Question

A certain seaweed plant is found in estuaries. At high tide, the plant is exposed to sea water; at low tide, the plant is exposed to brackish water (less salty water). The concentrations of some dissolved materials remain virtually constant in the cells of the seaweed.

Answer 1

To answer this question we need to remember some concepts first. Brackish water possesses less salt than seawater, this type of water is common in estuarine where seawater mixes with freshwater.

Each kind of ion mentioned here possesses a different form of transport. Calcium requires ATP that is to say active transport, however, there are Calcium channels so also can enter by passive transport. Sodium and Potassium are closely linked by the Na/K pump, which is also active transport, meanwhile, Chlorine enters by channel proteins that is to say passive transport.

Now when we see the ion concentration in both types of water we have that as expected seawater has more ions than brackish water, therefore when the cell is in seawater ions concentrations are higher on the outside, meanwhile in brackish water ion concentration is lower in the outer mean.

a) C

b) D

c) B

d) A