QCM : Fundamentals of Biological Chemistry — 12 questions

Explication

Nutrient classification refers to dividing nutrients based on the amount needed by the organism, categorizing them as macronutrients (needed in large amounts) and micronutrients (needed in small amounts), each with specific roles in maintaining health and supporting growth.

Explication

The autoionization constant ($K_w$) of water at 25°C is a well-established value of $1.0 imes 10^{-14}$. This constant represents the equilibrium concentration of hydrogen ions and hydroxide ions in pure water, which is fundamental in understanding pH and acid-base chemistry in biochemistry.

Explication

Water's polarity and hydrogen bonding enable it to dissolve a wide range of substances, making it essential as a universal solvent in biological systems. This property facilitates biochemical reactions, transport of nutrients, and waste removal, which are critical for life.

Explication

The concept of pH and water ionization was first established and published by Søren Sørensen in 1909, when he introduced the pH scale to measure acidity and alkalinity, based on the ionization of water.

Explication

Saturated fatty acids contain only single bonds between carbon atoms, leading to straight chains that pack tightly and are usually solid at room temperature. Unsaturated fatty acids contain one or more double bonds, which introduce kinks or bends in the chain, preventing tight packing and often making them liquid at room temperature. This structural difference significantly influences their physical state and biological functions.

Explication

Emil Fischer is credited with proposing the stereochemistry of sugars and developing the Fischer projection, which is a method to represent the three-dimensional structure of sugars in two dimensions. This was a fundamental contribution to understanding carbohydrate structure.

Explication

The amino acid sequence of a protein determines how it folds into its three-dimensional structure, which in turn dictates its specific function. Proper folding is essential for the protein's activity, making it the primary cause of its functional role.

Explication

The correct answer is phospholipids because they are the main structural component of cell membranes, forming a bilayer that influences membrane permeability and fluidity. Using phospholipids in drug delivery systems can help enhance the ability of the drug to pass through cell membranes. Steroids are involved in hormone signaling but are not primarily used to modify membrane permeability in delivery systems. Fats are energy storage molecules and do not directly influence membrane permeability. Waxes are waterproof and provide protective barriers but are not used to modify membrane permeability in drug delivery.

Explication

The covalent bond that links amino acids in a protein is called a peptide bond. It forms between the amino group of one amino acid and the carboxyl group of another through dehydration synthesis. Glycosidic bonds link sugars in carbohydrates, ester bonds link fatty acids to glycerol in lipids, and hydrogen bonds are weak interactions that stabilize secondary and tertiary structures but are not covalent bonds between amino acids.

Explication

The cell membrane mainly consists of a phospholipid bilayer with embedded proteins, forming a fluid mosaic that controls what enters and exits the cell.

Explication

Osmosis is the movement of water molecules from an area of low solute concentration to an area of high solute concentration across a semi-permeable membrane, which is a fundamental concept in transport mechanisms.

Explication

The main purpose of enzyme inhibition is to regulate enzyme activity, often decreasing it, to control metabolic pathways and prevent overreaction or imbalance in biochemical processes. It does not increase enzyme activity or permanently deactivate enzymes; rather, it modulates activity levels.