Question
The main difference between active and passive transport across cell membrane is [NEET (Odisha) 2019]
(a) passive transport is non-selective whereas active transport is selective
(b) passive transport requires a concentration gradient across a biological membrane whereas active transport requires energy to move solutes
(c) passive transport is confined to anionic carrier proteins whereas active transport is confined to cationic channel proteins
(d) active transport occurs more rapidly than passive transport
Answer/Explanation
Ans. (b)
The main difference between active and passive transport across the cell is that passive transport requires concentration gradient across biological membrane whereas during active transport, the movement of molecules is from high cancentration to low concentration that means they move against the concentration gradient by using ATP.
Question
Which of the following is not a feature of active transport of solutes in plants? [NEET (Odisha) 2019]
(a) Occurs against concentration gradient
(b) Non-selective
(c) Occurs through membranes
(d) Requires ATP
Answer/Explanation
Ans. (b)
Option (b) is not a feature of active transport of solutes in plants. Active transport of solutes in plants is carried out by membrane proteins. Like enzymes, the carrier proteins are very specific (i.e. selective) in what they carry across the membranes. Active transport uses energy (ATP) to pump molecules against a concentration gradient.
Question
Water entering root due to diffusion is part of [CBSE AIPMT 1996]
(a) endosmosis
(b) osmosis
(c) passive absorption
(d) active absorption
Answer/Explanation
Ans. (c)
Most of the water is absorbed by the plants passively. The force for this type of water absorption originates in the aerial parts of the plant due to the loss of water in transpiration. The root serves only as pathway and is not actively involved in this process.
Question
An innovative professor who wanted to give a live demonstration of a physiological process, filled a glass bottle with previously moistened mustard seeds and water. He screwcapped the bottle and kept it away in a corner and resumed his lecture. Towards the end of his lecture there was a sudden explosion with glass pieces of bottle thrown around.
Which of the following phenomena did the professor want to demonstrate? [CBSE AIPMT 1990]
(a)Diffusion
(b) Osmosis
(c) Anaerobic respiration
(d) Imbibition
Answer/Explanation
Ans. (d)
If certain substances for example seeds are dropped in water, within a few hour they absorbs the water and swell up considerably. These substances are called imbibants and the phenomenon
is known as imbibition. The blast occurred due to increasing imbibitional pressure whose magnitude is extremely high.