HESI A2 Biology Practice Test

During metaphase, the chromosomes align along the center of the cell. During prophase, chromosomes condense, and the nuclear envelope disappears during prometaphase. Anaphase is when the chromosomes start to separate from each other. Telophase is when the chromosomes gather on either side of the now dividing cell; it is followed by cytokinesis.

Ribosomes can be found in two places in a eukaryotic cell: on the rough endoplasmic reticulum (rough ER) or free floating in the cytoplasm.

The Golgi apparatus is responsible for the packaging and processing of materials for transport throughout the cell or for secretion. Lysosomes digest macromolecules into their components using hydrolytic enzymes. The smooth ER detoxifies drugs and other harmful products. Cellular respiration resulting in ATP production is the function of mitochondria.

The bonds between atoms within the water molecule are polar covalent bonds, resulting in the unequal sharing of electrons. Within a water molecule, the electrons in each covalent bond are held closer to the O atom compared to the H atoms. This makes the O-end of each water molecule have a partial negative charge, while the H ends have a partial positive charge. Therefore, a partial positive end of one water molecule is attracted to the partial negative charge of another water molecule, forming a hydrogen bond.

The most inclusive category is Kingdom. The most restrictive would be Species. The mnemonic “King Philip Came Over For Great Spaghetti,” can be used to recall the order of the categories within this organizational system from most inclusive to most restrictive.

The G₁, S, and G₂ phases are all phases within interphase. S phase is when DNA is replicated. The G₁ and G₂ phases are periods of cell growth (G₁ = first growth phase, G₂ = second growth phase and preparation for division). M phase includes mitosis and cytokinesis.

Mitosis makes two identical daughter cells from an original parent cell and does not reduce chromosome content. Meiosis is a process that begins with a diploid cell and results in the formation of haploid cells.

Meiosis results in the formation of gametes like sperm cells (in males) and egg cells (in females). All other body cells, called somatic cells, undergo mitosis, not meiosis, to produce more cells.

The Krebs cycle breaks down pyruvate fully to CO₂, producing energy in the form of ATPs and NADH (and FADH₂). Glycolysis breaks down glucose to produce NADH, ATP, and pyruvate. The passage of electrons through the electron transport chain results in the formation of H₂O and ATP. Photosynthesis results in the formation of O₂ and glucose.

The plasma membrane is composed of a bilayer of phospholipids into which proteins and cholesterol are inserted.

The various steps in cellular respiration (glycolysis, Krebs cycle, electron transport chain) each produce ATP. The Calvin cycle takes place during photosynthesis and does not produce ATP but rather uses it to produce sugar.

A heterozygote is diploid and has two different alleles for a given gene. Here, only Tt is a heterozygous genotype. Both TT and tt are homozygous, having two copies of the same allele for a given gene. The genotype T does not indicate a diploid cell.

Alleles are alternate versions of a single gene that codes for a certain trait. The genotype refers to what alleles for a given gene an individual possesses, while the phenotype refers to the physical characteristics that an individual displays related to a given gene. Chromosomes are the DNA structures that each contain many genes.

For simple dominance, an individual requires only one copy of the dominant allele (R in this case) to have the dominant phenotype. Therefore, individuals having the RR and Rr genotypes will have the dominant phenotype. An individual with the rr genotype will have the recessive phenotype.

Amphipathic is the term that describes how phospholipids each have a hydrophilic end as well as a hydrophobic end. A fatty acid having one or more double bonds is unsaturated. A saturated fatty acid lacks double bonds. Cell membranes composed of phospholipids with embedded proteins are selectively permeable, meaning that they allow some substances to freely flow through while restricting the movement of other substances.

Carbohydrates are composed of sugars like glucose. Lipids including fats and phospholipids are composed of fatty acids. Nucleic acids are composed of nucleotides. Proteins are composed of amino acids.

Transcription is the process that synthesizes mRNA using DNA as the template. Replication duplicates DNA using DNA as the template. Translation (protein synthesis) uses mRNA to make a protein. Cytokinesis is the process by which two newly made cells fully divider from each other.

A base-pairs with T in double-stranded DNA. There is no U in DNA, so A should not be seen base-pairing with U in double-stranded DNA. A does not typically base-pair with either C or G in double-stranded DNA.

Because the homozygous dominant individual can only provide the dominant allele to its offspring, all of the offspring will have the dominant allele and express the dominant phenotype. Thus, none of the offspring would show the recessive phenotype.

Pleiotropy refers to when one gene influences multiple seemingly unrelated phenotypic traits. Simple dominance refers to when being either homozygous dominant or heterozygous results in the individual having the same dominant phenotype. Epistasis refers to an situation where two or more genes interact whereby the genotype at one gene influences the expression of the genotype at another allele. Polygenic inheritance refers to when one phenotypic trait is influenced by multiple genes.

The nitrogenous bases of complementary nucleotides hydrogen bond with each other in a double-stranded DNA molecule. Within a single DNA strand, a sugar molecule of one nucleotide covalently bonds to the phosphate group of the next nucleotide to form the sugar-phosphate backbone.

Glycolysis is the conversion of glucose to pyruvate, and it is the first step in the process of cellular respiration. Cellular respiration is the group of processes that fully oxidizes glucose to CO₂ to make ATP; it includes glycolysis, the Krebs cycle, and the electron transport chain. Glucose is made from CO₂ during the Calvin cycle of photosynthesis, not during glycolysis.

The electron transport chain is the step of cellular respiration that oxidizes NADH molecules to produce ATP and water. The Calvin cycle is not a step within cellular respiration, but rather, is part of photosynthesis to make glucose. The Krebs cycle is the step within cellular respiration that oxidizes pyruvate to CO₂, producing ATP, NADH, and FADH₂ as a result. Glycolysis is the step within cellular respiration that breaks down glucose into two pyruvates, producing NADH and ATP as a result.

Cellular respiration can generate between 32 to 36 molecules of ATP for every glucose molecule broken down. The number of ATP is described as a range because the reaction is not perfectly efficient and will sometimes yield more or less ATP.

The ribosome is the location of protein synthesis in a eukaryotic cell. Free ribosomes are located in the cytosol while other ribosomes are attached to the rough endoplasmic reticulum. The mitochondrion is the location of ATP synthesis during cellular respiration. The lysosome is responsible for the digestion of large biological molecules into smaller components. The Golgi apparatus is responsible for modifying and packaging materials for transport within the cell or for secretion from the cell.

A hypothesis is a statement or explanation of certain events. A hypothesis is typically made after observation to explain the observation. Then, an experiment is designed to test the hypothesis. After collecting data generated from the experiment, a conclusion can be drawn to either refute or support the hypothesis.

Water molecules form a lattice structure in ice, which causes the water molecules in ice to be more spread out than they are in liquid water. This is the reason that ice appears to “expand” in comparison to liquid water and can float on the surface of liquid water. The water molecules in both liquid water and ice are equally polar.

Saturated fatty acids contain no double bonds, while unsaturated fatty acids do contain one or more double bonds. Neither saturated or unsaturated fatty acids contain phosphate groups. However, in a phospholipid, a phosphate group is attached to the glycerol molecule to which fatty acids are also attached.

Saturated fatty acids are the component of animal fats that cause them to solidify at room temperature. Oils have high amounts of unsaturated fatty acids which allow them to remain liquid at room temperature. Phosphate groups are found in phospholipids, but not typical fats. Steroids are a type of lipid, but are not the component of animal fats that make them solidify at room temperature.

Water stabilizes climate due to its high specific heat, meaning that it requires a relatively high amount of heat to raise the temperature by 1°C . Climate near large bodies of water tends to be pretty stable as a result.

Cohesion describes the tendency of molecules of the same substance to bond together, as is demonstrated in water beading. An ocean stabilizing local temperature refers to water’s high specific heat. Water dissolving salt to become saltwater refers to dissolve many substances. A bottle of water that cracking after being left in the freezer is an example of the expansion of water during freezing due to its lattice structure and decreased density.

Due to complementary base-pairing, cytosine base-pairs with guanine. Therefore, in double-stranded DNA, the amount of cytosine is always equal to the amount of guanine. Similarly, the amount of adenine is always equal to the amount of thymine. Uracil is specific to RNA and is not found in DNA.

For complete dominance, when at least one dominant allele is present, the pea plant will be tall. However, for incomplete dominance, being heterozygous will result in a height intermediate between tall and short: average.

Transfer RNA (tRNA) brings the correct amino acids to the site of protein synthesis in the ribosome. Ribosomes link together amino acids and then release them to create a protein. tRNA contains anticodons, not codons. Codons that each encode a specific amino acid to be added to the growing protein are found within the messenger RNA (mRNA), not the tRNA. Ribosomal RNA (rRNA), not tRNA, is a significant structural component of the ribosome.

One of the functions of the smooth endoplasmic reticulum is to detoxify harmful substances. Therefore, since the liver is the organ specialized to perform this function, one would expect liver cells to each have a high amount of smooth endoplasmic reticulum. The rough endoplasmic reticulum contains ribosomes for protein synthesis. Lysosomes are specialized for the digestion of large biological molecules into smaller components. Mitochondria are specialized to make ATP from cellular respiration.

The correct conclusion from this experiment is that pea plants grow better with music than without music. Because only one type of plant was tested (not “all plants”), one cannot conclude that all plants grow better with or without music. From this experiment, one can conclude that music affected pea plant growth positively.

Enzymes are a type of protein. Enzymes catalyze chemical reactions.

Prokaryotes lack membrane-bound organelles while eukaryotes have membrane-bound organelles. Thus, while both prokaryotes and eukaryotes have ribosomes (which are not membrane-bound organelles), eukaryotes additionally each have a nucleus, an endoplasmic reticulum, and mitochondria.

Proteins are the largest type of biological molecules. The other types of biological molecules are smaller.

Glycolysis is the part of cellular respiration that takes place in the cytosol of the eukaryotic cell. The Krebs cycle takes place in the mitochondrial matrix, and the electron transport chain is found embedded in the inner mitochondrial membrane. The Calvin cycle is not a part of cellular respiration; rather, it is part of photosynthesis and takes place in the stroma of chloroplasts.

The light reaction converts solar energy to chemical energy, using the solar energy to make ATP. The light reactions do not convert chemical energy to solar energy, breaking down ATP. The light reactions also do not make glucose; glucose production happens during the Calvin cycle, which uses the ATP and NADPH made during the light reactions to drive this process.

Anaphase is the phase of mitosis during which sister chromatids (a pair of which composes a chromosome) separate. Each individual sister chromatid is now a chromosome. Prophase is when chromosomes condense. During prometaphase, the nuclear envelope begins to break down, and chromosomes attach to the developing spindle. During metaphase, the chromosomes line up along the center of the cell. During telophase, each group of chromosomes aggregates at each pole of the cell, and a new nuclear envelope begins to develop around each.

A pedigree is a way to visualize a family’s history, indicating which individuals had a particular trait. A Punnett square is a device used in genetics to predict the genotypes and phenotypes of offspring when you know the genotypes of both parents. A DNA sequence is the order of nucleotides in a piece of DNA. A hypothesis is a statement or explanation of certain events.

There are 20 different amino acids found in biological proteins. There are 3 nucleotides in each codon as well as in each anticodon. There are 4 nucleotides found in DNA. There are 64 possible codons in mRNA.

The stop codon is 3-nucleotide sequence found within messenger RNA (mRNA) that does not code for an amino acid and therefore signals the termination of translation.

CO₂ is a reactant of photosynthesis; it is fixed to form glucose. O₂ is a product of photosynthesis. ATP is made during the light reactions but consumed during the Calvin cycle to fix CO₂.

Meiosis creates 4 genetically different haploid cells from 2 subsequent divisions (Meiosis I and Meiosis II) of a single diploid cell. Mitosis of a diploid cell results in 2 genetically identical diploid cells.

The exchange of genetic information between non-sister chromatids within a duplicated homologous chromosome pair only occurs during prophase I of meiosis. Such exchange does not happen during prophase II of meiosis nor does it happen during mitosis.

If a parent is heterozygous (Aa), half (50%) of its offspring will receive the dominant allele A and the other half (50%) of its offspring will receive the recessive allele a from this parent.

Since the homozygous recessive parent could only contribute the recessive allele to its offspring, any offspring that have the recessive trait have the homozygous recessive genotype and must have received a second recessive allele from the parent with the dominant phenotype. Therefore, the parent having the dominant phenotype must have both the dominant allele (making it phenotypically dominant) and the recessive allele and therefore must be heterozygous.