Question

1. Describe the path followed by water from the soil, through the plant and into the atmosphere. Where in the path are the important resistances to water movement?

2. What is meant by the term "active transport"? What is the difference between "primary" and "secondary" active transport?

3. Both membrane channels and carriers show changes in protein conformation. What is the role of such conformation changes (a) in channels, and (b) in carriers?

Answer 1

Question

1. The water present in the soil is absorbed by the roots hairs using osmosis process of the plants using osmosis . In roots, xylem tissue are present that transport water molecule. In the xylem , force of cohesion and adhesion cause the water molecules to move in xylem. Through xylem, water reach to the different part of the plant like leaves, stem , flower and other parts of the plant. This water molecules reach the mesophyll cells of the plants and water is removed by diffusion tthrough the specific pores on the leaves known as stomata. The important resistances to water movement are cell wall of the plant cells like casparian strip that made the resistance to flow of water.

2. The active transport is the molecules or ion against the concentartion gardient which require energy. The primary active transport use the energy directly from the ATP hydrolysis whereas secondary active transport uses the energy stored in the form of ionic concentartion differences across the biological membrane.

3.

a. Change in the conformation of the channel protein allow the molecules to bind to their specific site.

b. Change in the conformation of carrier protein allow binding of specific solute and transfer them across the lipid bilayer which is plasma membrane.