Biology Written Test Questions for Medical Entrance Exams on “Mechanism of Absorption of Nutrients – 2”.
1. Where do plants obtain most of their carbon and oxygen?
a) From nitrates in the soil
b) From ammonia in the soil
c) From nitrogen in the atmosphere
d) From carbon dioxide in the atmosphere
Answer: d
Clarification: Plants obtain most of their carbon and most of their oxygen from CO2 in the atmosphere. However, their remaining nutritional requirements are obtained from water and minerals in the soil.
2. Why can’t all minerals be passively absorbed through the roots?
a) They are present in the soil as charged particles
b) The concentration of minerals in the soil is very high
c) Minerals can never be transported
d) Roots only absorb water
Answer: a
Clarification: Unlike water, all minerals cannot be passively absorbed by the roots because the minerals are present in the soil as charged particles which cannot move across the cell membranes. Also, the concentration of the minerals in the soil is usually lower than the concentration of minerals in the roots.
3. How do most minerals enter the root?
a) Through guttation
b) Through transpiration
c) Through Active absorption
d) Through passive absorption
Answer: c
Clarification: Most minerals enter the root by active absorption into the cytoplasm of epidermal cells. This needs energy in the form of ATP. Some ions also move into the epidermal cells passively.
4. What are transport proteins?
a) They are restriction points
b) They are control points
c) They are not present in plants
d) These proteins are present in animals and absent in plants
Answer: b
Clarification: Transport proteins of endodermal cells are control points, where the plant adjusts the quantity and types of solutes that reach the xylem.
5. The root endodermis because of the layer of the cuticle can actively transport ions in all the directions.
a) True
b) False
Answer: b
Clarification: The root endodermis because of the layer of suberin can actively transport ions in one direction only. Like all the cells, the endodermal cells have many transport proteins embedded in their plasma membrane.
6. After active or passive absorption of all the mineral elements, how are minerals further transported?
a) Transported through guttation
b) Not transported at all
c) Through the transpiration stream
d) Through remobilisation
Answer: c
Clarification: After the active or passive absorption of all the mineral elements, minerals are further transported through the transpiration stream. Transpiration pull is the main mineral transporting force across the entire parts of the plants.
7. Which of the following is not a chief sink for the mineral elements?
a) Young leaves
b) Developing flower
c) Old leaves
d) Developing seeds
Answer: c
Clarification: The chief sinks for the mineral elements are the growing regions of the plant such as apical and lateral meristems, young leaves, developing flowers, fruits and seeds, and the storage organs.
8. Where does the unloading of mineral ions occur in the plants?
a) At the root endings
b) At the stem endings
c) At the root hair cells
d) At the fine vein endings