Module 5: Summary Quiz

[blank_start]Atoms[blank_end] are the basic building blocks of matter. They are composed of [blank_start]protons[blank_end] and [blank_start]neutrons[blank_end] that form the [blank_start]nucleus[blank_end] at the center of the atom as well as [blank_start]electrons[blank_end] that orbit the nucleus. Atoms have an [blank_start]equal number[blank_end] of protons and electrons, and the majority of an atom’s properties are determined by the [blank_start]number of electrons[blank_end] it has.

An [blank_start]element[blank_end] is a collection of atoms that all have the same number of protons.

A carbon atom has six protons and eight neutrons. The complete name of this atom is [blank_start]carbon-14[blank_end] and it has [blank_start]six[blank_end] electrons.

The more important biological elements and their abbreviations (in parentheses) are: [blank_start]carbon[blank_end] (C), [blank_start]hydrogen[blank_end] (H), [blank_start]oxygen[blank_end] (O), [blank_start]nitrogen[blank_end] (N), [blank_start]phosphorus[blank_end] (P), and [blank_start]sulfur[blank_end] (S)

“Sulfur-32” is the name of a specific [blank_start]atom[blank_end], while “sulfur” is the name of an [blank_start]element[blank_end].

When atoms link together, they form [blank_start]molecules[blank_end]. A molecule of ethyl alcohol, C2H6O, has [blank_start]two[blank_end] carbon atoms, [blank_start]six[blank_end] hydrogen atoms, and [blank_start]one[blank_end] oxygen atom.

Even though they both contain [blank_start]carbon[blank_end] and [blank_start]oxygen[blank_end] atoms, CO and CO2 are [blank_start]different[blank_end] molecules.

When sucrose is dissolved in water, a [blank_start]physical[blank_end] change has taken place. On the other hand, when sucrose reacts with water with the help of an enzyme to make glucose and fructose, a [blank_start]chemical[blank_end] change has occurred. In general, [blank_start]physical changes[blank_end] are reversible, while [blank_start]chemical changes[blank_end] are not.

All matter can exist in one of three phases: [blank_start]solid[blank_end], [blank_start]liquid[blank_end], and [blank_start]gas[blank_end]. Adding energy turns [blank_start]solids[blank_end] into [blank_start]liquids[blank_end] and liquids into [blank_start]gases[blank_end], while taking away energy tends to reverse the process.

When [blank_start]salt[blank_end] is dissolved in [blank_start]water[blank_end], salt is the solute, water is the solvent, and the solution is [blank_start]salt water[blank_end].

When a solute travels across a membrane in order to even out concentration, [blank_start]diffusion[blank_end] has occurred. When the solvent travels across a membrane in order to even out concentration, [blank_start]osmosis[blank_end] has occurred. Osmosis happens when a semipermeable membrane separates [blank_start]two solutions[blank_end].

A cell sits in a solution that has a higher concentration of solutes than that found in the cell. Water will tend to travel [blank_start]out of the cell[blank_end] and [blank_start]into the solution[blank_end].

In the balanced chemical equation: C18 H32 O16 + 2H2O → 3C6H12O6 [blank_start]One[blank_end] molecule of C18H32O16 reacts with [blank_start]two[blank_end] molecules of H2O to make [blank_start]three[blank_end] molecules of C6H12O6.

Photosynthesis requires [blank_start]carbon dioxide[blank_end], [blank_start]water[blank_end], [blank_start]energy from light[blank_end], and [blank_start]chlorophyll[blank_end] (which acts as a catalyst). It produces [blank_start]glucose[blank_end] and [blank_start]oxygen[blank_end] via the chemical equation: [blank_start]6CO2[blank_end] + [blank_start]6H2O[blank_end] → [blank_start]C6H12O6[blank_end] + [blank_start]6O2[blank_end]

Glucose and fructose both have the same chemical formula, [blank_start]C6H12O6[blank_end], which means they are [blank_start]isomers[blank_end]. They have different [blank_start]structural[blank_end] formulas. A molecule can have more than one [blank_start]structural formula[blank_end]. Glucose and fructose, for example, have both a [blank_start]ring[blank_end] structure and a [blank_start]chain[blank_end] structure.

A simple sugar is called a [blank_start]monosaccharide[blank_end]. Two such simple sugars can join to make a [blank_start]disaccharide[blank_end]. If three or more join, they form a [blank_start]polysaccharide[blank_end]. Simple sugars join together through [blank_start]dehydration[blank_end] reactions.

People and animals store excess sugars as a [blank_start]polysaccharide[blank_end] known as [blank_start]glycogen[blank_end]. When they need the simple sugars again, they break down this molecule into [blank_start]monosaccharides[blank_end] via [blank_start]hydrolysis[blank_end] reactions.

The pH scale runs from [blank_start]zero[blank_end] to [blank_start]fourteen[blank_end]. A pH of [blank_start]seven[blank_end] is neutral. A pH [blank_start]lower than seven[blank_end] indicates an [blank_start]acidic[blank_end] solution, while a pH [blank_start]greater than seven[blank_end] indicates an [blank_start]alkaline[blank_end] solution.

Lipids are formed in [blank_start]dehydration[blank_end] reactions where three [blank_start]fatty acid molecules[blank_end] are joined to one [blank_start]glycerol[blank_end] molecule. Lipids are [blank_start]hydrophobic[blank_end], meaning they are not attracted to water. If the [blank_start]fatty acid[blank_end] molecules that make up the lipid have no double bonds between the carbon atoms, it is a [blank_start]saturated fat[blank_end] and is generally [blank_start]solid[blank_end] at room temperature. If there are double bonds between the carbon atoms, it is an [blank_start]unsaturated fat[blank_end] and is generally [blank_start]liquid[blank_end] at room temperature.

Proteins are formed in [blank_start]dehydration[blank_end] reactions where [blank_start]amino acids[blank_end] are joined together. The bond that forms between them is called a [blank_start]peptide bond[blank_end]. [blank_start]Enzymes[blank_end] make up a special class of proteins that serve as [blank_start]catalysts[blank_end] for many biologically-important chemical reactions, and they typically work according to the [blank_start]lock and key theory of enzyme action[blank_end], in which an active site complements the shape of a reactant. Many of these molecules are quite [blank_start]fragile[blank_end], breaking down soon after they are formed.

[blank_start]DNA[blank_end] is a double chain of chemical units known as [blank_start]nucleotides[blank_end] that twist around one another in a double helix. The units that make up these chains are composed of three basic constituents: [blank_start]deoxyribose[blank_end], a [blank_start]phosphate group[blank_end], and a [blank_start]nucleotide base[blank_end]. The double helix is held together by [blank_start]hydrogen bonds[blank_end] that link certain [blank_start]nucleotide bases[blank_end] together. In DNA, [blank_start]guanine[blank_end] can link only to [blank_start]cytosine[blank_end] (and vice-versa), while the nucleotide base [blank_start]adenine[blank_end] can link only to [blank_start]thymine[blank_end] (and vice-versa).