Means of transport Questions in English

(B) The diagram shows the movement of molecules from a region of high concentration to a region of low concentration across a biological membrane.
Since the movement occurs along the concentration gradient,it is a passive process,which is characteristic of diffusion.
However,the process requires a specific membrane protein to facilitate the movement of molecules across the lipid bilayer.
Therefore,this process is identified as facilitated diffusion,and the structure marked as $A$ is a transport protein.

(B) Facilitated diffusion is a type of passive transport where molecules move across the membrane along the concentration gradient (from a region of higher concentration to a region of lower concentration).
Since it follows the concentration gradient,it is a 'downhill' process and does not require metabolic energy $(ATP)$.
It requires specific membrane proteins (carrier or channel proteins) to facilitate the movement of hydrophilic molecules.
It is also highly selective in nature.
Therefore,'Uphill transport' is the incorrect characteristic,as it describes active transport.

(C) Water channels are known as aquaporins.
They are membrane proteins that facilitate the movement of water molecules across the cell membrane.
They consist of eight different types of aquaporins.
Since they facilitate the movement of water along the concentration gradient without the expenditure of energy,they are involved in facilitated diffusion.

(D) Active transport is the movement of molecules or ions against a concentration gradient. This process requires the expenditure of metabolic energy in the form of $ATP$ (Adenosine Triphosphate) to move substances across the cell membrane.

(C) The correct matches are as follows:
$A$. Movement of ions into or out of the cell is defined as $Flux$ $(2)$.
$B$. Outward movement of ions from the cell is known as $Efflux$ $(3)$.
$C$. Inward movement of ions into the cell is known as $Influx$ $(4)$.
$D$. Passive uptake of ions occurs through the process of $Diffusion$ $(1)$.
Therefore, the correct matching is $A-2, B-3, C-4, D-1$.

(B) The movement of ions into and out of the symplast is an active transport process. Active transport involves the movement of molecules against their concentration gradient,which requires the expenditure of metabolic energy in the form of $ATP$.

(N/A) $\Rightarrow$ Active transport is the movement of ions or molecules across a cell membrane against their concentration gradient,i.e.,from a region of lower concentration to a region of higher concentration.
This process requires the expenditure of metabolic energy in the form of $ATP$.
It is essential for maintaining specific ion concentrations within the cell,such as the $Na^{+}/K^{+}$ pump,which actively transports sodium ions out of the cell and potassium ions into the cell.

(A) $\Rightarrow$ Most of the water is transported within the root through the apoplast pathway.
$\Rightarrow$ The cortical cells are loosely arranged,which provides little resistance to the movement of water,allowing for mass flow.
$\Rightarrow$ This mass flow is facilitated by the cohesive and adhesive forces of water molecules.
$\Rightarrow$ While the apoplast pathway is the primary route,the symplast pathway also contributes to water transport,particularly across the endodermis where the Casparian strip is present.

(B) Facilitated diffusion is a process of passive transport where molecules move across the cell membrane with the help of special membrane proteins (carrier proteins or channel proteins).
It is highly selective,meaning it allows only specific molecules to pass through.
It does not require metabolic energy $(ATP)$ because the movement occurs along the concentration gradient (from a region of higher concentration to a region of lower concentration).

(N/A) Based on the transport mechanisms across the membrane:
$(I)$ Uniport: $A$ single molecule moves across the membrane independently of other molecules.
$(II)$ Antiport: Two molecules move in opposite directions across the membrane.
$(III)$ Symport: Two molecules move in the same direction across the membrane simultaneously.

(D) The completed table is as follows:

Property	Simple Diffusion	Facilitated Transport	Active Transport
Highly selective	No	Yes	Yes
Uphill transport	No	No	Yes
Requires $ATP$	No	No	Yes

Explanation:
$1$. Simple Diffusion: Passive process,non-selective,no energy required,moves along the concentration gradient.
$2$. Facilitated Transport: Passive process,highly selective (uses membrane proteins),no energy required,moves along the concentration gradient.
$3$. Active Transport: Uses energy $(ATP)$ to pump molecules against the concentration gradient (uphill),highly selective,and requires carrier proteins.

(N/A) $\Rightarrow$ The movement of ions is generally referred to as flux.
$\Rightarrow$ The inward movement of ions into the cells is known as influx.
$\Rightarrow$ The outward movement of ions from the cells is known as efflux.
$\Rightarrow$ Both these processes often require the expenditure of metabolic energy,making them active transport processes.

(A) $P$. Diffusion is the movement of molecules along the concentration gradient without the help of membrane proteins. Thus, $P-III$.
$Q$. Facilitated transport is the movement of molecules along the concentration gradient with the help of specific membrane proteins. Thus, $Q-I$.
$R$. Active transport is the movement of molecules against the concentration gradient, which requires energy and membrane proteins. Thus, $R-II$.
Therefore, the correct matching is $(P-III), (Q-I), (R-II)$.

(D) Passive transport is the movement of molecules across a cell membrane without the expenditure of metabolic energy $(ATP)$.
Diffusion is a passive process where molecules move from a region of higher concentration to a region of lower concentration.
Facilitated diffusion is also a passive process that uses specific membrane proteins to move molecules across the membrane without the use of $ATP$.
Active transport,on the other hand,requires the expenditure of energy $(ATP)$ to move molecules against their concentration gradient.
Therefore,both diffusion and facilitated diffusion are types of passive transport.

(D) Transport along the concentration gradient means moving from a region of higher concentration to a region of lower concentration. This process does not require metabolic energy $(ATP)$.
Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration.
Facilitated diffusion also occurs along the concentration gradient,utilizing membrane proteins to transport molecules without the expenditure of energy.
Active transport,on the other hand,occurs against the concentration gradient and requires energy in the form of $ATP$.
Therefore,both diffusion and facilitated diffusion occur along the concentration gradient.

(C) Active transport is the process of moving molecules across a cell membrane from a region of lower concentration to a region of higher concentration.
This process requires energy in the form of $ATP$ because it moves substances against the concentration gradient.
In contrast,diffusion and facilitated diffusion are types of passive transport that move substances along the concentration gradient and do not require energy.

(B) $1$. Simple diffusion is a passive process that does not require membrane proteins.
$2$. Facilitated diffusion involves the movement of molecules across a membrane through specific transport proteins without the expenditure of energy.
$3$. Active transport involves the movement of molecules against the concentration gradient,which requires both energy $(ATP)$ and specific membrane transport proteins (pumps).
$4$. Therefore,both facilitated diffusion and active transport require membrane proteins for the transport of substances.

(C) In the given figure,the transport mechanisms are represented as follows:
$P$: $A$ single molecule moves in one direction independently of other molecules. This is called Uniport.
$Q$: Two molecules move in opposite directions. This is called Antiport.
$R$: Two molecules move in the same direction simultaneously. This is called Symport.
Therefore,the correct sequence is $P$ = Uniport,$Q$ = Antiport,$R$ = Symport.

(A) Facilitated diffusion is a type of passive transport where molecules move across a membrane with the help of transport proteins.
$1$. It occurs along the concentration gradient (from high to low concentration).
$2$. It does not require metabolic energy $(ATP)$.
$3$. It is highly selective and sensitive to inhibitors.
$4$. It is specifically required for hydrophilic (water-soluble) molecules that cannot pass through the lipid bilayer.
Therefore,the statement that facilitated diffusion occurs for lipid-soluble molecules is incorrect,as lipid-soluble molecules can easily pass through the lipid bilayer via simple diffusion.

(B) The membrane transport mechanisms are defined as follows:
$1$. $Uniport$: $A$ molecule moves across the membrane independent of other molecules $(P-I)$.
$2$. $Symport$: Two molecules cross the membrane in the same direction $(Q-III)$.
$3$. $Antiport$: Two molecules move in opposite directions $(R-II)$.
Therefore,the correct matching is $P-I, Q-III, R-II$.

(B) The image illustrates a molecule moving across a cell membrane with the help of a carrier protein.
$1$. Diffusion occurs directly through the lipid bilayer without the aid of proteins.
$2$. Facilitated diffusion involves the movement of molecules across the membrane with the help of special membrane proteins (carrier proteins or channel proteins) along the concentration gradient.
$3$. Active transport requires energy $(ATP)$ to move molecules against the concentration gradient.
Since the diagram shows the involvement of a carrier protein to facilitate the movement of molecules,it represents facilitated diffusion.

(C) Uphill transport refers to the movement of substances from a region of lower concentration to a region of higher concentration.
This process requires energy in the form of $ATP$.
Active transport is the only mechanism among the given options that moves molecules against the concentration gradient,which is known as uphill transport.
Diffusion and facilitated diffusion are passive processes that move molecules along the concentration gradient (downhill transport).

(B) $1$. Simple diffusion is a passive process that does not show transport saturation because it does not involve carrier proteins. Thus, $P = \text{No}$.
$2$. Active transport involves the movement of molecules against the concentration gradient (uphill transport), which requires energy. Thus, $Q = \text{Yes}$.
$3$. Facilitated transport is a passive process that uses carrier proteins but does not require metabolic energy $(ATP)$. Thus, $R = \text{No}$.
$4$. Therefore, the sequence $P, Q, R$ is $No, Yes, No$.

(A) The $Apoplast$ pathway is the system of adjacent cell walls that is continuous throughout the plant,except at the $Casparian$ strips of the endodermis in the roots.
Because the $Apoplast$ does not involve crossing cell membranes,it offers the least resistance to the movement of water.
Therefore,the majority of water transport in plants occurs through the $Apoplast$ pathway.

(A) In the given figure,pathway $P$ moves through the cytoplasm and plasmodesmata,which represents the Symplastic pathway.
Pathway $Q$ moves through the cell walls and intercellular spaces,which represents the Apoplastic pathway.
Therefore,$P$ is the Symplastic pathway and $Q$ is the Apoplastic pathway.

(D) In facilitated diffusion,carrier proteins are involved in the transport of molecules across the membrane.
When a molecule moves across the membrane independent of other molecules,it is called $Uniport$.
When two molecules move across the membrane in the same direction,it is called $Symport$.
When two molecules move across the membrane in opposite directions,it is called $Antiport$.
Therefore,the correct term for the movement of two molecules in the same direction is $Symport$.

(A) The movement and accumulation of ions across a membrane against their concentration gradient is defined as active transport.
Active transport requires metabolic energy (usually in the form of $ATP$) to move molecules from a region of lower concentration to a region of higher concentration.
Unlike passive transport,which moves substances along the concentration gradient without energy expenditure,active transport is an energy-dependent process.

(D) Facilitated diffusion is a type of passive transport that occurs across the cell membrane with the help of special membrane proteins.
These proteins provide a pathway for specific molecules or ions to move across the membrane along their concentration gradient without the expenditure of metabolic energy $(ATP)$.
Aquaporins are specialized integral membrane proteins that act as channels for the facilitated diffusion of water molecules across the cell membrane.
Therefore,aquaporins are responsible for facilitating the movement of water in cells.