Problem 40 - A Complete Resource Book in Chemistry for JEE Main

Question

Dialysis can separate which of the following in addition to the glucose from the human blood? (a) fructose (b) starch (c) proteins (d) sucrose

Step-by-Step Solution

Answer

Fructose can also be separated from blood using dialysis.

Step 1: Understanding Dialysis

Dialysis is a process used to separate small solute particles from larger molecules in a solution based on their size. It uses a semi-permeable membrane that only allows smaller particles to pass through, while larger molecules are retained.

Step 2: Analyzing the Options

Let's analyze the given compounds: (a) Fructose - a simple sugar similar to glucose, small in size. (b) Starch - a large polysaccharide composed of many glucose units, large in size. (c) Proteins - large molecules made of amino acids. (d) Sucrose - a disaccharide, made of glucose and fructose, relatively small.

Step 3: Applying Dialysis to Each Option

During dialysis, only small molecules can pass through the membrane. - Fructose, being similar in size to glucose, can likely pass through. - Starch is too large and will not pass through. - Proteins, being large, will not pass through. - Sucrose, being a disaccharide, can potentially pass through, but its size is larger than monosaccharides.

Step 4: Identifying the Most Likely Answer

Given the dialysis principle, fructose is the best candidate to be separated similarly to glucose due to its small size and monosaccharide structure.

Key Concepts

Separation of molecules by size

Dialysis is a fascinating process primarily used in chemistry to separate substances based on the size of their molecules. This method is particularly important in both laboratory settings and medical treatments. The basic idea of dialysis is simple: it relies on the ability to distinguish between molecules of different sizes.
During dialysis, a mixture containing various molecules is placed in direct contact with a semi-permeable membrane. This membrane acts like a sieve, selectively allowing smaller molecules to pass through, while retaining the larger ones.
This technique is especially useful when you want to isolate smaller solute particles from larger molecules. For example, in medical applications, dialysis is used to remove small waste products from the blood in patients with kidney failure, simulating the filtering function of the kidneys.

• It can separate small sugars, like glucose and fructose.
• Larger structures, such as proteins or polysaccharides, are excluded from passing through the membrane.
• This difference in size is the fundamental principle that allows dialysis to effectively separate molecules.

Semi-permeable membrane

The semi-permeable membrane is the heart of the dialysis process. This special barrier is crafted from materials that allow certain particles to pass through while blocking others. Its unique composition enables it to selectively allow only certain sizes of molecules to diffuse across it.
Typically, these membranes are made from materials such as cellulose or synthetic polymers. Their structure permits small solute particles or ions to move through while restricting the movement of larger molecules or particles.
This selective permeability is crucial in applications like removing toxins or waste products from biological fluids. It ensures that vital large biomolecules, such as proteins, remain in the biological system while smaller, waste materials are efficiently filtered out.

• The membrane's design permits the passage of water and solutes up to a certain size.
• The exact size and shape of the molecules that can pass through depend on the pore size of the membrane.
• This property makes semi-permeable membranes a powerful tool in both medical and scientific contexts.

Small solute particles vs large molecules

Understanding the difference between small solute particles and large molecules is crucial for grasping how dialysis works effectively. Small solute particles are typically single or simple compound molecules. They might include individual ions, simple sugars like glucose and fructose, or small organic molecules.
These particles have the ability to easily pass through the tiny pores of a semi-permeable membrane. As a result, during dialysis, these smaller entities are effectively separated from larger molecules.
Large molecules, on the other hand, comprise complex structures that are often unable to traverse the membrane. They include polymers like starch, long-chain sugars, and proteins. Due to their size and complexity, these molecules are too large to fit through the membrane pores and thus remain on one side of the dialysis membrane.

• Small solute particles like glucose have simple structures, permitting easier passage through membranes.
• Large molecules, such as proteins, have complex structures preventing them from crossing the membrane barrier.
• This size-based filtration allows for the precise separation of different molecular sizes in a mixture.