Chapter 2: The Chemical Basis of Life - Water & Carbon

Fill-in-the-blank practice flashcards covering chemical evolution, atomic structure, water properties, chemical bonding, energy, and organic functional groups.

Hydrogen, oxygen, carbon, and nitrogen make up __________ of all matter in living organisms.

96%

Protons and neutrons are located in the __________ of an atom.

nucleus

An element's atomic number is defined by its number of __________.

protons

Forms of an element that have different numbers of neutrons are known as __________.

isotopes

The mass number of an atom is equal to the number of protons plus __________.

neutrons

In a carbon atom with atomic number 6 and mass number 12, the total number of neutrons is __________.

6

The number of unpaired electrons in an atom's outer shell is equal to its __________.

valence

A chemical bond formed when unpaired valence electrons are shared between two nuclei is a(n) __________ bond.

covalent

An atom that loses an electron and becomes positively charged is called a(n) __________.

cation

An atom that gains an electron and becomes negatively charged is called a(n) __________.

anion

Molecular nitrogen ($N_2$) is held together by a __________ covalent bond.

triple

Relative electronegativity among common biological elements follows the trend $O > N >$ __________.

$$C = H$$

Ions and polar molecules that stay in solution through interactions with water's partial charges are described as __________.

hydrophilic

Uncharged and nonpolar compounds that do not dissolve in water are described as __________.

hydrophobic

Binding between like molecules, such as water binding to itself, is known as __________.

cohesion

Binding between unlike molecules, such as water binding to glass or plastic, is known as __________.

adhesion

Chemical reactions that must absorb heat to proceed are classified as __________ reactions.

endothermic

The active motion form of energy is known as __________ energy.

kinetic

In the first step of chemical evolution, energy input drives the formation of hydrogen cyanide ($HCN$) and __________.

formaldehyde ($H_2CO$)

Carbon is the most versatile atom on Earth because it possesses __________ valence electrons.

four

The functional group that acts as a base by tending to attract a proton is the __________ group.

amino

The functional group that acts as an acid by tending to lose a proton in solution is the __________ group.

carboxyl

When present in proteins, sulfhydryl functional groups ($-SH$) can form __________ bonds that contribute to protein structure.

disulfide