Question

Small amounts of monosaccharide like glucose, amino acids, and some electrolytes like chloride ions are absorbed by__(i)__. However, some of the substances like fructose and some amino acids are absorbed by the mechanism called the __(ii)__. Various nutrients like amino acids and electrolytes like \[N{a^ + }\] are absorbed into the blood by__(iii)___.
A. (i) Facilitated transport, (ii) active transport, (iii) simple diffusion
B. (i) Simple diffusion, (ii) facilitated transport, (iii) active transport
C. (i) Active transport, (ii) facilitated transport, (iii) Simple diffusion
D. (i) Simple diffusion, (ii) active transport, (iii) facilitated transport

Answer 1

Hint: The plasma membrane is the covering of cells and it is selectively permeable. It is composed of lipids, proteins, and carbohydrates. Similarly, our body contains a wide variety of lipids, proteins, and carbohydrates and involves different transport mechanisms for the intake and discharge of these biomolecules.

Complete answer:
There are two types of transport systems.
> Active transport
• It involves the $ATP$ and it happens against the concentration gradient.
• It requires a membrane protein, it can be primary or secondary.
• It transports the protein mediates.
For example- Sodium potassium pump.

> Passive transport
• There is no involvement of $ATP$
• It happens along the concentration gradient.
• It can happen without membrane protein or with the help of membrane protein.
• It is further of two types:
- Simple diffusion: It is a type of passive transport that involves simply the movement of solute which occurs when there is a difference in electrochemical potentials on the two sides of a permeable barrier.
- Facilitated diffusion- It is a type of membrane transport that happens with the help of membrane proteins. It can be carrier-mediated or Channel mediated.

Hence, the correct answer is option (B).

Additional information:
There is also co-transport which involves the following-
• Uniport- Two molecules are transported in the same direction
• Symport- It involves energy coupling and in the same direction. Example- Glucose and sodium.
• Antiport- They transport in the opposite direction. Example- Sodium potassium pump.

Note: So, now we can say that small amounts of monosaccharide like glucose, amino acids, and some of the electrolytes like chloride ions are absorbed by simple diffusion as it needs no transporter protein.
However, some of the substances like fructose and some amino acids are absorbed by the mechanism called the facilitated transport because it needs a transporter known as GLUT (glucose transporter) to enter inside the bloodstream.
Various nutrients like amino acids and electrolytes like $N{a^+}$ are absorbed into the blood by active transport as already mentioned above because they require $ATP$ .