Question

What is Active transport ?

Answer 1

Hint: Water absorption in plants occurs by two methods: Active absorption and passive absorption. In active type of absorption shoot does not play any role. There are two theories of active absorption: Osmotic theory of active absorption and non-osmotic theory of active absorption.

Complete answer:
Active transport moves ions and molecules across a membrane against the concentration gradient. It requires energy.
The characteristic features of active transport are:
-The movement of molecules in case of active transport is from lower concentration to higher concentration so it shows uphill transport.
-These have carrier proteins that are highly specific like enzymes for the substances to be carried across the membrane.
-The process of active transport can be inhibited by inhibitors that react with the protein side chains.
-The transport rate reaches its maximum when all the protein carriers are in use or get saturated with the substances to be carried.
The various types of processes that depend on active transport are:
-Absorption of amino acids from the gut.
-Absorption of mineral ions by plant roots.
-Excretion of urea and hydrogen ions by the mammalian kidney.
-Exchange of sodium and potassium ions in nerve cells.
-Filling of the contractile vacuole in amoeba.
The phloem in the leaves of a plant is rich in sugars because of the high rate of active transport.

Note: Some intrinsic protein molecules function as molecular pumps. These permit the cell to go for active transport to accumulate glucose or ions against the concentration gradient. Cells that undergo active transport have abundant mitochondria that provide ATP needed to power active transport.