TEAS Test of Essential Academic Skills - Set 4 - Part 1

Correct Answer: Mitochondrion

Mitochondria carry out cellular respiration on their inner membrane and matrix, producing the bulk of cellular ATP from glucose breakdown through the Krebs cycle and the electron transport chain. Option a is incorrect because ribosomes assemble amino acids into proteins by reading messenger RNA. They do not generate cellular energy or participate directly in the production of adenosine triphosphate within the cell. Option b is incorrect because lysosomes contain digestive enzymes that break down waste, old organelles, and ingested particles. They function as recycling centers, not as sites of cellular energy production through respiration. Option d is incorrect because the Golgi apparatus modifies, sorts, and packages proteins for transport to other locations. It does not generate energy or carry out reactions that produce adenosine triphosphate molecules.

Correct Answer: Prokaryotic

Prokaryotic cells, such as bacteria and archaea, lack a membrane-bound nucleus. Their genetic material floats freely within the cytoplasm, and they also lack other membrane-bound organelles found in eukaryotic cells. Option b is incorrect because plant cells are eukaryotic and contain a true nucleus surrounded by a nuclear envelope. They also have membrane-bound organelles, a cell wall, and chloroplasts for photosynthesis. Option c is incorrect because animal cells are eukaryotic. They contain a true nucleus that holds the genetic material, along with various membrane-bound organelles such as mitochondria and Golgi apparatus. Option d is incorrect because fungal cells are eukaryotic. They contain a membrane-bound nucleus and other organelles, distinguishing them from prokaryotic organisms like bacteria that lack nuclear envelopes entirely.

Correct Answer: Electron

Electrons carry a negative charge of one and orbit the nucleus in shells. They have very small mass relative to protons and neutrons, and their movement governs the chemical bonding behaviors of any atom. Option a is incorrect because protons carry a positive charge of one and reside in the nucleus. The number of protons defines the atomic number and determines which element the atom represents. Option b is incorrect because neutrons carry no electrical charge. They are located in the nucleus along with protons and contribute to the atom's mass number but not to its overall electrical charge. Option c is incorrect because the nucleus is not a subatomic particle. The nucleus is the dense central region of the atom that contains the positively charged protons and uncharged neutrons together.

Correct Answer: Single replacement

A single replacement reaction occurs when one element displaces another from a compound. Copper replaces silver in the nitrate compound, freeing solid silver metal and forming copper nitrate solution as the reaction proceeds. Option a is incorrect because synthesis reactions combine two or more reactants into a single product. The copper and silver nitrate reaction produces multiple products, not just one larger combined compound from the reactants. Option c is incorrect because decomposition reactions involve a single compound breaking into two or more simpler substances. Here, the reactants include both an element and a compound, not a single decomposing compound by itself. Option d is incorrect because double replacement reactions involve two compounds exchanging partners. Here a free element copper reacts with a compound, indicating a single replacement instead of a double replacement reaction.

Correct Answer: Thymine

In DNA, adenine always pairs with thymine through two hydrogen bonds. This complementary base pairing rule maintains the consistent width of the double helix and ensures faithful replication of genetic material during cell division. Option a is incorrect because cytosine pairs with guanine, forming three hydrogen bonds. Cytosine and guanine are partners, not adenine and cytosine, so this base pairing combination does not occur in DNA. Option b is incorrect because guanine pairs with cytosine in DNA. Guanine is a purine that bonds with the pyrimidine cytosine through three hydrogen bonds, not with adenine in the helix. Option d is incorrect because uracil is found in RNA, not DNA. Uracil pairs with adenine during transcription, but DNA uses thymine as the complementary base for adenine in the double helix.

Correct Answer: Ribosome

Ribosomes are the cellular structures that read messenger RNA codons and link the corresponding amino acids together with peptide bonds. They may float freely in the cytoplasm or attach to the rough endoplasmic reticulum. Option b is incorrect because lysosomes contain digestive enzymes used to break down old organelles, ingested pathogens, and waste products. They are recycling centers and do not synthesize proteins from amino acids inside the cell. Option c is incorrect because mitochondria primarily produce ATP through cellular respiration. While they do have their own small ribosomes, the question asks about the organelle dedicated to general protein assembly itself. Option d is incorrect because the nucleolus is the dense region inside the nucleus where ribosomes are manufactured. The nucleolus assembles ribosome subunits but does not itself synthesize proteins from amino acids directly.

Correct Answer: Exothermic

An exothermic reaction releases energy, usually in the form of heat, to the surroundings. The products contain less stored chemical energy than the reactants, so excess energy is given off during the reaction. Option a is incorrect because an endothermic reaction absorbs heat from its surroundings rather than releasing it. The products end up with more chemical energy than the reactants in this type of reaction. Option b is incorrect because a reversible reaction simply means the process can run in either direction. Reversibility does not specify whether energy is released or absorbed during the forward reaction at equilibrium. Option c is incorrect because a catalyzed reaction is one whose rate is increased by a catalyst. The label refers to the presence of a catalyst, not whether heat is released or absorbed during the reaction.

Correct Answer: Transcription

Transcription occurs in the nucleus when RNA polymerase reads one strand of DNA and assembles a complementary RNA molecule. This messenger RNA then carries the genetic information out to ribosomes for protein synthesis. Option a is incorrect because translation is the next step, where ribosomes read messenger RNA and assemble amino acids into a protein. Translation uses RNA as a template, not DNA, to build polypeptides during synthesis. Option b is incorrect because replication copies an entire DNA molecule into two identical DNA molecules before cell division. Replication produces DNA from DNA, not RNA from DNA as in transcription. Option d is incorrect because a mutation is a permanent change in the DNA sequence. Mutations can affect transcribed RNA, but mutation itself is not the process that creates RNA from a DNA template.

Correct Answer: Heterozygous

Heterozygous means an individual carries two different alleles for the same gene, such as Bb. The dominant allele typically masks the recessive allele in the resulting phenotype unless inheritance is incomplete or codominant in nature. Option b is incorrect because homozygous dominant means an individual has two identical dominant alleles, such as BB. Both alleles are the same, not different, so this term does not apply to the question. Option c is incorrect because homozygous recessive means an individual has two identical recessive alleles, such as bb. The two alleles match, so this is not the correct description for an organism with differing alleles. Option d is incorrect because hemizygous refers to having only one allele for a gene, often seen for X-linked genes in males. It does not describe an individual with two differing alleles for the gene.

Correct Answer: Group eighteen

Group eighteen contains the noble gases, including helium, neon, argon, krypton, xenon, and radon. These elements have full outer electron shells, which makes them very stable and generally unreactive under normal conditions in chemistry. Option a is incorrect because group one contains the alkali metals such as lithium, sodium, and potassium. These elements are very reactive due to their single valence electron, the opposite of stable noble gases. Option b is incorrect because group two contains the alkaline earth metals such as beryllium, magnesium, and calcium. They have two valence electrons and form positive two ions, unlike the unreactive noble gases. Option c is incorrect because group seventeen contains the halogens such as fluorine, chlorine, and bromine. Halogens are highly reactive nonmetals with seven valence electrons, very different from the unreactive noble gases of group eighteen.

Correct Answer: Amino acid

Proteins are polymers of amino acids linked together by peptide bonds. Twenty standard amino acids combine in different sequences to form polypeptides, which fold into functional shapes that perform a wide range of cellular tasks. Option a is incorrect because nucleotides are the building blocks of nucleic acids such as DNA and RNA. Each nucleotide contains a sugar, a phosphate group, and a nitrogenous base, not amino acid components. Option b is incorrect because glucose is a monosaccharide that serves as a building block for carbohydrates such as starch and glycogen. It does not link together to form proteins through peptide bonding within the cell. Option d is incorrect because fatty acids are components of triglycerides and phospholipids, which are lipids. Fatty acids form chains attached to glycerol, not the polymer chains that make up proteins.

Correct Answer: Isotopes

Isotopes are atoms of the same element that share the same number of protons but differ in the number of neutrons. Carbon twelve and carbon fourteen are common examples of naturally occurring isotopes of carbon. Option b is incorrect because ions are atoms or molecules that have gained or lost electrons, giving them an electrical charge. Differences in neutron count create isotopes, not ions, of the same element atom. Option c is incorrect because compounds are pure substances containing two or more different elements chemically bonded together. The question describes atoms of the same element, not chemically combined different elements joined into a compound. Option d is incorrect because molecules are groups of two or more atoms held together by chemical bonds. Atoms differing only in neutron number are still single atoms, not bonded molecular groupings of multiple atoms.

Correct Answer: DNA to RNA to protein

The central dogma of molecular biology states that genetic information flows from DNA to RNA through transcription, then from RNA to protein through translation. This pathway describes how genes ultimately produce functional cellular products in the body. Option a is incorrect because RNA does not normally produce DNA inside most cells. Although certain viruses use reverse transcription, the standard cellular flow begins with DNA, not RNA, as the original source. Option b is incorrect because proteins do not encode RNA or DNA. Proteins are end products of gene expression, not templates for nucleic acids, so this sequence reverses the actual molecular flow direction. Option c is incorrect because proteins cannot be translated directly from DNA without an RNA intermediate. Messenger RNA carries the genetic message from the nucleus to ribosomes, which then assemble proteins.

Correct Answer: Twenty-five percent

Crossing two heterozygous parents yields offspring in a one to two to one genotype ratio. One quarter are homozygous dominant, half are heterozygous, and one quarter are homozygous recessive in the resulting Punnett square. Option a is incorrect because both parents carry a recessive allele that can be passed on. There is a real chance, not zero, that a child inherits two recessive alleles from this cross of parents. Option c is incorrect because fifty percent represents the heterozygous offspring fraction in this cross. Half of the children are expected to be Bb, but only a quarter will be homozygous recessive overall. Option d is incorrect because seventy-five percent reflects the proportion showing the dominant phenotype, including BB and Bb together. The homozygous recessive genotype itself appears in only a quarter of the offspring.

Correct Answer: Melting ice

Melting ice involves a change in state from solid to liquid without altering the chemical composition. Water molecules remain water molecules, so the substance keeps its identity, defining the process as a physical change clearly. Option a is incorrect because burning paper is a chemical change. Combustion produces new substances such as carbon dioxide, water vapor, and ash, and the original paper cannot be recovered by any physical means. Option b is incorrect because digesting food is a chemical change. Enzymes break down macromolecules into smaller substances such as amino acids and simple sugars, producing new compounds that did not exist before digestion. Option d is incorrect because rusting iron is a chemical change in which iron reacts with oxygen to form iron oxide. A new substance with different properties is produced, indicating a chemical transformation rather than physical.

Correct Answer: Bacterium

A bacterium is a single-celled prokaryotic organism without a nucleus or membrane-bound organelles. Pathogenic bacteria cause illnesses such as strep throat, tuberculosis, and certain urinary tract infections, and they are typically treated with antibiotics. Option b is incorrect because a virus is not a cell at all. Viruses are non-cellular infectious agents made of genetic material wrapped in a protein coat, and they cannot reproduce outside a host cell. Option c is incorrect because protozoa are eukaryotic single-celled organisms, not prokaryotic. They have a true nucleus and other membrane-bound organelles, distinguishing them from prokaryotes such as bacteria and archaea in classification. Option d is incorrect because fungi are eukaryotic. While yeasts are single-celled, they have a nucleus and membrane-bound organelles, so they are not prokaryotic organisms like bacteria are in cellular structure.

Correct Answer: Lower left corner

Atomic radius increases moving down a group because more electron shells are added, and decreases across a period because the nuclear charge pulls electrons in tighter. The lower left corner holds the largest atoms. Option a is incorrect because the upper right corner contains nonmetals such as fluorine and neon, which are among the smallest atoms due to high effective nuclear charge pulling electrons very tightly inward toward the nucleus. Option b is incorrect because the upper left contains small period two atoms such as lithium and beryllium. Although they are metals, their few electron shells make them much smaller than the heavier alkali metals. Option c is incorrect because the lower right contains heavier nonmetals and noble gases. While larger than upper right elements, they are smaller than lower left metals because of the greater effective nuclear charge.

Correct Answer: Nucleic acids

DNA and RNA are nucleic acids made of repeating nucleotide units. Each nucleotide contains a sugar, a phosphate group, and a nitrogenous base. Nucleic acids store and transmit the genetic information needed by all living cells. Option a is incorrect because carbohydrates include sugars and polysaccharides used for energy and structure. They are not built from nucleotides and do not store the genetic instructions used to construct proteins inside cells. Option b is incorrect because lipids include fats, phospholipids, and steroids. Lipids store energy and form membranes, but they are not built from nucleotides and do not encode any hereditary information for cells. Option d is incorrect because proteins are made of amino acids and serve as enzymes, structural components, and signaling molecules. Proteins are not nucleic acids and do not contain the bases adenine, thymine, guanine, or cytosine.

Correct Answer: Swell and possibly burst

A hypotonic solution has a lower solute concentration outside the cell. Water moves into the red blood cell by osmosis to balance solute levels, causing it to swell. Because animal cells lack walls, they may rupture. Option b is incorrect because shriveling occurs when a cell is placed in a hypertonic solution, where water moves out of the cell. Hypotonic conditions cause water to move in, leading to cell swelling instead of shrinking. Option c is incorrect because staying the same occurs in an isotonic solution, where solute concentrations are equal on both sides. In a hypotonic environment, net water movement causes a noticeable change in cell volume. Option d is incorrect because red blood cells lack chloroplasts and cannot perform photosynthesis. The presence of a hypotonic environment does not enable a human animal cell to begin synthesizing glucose from light.

Correct Answer: Basic

A pH greater than seven indicates a basic, or alkaline, solution. A pH of nine is moderately basic, similar to a baking soda solution, with a higher concentration of hydroxide ions than hydrogen ions. Option a is incorrect because strongly acidic solutions have very low pH values, typically zero through three. A pH of nine indicates the opposite end of the scale, where hydroxide ions are more abundant than hydrogen ions. Option c is incorrect because slightly acidic solutions have pH values just below seven, such as five or six. A pH of nine is above seven and therefore indicates a basic solution rather than an acidic one. Option d is incorrect because a neutral solution has a pH of exactly seven. A pH of nine indicates more hydroxide ions than hydrogen ions, placing the solution above neutral on the basic side.