MECHANISM OF ABSORPTION OF ELEMENTS Questions in English

(C) Lecithin is a phospholipid (often associated with proteins in membranes) that acts as a carrier molecule in the process of active ion absorption.
It possesses both hydrophilic and hydrophobic ends,allowing it to bind with ions on the membrane surface and transport them across the membrane against the concentration gradient using metabolic energy $(ATP)$.

(C) Plants absorb mineral nutrients from the soil primarily through their roots.
These nutrients exist in the soil solution as electrically charged ions (cations and anions).
For example,nitrogen is absorbed as $NO_3^-$ or $NH_4^+$,potassium as $K^+$,and phosphorus as $H_2PO_4^-$.
Therefore,the correct form in which inorganic nutrients are present and available for uptake is as electrically charged ions.

(A) Plants obtain their essential mineral nutrients from the soil through their roots.
$Nitrogen$ is absorbed from the soil in the form of $NO_3^-$ or $NH_4^+$.
$Potassium$ is absorbed from the soil in the form of $K^+$.
$Carbon$ is not absorbed from the soil; instead, it is obtained from the atmosphere in the form of $CO_2$ during the process of photosynthesis.
Therefore, the correct option is $A$.

(B) Plants,including cabbage,absorb phosphorus primarily in the form of phosphate ions ($H_2PO_4^-$ or $HPO_4^{2-}$) from the soil solution.
For these ions to be available for uptake by the root hairs,the soil must be moist,as nutrients are dissolved in soil water.
Dry soil does not allow for the movement of these ions to the root surface,and phosphate rocks are generally insoluble and not directly available for plant uptake without weathering or microbial action.
Therefore,water-irrigated soil provides the necessary medium for the absorption of phosphorus.

(B) Plants absorb phosphorus from the soil primarily in the form of phosphate ions,specifically as $H_2PO_4^-$ and $HPO_4^{2-}$.
These ions are dissolved in the soil solution,making them available for uptake by the plant roots.

(A) Boron is an essential micronutrient for plants.
It is primarily absorbed from the soil solution by the roots in the form of borate ions,specifically as $BO_3^{3-}$ (borate) or $B_4O_7^{2-}$ (tetraborate) anions.

(C) Plants absorb iron primarily in the form of ferric ions $(Fe^{3+})$.
However,it is also absorbed in the ferrous form $(Fe^{2+})$.
Once inside the plant,iron is metabolically active in the ferrous state $(Fe^{2+})$.
Therefore,plants can absorb iron in both forms,making $(c)$ the correct answer.

(B) Plants absorb essential mineral elements from the soil primarily in their ionic forms. Zinc $(Zn)$ is absorbed by plants from the soil solution in the form of divalent zinc ions,denoted as $Zn^{2+}$.

(B) It is a mode of mineral absorption which involves the expenditure of metabolic energy. Energy is generally obtained from $ATP$.

(A) Plants absorb mineral salts from the soil solution primarily through the plasma membrane of root hair cells.
This membrane acts as a semipermeable barrier that regulates the entry of ions into the cytoplasm.
While the cell wall is permeable to water and minerals,it is the semipermeable nature of the plasma membrane that controls the selective uptake of mineral salts.

(B) The $CO_2$ produced during respiration reacts with water in the soil solution to form carbonic acid $(H_2CO_3)$.
This acid dissociates into $H^+$ and $HCO_3^-$ ions.
The $H^+$ ions released into the soil solution can be exchanged for mineral cations (like $K^+$,$Ca^{2+}$,etc.) adsorbed on the surface of soil particles.
This mechanism is known as the Carbonic acid exchange theory.

(A) Mineral salts are absorbed by plant cells primarily in the form of $Ions$,which include both anions and cations.
These $Ions$ are accumulated by the plants from the soil,often against their concentration gradient,through active transport mechanisms.

(C) Minerals are absorbed by plants through both active and passive processes.
In passive absorption,minerals move along the concentration gradient without the expenditure of metabolic energy.
In active absorption,minerals are moved against the concentration gradient,which requires the expenditure of metabolic energy in the form of $ATP$.

(A) The movement of mineral ions into plant root cells via diffusion occurs along the concentration gradient without the expenditure of metabolic energy $(ATP)$.
This process is known as passive absorption.
Passive absorption is driven by purely physical forces such as diffusion and mass flow,rather than active transport mechanisms.

(A) Active uptake of minerals is an energy-dependent process that requires $ATP$.
Since $ATP$ is generated through aerobic respiration,the process of active mineral absorption is directly linked to the metabolic activity of root cells.
Oxygen is essential for aerobic respiration to produce the energy required for the active transport of ions against the concentration gradient.
Therefore,the availability of oxygen is the primary factor influencing the active uptake of minerals.

(D) The absorption of minerals by roots from the soil primarily occurs against the concentration gradient,which requires the expenditure of metabolic energy in the form of $ATP$.
This process is known as active absorption.
Since the concentration of minerals in the soil is usually lower than that in the root cells,passive diffusion is insufficient for the plant's requirements,necessitating active transport mechanisms.

(C) The absorption of mineral ions by plants occurs primarily through active transport.
Since the concentration of minerals in the soil is usually lower than the concentration of minerals in the roots,they cannot be absorbed by simple diffusion.
Therefore,plants use specific proteins called carriers and energy-dependent pumps to transport ions against the concentration gradient into the root cells.
Thus,the correct method is by carriers and pumps.

(B) The uptake of mineral ions like sulphate $(SO_4^{2-})$ from the soil into the plant roots occurs against the concentration gradient.
This process requires metabolic energy in the form of $ATP$.
Therefore,the uptake of sulphate is an example of active transport.

(A) The absorption of mineral salts by plants is an active process that occurs independently of water absorption.
While water is absorbed primarily through the root hair zone via osmosis,mineral ions are absorbed mainly through the zone of elongation and the epiblema cells.
Since mineral absorption involves active transport against the concentration gradient,it does not rely on the passive movement of water.

(A) Carrier proteins are specialized membrane proteins that facilitate the movement of specific solutes across the cell membrane.
In the context of mineral nutrition,these proteins are primarily involved in the active transport of ions.
Active transport requires energy,typically derived from $ATP$,to move ions against their electrochemical gradient.
Therefore,carrier proteins play a crucial role in the uptake of mineral ions from the soil into the root cells.

(C) The absorption of ions that involves the use of metabolic energy is known as active absorption.
Active transport of ions against the concentration gradient requires energy,which is primarily supplied by the hydrolysis of $ATP$.
Therefore,an increase in ion absorption in the presence of $ATP$ directly demonstrates that metabolic energy is essential for this process.

(B) When cations are absorbed by plant roots,the electrical neutrality of the cells must be maintained.
To balance the positive charge of the absorbed cations,the plant cells produce organic acids (like malic acid).
These organic acids dissociate to release $H^+$ ions,which are then exchanged for the cations in the external medium.
Consequently,the synthesis and level of organic acids increase to facilitate the continuous absorption of cations.

(B) The absorption of mineral ions from the soil into the root cells occurs through active transport. In this process,specific proteins present in the cell membrane act as carrier molecules. These carrier molecules bind with the ions on the outer surface of the cell membrane to form an $Ion-carrier$ complex. This complex then moves across the membrane and releases the ions into the cytoplasm,utilizing energy in the form of $ATP$.

(A) Plants primarily absorb inorganic mineral elements from the soil through their root system. The root hairs increase the surface area for the absorption of water and dissolved minerals,which are then transported to other parts of the plant via the xylem.

(A) The mechanism of absorption of elements involves two phases:
$1$. The first phase involves an initial rapid uptake of ions into the 'free space' or 'outer space' of cells,known as the apoplast. This is a passive process.
$2$. The second phase involves the entry of ions into the 'inner space' or the symplast of the cells. This is an active process and requires the expenditure of metabolic energy.
Option $A$ states 'free space' or 'inner space' for the apoplast,which is incorrect because the apoplast is the 'outer space'. Therefore,the statement in option $A$ is incorrect.

(C) The movement of mineral ions from the soil into the root cells can occur through two main processes: active and passive absorption.
Passive absorption is the process where mineral ions move into the root cells along the concentration gradient without the expenditure of metabolic energy $(ATP)$.
Since diffusion is a passive process that occurs along the concentration gradient,the movement of mineral ions into root cells via diffusion is termed as passive absorption.

(B) Soil particles are generally negatively charged.
Because of this negative charge,they tend to attract and hold positively charged ions (cations) like $K^+$,$Ca^{2+}$,and $Mg^{2+}$.
Conversely,negatively charged ions (anions) like $NO_3^-$ (nitrate) and $PO_4^{3-}$ (phosphate) are repelled by the negatively charged soil particles.
Due to this repulsion,these anions do not bind to the soil and are easily washed away or leached out by water,especially during heavy rainfall or irrigation.

(B) Plants absorb mineral nutrients from the soil primarily in the form of ions.
Zinc is an essential micronutrient for plants.
It is absorbed by plants from the soil in the form of divalent zinc ions,represented as $Zn^{2+}$.

(A) Passive absorption of minerals is a process that does not require metabolic energy $(ATP)$.
Since it is a physical process (like diffusion or mass flow),it is not affected by metabolic inhibitors that block $ATP$ production.
However,passive absorption is influenced by physical factors such as temperature,which affects the kinetic energy of ions and the permeability of the membrane.

(C) Plants absorb iron primarily in the form of ferric ions $(Fe^{3+})$.
Although iron can exist in both ferrous $(Fe^{2+})$ and ferric $(Fe^{3+})$ states in the soil,the uptake mechanism in most plants is specifically adapted to absorb the ferric form.

(A) Minerals enter plant roots through various mechanisms such as active transport,proton $(H^+)$ pumps,and cation exchange.
Active transport involves the movement of ions against the concentration gradient using energy.
Proton pumps create an electrochemical gradient that facilitates the uptake of minerals.
Cation exchange is the process where cations adsorbed on soil particles are exchanged with $H^+$ ions released by roots.
Foliar feeding is a technique of feeding plants by applying liquid fertilizer directly to their leaves,not a mechanism for mineral uptake through roots.

(C) Plants primarily absorb nitrogen as nitrates $(NO_3^-)$ or nitrites $(NO_2^-)$.
Phosphorus is absorbed mainly as phosphate ions ($H_2PO_4^-$ or $HPO_4^{2-}$).
Sulphur is absorbed by plants in the form of sulphate ions $(SO_4^{2-})$,not as sulphuric acid $(H_2SO_4)$.
Iron is absorbed in the form of ferric ions $(Fe^{3+})$.
Therefore,the pair Sulphur $\to H_2SO_4$ is mismatched.

(C) The absorption of soil nutrients by the roots of plants occurs in two main phases: apoplast and symplast.
During the initial phase,or apoplast,there is a rapid uptake of nutrients from the soil into the free spaces or cell walls of plant cells. This process is passive and occurs through transmembrane proteins and ion channels.
In the second phase,or symplast,the ions are taken slowly into the inner spaces (cytoplasm) of the cells. This pathway generally involves the expenditure of energy in the form of $ATP$,representing active transport.
Therefore,plants absorb minerals through both passive and active transport mechanisms.

(N/A) $\Rightarrow$ The studies on the mechanism of absorption of elements by plants have been carried out in isolated cells,tissues,or organs.
$\Rightarrow$ In the first phase,an initial rapid uptake of ions into the 'free space' or 'outer space' of cells,known as the apoplast,is a passive process.
$\Rightarrow$ In the second phase of uptake,the ions are taken in slowly into the inner space,known as the symplast of the cells.
$\Rightarrow$ The passive movement of ions into the apoplast usually occurs through ion-channels,which are trans-membrane proteins that function as selective pores.
$\Rightarrow$ On the other hand,the entry or exit of ions to and from the symplast requires the expenditure of metabolic energy,which is an active process.
$\Rightarrow$ The movement of ions is usually called flux.
$\Rightarrow$ The inward movement into the cells is called influx,and the outward movement is called efflux.

(N/A) $\Rightarrow$ The studies on the mechanism of absorption of elements by plants have been carried out in isolated cells,tissues,or organs.
$\Rightarrow$ In the first phase,an initial rapid uptake of ions into the 'free space' or 'outer space' of cells,known as the apoplast,is passive.
$\Rightarrow$ In the second phase of uptake,the ions are taken in slowly into the inner space,the symplast of the cells.
$\Rightarrow$ The passive movement of ions into the apoplast usually occurs through ion-channels,which are transmembrane proteins that function as selective pores.
$\Rightarrow$ On the other hand,the entry or exit of ions to and from the symplast requires the expenditure of metabolic energy,which is an active process.
$\Rightarrow$ The movement of ions is usually called flux.
$\Rightarrow$ The inward movement into the cells is called influx,and the outward movement is called efflux.

(C) Ions are absorbed from the soil by both passive and active transport mechanisms.
$1$. Passive transport: Ions move along the concentration gradient without the expenditure of metabolic energy.
$2$. Active transport: Ions are moved against the concentration gradient,which requires the expenditure of metabolic energy in the form of $ATP$.

(A) Most minerals cannot passively move across the cell membrane because they are present in the soil as charged particles (ions).
Since the plasma membrane is impermeable to charged ions,they cannot cross the lipid bilayer by simple diffusion.
Therefore,minerals must enter the root cells through active absorption,which requires energy in the form of $ATP$ and specific transport proteins.
Thus,both the Assertion and the Reason are correct,and the Reason correctly explains why active absorption is necessary.

(B) The process of mineral absorption occurs in two phases.
In the first phase,an initial rapid uptake of ions into the 'free space' or 'outer space' of cells (the apoplast) occurs.
This process is passive and does not require metabolic energy.
Therefore,the pathway followed in the first phase is called passive uptake.

(A) Plants absorb essential mineral ions from the soil primarily through their root system. The root hairs,which are extensions of the epidermal cells of the roots,provide a large surface area for the absorption of water and minerals. These ions are absorbed in varying amounts depending on the plant's specific physiological requirements and the availability of ions in the soil solution.

(B) The process of mineral absorption occurs in two phases. In the initial phase,there is a rapid uptake of ions into the free space or outer space of cells (apoplast). In the final phase,ions are taken up into the inner space of cells (symplast) through active transport,which requires metabolic energy.

(B) Plants primarily absorb phosphorus from the soil in the form of phosphate ions.
These ions are mainly absorbed as $H_{2}PO_{4}^{-}$ and $HPO_{4}^{2-}$.

(B) The absorption of minerals occurs in two phases. In the first phase,an initial rapid uptake of ions into the free space or outer space of cells occurs,which is a passive process. In the second phase,ions are taken into the inner space (the cytoplasm or vacuole) of the cells. This movement of ions into the inner space is against the concentration gradient and requires metabolic energy,therefore it is called active uptake.

(A) In the initial phase of mineral absorption,ions are taken up into the outer space of cells,which is known as the apoplast. This is a passive process where ions move into the free space or extracellular space of the cell wall.

(B) The process of mineral absorption occurs in two phases. In the initial phase,ions are taken up rapidly into the 'free space' or 'outer space' of the cells,which is a passive process. In the second phase,ions are taken up slowly into the 'inner space' of the cells,which is an active process requiring metabolic energy.

(A) Plants primarily absorb nitrogen from the soil in the form of nitrate $(NO_3^-)$.
Although some plants can also absorb nitrogen as ammonium $(NH_4^+)$ or nitrite $(NO_2^-)$,nitrate is the most common and preferred form for the majority of terrestrial plants.

(B) Plants absorb essential mineral elements from the soil primarily in the form of ions.
These ions are dissolved in the soil solution and are taken up by the roots through various transport mechanisms.
The movement of these ions into the plant body is referred to as flux.

(D) Mineral absorption in plants occurs in two distinct phases:
$(i)$ Initial phase: Ions are rapidly taken up into the 'outer free space' or the $apoplast$ of the cells. This is a passive process that does not require metabolic energy.
$(ii)$ Final phase: Ions are slowly transported into the 'inner space' or the $symplast$ of the cells. This is an active process that requires metabolic energy in the form of $ATP$.
$(iii)$ The passive movement of ions into the $apoplast$ is facilitated by ion channels,which are transmembrane proteins acting as selective pores for specific ions.
Therefore,all the given statements are correct.

(C) Plants absorb zinc from the soil primarily in the form of divalent zinc ions,denoted as $Zn^{2+}$. These ions are taken up by the root system through various transport mechanisms.

(A) The movement of electrolytes through the roots is generally against the electro-chemical gradient and requires energy.
This is because the concentration of minerals in the soil is usually lower than the concentration of minerals in the roots.
Therefore,plants absorb minerals from the soil through an active transport process,which consumes $ATP$.

(D) Plants absorb iron from the soil primarily in the form of ferric ions,which is $Fe^{+3}$.
Although plants can also take up ferrous ions $(Fe^{+2})$,the most common and standard form recognized in plant physiology for uptake is $Fe^{+3}$.