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DC CAPE 2.0 Science Biology study materials
DC CAPE 2.0 Science Biology study resources

DC CAPE 2.0 Science Biology practice questions

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Question 1Molecules and Cells

Which molecule stores the genetic instructions that a cell uses to build proteins?

  1. DNA Correct answer.
  2. Phospholipid
  3. ATP
  4. Glucose

Explanation

DNA carries the sequence of nucleotide bases that encodes the information for protein synthesis. ATP transfers energy, glucose is a fuel, and phospholipids are structural membrane components.

Question 2Molecules and Cells

Which organelle is the main site of ATP production during aerobic cellular respiration?

  1. Golgi apparatus
  2. Mitochondrion Correct answer.
  3. Lysosome
  4. Ribosome

Explanation

The mitochondrion houses the electron transport chain and ATP synthase, where most ATP is generated in aerobic respiration. Ribosomes build proteins, the Golgi modifies and packages them, and lysosomes digest materials.

Question 3Molecules and Cells

A solution with a pH of 3 contains how much more hydrogen ion concentration than a solution with a pH of 5?

  1. 2 times
  2. 100 times Correct answer.
  3. 1000 times
  4. 10 times

Explanation

The pH scale is logarithmic, so each unit represents a tenfold change in hydrogen ion concentration. A difference of two pH units therefore corresponds to 10 × 10 = 100 times the concentration.

Question 4Molecules and Cells

Which property of water allows insects to walk on the surface of a pond?

  1. Low density when frozen
  2. Surface tension Correct answer.
  3. Universal solvent ability
  4. High specific heat

Explanation

Hydrogen bonding between water molecules creates strong cohesive forces at the surface, producing surface tension that can support small organisms. The other properties listed describe different behaviors of water.

Question 5Molecules and Cells

Which statement best describes the role of enzymes in metabolic reactions?

  1. They change the equilibrium constant of the reaction.
  2. They increase the activation energy required.
  3. They lower the activation energy without being consumed. Correct answer.
  4. They are consumed in the reaction they catalyze.

Explanation

Enzymes are biological catalysts that speed reactions by lowering activation energy while remaining unchanged and reusable. They do not alter the overall energy difference between reactants and products.

Question 6Molecules and Cells

A competitive inhibitor is added to a reaction mixture. Which change would most effectively restore the reaction rate?

  1. Lowering the temperature
  2. Increasing the substrate concentration Correct answer.
  3. Increasing the enzyme concentration
  4. Adding a noncompetitive inhibitor

Explanation

A competitive inhibitor binds the active site, so raising substrate concentration increases the chance that substrate outcompetes the inhibitor for that site. Adding more enzyme does not overcome competition for the same active sites.

Question 7Molecules and Cells

Which part of a phospholipid molecule is oriented toward the watery exterior of a cell membrane?

  1. The integral protein channel
  2. The hydrophobic fatty acid tails
  3. The cholesterol ring
  4. The hydrophilic phosphate head Correct answer.

Explanation

Phospholipids are amphipathic; their hydrophilic phosphate heads face the aqueous environments on both sides of the membrane. The hydrophobic tails cluster in the interior away from water.

Question 8Molecules and Cells

Which process moves water across a selectively permeable membrane from lower to higher solute concentration?

  1. Osmosis Correct answer.
  2. Phagocytosis
  3. Active transport
  4. Facilitated diffusion of ions

Explanation

Osmosis is the diffusion of water across a selectively permeable membrane toward the region of higher solute concentration. It is a passive process that requires no energy input.

Question 9Molecules and Cells

A red blood cell is placed in a hypertonic solution. What is the most likely result?

  1. The cell remains unchanged.
  2. The cell actively pumps water inward.
  3. The cell shrinks as water leaves. Correct answer.
  4. The cell swells and may burst.

Explanation

In a hypertonic solution the surrounding fluid has a higher solute concentration than the cytoplasm, so water leaves the cell by osmosis and the cell shrinks. Cells swell in hypotonic solutions and stay stable in isotonic ones.

Question 10Molecules and Cells

Which statement best describes the difference between active transport and facilitated diffusion?

  1. Active transport moves only water molecules.
  2. Both processes move substances against their concentration gradient.
  3. Facilitated diffusion requires ATP while active transport does not.
  4. Active transport requires energy and can move substances against a gradient. Correct answer.

Explanation

Active transport uses energy, often from ATP, to move substances against their concentration gradient, whereas facilitated diffusion is passive and moves substances down their gradient through proteins.

Question 11Molecules and Cells

Which molecule serves as the direct energy currency that powers most cellular work?

  1. Cholesterol
  2. ATP Correct answer.
  3. NADH
  4. RNA

Explanation

ATP releases usable energy when its terminal phosphate bond is hydrolyzed, powering many cellular processes. NADH carries electrons to the electron transport chain but is not the direct energy currency.

Question 12Molecules and Cells

In aerobic cellular respiration, where does glycolysis occur?

  1. In the mitochondrial matrix
  2. In the cytoplasm Correct answer.
  3. In the nucleus
  4. On the inner mitochondrial membrane

Explanation

Glycolysis takes place in the cytoplasm, where glucose is split into pyruvate with a net gain of ATP and NADH. The later stages of aerobic respiration occur in the mitochondria.

Question 13Molecules and Cells

Which products of the light-dependent reactions of photosynthesis are used in the Calvin cycle?

  1. Carbon dioxide and water
  2. ATP and NADPH Correct answer.
  3. Glucose and oxygen
  4. Pyruvate and NADH

Explanation

The light-dependent reactions generate ATP and NADPH, which supply energy and reducing power for carbon fixation in the Calvin cycle. Oxygen is released as a byproduct, and carbon dioxide is the input to the Calvin cycle.

Question 14Molecules and Cells

A plant is kept in bright light but given air with no carbon dioxide. Which outcome is most likely?

  1. The light reactions stop immediately.
  2. The Calvin cycle slows because carbon fixation cannot proceed. Correct answer.
  3. Glucose production increases.
  4. Oxygen production increases sharply.

Explanation

The Calvin cycle requires carbon dioxide as the carbon source for sugar production, so removing it stalls carbon fixation even while light reactions continue briefly. Without CO2, sugar output falls.

Question 15Molecules and Cells

Which process produces the greatest number of ATP molecules per glucose molecule during aerobic respiration?

  1. Oxidative phosphorylation Correct answer.
  2. Pyruvate oxidation
  3. The Krebs cycle
  4. Glycolysis

Explanation

Oxidative phosphorylation, driven by the electron transport chain and ATP synthase, yields the majority of ATP from glucose. Glycolysis and the Krebs cycle contribute smaller amounts directly.

Question 16Molecules and Cells

During DNA replication, which enzyme joins nucleotides to form the new strand by adding them complementary to the template?

  1. RNA polymerase
  2. DNA polymerase Correct answer.
  3. Ligase
  4. Helicase

Explanation

DNA polymerase adds nucleotides complementary to the template strand and also proofreads the new strand. Helicase unwinds the DNA, and ligase joins fragments after synthesis.

Question 17Molecules and Cells

A DNA template strand has the sequence 3'-TAC-5'. Which mRNA codon is transcribed from it?

  1. 5'-TAC-3'
  2. 5'-AUG-3' Correct answer.
  3. 5'-UAC-3'
  4. 5'-ATG-3'

Explanation

Transcription builds mRNA complementary to the template strand, pairing adenine with uracil. The template 3'-TAC-5' therefore yields the mRNA codon 5'-AUG-3'.

Question 18Molecules and Cells

Which statement best distinguishes transcription from translation?

  1. Transcription occurs in the cytoplasm; translation occurs in the nucleus.
  2. Both processes occur on ribosomes.
  3. Transcription builds protein; translation builds RNA.
  4. Transcription makes RNA from DNA; translation makes protein from mRNA. Correct answer.

Explanation

Transcription copies a DNA sequence into RNA, while translation uses the mRNA sequence to assemble a polypeptide at the ribosome. The two processes occur in different locations and use different machinery.

Question 19Molecules and Cells

A mutation changes a single DNA base but the resulting protein has the same amino acid sequence. What is this type of mutation called?

  1. Missense mutation
  2. Nonsense mutation
  3. Frameshift mutation
  4. Silent mutation Correct answer.

Explanation

A silent mutation changes a base but, because the genetic code is redundant, the same amino acid is still specified. Missense and nonsense mutations change the amino acid or create a stop codon.

Question 20Molecules and Cells

Which feature of the genetic code explains why many single-base changes do not alter the protein produced?

  1. The code is universal across organisms.
  2. Codons are read in overlapping triplets.
  3. Each codon contains four bases.
  4. The code is redundant, with multiple codons for some amino acids. Correct answer.

Explanation

Redundancy means several codons can specify the same amino acid, so some base changes leave the amino acid unchanged. Universality describes shared usage across organisms, not tolerance of substitutions.

Question 21Molecules and Cells

Which of the following correctly pairs a stage of mitosis with its key event?

  1. Telophase: sister chromatids separate
  2. Metaphase: chromosomes align at the cell equator Correct answer.
  3. Anaphase: nuclear envelope re-forms
  4. Prophase: chromosomes line up at the cell equator

Explanation

During metaphase, condensed chromosomes align along the metaphase plate at the cell equator. Prophase involves condensation, anaphase involves chromatid separation, and telophase involves re-forming nuclear envelopes.

Question 22Molecules and Cells

A cell that begins meiosis with 20 chromosomes will produce gametes containing how many chromosomes?

  1. 5
  2. 10 Correct answer.
  3. 40
  4. 20

Explanation

Meiosis halves the chromosome number through two divisions, so a starting cell with 20 chromosomes produces haploid gametes with 10. The diploid number is restored at fertilization.

Question 23Molecules and Cells

Which process generates new combinations of alleles on a single chromosome during meiosis?

  1. Replication of DNA before meiosis
  2. Cytokinesis after telophase I
  3. Separation of sister chromatids
  4. Crossing over between homologous chromosomes Correct answer.

Explanation

Crossing over exchanges segments between homologous chromosomes during prophase I, creating new allele combinations along a chromosome. DNA replication copies existing alleles rather than recombining them.

Question 24Molecules and Cells

Which statement best explains why cells must regulate gene expression?

  1. Gene expression prevents DNA replication.
  2. Cells conserve resources by producing proteins only when needed. Correct answer.
  3. Regulation permanently deletes unneeded genes.
  4. All genes must be expressed at equal levels at all times.

Explanation

Regulating gene expression allows cells to produce proteins when they are needed, conserving energy and materials while enabling specialization. Genes are not expressed equally or constantly.

Question 25Molecules and Cells

Which structural feature allows a protein to fold into its functional three-dimensional shape?

  1. The presence of a lipid bilayer
  2. Its sequence of amino acids Correct answer.
  3. Its ability to replicate itself
  4. The number of phosphate groups in DNA

Explanation

The primary amino acid sequence determines the interactions that drive folding into secondary, tertiary, and sometimes quaternary structures. The final shape, in turn, determines the protein's function.

Question 26Molecules and Cells

Which property of water allows it to dissolve many ionic and polar substances in a cell?

  1. It has a very high density compared with other liquids.
  2. Its molecules are nonpolar and repel ions.
  3. Its molecules are polar and form hydrogen bonds with solutes. Correct answer.
  4. It exists as a gas at typical cellular temperatures.

Explanation

Water is a polar molecule whose partial charges attract ions and other polar molecules, allowing it to surround and separate them. This polarity and the resulting hydrogen bonding make water an effective solvent for most biological substances.

Question 27Molecules and Cells

A student examines a cell and finds a rigid outer layer surrounding the plasma membrane. Which additional structure would confirm that this cell is a plant cell rather than an animal cell?

  1. Mitochondria with folded membranes
  2. Ribosomes free in the cytoplasm
  3. A large central vacuole Correct answer.
  4. A nucleus containing DNA

Explanation

A rigid cell wall plus a large central vacuole are characteristic features of plant cells. Ribosomes, a nucleus, and mitochondria occur in both plant and animal cells, so they do not distinguish the two.

Question 28Molecules and Cells

Which type of biological macromolecule is built from amino acids linked by peptide bonds?

  1. Nucleic acids
  2. Proteins Correct answer.
  3. Carbohydrates
  4. Lipids

Explanation

Proteins are polymers of amino acids joined by peptide bonds. Carbohydrates are built from sugars, nucleic acids from nucleotides, and most lipids are not polymers of amino acids.

Question 29Molecules and Cells

Which organelle is the primary site of protein synthesis in a cell?

  1. The lysosome
  2. The smooth endoplasmic reticulum
  3. The Golgi apparatus
  4. The ribosome Correct answer.

Explanation

Ribosomes translate mRNA into polypeptide chains, making them the primary site of protein synthesis. The other organelles modify, package, or degrade materials rather than assemble proteins.

Question 30Molecules and Cells

An enzyme catalyzes a reaction in the small intestine at pH 8. If the pH drops to 3, the reaction rate falls sharply even though substrate is plentiful. Which explanation is most consistent with these observations?

  1. The enzyme is converted into a competitive inhibitor at low pH.
  2. The substrate concentration becomes limiting at low pH.
  3. The reaction becomes endergonic at low pH and cannot proceed.
  4. The enzyme's active site changes shape and loses its ability to bind substrate. Correct answer.

Explanation

Enzymes have an optimal pH, and extreme pH changes alter the ionic and hydrogen bonds that maintain the active site's shape. When the active site is distorted, substrate binding and catalysis decline even if substrate is abundant.

Question 31Molecules and Cells

A cell is placed in a solution, and over time it loses water and shrinks. Which description of the solution best accounts for this result?

  1. It is isotonic, so water moves equally in both directions.
  2. It is hypotonic, so solute moves into the cell.
  3. It is hypertonic, so solute moves out of the cell by osmosis.
  4. It is hypertonic, so water leaves the cell by osmosis. Correct answer.

Explanation

In a hypertonic solution the solute concentration outside is higher than inside, so water moves out of the cell by osmosis and the cell shrinks. Solute itself does not move by osmosis; osmosis refers specifically to water movement.

Question 32Molecules and Cells

Which statement correctly describes the role of ATP hydrolysis in cells?

  1. It permanently inactivates the enzymes it binds.
  2. It produces oxygen as a byproduct of the reaction.
  3. It releases energy that can drive endergonic reactions. Correct answer.
  4. It stores energy by building ATP from ADP and phosphate.

Explanation

Hydrolysis of ATP breaks the bond to the terminal phosphate and releases free energy that can be coupled to energy-requiring reactions. Building ATP from ADP and phosphate is the reverse process, which stores energy.

Question 33Molecules and Cells

In the light-dependent reactions of photosynthesis, what is the primary source of the electrons that replace those lost by chlorophyll?

  1. Oxygen gas
  2. Carbon dioxide
  3. Glucose
  4. Water Correct answer.

Explanation

Water is split in the light-dependent reactions, supplying electrons to replace those excited from chlorophyll and releasing oxygen as a byproduct. Carbon dioxide and glucose are involved in the Calvin cycle, not as the electron donor here.

Question 34Molecules and Cells

A cell is treated with a drug that blocks the electron transport chain but leaves glycolysis intact. Which immediate consequence is most likely?

  1. Glycolysis stops because it requires oxygen directly.
  2. Carbon dioxide production by the Krebs cycle increases sharply.
  3. The Krebs cycle produces more NADH than usual.
  4. NADH accumulates and ATP production from oxidative phosphorylation falls. Correct answer.

Explanation

The electron transport chain reoxidizes NADH and FADH2 while driving ATP synthesis, so blocking it causes these carriers to accumulate in their reduced forms and sharply reduces ATP from oxidative phosphorylation. Glycolysis does not require oxygen directly and can continue using substrate-level phosphorylation.

Question 35Molecules and Cells

During DNA replication, what ensures that each new double helix contains one original strand and one newly synthesized strand?

  1. Translation of the new strand
  2. Conservative replication
  3. Semi-conservative replication Correct answer.
  4. Transcription of the template

Explanation

Semi-conservative replication means the two strands separate and each serves as a template, so every daughter molecule has one old and one new strand. Transcription and translation are steps of gene expression, not DNA duplication.

Question 36Molecules and Cells

A DNA sequence changes from 5'-ATG-3' to 5'-ATC-3' in the coding strand. Using the standard genetic code, what is the effect on the resulting polypeptide?

  1. One amino acid is substituted for another. Correct answer.
  2. A frameshift changes every downstream amino acid.
  3. No change occurs because both codons specify methionine.
  4. A stop codon appears and translation ends early.

Explanation

The mRNA changes from AUG to AUC, which specify methionine and isoleucine respectively, so a single amino acid substitution results. Because only one base changed and no codon was added or removed, the reading frame stays intact.

Question 37Molecules and Cells

A cell in meiosis has completed meiosis I but not meiosis II. Which statement best describes its chromosomes at this stage?

  1. Each chromosome consists of two sister chromatids, and the cell is haploid. Correct answer.
  2. Each chromosome consists of a single chromatid, and the cell is diploid.
  3. Homologous chromosomes are paired and aligned at the metaphase plate.
  4. The chromosome number has doubled compared with the original cell.

Explanation

After meiosis I, homologous chromosomes have separated, so the cell is haploid, but sister chromatids remain attached, so each chromosome still has two chromatids. Homologous pairing occurred earlier, and the chromosome number does not double.

Question 38Molecules and Cells

A liver cell and a neuron from the same organism contain identical DNA, yet they produce very different proteins. Which explanation best accounts for this difference?

  1. Different genes are expressed because different transcription factors are active. Correct answer.
  2. The liver cell translates RNA differently from the neuron.
  3. The two cell types contain different genes in their nuclei.
  4. The neurons have lost the genes for liver-specific proteins.

Explanation

Cells with the same genome differ because selective gene expression is controlled by cell-specific transcription factors and regulatory signals. Differences in protein content arise from which genes are transcribed, not from loss or gain of genes.

Question 39Molecules and Cells

In a eukaryotic cell, a mutation prevents the addition of the poly-A tail to mRNA. Which outcome is most likely?

  1. The mRNA will be translated at a higher rate than normal.
  2. The mRNA will be unable to leave the nucleus because it lacks a start codon.
  3. The mRNA will fail to be transcribed from DNA.
  4. The mRNA will be less stable and more rapidly degraded in the cytoplasm. Correct answer.

Explanation

The poly-A tail protects mRNA from degradation and contributes to its stability and export. Without it, the transcript is more vulnerable to nucleases and is degraded sooner, reducing protein output.

Question 40Molecules and Cells

Two enzymes in a pathway are compared. Enzyme A has a much lower Michaelis constant (Km) for its substrate than Enzyme B. What does this indicate about Enzyme A?

  1. It is inhibited more strongly by its product than Enzyme B.
  2. It has a higher maximum reaction rate than Enzyme B.
  3. It requires a higher substrate concentration to reach half its maximum rate.
  4. It has a greater affinity for the substrate at low concentrations. Correct answer.

Explanation

Km reflects the substrate concentration at which an enzyme reaches half its maximum rate, so a lower Km indicates tighter substrate binding and greater affinity. Km does not by itself indicate maximum velocity or product inhibition.

Question 41Genetics and Heredity

In a certain plant species, the allele for tall stems (T) is dominant to the allele for short stems (t). A heterozygous tall plant is crossed with a short plant. What fraction of the offspring is expected to be short?

  1. Zero
  2. Three quarters
  3. One half Correct answer.
  4. One quarter

Explanation

A heterozygous tall plant (Tt) crossed with a short plant (tt) gives gametes T and t from one parent and only t from the other, producing Tt and tt offspring in equal proportions. Half of the offspring are therefore expected to be short.

Question 42Genetics and Heredity

Which term describes an organism that carries two identical alleles for a given gene?

  1. Hemizygous
  2. Homozygous Correct answer.
  3. Codominant
  4. Heterozygous

Explanation

Homozygous organisms carry two copies of the same allele at a locus. Heterozygous organisms carry two different alleles, and hemizygous organisms carry only one copy of a gene, as males do for X-linked genes.

Question 43Genetics and Heredity

A human somatic cell in G1 phase contains 46 chromosomes. After the S phase of the cell cycle, how many chromatids does the cell contain?

  1. 23
  2. 92 Correct answer.
  3. 138
  4. 46

Explanation

During S phase each chromosome is replicated into two sister chromatids joined at the centromere. The chromosome count stays at 46, but the chromatid count doubles to 92.

Question 44Genetics and Heredity

Which process produces gametes with half the chromosome number of the parent cell?

  1. Mitosis
  2. Cytokinesis
  3. Binary fission
  4. Meiosis Correct answer.

Explanation

Meiosis includes two consecutive divisions that reduce the chromosome number by half, producing haploid gametes. Mitosis and binary fission maintain the chromosome number, and cytokinesis is only the physical division of the cytoplasm.

Question 45Genetics and Heredity

Which of these is the correct base-pairing rule in DNA?

  1. Adenine pairs with guanine, and thymine pairs with cytosine
  2. Adenine pairs with cytosine, and guanine pairs with thymine
  3. Adenine pairs with uracil, and guanine pairs with cytosine
  4. Adenine pairs with thymine, and guanine pairs with cytosine Correct answer.

Explanation

In DNA, adenine forms two hydrogen bonds with thymine and guanine forms three with cytosine. This complementary pairing keeps the helix uniform in width and allows accurate replication.

Question 46Genetics and Heredity

A dihybrid cross is made between two plants heterozygous for both seed shape (Rr) and seed color (Yy). Assuming independent assortment, what fraction of the offspring is expected to show both recessive traits (rryy)?

  1. 1/16 Correct answer.
  2. 9/16
  3. 1/4
  4. 3/16

Explanation

Each parent produces ry gametes with probability 1/4, so the chance of an rryy offspring is 1/4 × 1/4 = 1/16. This is the expected fraction when the genes assort independently.

Question 47Genetics and Heredity

A woman who is a carrier of an X-linked recessive disorder has children with a man who does not have the disorder. What proportion of their sons is expected to be affected?

  1. None
  2. One quarter
  3. One half Correct answer.
  4. All

Explanation

Sons receive their X chromosome from the mother and a Y from the father. A carrier mother passes the affected allele to half of her sons, so half of the sons are expected to be affected.

Question 48Genetics and Heredity

Which of these describes the phenotype of an organism?

  1. Its observable traits, such as flower color Correct answer.
  2. The set of alleles it carries at a locus
  3. The sequence of bases in one gene
  4. The number of chromosomes in a gamete

Explanation

Phenotype refers to observable or measurable traits, which result from genotype interacting with the environment. Genotype refers to the alleles present.

Question 49Genetics and Heredity

In snapdragons, red-flowered plants (RR) crossed with white-flowered plants (WW) produce pink-flowered offspring (RW). When two pink plants are crossed, what phenotypic ratio is expected?

  1. 1 red : 2 pink : 1 white Correct answer.
  2. 1 red : 1 white
  3. All pink
  4. 3 red : 1 white

Explanation

The heterozygote shows an intermediate phenotype, which is incomplete dominance. A cross of two RW plants yields RR, RW, and WW in a 1:2:1 ratio, producing red, pink, and white flowers.

Question 50Genetics and Heredity

Which process creates new combinations of alleles on chromosomes during meiosis?

  1. Formation of the spindle apparatus
  2. Replication of DNA before meiosis
  3. Crossing over between homologous chromosomes Correct answer.
  4. Separation of sister chromatids in meiosis II

Explanation

Crossing over exchanges segments between homologous chromosomes, producing new allele combinations on a single chromatid. Independent assortment also reshuffles chromosomes, but crossing over creates recombinant chromatids.