Small Molecules: Videos & Practice Problems

Water is considered a universal solvent in cell biology due to its polarity and ability to form hydrogen bonds. The polar nature of water molecules, with a slight negative charge on the oxygen atom and a slight positive charge on the hydrogen atoms, allows them to interact with various solutes. Hydrophilic (water-loving) molecules, such as salts and sugars, dissolve easily in water because they can form hydrogen bonds with water molecules. This property is crucial for cellular processes, as it enables the transport and reaction of various biomolecules within the cell. Additionally, water's high specific heat helps stabilize cellular temperatures, further supporting its role as a universal solvent.

The polarity of water molecules contributes to their cohesive properties through hydrogen bonding. Each water molecule has a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms. This polarity allows water molecules to attract each other, with the negative oxygen of one molecule forming a hydrogen bond with the positive hydrogen of another. These hydrogen bonds create a cohesive force, making water molecules stick together. This cohesion is responsible for water's high surface tension and its ability to form droplets. It also plays a role in various biological processes, such as the transport of water in plants through capillary action.

Stereoisomers are molecules that have the same chemical formula and sequence of bonded atoms but differ in the three-dimensional arrangement of their atoms. In cell biology, stereoisomers are important because they can have different biological activities and properties. For example, enzymes and receptors in cells are often specific to one stereoisomer over another. This specificity can affect how drugs interact with their targets, how metabolic pathways function, and how signals are transmitted within cells. The concept of stereoisomers is crucial for understanding the structure-function relationship of biomolecules and their roles in cellular processes.

Functional groups are specific groups of atoms within molecules that have characteristic properties and reactivity. In carbon-based molecules, functional groups determine the chemical behavior and properties of the molecule. For example, hydroxyl groups (-OH) make molecules more hydrophilic, while carboxyl groups (-COOH) can act as acids. Functional groups are essential in cell biology because they influence how molecules interact with each other, participate in chemical reactions, and contribute to the structure and function of biomolecules like proteins, nucleic acids, and lipids. Understanding functional groups helps in predicting the behavior of complex biological molecules.

Carbon is considered a versatile element in biological systems because it can form four covalent bonds with other atoms, allowing for a wide variety of stable and complex structures. This versatility enables carbon to form long chains, branched molecules, and rings, which are the backbone of organic molecules. Carbon's ability to bond with elements like hydrogen, oxygen, nitrogen, and sulfur further increases the diversity of possible compounds. This structural diversity is crucial for the formation of biomolecules such as carbohydrates, proteins, lipids, and nucleic acids, which are essential for life. Carbon's versatility underpins the complexity and functionality of biological systems.