Question

An unknown liquid collected from a sample of peas, is added to a beaker of water and is vigorously shaken. After few minutes, water and the unknown liquid made two separate layers. To which class of biomolecules, does the unknown liquid most likely belong? (a) Polysaccharides (b) Proteins (c) Lipids (d) Enzymes

Short answer

The unknown liquid most likely belongs to the class of biomolecules known as lipids, because lipids are insoluble in water and would form a separate layer.

Step-by-step solution

Observing the Properties

The unknown liquid and water formed two separate layers after being mixed and shaken, indicating that the unknown liquid is not soluble in water.

Inferring the Biomolecule Class

Biomolecules that are insoluble in water and form a separate layer are typically non-polar substances. Among the options given, lipids are known to be insoluble in water and would separate out to form their own layer when mixed with water.

Eliminating Other Options

Polysaccharides, proteins, and enzymes are all soluble in water to a certain extent and would not form a separate layer. Therefore, the class of biomolecule is not any of these options.

Key concepts

Lipids Solubility

Understanding the solubility of lipids is crucial for identifying their presence in different environments. As encountered in the exercise, when an unknown liquid forms a separate layer on top of water, it indicates a lack of solubility in water. This characteristic is a hallmark of lipids.

Lipids, including fats, oils, and certain types of vitamins and hormones, are hydrophobic, meaning they do not mix well with water. This is due to their molecular structure, which contains long chains of hydrocarbons that are non-polar. Water, on the other hand, is polar, which leads to a repulsion between water and lipid molecules.

In a practical setting such as in a lab observation or during digestion in the body, the insolubility of lipids requires special mechanisms for transport and breakdown. For instance, in the human body, bile is used to emulsify lipids, enabling their absorption and usage.

Biomolecules in Water

The solubility of biomolecules in water can differ vastly based on their structure and function. Many biomolecules are designed to interact with water, making water a versatile solvent in biological systems.

Polysaccharides and proteins, unlike lipids, have polar or charged groups that allow them to dissolve or be suspended in water. For example, the glycosidic linkages in polysaccharides can form hydrogen bonds with water, assisting in their solubility.

However, not all portions of these molecules are compatible with water. Proteins can have regions that are hydrophobic, affecting their overall solubility and leading to complex folding patterns driven by interactions with the aqueous cellular environment. Understanding the solubility and interaction of biomolecules with water is essential in fields such as pharmacology, where the effectiveness of drugs often depends on these properties.

Biological Macromolecules

Biological macromolecules are large molecules that are vital for life, including carbohydrates, lipids, proteins, and nucleic acids. Each class of these macromolecules has unique properties that define their roles within organisms.

Carbohydrates provide energy and structural support, proteins perform a vast array of functions from catalysis to structure, lipids make up cell membranes and store energy, while nucleic acids like DNA and RNA are responsible for storing and expressing genetic information.

The diversity in the structure of these biological macromolecules allows for a wide range of solubility and interactions with water, dictating where and how they function within cells. For example, the hydrophobic nature of lipids makes them ideal for forming cell membranes, providing a barrier that manages the flow of substances in and out of the cell.