A&P Chapter 2 Chemistry Comes Alive - Practice Test

Which of the following is NOT one of the four basic elements that comprise approximately 96% of a human's body weight?

potassium. Four elements—carbon, oxygen, hydrogen, and nitrogen—make up about 96% of body weight, and 20 others are present in the body, some in trace amounts.

Match the following organic molecules to their biochemical building blocks/precursors.

The molecular building blocks of proteins are amino acids. Lipids are built from glycerol and fatty acids. Nucleic acids, which include DNA and RNA, are built from nucleotides. Carbohydrates are built from monosaccharides.

In biochemistry, and thus in the body, the universal solvent is __________.

water. A solvent is something that dissolves a solute. Water is the body's chief solvent. In fact, more things can dissolve in water than in any other solvent known to mankind. For this reason water is often called the "universal solvent."

Which of the following is the primary energy-transferring molecule in cells?

ATP ATP is the main energy currency of a cell.

Which of the following is NOT a way to distinguish an acid from a base?

An acidic substance will have a sticky feel. Acids have a sour taste, can react with (dissolve) many metals, and "burn" a hole in your rug. Bases have a bitter taste and feel slippery.

Which of the following is true of atoms?

Atoms of any given element will differ from those of all other elements and provide its unique physical and chemical properties. Each element is composed of particles or building blocks, called atoms. Every element's atoms differ from those of all other elements and give the element its unique physical and chemical properties.

Which of the following is NOT true of DNA?

DNA carries out the orders for protein synthesis issued by RNA. DNA has two fundamental roles: (1) replicating itself before the cell divides, ensuring that all genetic information in the descendent cells is identical; and (2) providing the basic instructions for building every protein in the body. The whole molecule is coiled into a spiral staircase-like structure called a double helix.

Polar molecules are electrically balanced, due to the equal sharing of electrons between the atoms of the molecules.

False. Nonpolar molecules are electrically balanced due to the equal sharing of electrons between the atoms of the molecules. Polar molecules are created due to unequal electron pair sharing. Water is one of the most important polar molecules in a living system.

Electrons bear a positive charge equal in strength to the negative charge of the proton.

False. The tiny electrons (e-) bear a negative charge equal in strength to the positive charge of the proton.

Which of the following is true of an isotope?

Isotopes have the same number of protons, but differ in the number of neutrons they contain. The majority of elements have two or more structural variations called isotopes. Isotopes of an element have the same number of protons, but differ in the number of neutrons they contain. Isotopes are not necessarily present in equal amounts in a given element.

Which of the following is a property of matter?

Matter can exist in solid, liquid, or gaseous states. Matter is anything that occupies space and has mass. In most cases, it can be seen, smelled, or felt. The mass of an object is equal to the amount of matter in the object, and it remains constant wherever the object is. In contrast, weight varies with gravity. For example, the mass of an object would be the same on the moon and on Earth; however, the weight of the same object would be less on the moon than on Earth. This is because the force of gravity is less on the moon than on Earth. Matter exists in solid, liquid, or gaseous states.

Which of the following best defines potential energy?

Potential energy is stored energy, which has the capacity to do work, but is not presently doing so. Kinetic energy is energy in action. We see evidence of kinetic energy in the constant movement of the tiniest particles of matter, as well as in larger objects. Potential energy is stored energy that has the capacity to do work, but is not presently doing so.

Which of the following types of chemical reactions always involves atoms or molecules combining to form a larger, more complex molecule?

Synthesis. When atoms or molecules combine to form a larger, more complex molecule, the process is a synthesis reaction.

Enzymes are unchanged in a reaction; they can be reused, and are not needed in large quantities.

True Three basic steps appear to be involved in enzyme action: The enzyme's active site binds to the substrate(s) on which it acts, temporarily forming an enzyme-substrate complex. The enzyme-substrate complex undergoes internal rearrangements that form the product(s). The enzyme releases the product(s) of the reaction. Because enzymes are unchanged by their catalytic role and can act again and again, cells need only small amounts of each enzyme.

All organic molecules contain carbon.

True All organic compounds contain carbon.

The major function of RNA is to carry out the genetic instructions for protein synthesis.

True RNA carries out the genetic instructions for protein synthesis.

Emulsions are heterogeneous mixtures.

True. Colloids, also called emulsions, are heterogeneous mixtures, which means that their composition is dissimilar in different areas of the mixture.

The atomic number of an atom is equal to the number of protons in its nucleus.

True. The atomic number of any atom is equal to the number of protons in its nucleus.

Which of the following does NOT represent an accurate hierarchy in the natural combination of matter?

When two or more similar kinds of atoms bind, they form an isotope. Most atoms do not exist in the free state, but are chemically combined with other atoms. Such a combination of two or more atoms held together by chemical bonds is called a molecule. Two or more identical atoms bonded together form molecules of that element. When two or more different kinds of atoms combine, they form molecules of a compound. Compounds are chemically pure, and all of their molecules are identical. Mixtures are substances composed of two or more components.

If the pH or temperature of the environment that contains a protein is altered dramatically, then the protein may __________.

become denatured. Proteins are sensitive to changes in pH and temperature. This is one reason why it is so important to tightly regulate body temperature and pH. If a protein is exposed to dramatic changes in pH or temperature, it can be denatured. A denatured protein is not functional.

Something with a pH of 5 would __________.

have more H+ ions than OH- ions Acids have a pH below 7, while bases have a pH above 7. A neutral solution has a pH of 7. The lower the pH, the more acidic the substance. A substance's pH is related to the balance of H+ (hydrogen) ions and OH- (hydroxide) ions. A substance with more H+ ions than OH- ions will have a pH below 7, and thus will be acidic. A substance that has an equal concentration of H+ and OH- is neutral (pH of 7). When the concentration of H+ is less than the concentration of OH- the substance will have a pH above 7 and be considered basic.

Buffers __________.

stabilize pH Buffers help to stabilize pH. In biological systems, a constant pH is essential for normal physiology. If the pH of the environment is too low, then buffers can absorb H+ ions to raise the pH. If the pH is too high, then buffers can release H+ ions to lower the pH. This balance of absorbing and releasing H+ ions helps to stabilize pH in a system.

In an ionic bond, __________.

there is a transfer of one or more electrons from one atom to the other. An ionic bond is a chemical bond between atoms formed by the transfer of one or more electrons from one atom to the other.