. Moving materials along a concentration gradient (high concentration low concentration) is known as passive transport.
2. There is no energy expended since materials are traveling down a concentration gradient (ATP hydrolysis)
3. Three main categories of passive transportation exist:

• The movement of tiny or lipophilic molecules is known as simple diffusion (e.g. O₂, CO₂, etc.)
• Moving water molecules is called osmosis (dependent on solute concentrations)
• The movement of big or charged molecules is facilitated by membrane proteins (e.g. ions, sucrose, etc.)
  

Active Transport

1. Moving materials up and down a concentration gradient (low concentration to high concentration) is known as active transport.
2. Materials must expend energy since they are moving against the gradient (e.g. ATP hydrolysis)
3. Active transportation comes in two primary categories:

• Using metabolic energy directly to mediate transport, such as by the hydrolysis of ATP, is known as primary (direct) active transport.
• Coupling a molecule with another while it travels along an electrochemical gradient is known as secondary (indirect) active transport.