Mastering Biology Test 1

It is possible to test hypotheses, such as those involving historical events, without conducting experiments. Although it is not possible to carry out experiments to test hypotheses about evolutionary relationships between living groups or about the timing of the origin of major evolutionary innovations, such hypotheses can be evaluated by making predictions about the expected findings that would result from these hypotheses. Data can then be collected to test whether these predictions are correct. Read about the forms of scientific inquiry and the scientific method.

Van der Waals interactions can form between atoms of equal electronegativity. Even nonpolar covalent bonds have temporary regions of partial positive and negative charge, due to the chance movements of electrons. Attractions between such transient positive and negative charges create weak Van der Waals interactions.

Dissociation of water is reversible. Water ionizes to form hydroxide and hydronium ions. Dissociation of water produces equal numbers of OH- and H+.

An electron orbital describes a three-dimensional space where an electron can be found 90% of the time. We cannot know the exact location of an electron. Instead, we can describe a three-dimensional space in which an electron spends most of its time.

Weak bonds are transient and easily reversible. Molecules that form weak bonds can come together, interact, and then separate. The combined effect of many weak and transient hydrogen bonds or Van der Waals interactions can produce important emergent properties. Read about the importance of the transience of weak bonds such as hydrogen bonds, ionic bonds, and Van der Waals interactions.

A methyl group consists of a carbon bonded to three hydrogen atoms. A methyl group consists of a carbon covalently bonded to three hydrogen atoms.

You learned in elementary school that as temperature drops, liquids change into solid form. You are given an unfamiliar liquid and hypothesize that it will become solid if you put it in the freezer. This is deductive reasoning. You are predicting specific results based on general principles.

water's high surface tension Water's high surface tension, related to its cohesion, makes water behave as though coated with an invisible film.

A chemical bond forms when two atoms transfer or share outer electrons to complete their outer shells. Only the electrons of atoms participate in chemical bonds, which form when atoms transfer or share outer or valence electrons.

Starch and cellulose differ in the glycosidic linkages between their glucose monomers. Both starch and cellulose are glucose polymers, but the glycosidic linkages in these two polymers differ. Glucose can have two slightly different ring structures. When glucose forms a ring, the hydroxyl group attached to the number 1 carbon is positioned either below (alpha) or above (beta) the plane of the ring. In starch, all the glucose monomers are in the alpha configuration. In cellulose, all the glucose monomers are in the beta configuration. As a result, every other glucose monomer is "upside down" with respect to its neighbors. The differing glycosidic linkages in starch and cellulose give the two molecules distinct three-dimensional shapes, leading to key functional differences.

adhesion of water molecules to other kinds of molecules Water adheres to the cellulose molecules in a paper towel, allowing the towel to pick up a puddle of water. This is similar to the adhesion between water molecules and cellulose in cell walls responsible for water transport in plants.

Enantiomers differ in biological activity. Because enantiomers are mirror images of each other, working molecules distinguish the two versions by shape. Usually, one isomer is biologically active and the other is inactive.

Primary, tertiary and quaternary levels of protein structure The primary structure of a protein is the specific linear sequence of amino acids forming the protein. The amino acids are joined by covalent peptide bonds. Tertiary structure, producing the unique structure of a protein, is stabilized by interactions among the R groups on each amino acid in the protein. Tertiary structure may be stabilized by covalent bonds, called disulfide bridges, that form between the sulfhydryl groups (SH) of two cysteine monomers. Tertiary structure may also be stabilized by weaker interactions, including hydrogen bonds between polar and/or charged areas, ionic bonds between charged R groups, and hydrophobic interactions and van der Waals interactions among hydrophobic R groups. Many globular proteins are made up of several polypeptide chains called subunits stuck to each other by a variety of attractive forces but rarely by covalent bonds. Protein chemists describe this as quaternary structure.

An electron in the 3 p orbital of the third electron shell has more potential energy than an electron in the 2 p orbital of the second electron shell.

Quaternary level of protein structure Quaternary structure results from the aggregation of two or more polypeptide subunits, and not all proteins are composed of more than one polypeptide.

A tree and its physical environment alter each other This answer is the most accurate statement. Read the themes about the interactions among organisms and their physical environment.

Isomers differ in the arrangement or bonding of atoms. Isomers may differ in the covalent arrangements of their atoms or the position of double bonds within the molecule and thus have different chemical properties

Metabolic cooperation between prokaryotic cells forms a biofilm that allows bacterial colonies to transport nutrients and wastes. Biofilms may damage industrial equipment or cause tooth decay. This emergent property emerges at the community level, due to the interactions among prokaryotic species forming the biofilm. Read about levels of biological organization in and emergent properties.

The H+ concentration of lemon juice is higher than the H+ concentration of household bleach by a factor of 1011 (100 billion). The figure shows the pH scale and pH values of some aqueous solutions, including lemon juice and household bleach. The pH of a solution is the negative logarithm of H+ concentration.

All living things share a common genetic language of DNA because they share a common ancestry. The genetic code is arbitrary, at least to some extent. The fact that all organisms share a single genetic code is due to their common ancestry. Read about the core theme of biology: Evolution accounts for the unity and diversity of life.

The many ways that monomers of each class of biological molecule can be combined into polymers. Biological molecules belong to four main classes, and are constructed from only 40 to 50 common monomers (and a few rare ones) made of only a few of the 92 naturally occurring elements. The diversity of biological molecules is due to differences in the arrangements of the monomers in each molecule.

Amino and carboxyl are functional groups. Read about the variety of biologically important functional groups and note the structure and functional properties of amino and carboxyl groups.

ATP A nucleotide consists of three parts: a nitrogenous base, a pentose sugar, and one or more phosphate groups. ATP consists of a nitrogenous base (adenine), a pentose sugar, and three phosphate groups.

water's high heat of vaporization Evaporative cooling takes place when molecules with the greatest kinetic energy leave a fluid as gas molecules. Because of water's high heat of vaporization, a large amount of heat must be absorbed for 1 gram of water to be converted from liquid to gas. The dog loses this heat as the water on its tongue evaporates, allowing him to cool down by panting. To understand why this answer is correct, read about evaporative cooling.