Lecture 06/Water transport

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Bio 220 Lecture 6: Water transport in plants
Campbell, pp 139-mid 143, 695-mid 709

I. Transport (continued)
I'd like to conclude our discussion of movement of substances into and out of cells and then discuss how these principles can be used to understand the short range movement of water within plants.

B. Active vs Passive
1. Active transport requires ATP
We talked last time about the difference between free and facilitated transport.
Transport can also be considered passiveor active.
Passive transport always moves downa concentration gradient; Active transport can move up a concentration gradient.

This is like moving water up a hill, what does that tell you? -that you need to add energy.

Facilitated transport can be active or passive;
free diffusion can only be passive.

Q. Where does energy come from in a cell?
ATP hydrolysis
Q. How can you tell if a substance is being moved by active or passive transport?
See if substance can move up conc. gradient, Block ATP hydrolysis

2. Proton pump (plants)
3. Electrogenic pumps and membrane potential

8.16

Fig 8.16An important example of active transport in plants is the proton pump.
The proton pump uses the energy of ATP hydrolysis to power the transport of protons out of the cell. This creates a concentration gradientand also an electrical charge differencebetween the inside and the outside of the plasma membrane. This difference in electrical charge is called the membrane potential. Transport proteins that contribute to the membrane potential are called electrogenic pumps.


Bio 220 Lecture 6: Water transport in plants Campbell, pp 139-mid 143, 695-mid 709 I. Transport (continued) I'd like to conclude our discussion of movement of substances into and out of cells and then discuss how these principles can be used to understand the short range movement of water within plants. B. Active vs Passive 1. Active transport requires ATP We talked last time about the difference between free and facilitated transport. Transport can also be considered passiveor active. Passive transport always moves downa concentration gradient; Active transport can move up a concentration gradient. This is like moving water up a hill, what does that tell you? -that you need to add energy. Facilitated transport can be active or passive; free diffusion can only be passive. Q. Where does energy come from in a cell? ATP hydrolysis Q. How can you tell if a substance is being moved by active or passive transport? See if substance can move up conc. gradient, Block ATP hydrolysis
	2. Proton pump (plants) 3. Electrogenic pumps and membrane potential	8.16
Fig 8.16An important example of active transport in plants is the proton pump. The proton pump uses the energy of ATP hydrolysis to power the transport of protons out of the cell. This creates a concentration gradientand also an electrical charge differencebetween the inside and the outside of the plasma membrane. This difference in electrical charge is called the membrane potential. Transport proteins that contribute to the membrane potential are called electrogenic pumps.