TEAS Test of Essential Academic Skills - Set 4 - Part 3

Correct Answer: Production of a gas

The production of a gas, often seen as bubbling or fizzing, is a strong indicator of a chemical change. Other indicators include color change, formation of a precipitate, release of heat, and the appearance of new odors. Option a is incorrect because a change in shape, such as bending or crushing, is a physical change. The chemical identity of the substance remains the same, even though its appearance has been altered noticeably to the eye. Option c is incorrect because a change in size, such as cutting or grinding, is a physical change. The substance is broken into smaller pieces but retains its chemical composition and original molecular identity throughout the process completely. Option d is incorrect because a change in physical state, such as melting or freezing, is a physical change. Water remains water whether it is solid, liquid, or vapor, so its chemical identity does not change.

Correct Answer: Toward the products

Removing a product as it forms decreases its concentration. The equilibrium responds by shifting to replace the missing product, which means the forward reaction speeds up and produces more product over time as a compensation. Option a is incorrect because shifting toward the reactants would happen if a product were added or a reactant were removed. Removing a product produces the opposite shift, favoring more product formation, not reactant formation in the system. Option b is incorrect because removing a product does not stop the reaction. The forward reaction actually continues at a faster rate to replenish the product and restore equilibrium between forward and reverse reactions in the system. Option c is incorrect because removing a product does not change the temperature of the system. Le Chatelier's principle predicts a shift in equilibrium position rather than a change in the system's temperature in response.

Correct Answer: Lowers the activation energy

Enzymes are biological catalysts, usually proteins, that lower the activation energy needed for a cellular reaction. They speed up reactions without being consumed and can be reused many times to catalyze additional substrate molecules during cellular activity. Option b is incorrect because enzymes do not provide the energy that drives a reaction. Energy comes from cellular sources such as ATP or from breaking chemical bonds, while enzymes only reduce the energy barrier needed for reactions. Option c is incorrect because enzymes are not consumed in the reactions they catalyze. They release the product and then bind a new substrate molecule, allowing them to be reused without becoming part of the final product. Option d is incorrect because enzymes lower activation energy rather than increasing it. Higher activation energy would slow a reaction, but enzymes accelerate reactions by reducing the energy required to start them in cells.

Correct Answer: Three

A codon is a sequence of three consecutive nitrogenous bases on messenger RNA. Each codon specifies one amino acid during translation, except for stop codons, which signal the end of protein synthesis at the ribosome during translation. Option a is incorrect because a single base does not specify an amino acid. With only four possible bases, a one-base code could represent at most four amino acids, far fewer than the twenty needed for protein synthesis. Option b is incorrect because two bases would yield only sixteen possible combinations. This is still not enough to specify the twenty standard amino acids found in proteins, so the genetic code uses a longer codon unit. Option d is incorrect because using four bases per codon would create far more combinations than needed. The genetic code uses three bases per codon, which gives sixty-four possibilities and is sufficient for amino acid coding in cells.

Correct Answer: A base

According to the Arrhenius definition, a base is a substance that produces hydroxide ions when dissolved in water. Sodium hydroxide and potassium hydroxide are common examples, and bases generally have a pH greater than seven on the scale. Option a is incorrect because a salt is the ionic compound formed during a neutralization reaction between an acid and a base. Salts do not specifically produce hydroxide ions when they dissolve in water under normal conditions in chemistry. Option c is incorrect because a buffer is a solution that resists pH changes when small amounts of acid or base are added. Buffers contain weak acids and conjugate bases but are not defined by hydroxide ion production in solution. Option d is incorrect because an acid produces hydrogen ions when dissolved in water, not hydroxide ions. Acids have a pH below seven and react with bases in neutralization reactions to form salts and water as products.

Correct Answer: An endocytic vesicle

During endocytosis, the plasma membrane folds inward and pinches off to form an endocytic vesicle. This vesicle carries the engulfed material into the cytoplasm, where lysosomes may digest its contents later within the cell. Option b is incorrect because Golgi vesicles bud off from the Golgi apparatus and carry modified proteins to their destinations inside or outside the cell. They do not form during the endocytosis process at the plasma membrane. Option c is incorrect because secretory vesicles are produced by the Golgi apparatus and fuse with the plasma membrane during exocytosis. They release contents outward, the opposite of bringing material into the cell from outside. Option d is incorrect because smooth endoplasmic reticulum is a membrane network that synthesizes lipids and detoxifies substances. It is not formed by inward folding of the plasma membrane around any external particle.

Correct Answer: A salt and water

In a neutralization reaction, the hydrogen ion from the acid combines with the hydroxide ion from the base to form water. The remaining cation and anion combine to form an ionic compound called a salt as a product. Option a is incorrect because hydrogen gas is typically produced when an acid reacts with certain metals, not with a base. Acid-base neutralization releases water along with a salt, not hydrogen gas alone as the only product. Option b is incorrect because carbon dioxide is released when an acid reacts with a carbonate compound. A simple acid-base reaction without carbonate produces water and a salt, not gaseous carbon dioxide as the main product. Option c is incorrect because acid and base reactions neutralize each other rather than producing two new acids. The hydrogen ion combines with the hydroxide ion, removing acidic and basic character from the resulting solution as water forms.

Correct Answer: Ionizes completely in water

A strong acid such as hydrochloric acid ionizes completely when dissolved in water, releasing all of its hydrogen ions. This complete ionization is what distinguishes strong acids from weak acids, which only partially ionize in solution. Option a is incorrect because a pH near fourteen indicates a strong base, not a strong acid. Strong acids have very low pH values, typically near zero, with abundant hydrogen ions in solution at any concentration. Option c is incorrect because a bitter taste is characteristic of bases, not acids. Acids generally taste sour, like lemon juice or vinegar, although tasting laboratory chemicals is unsafe and not recommended in any setting. Option d is incorrect because a slippery feel is typical of bases such as soap or sodium hydroxide solution. Acids do not feel slippery; this property is associated with hydroxide-containing solutions and basic compounds in general.

Correct Answer: Virus

Viruses lack the cellular machinery needed to replicate independently. They must enter a living host cell and hijack its enzymes, ribosomes, and other components to copy their genetic material and assemble new viral particles for spreading. Option a is incorrect because bacteria are independent single-celled organisms that reproduce on their own through binary fission. They do not need to enter a host cell to copy their genetic material and divide successfully. Option b is incorrect because fungi are independent eukaryotic organisms that reproduce through spores or budding. Yeasts and molds do not require a host cell to grow and produce additional offspring of their kind in any environment. Option d is incorrect because protozoa are independent single-celled eukaryotes that reproduce on their own. Although some are parasitic, they have all the cellular machinery needed for division without requiring host hijacking of any cell.

Correct Answer: Nitrogen

Nitrogen makes up approximately seventy-eight percent of Earth's atmosphere, making it the most abundant gas. Because air is a homogeneous mixture and nitrogen is by far the largest component, it acts as the solvent for the other gases. Option b is incorrect because oxygen makes up about twenty-one percent of the atmosphere. Although it is essential for cellular respiration, oxygen is the second most abundant gas and acts as a solute in air, not solvent. Option c is incorrect because carbon dioxide is present in air at very low percentages. It plays an important role in photosynthesis and the greenhouse effect, but it is not abundant enough to serve as the solvent for air. Option d is incorrect because argon makes up less than one percent of the atmosphere. While it is the most abundant noble gas in air, its concentration is far too low for it to be considered the solvent component.