8 Units · 122 Quiz Questions · 64 Flashcards · Diagnostic · Full Reference Tables · Diagrams · Saved Progress
Based on this guide's real question bank — 122 practice questions across 8 units. Slide to match your situation.
Water's high specific heat is primarily due to:
Hydrogen bonds must absorb significant energy to break before water's temperature rises, giving water its high specific heat.
Ice floats on liquid water because:
The hexagonal hydrogen-bonded lattice in ice spaces molecules farther apart than in liquid water, making ice less dense.
Which best describes dehydration synthesis?
Dehydration synthesis joins monomers into polymers, releasing one water molecule per bond formed.
A carboxyl group (-COOH) found in amino acids and fatty acids is best described as:
The carboxyl group is acidic — it can ionize to -COO⁻, releasing an H⁺.
Which level of protein structure is described as the linear sequence of amino acids?
Primary structure is simply the order of amino acids linked by peptide bonds.
A protein loses its function after being placed in boiling water. This is best explained by:
Heat denatures a protein by disrupting hydrogen bonds and other weak interactions, not the covalent peptide bonds of primary structure.
Enzymes speed up reactions by:
Enzymes lower activation energy; they do not change ΔG or reaction spontaneity.
A noncompetitive inhibitor reduces enzyme activity by:
Noncompetitive (allosteric) inhibitors bind elsewhere and change the enzyme's shape so the active site functions poorly.
Increasing substrate concentration would most effectively counteract the effect of a:
Competitive inhibitors compete with substrate for the same active site, so excess substrate can outcompete the inhibitor.
Which macromolecule's monomer is a nucleotide?
Nucleic acids (DNA, RNA) are polymers of nucleotide monomers.
Cohesion in water is responsible for:
Cohesion (water-water attraction via H-bonds) creates surface tension and allows continuous water columns in xylem.
An enzyme functions best within a specific pH range because:
pH extremes disrupt the weak bonds that hold the enzyme's tertiary structure, altering the active site's shape.
Which is an example of a phospholipid's role?
Phospholipids' amphipathic structure (polar head, nonpolar tails) makes them ideal for forming membrane bilayers.
The induced fit model of enzyme action states that:
Induced fit describes a slight conformational change in the enzyme's active site upon substrate binding.
Hydrolysis reactions are used by the digestive system to:
Digestion breaks polymers (starch, protein) into monomers via hydrolysis, adding a water molecule at each bond broken.
Which functional group would most increase a molecule's water solubility?
The polar hydroxyl group (-OH) can hydrogen bond with water, increasing solubility; methyl groups are nonpolar and decrease it.
Which structure is found in both prokaryotic and eukaryotic cells?
Both cell types contain ribosomes (though prokaryotic 70S ribosomes are smaller than eukaryotic 80S), a plasma membrane, cytoplasm, and DNA.
The best evidence for the endosymbiotic theory is that mitochondria and chloroplasts:
These features closely resemble free-living bacteria, supporting the idea that these organelles originated as engulfed prokaryotes.
As a cell increases in size, its surface-area-to-volume ratio:
Volume increases faster (cubed) than surface area (squared) as size increases, so SA:V ratio decreases, limiting exchange.
In the fluid mosaic model, membrane fluidity increases with:
Unsaturated fatty acids have kinks from double bonds that prevent tight packing, increasing membrane fluidity.
Facilitated diffusion differs from active transport because facilitated diffusion:
Facilitated diffusion is passive (no ATP) and moves solutes down their gradient via channel/carrier proteins.
A red blood cell placed in a hypertonic solution will:
In a hypertonic solution, water moves out of the cell (toward higher solute concentration), causing the cell to shrink/crenate.
A plant cell placed in a hypotonic solution becomes:
Water enters the cell, but the cell wall prevents lysis, resulting in a firm, turgid cell — this is the healthy state for plant cells.
The Golgi apparatus functions primarily to:
The Golgi receives products from the ER at its cis face and modifies/sorts/packages them, shipping them from its trans face.
The sodium-potassium pump is an example of:
It moves Na⁺ and K⁺ against their gradients using ATP, making it active transport.
Which is true of both mitochondria and chloroplasts?
Both organelles have double membranes and circular DNA, consistent with endosymbiotic origin.
Integral membrane proteins differ from peripheral membrane proteins in that integral proteins:
Integral proteins are embedded in or span the bilayer; peripheral proteins are attached to the membrane surface only.
Which of the following would most likely increase the rate of facilitated diffusion?
A steeper concentration gradient increases the rate of passive transport processes like facilitated diffusion, up to a saturation point.
Lysosomes primarily function to:
Lysosomes contain hydrolytic enzymes for intracellular digestion (autophagy, pathogen destruction).
Why can eukaryotic cells generally be larger than prokaryotic cells?
Internal membranes (organelles) provide additional surface area for reactions, helping overcome surface-area-to-volume limitations.
A cell surrounded by a solution with the same solute concentration as its cytoplasm is in a(n):
Isotonic solutions have equal solute concentration, so there is no net water movement.
Cholesterol embedded in the animal cell membrane functions to:
Cholesterol has a dual buffering role — it restrains excess fluidity at high temperatures and prevents excess rigidity at low temperatures.
Which process directly produces the most ATP per glucose molecule?
Oxidative phosphorylation via the electron transport chain and chemiosmosis produces roughly 26-28 of the ~30-32 total ATP per glucose.
The main purpose of fermentation is to:
Fermentation regenerates NAD⁺ from NADH, allowing glycolysis to continue producing its small net ATP yield in the absence of O₂.
In the electron transport chain, the final electron acceptor in aerobic respiration is:
Oxygen accepts electrons at the end of the ETC, combining with H⁺ to form water.
The oxygen released during photosynthesis comes from:
Photolysis of water in Photosystem II releases O₂ as a byproduct; CO₂ becomes part of the sugar produced, not O₂.
Which molecules directly power the Calvin cycle?
The Calvin cycle uses ATP and NADPH (produced in the light reactions) to fix CO₂ into G3P/glucose.
Chemiosmosis refers to:
Chemiosmosis is the process where a proton gradient drives ATP synthase to produce ATP, used in both respiration and photosynthesis.
Glycolysis occurs in the:
Glycolysis takes place in the cytoplasm and does not require oxygen.
An athlete experiencing muscle burn during intense exercise is most likely undergoing:
When oxygen delivery can't keep up with demand, muscle cells use lactic acid fermentation to regenerate NAD⁺.
Rubisco catalyzes which step of the Calvin cycle?
Rubisco fixes atmospheric CO₂ onto the 5-carbon RuBP, the first step of the Calvin cycle.
Which best describes the relationship between mitochondria and chloroplasts regarding ATP synthesis?
Both organelles use ATP synthase and a proton gradient (chemiosmosis) to generate ATP, despite different electron sources.
Alcoholic fermentation, used by yeast, converts pyruvate into:
Yeast converts pyruvate to acetaldehyde, releasing CO₂, then to ethanol, regenerating NAD⁺.
During the Krebs cycle, most of the energy extracted from acetyl-CoA is stored in the form of:
The Krebs cycle produces mostly NADH and FADH₂, which later fuel the ETC to make most of the cell's ATP; only 2 ATP form directly.
If a poison blocked Photosystem II specifically, which process would be directly impaired first?
PS II absorbs light and splits water; blocking it stops electron flow to PS I and halts water-splitting (O₂ release).
The net ATP yield of glycolysis (before considering the electron transport chain) is:
Glycolysis uses 2 ATP to invest and produces 4 ATP, for a net gain of 2 ATP via substrate-level phosphorylation.
Which process produces ATP directly by substrate-level phosphorylation rather than chemiosmosis?
Glycolysis and the Krebs cycle each generate a small amount of ATP directly (substrate-level phosphorylation), unlike the ETC's chemiosmotic mechanism.
In cell signaling, 'transduction' refers to:
Transduction is the relay/amplification stage that converts receptor activation into intracellular molecular changes.
Which cell cycle checkpoint verifies that all chromosomes are properly attached to spindle fibers?
The M/spindle assembly checkpoint ensures proper chromosome attachment before anaphase proceeds.
Cyclins differ from CDKs in that:
Cyclin concentration rises and falls at specific points in the cycle, binding and activating the constantly-present CDKs at the right time.
A mutation that converts a proto-oncogene into an oncogene is best described as a:
Proto-oncogenes normally promote division; a gain-of-function mutation makes them overactive, driving excess division.
The p53 gene is best classified as a:
p53 halts the cell cycle for repair or triggers apoptosis when DNA is damaged, functioning as a tumor suppressor.
Apoptosis differs from necrosis in that apoptosis is:
Apoptosis is a regulated form of cell death that safely removes cells without releasing harmful contents, unlike necrosis.
During which phase of the cell cycle does DNA replication occur?
S phase (synthesis phase) is when DNA replication occurs, producing sister chromatids.
A cell that permanently exits the cell cycle (e.g., a mature neuron) enters:
G0 is a non-dividing state that some differentiated cells enter permanently.
Second messengers like cAMP function in signal transduction primarily to:
Second messengers amplify a small initial signal into a much larger intracellular response.
Sister chromatids separate during which stage of mitosis?
Anaphase is when sister chromatids are pulled apart to opposite poles of the cell.
Loss of contact inhibition and anchorage dependence in a cell most directly suggests:
Cancer cells typically ignore normal growth-limiting signals like contact inhibition, allowing invasive, uncontrolled growth.
Which statement about the cell cycle checkpoints is correct?
The G2 checkpoint ensures DNA was replicated correctly and without damage before the cell proceeds into mitosis.
A cell with damaged DNA that cannot be repaired is normally directed by p53 to:
When DNA damage is irreparable, functional p53 triggers apoptosis, eliminating the potentially dangerous cell.
A phosphorylation cascade in a signal transduction pathway most directly:
A phosphorylation cascade uses a chain of kinases, each activating the next, to relay and amplify the original signal.
Chromosomes align at the metaphase plate during which stage of mitosis?
During metaphase, chromosomes line up at the cell's equator (metaphase plate) before separating in anaphase.
Crossing over occurs during which stage of meiosis?
Crossing over occurs during prophase I, when homologous chromosomes synapse and exchange genetic material.
For an organism with n=4 chromosome pairs, independent assortment alone can produce how many different chromosome combinations in gametes?
2ⁿ = 2⁴ = 16 possible combinations from independent assortment of 4 chromosome pairs.
A cross between a heterozygous (Rr) and a heterozygous (Rr) pea plant for a completely dominant trait produces what phenotypic ratio?
Rr × Rr gives genotypes 1 RR : 2 Rr : 1 rr, which is 3 dominant : 1 recessive phenotypically.
A cross between two heterozygous individuals for two independently assorting genes (AaBb × AaBb) produces which phenotypic ratio?
Independent dihybrid crosses produce the classic 9:3:3:1 phenotypic ratio.
Red (RR) crossed with white (WW) snapdragons produces all pink (RW) offspring. This demonstrates:
The blended pink phenotype is the hallmark of incomplete dominance, unlike codominance where both traits appear fully and separately.
AB blood type, where both A and B antigens appear on red blood cells, is an example of:
Both IA and IB alleles are expressed fully and simultaneously — this is codominance, not blending.
A colorblind son is born to a mother who is a carrier (heterozygous) for the X-linked recessive trait and a father with normal vision. This is explained because the son:
Males have only one X chromosome (hemizygous), so a single recessive allele inherited from the mother is enough to express an X-linked recessive trait.
Two genes located very close together on the same chromosome will:
Linked genes tend to travel together during meiosis; only crossing over can separate them, and this happens more often the farther apart the genes are.
Nondisjunction during meiosis I most directly leads to:
Failure of homologous chromosomes to separate properly produces gametes with too many or too few chromosomes.
A test cross is used to determine:
Crossing the unknown individual with a homozygous recessive reveals its genotype based on the offspring ratio produced.
Which is a source of genetic variation unique to meiosis (not mitosis)?
Crossing over (prophase I) and independent assortment (metaphase I) are meiosis-specific processes generating genetic variation.
Human skin color, controlled by multiple genes with additive effects producing a continuous range of phenotypes, is an example of:
Polygenic traits are influenced by multiple genes, producing a continuous distribution of phenotypes rather than discrete categories.
Meiosis II is most similar to mitosis because in both processes:
Both meiosis II and mitosis separate sister chromatids; meiosis I (not II) is the reductional division that separates homologs.
An offspring's blood type is O, meaning its genotype is ii. If one parent is IAi and the other is IBi, this outcome is:
Each heterozygous parent carries one i allele; if both contribute i, the child is ii (type O), which is fully expected under multiple allele inheritance.
Genes located far apart on the same chromosome are more likely to be separated by crossing over than genes located close together because:
Recombination frequency increases with the physical distance between two linked genes, since there is more opportunity for a crossover to occur between them.
DNA replication is described as semiconservative because:
Semiconservative replication means each daughter molecule retains one parental strand paired with one new strand.
Why is the lagging strand synthesized in short (Okazaki) fragments?
Since DNA polymerase synthesizes only 5'→3', the lagging strand (running away from the fork direction) must be made discontinuously.
A mutation that inserts 1 nucleotide into a gene's coding sequence would most likely:
A single nucleotide insertion (not a multiple of 3) shifts the reading frame for all codons downstream, typically producing a nonfunctional protein.
A silent mutation has no effect on the protein produced because:
The genetic code is degenerate — several codons can specify the same amino acid, so some substitutions don't change the protein.
In the lac operon, when lactose is present in the cell, it:
Lactose acts as an inducer — it binds the repressor protein, changing its shape so it can no longer bind the operator, allowing transcription.
In gel electrophoresis, DNA fragments migrate toward the positive electrode because:
DNA's phosphate groups give it an overall negative charge, so it migrates toward the positive electrode in an electric field.
Which best describes the role of DNA polymerase's proofreading function?
DNA polymerase proofreads newly added nucleotides, removing errors to keep the mutation rate very low.
During eukaryotic mRNA processing, which of the following occurs?
Eukaryotic pre-mRNA is processed by adding a 5' cap and poly-A tail and splicing out introns, leaving only exons in the mature mRNA.
DNA methylation is an example of:
Epigenetic modifications like DNA methylation alter gene expression heritably without changing the underlying DNA sequence.
PCR requires all of the following EXCEPT:
PCR amplifies DNA using primers and heat-stable polymerase through thermal cycling — ribosomes are involved in translation, not PCR.
The trp operon is best described as:
The trp operon is repressible: it's normally active, but abundant tryptophan activates the repressor to shut off transcription (negative feedback).
Heterochromatin, compared to euchromatin, is:
Heterochromatin is densely packed DNA that is generally inaccessible to transcription machinery, keeping those genes silent.
A restriction enzyme used in genetic engineering functions to:
Restriction enzymes recognize specific sequences and cut DNA there, generating fragments (often with complementary sticky ends) for cloning.
Which best describes the relationship between a gene's exons and introns in eukaryotic pre-mRNA processing?
Splicing removes noncoding introns, leaving only the coding exons joined together in the mature mRNA.
A missense mutation results in:
A missense mutation changes the codon so that it now codes for a different amino acid than the original.
Homologous structures such as the forelimbs of humans, whales, and bats provide evidence for:
Homologous structures share the same underlying anatomical origin, indicating descent from a common ancestor even though functions differ.
Bird wings and insect wings are considered analogous structures because they:
Analogous structures perform similar functions but arose independently, so they do NOT indicate a recent common ancestor.
If observed genotype frequencies in a population differ substantially from those predicted by Hardy-Weinberg, this suggests:
Deviation from Hardy-Weinberg predictions indicates evolutionary forces (selection, drift, migration, mutation, or nonrandom mating) are acting.
A population has an allele frequency q=0.2 for a recessive allele. What is the expected frequency of homozygous recessive individuals?
q² = 0.2² = 0.04, so about 4% of the population is expected to be homozygous recessive.
A population's allele frequencies change dramatically after a natural disaster kills most of its members randomly, unrelated to genotype. This illustrates:
The bottleneck effect is a form of genetic drift caused by a drastic, random reduction in population size.
Stabilizing selection is best illustrated by:
Stabilizing selection favors intermediate phenotypes and reduces variation — average birth weight has the highest survival rate.
Disruptive selection tends to:
Disruptive selection favors both phenotypic extremes, which can increase variation and sometimes drive speciation.
Two populations of the same species become separated by a newly formed mountain range and evolve independently until they can no longer interbreed. This is an example of:
Geographic separation preventing gene flow, leading to independent divergence, defines allopatric speciation.
A mule (offspring of a horse and donkey) being sterile is an example of which reproductive isolating mechanism?
Hybrid sterility is a postzygotic barrier — the hybrid survives but cannot produce viable offspring.
On a phylogenetic tree, a node represents:
Each node/branch point on a cladogram represents the most recent common ancestor shared by the descendant lineages.
Which condition is NOT required for a population to remain in Hardy-Weinberg equilibrium?
Hardy-Weinberg equilibrium requires the ABSENCE of natural selection (along with no mutation, no gene flow, large population, and random mating).
The high similarity of cytochrome c protein sequences between humans and chimpanzees compared to humans and yeast provides evidence that:
Greater molecular similarity generally indicates a more recent shared common ancestor.
The human appendix, a reduced structure with little current function, is best classified as a:
Vestigial structures are reduced remnants of structures that were functional in an ancestral species.
A new plant species arises instantly from a doubling of chromosome number (polyploidy) in a single generation, without any geographic separation. This is an example of:
Sympatric speciation occurs without geographic isolation; polyploidy is a common mechanism, especially in plants.
Sexual selection, a special case of natural selection based on mating success, can explain the evolution of traits like a peacock's tail because:
Sexual selection favors traits that increase mating success, which can evolve even when they carry some survival cost (e.g., increased predation risk).
Exponential population growth is best modeled by a curve that:
Exponential growth produces a J-shaped curve because growth rate is proportional to population size, without resource limits.
Logistic growth differs from exponential growth because logistic growth:
Logistic growth incorporates carrying capacity (K), producing an S-shaped curve as density-dependent factors slow growth.
Which is a density-dependent limiting factor?
Density-dependent factors like competition, predation, and disease intensify as population density increases.
In a predator-prey relationship, this interaction is best classified as:
Predation benefits the predator (+) while harming the prey (−).
Only about 10% of energy is transferred between trophic levels mainly because:
Metabolic processes (respiration) release most energy as heat rather than passing it on to the next trophic level, following the 10% rule.
Nitrogen-fixing bacteria such as Rhizobium are important because they:
Nitrogen-fixing bacteria convert unusable atmospheric N₂ into ammonia, which plants can use to build proteins and nucleic acids.
Which biogeochemical cycle has essentially no significant atmospheric gas phase?
Phosphorus cycles mainly through rock weathering, soil, and water — it lacks a major atmospheric gas component, unlike C, N, and water cycles.
Two species of birds that feed on different parts of the same tree (one on insects in the bark, one on seeds in the canopy) illustrate:
Resource partitioning (niche differentiation) allows similar species to coexist by using different parts of a shared resource.
An r-selected species is most likely to:
r-selected species prioritize rapid reproduction (many offspring, minimal care) suited to unstable or resource-rich environments.
Ocean acidification, caused by increased atmospheric CO₂ dissolving into seawater, primarily threatens:
Increased CO₂ forms carbonic acid in seawater, lowering pH and interfering with calcium carbonate shell/skeleton formation.
Habitat fragmentation reduces biodiversity primarily by:
Fragmentation splits habitats into smaller, isolated patches, reducing gene flow and resource availability, threatening population viability.
Net primary productivity (NPP) is calculated as:
NPP = GPP − respiration by producers; it represents the energy actually available to consumers.
Which best describes commensalism?
Commensalism is a (+/0) relationship — one organism benefits while the other experiences neither benefit nor harm.
A greater number of species and stronger species interactions in an ecosystem generally leads to:
Higher biodiversity is generally associated with greater ecosystem stability and resilience to environmental disturbances.
The competitive exclusion principle states that:
When two species compete for the identical niche and resources, one typically outcompetes the other, or resource partitioning allows coexistence.