Basic Biology Practice Test: The Chemical Basis of Life | Practice Test / Quiz / MCQs

1. The organic molecules in living organisms have a measurably lower ratio of carbon-13/carbon-12, two stable isotopes of carbon that comprise approximately 1.1% and 98.9% of atmospheric carbon, respectively. What is a reasonable explanation for this phenomenon?

Carbon dioxide molecules with carbon-13 stay in the upper atmosphere and are less available to terrestrial plants and algae.Oxygen atoms preferentially react with carbon-13, thereby enriching the atmosphere with carbon dioxide molecules containing carbon-13 atoms.Carbon dioxide molecules containing carbon-13 are heavier and sink into the ocean depths, making them less available to living organisms.Carbon-13 has a different valence electron configuration and is therefore less chemically reactive than carbon-12.Photosynthesis preferentially uses carbon dioxide molecules with carbon-12, and the lower carbon-13/carbon-12 ratio propagates through the food chain.

2. Why is each element unique and different from other elements in chemical properties?

Each element has a unique number of neutrons in its nucleus.Each element has a unique atomic weight.Each element has a unique number of protons in its nucleus.Each element has a unique atomic mass.Each element has different radioactive properties.

3. What bonding or interaction is most likely to occur among a broad array of molecules of various types (polar, nonpolar, hydrophilic, hydrophobic)?

ionic bondingvan der Waals interactionscovalent bondinghydrogen bondingpolar covalent bonding

4. Van der Waals interactions result when

hybrid orbitals overlap.two polar covalent bonds react.electrons are not symmetrically distributed in a molecule.molecules held by ionic bonds react with water.a hydrogen atom loses an electron.

5. In what way are elements in the same column of the periodic table the same?

They have the same number of electron shells.They have the same number of neutrons.They have the same number of electrons in their valence shell.They have the same number of protons.They have the same number of electrons.

7. We can represent atoms by listing the number of protons, neutrons, and electrons - for example, 2p+; 2n0; 2e- for helium. Which of the following represents the 18O isotope of oxygen?

6p+, 8n0, 6e-9p+, 9n0, 9e-7p+, 2n0, 9e-8p+, 10n0, 8e-10p+, 8n0, 9e-

8. In comparing covalent bonds and ionic bonds, which of the following would you expect?

Ionic interactions remain when covalent bonds are broken in water. Ionic bonds are much stronger than covalent bonds.Both involve electrical attraction between the electrons of one atom and the nucleus of the other atom.An atom can form covalent bonds with multiple partner atoms, but only a single ionic bond with a single partner atom.Covalent bonds and ionic bonds occupy opposite ends of a continuous spectrum, from nearly equal to completely unequal sharing of electrons.

12. If a salamander relied on hydrogen bonds to cling to surfaces, what type of surface would cause the most problems for this animal?

a surface made with carbon, hydrogen, and oxygen atoms covalently bonded togethera surface made with silicon and oxygen atoms covalently bonded togethera surface made with carbon, hydrogen, nitrogen, and oxygen atoms covalently bonded togethera surface made with carbon and hydrogen atoms covalently bonded togethera surface coated with a thin film of water

13. A covalent chemical bond is one in which

electrons are removed from one atom and transferred to another atom so that the two atoms become oppositely charged.outer-shell electrons of one atom are transferred to fill the inner electron shell of another atom.an electron occupies a hybrid orbital located between the nuclei of two atoms.outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms.protons and neutrons are shared by two atoms so as to satisfy the requirements of both atoms.

14. About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?

carbon, oxygen, phosphorus, hydrogencarbon, hydrogen, nitrogen, oxygenoxygen, hydrogen, calcium, nitrogencarbon, sodium, hydrogen, nitrogencarbon, oxygen, nitrogen, calcium

15. Which of the following is not considered to be a weak molecular interaction?

both a hydrogen bond and a covalent bonda hydrogen bonda covalent bonda van der Waals interactionan ionic bond in the presence of water

18. Knowing just the atomic mass of an element allows inferences about which of the following?

the number of neutrons in the elementthe chemical properties of the elementboth the number of protons and the chemical properties of the elementthe number of protons plus neutrons in the elementthe number of protons in the element

19. Which of the following correctly describes chemical equilibrium?

There are equal concentrations of reactants and products, and the reactions have stopped.Forward and reverse reactions continue with no effect on the concentrations of the reactants and products.Reactions stop only when all reactants have been converted to products.Forward and reverse reactions have stopped so that the concentration of the reactants equals the concentration of the products.Concentrations of products are higher than the concentrations of the reactants.

20. Which of these systems is least likely to be at chemical equilibrium?

a test tube of dry organic molecules, kept at room temperaturea test tube of organic molecules, kept in the freezera test tube of living cellsa test tube of organic molecules dissolved in water, kept at room temperaturea test tube of dead cells in water, kept at room temperature

21. Which of the following correctly describes any reaction that has reached chemical equilibrium?

Both the forward and the reverse reactions have stopped with no net effect on the concentration of the reactants and the products.The rate of the forward reaction is equal to the rate of the reverse reaction.All of the reactants have been converted to the products of the reaction.All of the products have been converted to the reactants of the reaction.The concentration of the reactants equals the concentration of the products.

22. Carbon-12 is the most common isotope of carbon, and has an atomic mass of 12 daltons. A mole of carbon in naturally occurring coal, however, weighs slightly more than 12 grams. Why?

Some carbon atoms in nature have undergone radioactive decay.Some carbon atoms in nature have a different valence electron distribution.Some carbon atoms in nature have more neutrons.The atomic mass does not include the mass of electrons.Some carbon atoms in nature have an extra proton.

24. The atomic number of sulfur is 16. Sulfur combines with hydrogen by covalent bonding to form a compound, hydrogen sulfide. Based on the number of valence electrons in a sulfur atom, predict the molecular formula of the compound:

H3S2HS2HSH4SH2S

25. Trace elements are those required by an organism in only minute quantities. Which of the following is a trace element that is required by humans and other vertebrates, but not by other organisms such as bacteria or plants?

phosphorusnitrogensodiumiodinecalcium

25 Questions

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25 Questions

❤ If you liked Fatskills, consider supporting us by checking out The Life Manuals You Never Got.

About | Explore | User Guide | Topics | Subjects | Doubt Solver | Career Aptitude Test | Answers | Free Tools | What Should We Know? Privacy | Terms |

Without work one finishes nothing. - Ralph Waldo Emerson© 2026 Fatskills.com

All trademarks, logos and brand names are the property of their respective owners. All company, product and service names used in this website are for identification purposes only. Use of these names, trademarks and brands does not imply endorsement.

About | Explore | User Guide | Topics | Subjects | Doubt Solver | Career Aptitude Test | Answers | Free Tools | What Should We Know?
Privacy | Terms |

Without work one finishes nothing. - Ralph Waldo Emerson
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