- Transport Process
One fundamental aspect of life itself is the ability to transport specific substances to particular site.
Transport processes consume energy, and many are driven by the exergonic breaking of ATP's high-energy phosphate-bonding orbitals.
Isolation mechanisms inhibit the movement of substances.
Diffusion
osmosis
Active Transport
Movement of by which the materials move from higher concentration to areas where they are relatively low concentration
Osmosis is a passive transport process during which water moves from areas where solutes are less concentrated to areas where they are more concentrated.
Membranes are of three types: freely permeable membrane, completely impermeable membranes, differentially or selectively permeable membranes.
Water molecules, even though highly polar, pass through all membranes, but their movement is more rapid if the membrane has protein channels called aquaporins.
Passive transport
The forced pumping of molecules from one side of a membrane to the other by means of molecular pumps located in the membrane.
These crystals located in a cell vacuole is a perfect example of active transport.
All cell membranes in transport process; are plasma membrane governs movement of material into and out of the cell.
Water potential
The chemical potential of water; a measure of the ability of a substance to absorb or release water relative to another substance. It is pronounced as "sigh".
Components: osmotic potential, pressure potential, matric potential.
“ψ = ψπ + ψp + ψm”
Excerpt From: James D. Mauseth. “Botany.”
Cells and water movement
Short-Distance intercellular transport
Guard cells
Motor cells
Transfer Cells
Cells that swell and shrink in plant organs capable of repeated, reversible movements, such as insect traps and petioles of leaves that undergo sleep movement.
Cells involved in rapid short-distance transfer to material; they have transfer (labyrinthine) walls.
Long-distance transport: Phloem
The exact mechanism by which water and nutrients are moved through phloem is not known, most evidence supports the pressure-flow hypothesis.
Long-distance Transport: Xylem
“Hypothesis that as water is pulled upward by transpiration, its molecules cohere sufficiently to withstand the tension.”
Excerpt From: James D. Mauseth. “Botany.” Apple Books.
Water movement through xylem and plants are through cohesion-tension hypothesis.
Properties of water
Water transport through xylem
Control of water thransport by guard cells