Biology Unit Review: Organic Molecules, Isotopes, and Intermolecular Forces

A set of question-and-answer flashcards covering organic vs inorganic molecules, bond types, isotopes/isotopes, isomers, and intermolecular forces in biology.

What is the general difference between organic and inorganic molecules in biology?

Organic molecules contain carbon and hydrogen; inorganic molecules do not contain carbon and hydrogen.

Name the four major classes of organic compounds discussed in this unit.

Nucleic acids, carbohydrates, proteins, and lipids.

What is a hydrocarbon?

A compound that contains only carbon and hydrogen.

Give an example of an inorganic molecule.

Sodium chloride (NaCl).

Give another example of an inorganic molecule.

Magnesium hydroxide (Mg(OH)2).

What are nucleic acids an example of, and what are two common examples?

They are organic compounds; DNA and RNA are nucleic acids.

What are carbohydrates? Name at least two forms.

Carbohydrates are sugars and starches; forms include monosaccharides and disaccharides (sugars) and cellulose (a polysaccharide).

What are proteins? Provide two examples.

Proteins are organic compounds; examples include keratin (hair) and muscle proteins; enzymes are also proteins (e.g., maltase).

What are lipids? Give two examples.

Lipids are fats/oils; examples include triglycerides and fats/oils.

What is a monosaccharide?

A simple sugar; the monomer unit of carbohydrates.

What is an isomer?

Compounds with the same molecular formula but different structures or arrangements.

Which three molecules are isomers with the formula C6H12O6?

Glucose, fructose, and galactose.

What is the general formula for glucose, fructose, and galactose that makes them isomers?

C6H12O6.

What is an isotope?

Atoms of the same element with different numbers of neutrons, leading to different mass numbers.

What is a radioisotope?

An unstable isotope that emits radiation.

Why are radioisotopes useful in biology and medicine?

They can be used as tracers to follow processes or to image/treat diseases.

Give a physiological example of using a radioisotope as a tracer.

Tracing iodine uptake by the thyroid to assess thyroid function.

What is a covalent bond?

A bond formed by sharing electrons between atoms.

What is an ionic bond?

A bond formed by transfer of electrons, creating oppositely charged ions that attract each other.

What is a polar covalent bond?

A covalent bond where electrons are shared unequally, giving partial charges (e.g., H-Cl).

What is a nonpolar covalent bond?

A covalent bond where electrons are shared equally (e.g., Cl-Cl).

What determines whether a bond is polar, nonpolar, or ionic?

The electronegativity difference between atoms:

What is intramolecular force?

Forces within a molecule, such as ionic or covalent bonds.

What is intermolecular force?

Forces between molecules, such as London dispersion forces (LDFs), dipole-dipole interactions, and hydrogen bonding.

Which intermolecular force is typically the strongest among those listed?

Hydrogen bonding.

What is London dispersion force (LDF)?

Weak intermolecular force between nonpolar molecules; strength increases with molecule size.

What is dipole-dipole interaction?

Intermolecular force between polar molecules.

What is hydrogen bonding?

A strong intermolecular force where hydrogen bound to N, O, or F is attracted to NOF of another molecule.

What is cohesion?

Attraction between like molecules, such as water–water.

What is adhesion?

Attraction between unlike substances, such as water to glass.

What is capillary action?

Upward movement of water in narrow tubes due to adhesion to surfaces and cohesion among water molecules.

What do hydrophilic and hydrophobic mean?

Hydrophilic = water-loving; hydrophobic = water-hating (nonpolar) substances.

What makes water a universal solvent?

Water's polarity allows it to dissolve polar and ionic substances, enabling transport of dissolved salts and ions in body fluids.

What is surface tension in water caused by?

Cohesion via hydrogen bonding between water molecules at the surface.

What is the difference between hydrophilic and hydrophobic substances in practical terms?

Hydrophilic substances mix with water; hydrophobic substances tend to separate from water (e.g., oil and water).

Why is capillary action particularly important in biology?

It helps transport water in narrow tubes (e.g., plant xylem) due to adhesion and cohesion.