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Ch 13. Transport Processes - Coggle Diagram
Ch 13. Transport Processes
Concepts
Transport processes consume energy, and many are driven by the exergonic breaking of ATP's high energy phosphate bonding orbitals
Specific transport occurs at virtually every level of biological organization
Enzymes transport electrons, protons, and acetyl groups.
Membranes transport material across themselves
Cells transport materials into and out of themselves as well as circulate it within the Protoplasm.
Entire organisms transport water, carbohydrates, minerals, and other nutrients from one organism to another- between roots, leaves, flowers, and fruits.
Types of transporting
Short-distance transport
- Involves distances of a few cell diameters or less. Mini involve transfer of basic nutrients from cells with access to the nutrients to cells that need them but are not in direct contact with them.
Long-distance Transport
- Occurs between cells that are not close neighbors. This is not absolutely essential in the construction of a large plant. Many large algae have no long distance transport, nor do sponges or similar animals. Disability is adaptive especially for land plants.
Related to transporting
Isolation mechanisms
- Inhibit movement of substances.
Diffusion, Osmosis, and Active Transport
Diffusion
- The random movement of particles in solution causes them to move from areas where they are relatively high concentration to areas where they are relatively low concentration this is technically known as
osmosis
.
Water molecules, even though highly polar, pass through all membranes, but their movement is more rapid if the membrane has protein channels called
aquaporins
3 Types of Membranes
Freely Permeable
- These membranes allow all salutes to diffuse through them and have little biological significance.
Completely Impermeable
- These membranes do not allow anything to pass through and occur as isolation barriers.
Differentially
or
Selectively permeable membranes
- Membranes that only allow certain substances to pass through; all lipid/Protein cell membranes are differentially permeable.
Most membranes also have membrane-bound
molecular pumps
that use the energy of ATP to force molecules across the membrane, even if that type of molecule is extremely concentrated on the receiving side; this is
active transport
.
The endoplasmic reticulum and dictyosome membranes transport material that accumulates in vesicles. these vesicles may be relatively permanent, Remaining in the cell for long periods of time, or they may be a means of
intracellular transport
.
Water Potential
Water has free energy, a capacity to do work. Water is so important in botany that its chemical potential is referred to as
water potential
and has this symbol (pronounced sigh)
Water potential, the free energy of water, can be increased in several ways: Water can be heated, put under pressure, or elevated. It can be decreased by cooling it, reducing pressure, or lowering it.
Pressure Potential
the effect that pressure has on water potential. If water is under pressure, the pressure potential increases and sodas water potential. If the pressure decreases so does the pressure potential and water potential. It can be positive (compressed) or negative (stretched).
Tensional is measured in units of pressure, usually in
megapascals (MPa)
or
bars
. One megapascal is approximate to to 10 bars or 10 atmospheres of pressure.
Osmotic Potential
- The effect that solutes have on water potential. In pure water no solutes are present and osmotic potential is given the value of 0.0 MPa
Matric Potential
- Waters adhesion to non-dissolved structures such as cell walls, membranes, and soil particles. Adhesion can only decrease waters free energy enters matric potential is always negative
Poikilohydry
- Having a body water content that changes with habitat moisture
Movement of water is related to water potential
Water moves whenever there is a difference in water potential within the mass of water. All protoplasts are interconnected and most the walls are fully hydrated; therefore basically all of the plant body is one mass of water. Water can move between the regions of the plant if the water potential's are not equal
If the water potential's of two regions are equal, the regions are in equilibrium and there is no net movement of water. Water still diffuses back-and-forth but the amount is about equal
Water potential must always be considered in pairs or groups. Or water moves from one side to another so the water potential's of the two sets are important. Knowing one regions water potential does not allow us to predict whether water will move.
Incipient plasmolysis
- The point at which the protoplast has lost just enough water to pull slightly away from the wall.
Plasmolyzed
- When the protoplast pools completely away from the wall and shrinks
Short distance intercellular transport
Symplast
- All of the protoplasm of one plant, which is considered one continuous mass
apoplast
- the wall and intercellular spaces together
Motor Cells
-Many species move slowly and re-orient themselves by flexing and folding in response to a variety of stimuli. The location of flexure is either the entire mid rib or the point I wish the petiole attaches to the laminate or stem. The cells of these joints are called motor cells
Transfer Cells
- Certain cells the walls are smooth on the outer surface but have numerous fingerlike and ridge like out growths on the inner surface.
Long Distance Transport: Phloem
The exact mechanism by which water and nutrients and move through film is not known. Most evidence supports the
Pressure flow hypothesis
. Membrane-bound molecular pumps and active transport or postulated to be important driving forces
Sources are the sites from which water and nutrients are transported.
Polymer trap mechanism
- Conducting sell plasma membrane's are permeable to monosaccharides and disaccharides but not to polysaccharides. Simple sugars merely diffuse into the conducting cells and they're polymerized into polysaccharides that cannot diffuse back out.
Mass Transfer
- The actual amount of sugars and other nutrients (excluding water) transported by flu and per hour. Mass transfer can be divided by the cross-sectional area of phloem to obtain the
specific mass transfer
Sinks
- Sites that receive transported from phloem sap and they are extremely diverse.
Phloem sap is under pressure so the danger exists of uncontrolled "bleeding" if phloem is cut. Vascular bundles are broken open frequently by insects and larger animals. Two mechanisms seal broken sieve elements
P-protein
is found as a fine network adjacent to the plasma membrane's inner surface of uninjured sieve elements.
When phloem is ruptured, the phloem sap initially surges towards the break. This rapid movement sweeps p-protein into the cell center where it becomes a tangled mess. It is the carried to a sieve area or a sieve plate, it is too large to pass through and forms a
P-protein plug
Callose
is another polymer in solution while under pressure. When there is a leak, callose is also carried along with p-protein to plug the break.
Long-Distance Transport: Xylem
cohesive
- any force that acts on one molecule, also acts on all neighboring acts as well.
Cohesion-tension hypothesis
- that water can be under tension in the special circumstances that exist in plants. The tension is supposed to be generated in the leaves at the liquid-air interface where water evaporates from leaves.
Adhesive
- Molecules interact with many other substances
Transpiration
Transstomatal- The apoplastic space of spongy mesophyll in Palisade parenchyma is filled with moisture saturated air, so water molecules have a strong tendency to diffuse from intercellular spaces to the atmosphere
Transcuticular- Water loss directly through the cuticle
Cavitation
- Hydrogen bonds break over a large region and the water column break
Embolism
- (often called an air bubble) which expands until its surface encounters a solid barrier such as a pit membrane
