Cells (Units 1&2)
Which statement best describes why water is an effective solvent?
A. Water is an ionic compound that attracts other like molecules.
B. Water’s hydrophobic nature separates polar and non-polar substances.
D. Water's polarity allows it to dissolve ionic and polar compounds
What is the main effect of an enzyme on a chemical reaction?
A. It increases the reaction’s activation energy.
B. It makes all reactions proceed at the same rate.
C. It lowers the activation energy required for the reaction.
D. It changes the final amount of product formed at equilibrium.
C. It lowers the activation energy required for the reaction.
Which term describes a molecule that binds to a receptor and initiates cell signaling?
A. Ligand
B. Enzyme
C. Ribosome
D. Chromosome
A.Ligand
In pea plants, purple flower color P is dominant to white p. Two heterozygous plants Pp×Pp are crossed. What proportion of their offspring is expected to have white flowers?
A. 3/4
B. 1/2
C. 1/16
D. 1/4
D. 1/4
Which best describes carrying capacity KK in a population?
A. The number of individuals present when population growth is exponential
B. The minimum population size needed to avoid extinction
C. The birth rate minus the death rate at any moment
D. The maximum number of individuals the environment can sustain over time
D. The maximum number of individuals the environment can sustain over time
Which of the following statements is true for both prokaryotic and eukaryotic cells?
C. Ribosomes synthesize proteins using mRNA sequences
Which of the following describes a metabolic consequence of a shortage of oxygen in muscle cells?
A. An increase in blood pH due to the accumulation of lactic acid
B. No ATP production due to the absence of substrate-level phosphorylation
C. A buildup of lactic acid in the muscle tissue due to fermentation
D. A decrease in oxidation of fatty acids due to a shortage of ATP
C. A buildup of lactic acid in the muscle tissue due to fermentation
A student is examining an onion root tip cell under a microscope. Based on her observations, the student proposes that the onion root tip cell has completed interphase and is now in the first phase of mitosis.
Which of the following pieces of evidence would best support the student’s claim?
A. A cell's chromosomes are aligned across the metaphase plate
B. The cells DNA is dispersed within the nucleus as chromatin
C. Separated sister chromatids are being pulled towards opposite ends of the cell
D. Discrete chromosomes are scattered through the cell's nucleus
D - Discrete chromosomes are scattered throughout the cell’s nucleus.
A nondisjunction event occurs during meiosis I. Which outcome is most likely?
A. All gametes produced will be normal.
B. Some gametes will have an extra chromosome or be missing one.
C. The organism will no longer be able to undergo DNA replication.
D. The zygote will always remain diploid and unaffected.
B. Some gametes will have an extra chromosome or be missing one.
In a food web, which statement best explains why top-level predators, such as hawks, are fewer in number than herbivores?
A. Top predators need less food because they are larger.
B. Energy transfer between trophic levels is inefficient, limiting the number of organisms supported at higher levels.
C. Herbivores reproduce faster than predators in all ecosystems.
D. Predators always compete more directly with each other than with prey.
B. Energy transfer between trophic levels is inefficient, limiting the number of organisms supported at higher levels.
Which of the following is evidence that eukaryotes and prokaryotes share a common ancestor?
A. All eukaryotes and prokaryotes contain linear DNA.
B. All eukaryotes and prokaryotes contain ribosomes.
C. All eukaryotes and prokaryotes use organic molecules as an energy source.
D. All eukaryotes and prokaryotes are capable of mitosis.
B. All eukaryotes and prokaryotes contain ribosomes.
Acetylcholine (ACh) is an important signaling molecule in the nervous system. After it transmits a signal, ACh is broken down by the enzyme acetylcholinesterase (AChE) in a reaction known as ACh hydrolysis.
Which of the following best describes the effect AChE has on the hydrolysis of ACh?
A. AChE increases the activation energy of ACh hydrolysis, increasing the rate of the reaction.
B. AChE increases the activation energy of ACh hydrolysis, decreasing the rate of the reaction.
C. AChE decreases the activation energy of ACh hydrolysis, increasing the rate of the reaction.
D. AChE decreases the activation energy of ACh hydrolysis, decreasing the rate of the reaction.
C. AChE decreases the activation energy of ACh hydrolysis, increasing the rate of the reaction.
A mutation causes a cell to produce a nonfunctional protein that normally forms part of the mitotic spindle. Which direct consequence is most likely during the cell cycle?
- A. DNA replication cannot initiate during S phase.
- B. Nuclear envelope re-forms prematurely during metaphase.
- C. Chromosomes fail to condense during prophase.
- D. Sister chromatids do not separate properly during anaphase.
D. Sister chromatids do not separate properly during anaphase.
Which scenario best demonstrates the Law of Independent Assortment?
A. Two alleles for height separate during meiosis
B. Genes located close together on the same chromosome are inherited together
C. Alleles of different genes segregate into gametes independently when on different chromosomes
D. Crossing over increases genetic variation within a gene
C. Alleles of different genes segregate into gametes independently when on different chromosomes
A population of birds is separated by a newly formed river, preventing interbreeding between the two groups. Over many generations, the groups accumulate genetic differences and can no longer produce fertile offspring even if brought back together. Which process best explains this scenario?
A. Allopatric speciation due to geographic isolation
B. Hardy–Weinberg equilibrium maintaining allele frequencies
C. Sympatric speciation driven by polyploidy
D. Genetic drift within a single panmictic population
A. Allopatric speciation due to geographic isolation
Which statement best explains why water has a high specific heat?
A. Water molecules contain many covalent bonds that store heat energy.
B. Water is nonpolar, so its temperature changes slowly.
C. Water molecules must absorb a large amount of energy to break hydrogen bonds.
D. Water has a low density, which resists temperature change
C. Water molecules must absorb a large amount of energy to break hydrogen bonds.
Two nutrient solutions are maintained at the same pH. Actively respiring mitochondria are isolated and placed into each of the two solutions. Oxygen gas is bubbled into one solution. The other solution is depleted of available oxygen. Which of the following best explains why ATP production is greater in the tube with oxygen than in the tube without oxygen?
A. The rate of proton pumping across the inner mitochondrial membrane is lower in the sample without oxygen.
B. Electron transport is reduced in the absence of a plasma membrane.
C. In the absence of oxygen, oxidative phosphorylation produces more ATP than does fermentation.
D. In the presence of oxygen, glycolysis produces more ATP than in the absence of oxygen.
A. The rate of proton pumping across the inner mitochondrial membrane is lower in the sample without oxygen.
A cell exposed to DNA damage does not enter S phase. Which checkpoint is most likely responding to the damage?
A. G1 checkpoint
B. M checkpoint
C. Cytokinesis checkpoint
D. Telophase checkpoint
A. G1 Checkpoint
In a population, a recessive lethal allele (aa) causes death before reproductive age. If the frequency of the dominant allele (A) is 0.8, what is the expected frequency of heterozygous individuals (Aa), assuming Hardy-Weinberg equilibrium before selection?
A. 0.16
B. 0.32
C. 0.48
D. 0.64
B.0.32
A trait has high heritability, yet does not respond to selection over multiple generations. Which explanation is most consistent with this observation?
A. The trait is not genetically determined
B. There is no variation in the trait within the population
C. Selection pressure is not aligned with the genetic variation
D. Mutations are occurring too slowly
C. Selection pressure is not aligned with the genetic variation
Amylase in an enzyme that converts carbohydrate polymers into monomers. Glycogen synthase is one of the enzymes involved in converting carbohydrates monomer into polymers
Which of the following best explains the reaction of these enzymes:
A. Amylase aids in the removal of a water molecule to break covalent bonds whereas glycogen synthase aids in the addition of a water molecule to form covalent bonds.
B. Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen synthase aids in the removal of a water molecule to form covalent bonds.
C .Amylase aids in the addition of a water molecule to form covalent bonds whereas glycogen synthase aids in the removal of a water molecule to break covalent bonds.
D. Amylase aids in the removal of a water molecule to form covalent bonds whereas glycogen synthase aids in the addition of a water molecule to break covalent
B. Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen synthase aids in the removal of a water molecule to form covalent bonds.
A plant is kept in a chamber with normal CO₂ and light, but an inhibitor is added that blocks the regeneration of RuBP in the Calvin cycle. Which outcome is most likely over time?
A. NADPH and ATP will accumulate because the light‑dependent reactions continue to run.
B. Oxygen production will increase because the light‑dependent reactions are no longer constrained.
C. CO₂ will be rapidly converted into lipids instead of sugars.
D. The light‑dependent reactions will stop because NADP⁺ is not regenerated.
A. NADPH and ATP will accumulate because the light‑dependent reactions continue to run.
Which of the following best explains how amplification occurs in a signal transduction pathway involving a G protein–coupled receptor (GPCR)?
A. A single ligand binds multiple receptors simultaneously
B. One activated receptor can activate many G proteins, each triggering production of numerous second messengers
C. Protein kinases deactivate signaling molecules to conserve energy
D. Ligands diffuse across the membrane and bind intracellular receptors
B. One activated receptor can activate many G proteins, each triggering production of numerous second messengers
A mutation disrupts the poly-A tail addition site of a eukaryotic mRNA. Which outcome is most likely?
A. Increased translation due to faster ribosome binding
B. Decreased mRNA stability and reduced protein production
C. Enhanced transcription initiation
D. Increased splicing efficiency
B. Decreased mRNA stability and reduced protein production
A population follows logistic growth. At time t, the population size (N) is very close to carrying capacity (K). Which condition is most accurate?
A. dN/dt is at its maximum
B. Birth rate equals death rate
C. Death rate exceeds birth rate
D. Population growth is exponential
B. Birth rate equals death rate