Absorption Of Molecules 1 Flashcards
Question: What are the three stages involved in the solution process of a drug molecule?
Removal of the drug molecule from its crystal.
Creation of a cavity from the molecule in the solvent.
Insertion of the drug molecule into this cavity.
Question: How is the solubility of a substance defined?
Answer: The solubility of a substance is defined as the amount that goes into a solution when equilibrium is established between the solute in solution and the excess (undissolved) substance.
Question: How is a solution described when it contains a drug at the limit of its solubility at a specific temperature and pressure?
Answer: When a solution contains a drug at the limit of its solubility at any given temperature and pressure, it is described as saturated.
Question: What may occur if the solubility limit of a substance is exceeded in a solution?
Answer: If the solubility limit is exceeded, solid particles of the solute may be present in the solution.
Question: What is the distinction between the dissolution rate and solubility of a substance?
Answer: The dissolution rate and solubility are not the same; the dissolution rate refers to how quickly something dissolves, while solubility refers to the amount that can be dissolved.
Question: What are the factors that can influence the solubility of drugs in a solution?
- Temperature
- Molecular structure of the drug
a) Shape and surface area
b) Hydrophobicity and degree of ionization (influenced by pH) - Nature of the solvent
a) pH, cosolvents, solubilizing agents - Crystal characteristics
Question: What is the relationship between temperature and the solubility of a drug?
Answer: The solubility of a drug typically depends on temperature.
Question: What do the melting and boiling points of a substance reflect?
Answer: The melting and boiling points of a substance reflect the strengths of interactions between the molecules.
Question: How does the surface area of a drug molecule affect solubility?
Answer: The surface area of the drug molecule affects solubility because placing the solute molecule in the solvent cavity requires a number of solute-solvent contacts.
Question: How do polar groups, such as -OH, in a drug molecule influence solubility?
Answer: Polar groups, such as -OH, capable of hydrogen bonding with water molecules, give higher solubility.
Question: What effect do non-polar groups, such as -CH3 and -Cl, have on the solubility of a drug?
Answer: Non-polar groups, such as -CH3 and -Cl, are hydrophobic and impart low solubility.
Question: How does ionization impact the solubility of a drug?
Answer: Ionization increases solubility.
Question: Provide examples of relatively hydrophilic and hydrophobic functional groups.
Question: How does ionization impact the hydrophilicity of a molecule?
Answer: Ionization causes increased hydrophilicity.
Question: Define partitioning of drugs between immiscible solvents.
Answer: Partitioning refers to the distribution of drugs between solvents, typically occurring due to differences in solubility in different phases.
Question: Provide an example of partitioning involving aqueous and lipid phases.
Answer: Drugs moving across cell walls, interacting with both aqueous and lipid phases.
Question: How can antibiotics be involved in partitioning?
Answer: Antibiotics may partition into micro-organisms, reflecting their distribution between aqueous and lipid components in microbial cells.
Question: Give an instance of drugs partitioning into materials like plastics.
Answer: Drugs may partition into plastics, indicating their distribution between the drug and the plastic material.
Question: What does “Log P” refer to in molecular properties?
Answer: Log P is the logarithm of the partition coefficient, a measure indicating the lipophilicity or hydrophilicity of a molecule when it is in a unionized state.
Question: How is Log P related to a drug’s ability to cross lipid membranes?
Answer: Log P is a crucial factor in a drug’s ability to cross lipid membranes, as it reflects the balance between a drug’s affinity for lipids (lipophilicity) and water (hydrophilicity).
Question: What does the term “partition coefficient” signify in the context of Log P?
Answer: The partition coefficient, represented by Log P, measures the distribution of a substance between a lipophilic solvent (usually octanol) and a hydrophilic solvent (usually water).
Question: How do you calculate Log P?
Answer:
𝐿𝑜𝑔 𝑃=𝐿𝑜𝑔 ([𝐶𝑜])/([𝐶𝑤])
It calculated as the ratio of the concentration of a compound in an organic solvent ([Co]) to its concentration in water ([Cw]).
Question: What does a positive Log P value indicate about a molecule?
Answer: A positive Log P value suggests that the molecule is lipophilic, meaning it has a higher affinity for lipid (organic) phases.
Question: How is a negative Log P interpreted in terms of a molecule’s properties?
Answer: A negative Log P value indicates hydrophilicity, signifying a greater affinity for water or aqueous phases.
Question: What is the fundamental characteristic of crystals in terms of molecular arrangement?
Answer: Crystals exhibit highly ordered arrays of molecules and atoms, held together by non-covalent interactions.
Question: Describe the variation observed in crystals of a particular substance.
Answer: Crystals of a given substance can vary in terms of size, the number of faces, and the types of faces present.
Question: Provide examples of substances that form ionic solids.
Answer: Ionic solids include compounds such as aluminum hydroxide (Al(OH)₃), magnesium carbonate (MgCO₃), and magnesium trisilicate (Mg₂(Si₃O₈)).
Question: Name a representative example of a molecular solid.
Answer: Omeprazole is an example of a molecular solid.
Question: What characterizes molecular salts, and provide an example
Answer: Molecular salts are compounds formed between molecular substances and salts. An example is loperamide hydrochloride.
Question: What influences the crystalline habits of compounds during crystallization?
Answer: Crystalline habits depend on the conditions of crystallization when compounds precipitate out of a solution.
Question: What is a common feature of crystal habits formed under different conditions?
Answer: Crystal habits formed under different conditions typically have the same internal structure.
Question: Can compounds crystallize with different internal structures, and what is this phenomenon called?
Answer: Yes, compounds can crystallize with different internal structures, and this phenomenon is known as polymorphism.
Question: How do molecules arrange themselves in polymorphism?
Answer: In polymorphism, molecules can arrange themselves in different ways within the crystal structure.
Question: What is the term commonly used to refer to different polymorphs?
Answer: Different polymorphs are often referred to as “Forms.”
