Most Repeated MDCAT Biology: Biological Molecules MCQs

Explanation

This is the correct answer. The quaternary structure of a protein refers to the arrangement of multiple polypeptide chains (subunits) within a protein complex.In the case of hemoglobin, it consists of four subunits: two alpha chains and two beta chains. These subunits interact to form the final, functional structure of the hemoglobin molecule.

Explanation

Adhesion is the tendency of dissimilar particles or surfaces to cling to one another. It's the force of attraction that causes different substances to stick together. Adhesion is the opposite of cohesion, which refers to the tendency of like particles or surfaces to stick together.Water molecules exhibit adhesion when they "stick" to other surfaces, such as the walls of a tube or the surface of a solid. Adhesion, along with cohesion, contributes to capillary action, where liquids move against gravity in narrow spaces. It also influences the behavior of liquids in containers, such as meniscus formation in a graduated cylinder.

Explanation

The correct answer is Option D: Both A & C. During digestion, starch is initially broken down into maltose by salivary amylase in the mouth. This process is further continued by pancreatic amylase in the small intestine. Option A, salivary amylase, alone is not sufficient as it only begins the process. Option C, pancreatic amylase, alone does not account for the initial breakdown that occurs in the mouth. Option B, maltose, is incorrect because it is the product of the reaction, not an enzyme that facilitates it.

Explanation

C-H is the potential source of chemical energy for cellular This option is not correct. C-N bonds are typically involved in protein synthesis and structural stability but are not known for their high energy potential.This option is also incorrect. C-O bonds are found in many organic molecules, including carbohydrates and lipids, and can store energy, but they are not as energy-rich as C-H bonds.This option is also incorrect.

Explanation

Correct answer is Oleic Acid as it is a monounsaturated fatty acid.The example of an unsaturated fatty acid among the options provided is Oleic acid.Unsaturated fatty acids are a type of fatty acid that contains one or more double bonds in their carbon chain.Butyric acid is a saturated fatty acid. It is a four-carbon chain fatty acid with no double bonds.Oleic acid is an unsaturated fatty acid. It is an eighteen-carbon chain fatty acid with one double bond located between the ninth and tenth carbon atoms from the methyl (CH3) end of the chain.Palmitic acid is a saturated fatty acid. It is a sixteen-carbon chain fatty acid with no double bonds.Acetic acid is not a fatty acid.

Explanation

Tertiary structure of protein represents the unique three-dimensional shape of the fully folded polypeptide.

Explanation

Hydrolysis is a chemical reaction where water is used to break down a compound, resulting in the separation of the compound into its constituent parts.

Explanation

Carbohydrates are a group of organic compounds having carbon, oxygen, and hydrogen, in which hydrogen and oxygen are mostly found in the same ratio as in water, i.e., 2:1, and are thus called hydrated carbons.

Explanation

Trioses are type of monosaccharides containing 3 carbon atoms. They include glyceraldehyde and dihydroxyacetone. Hence, this option is correct.

Explanation

Lysozyme has a well-defined tertiary structure, meaning its polypeptide chain folds into a specific three-dimensional shape. Because of this folded conformation, the option stating that lysozyme possesses tertiary structure is correct.

Explanation

One of the most important steroids is cholesterol, a component of animal cell membranes and a precursor for the synthesis of a number of steroids and sex hormones such as testosterone, progesterone, and estrogens. Hence, this option is correct.

Explanation

The phospholipid molecule consists of two parts: hydrophobic tails and a hydrophilic head. The hydrophilic head is present on the surface of the membrane, while hydrophobic tails are present in the interior of the membrane.

Explanation

The correct answer is Hydrophobic exclusion. This property is critical for the formation and stability of lipid membranes, as lipid molecules are hydrophobic and tend to exclude water. This exclusion leads to the formation of a lipid bilayer, creating a barrier between the aqueous environments inside and outside the cell. The other options, such as specific heat capacity, cohesion and adhesion, and hydrogen bonding, are important properties of water but do not directly contribute to the structural integrity of lipid membranes.

Explanation

Disaccharides are carbohydrates composed of two sugar units joined by a glycosidic bond. Lactose is made up of glucose and galactose, maltose is made up of two glucose molecules, and sucrose is made up of glucose and fructose.In summary, lactose, maltose, and sucrose are disaccharides, which are composed of two sugar units bonded together. Polysaccharides are more complex carbohydrates with multiple sugar units, monosaccharides are single sugar units, and oligosaccharides have a small number of sugar units, typically 3 to 10.

Explanation

So, when it comes to linking a specific amino acid with its corresponding tRNA molecule during protein synthesis, there's a special enzyme called aminoacyl-tRNA synthetase that does the job. It acts like a matchmaker, making sure that the right amino acid is paired with the right tRNA molecule. This process is crucial for building proteins correctly.

Explanation

Sucrose, also known as table sugar, is a disaccharide that is hydrolyzed into two monosaccharides: glucose and fructose.

Explanation

The heat of vaporization is the amount of heat energy required to convert a unit mass of a substance (in this case, water) from its liquid phase to its vapor phase at its boiling point. For water, the heat of vaporization is approximately 2250 kJ/kg or 540 cal/g.

Explanation

Carboxyl groups are commonly found in amino acids, fatty acids, and other biomolecules. Whereas carbohydrates only contain atoms of carbon hydrogen and oxygen they don't have any functional group.

Explanation

Protoplasm is a mixture of small molecules such as ions, monosaccharides, amino acids, and macromolecules such as proteins, polysaccharides, lipids, etc.On the average protoplasm contains 84 percent water. Most of the water is present in free unbounded form and provides a medium for metabolic reactions occurring in a cell.

Explanation

We set the water potential of pure water to zero simply to give us a clear starting point. At standard temperature and pressure, pure water has nothing dissolved in it and nothing pressing on it, so its water molecules are as free to move as they can be. Since you cannot get a higher freedom of movement than this, it becomes the reference. Anything added, like solutes or pressure changes, only lowers that value below zero.