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Gaokao Biology study materials
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Gaokao Biology practice questions

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Question 1Biological inquiry and interpretation of evidence

A researcher predicts that tomato plants given a nitrogen-enriched fertilizer will produce more fruit than plants given a standard fertilizer. In this study, the amount of fruit produced is best described as which of the following?

  1. The hypothesis
  2. A controlled variable
  3. The dependent variable Correct answer.
  4. The independent variable

Explanation

The dependent variable is the measured outcome that responds to the manipulation, which here is fruit yield. The fertilizer type is the factor the researcher deliberately changes, so it is the independent variable rather than the measured result.

Question 2Biological inquiry and interpretation of evidence

A student measures the mass of the same sample five times and obtains nearly identical values, but the balance was never zeroed and reads 2.0 g too high. How should these measurements be described?

  1. Both accurate and precise
  2. Precise but not accurate Correct answer.
  3. Accurate but not precise
  4. Neither accurate nor precise

Explanation

Precision refers to how closely repeated measurements agree with one another, while accuracy refers to how close they are to the true value. Because the readings cluster tightly but are systematically offset by the unzeroed balance, they are precise but inaccurate.

Question 3Biological inquiry and interpretation of evidence

Which of the following best distinguishes a scientific hypothesis from a scientific theory?

  1. A hypothesis is a testable proposed explanation, while a theory is a well-supported explanatory framework built from extensive evidence Correct answer.
  2. A hypothesis is always correct once tested, while a theory remains an untested guess
  3. A hypothesis is a broad framework, while a theory is a single testable prediction
  4. A hypothesis applies only to biology, while a theory applies only to physics

Explanation

In science, a hypothesis is a testable proposed explanation for a specific observation, whereas a theory is a broad, well-substantiated explanation supported by many lines of evidence. The common usage of theory as a mere guess is incorrect in scientific contexts.

Question 4Biological inquiry and interpretation of evidence

A scientist repeats an experiment several times and obtains consistent results. Which conclusion is most justified?

  1. The findings are reliable and reproducible under the tested conditions Correct answer.
  2. The results now apply to all organisms everywhere
  3. The hypothesis has been proven true beyond any doubt
  4. The experiment has no remaining sources of error

Explanation

Reproducible results indicate reliability, meaning the procedure yields consistent outcomes under the tested conditions. Science does not establish absolute proof, and replication does not eliminate error or guarantee universal applicability.

Question 5Biological inquiry and interpretation of evidence

A graph plots plant height on the y-axis against days of growth on the x-axis. Which statement correctly identifies the placement of these variables?

  1. Days of growth is the independent variable on the x-axis, and height is the dependent variable on the y-axis Correct answer.
  2. Both variables are dependent and should share the x-axis
  3. Days of growth is the dependent variable because it is measured over time
  4. Height is the independent variable on the y-axis, and days of growth is the dependent variable on the x-axis

Explanation

By convention, the independent variable is placed on the x-axis and the dependent variable on the y-axis. Height responds to elapsed time, so time is independent and height is dependent.

Question 6Biological inquiry and interpretation of evidence

A student notices that mold grows on bread left in a warm, humid place but not on bread stored in a dry, cool place. Which of the following is the most appropriate next step in the scientific process?

  1. Formulate a testable hypothesis and design a controlled experiment to test it Correct answer.
  2. Conclude immediately that warmth and moisture cause mold growth
  3. Publish the observation as a confirmed scientific law
  4. Discard the observation because it was not made in a laboratory

Explanation

An observation generates questions that should be framed as a testable hypothesis and examined through a controlled experiment. Reaching a firm causal conclusion from a single uncontrolled observation is premature.

Question 7Biochemistry

Which property of water is most directly responsible for its ability to moderate temperature in living organisms and large bodies of water?

  1. Its low specific heat
  2. Its inability to form hydrogen bonds
  3. Its nonpolar covalent bonds
  4. Its high specific heat Correct answer.

Explanation

Water has a high specific heat because hydrogen bonds must absorb or release substantial energy before water molecules change temperature. This allows water and water-rich organisms to resist large temperature swings, helping maintain homeostasis.

Question 8Cell structure, membranes and division

Which structure is found in a typical plant cell but NOT in a typical animal cell?

  1. Mitochondrion
  2. Nucleus
  3. Ribosome
  4. Cell wall made of cellulose Correct answer.

Explanation

Plant cells have a rigid cell wall composed primarily of cellulose that surrounds the plasma membrane, providing structural support. Animal cells lack a cell wall, relying on the cytoskeleton and extracellular matrix instead.

Question 9Genetics, inheritance and molecular information

Meiosis differs from mitosis in that meiosis produces

  1. Two genetically identical diploid cells
  2. One diploid cell with double the chromosomes
  3. Two haploid cells identical to the parent
  4. Four genetically varied haploid cells Correct answer.

Explanation

Meiosis consists of two divisions that produce four haploid gametes, each with half the chromosome number of the parent. Crossing over and independent assortment generate genetic variation, distinguishing meiosis from the identical-diploid products of mitosis.

Question 10Metabolism

An enzyme lowers the activation energy of a reaction. Which statement best describes how this affects the reaction?

  1. It increases the reaction rate without being consumed in the reaction Correct answer.
  2. It changes the overall free-energy difference between reactants and products
  3. It supplies the energy needed to make an endergonic reaction exergonic
  4. It permanently binds to the product to stop the reaction

Explanation

Enzymes are biological catalysts that lower activation energy, speeding up reactions without being consumed. They do not change the net free-energy difference (delta G) between reactants and products; they only make the reaction reach equilibrium faster.

Question 11Evolution

Which of the following is a necessary condition for natural selection to occur in a population?

  1. All individuals are genetically identical
  2. Heritable variation exists and affects survival or reproduction Correct answer.
  3. The environment never changes
  4. Every individual produces the same number of offspring

Explanation

Natural selection requires heritable variation among individuals and differences in reproductive success linked to that variation. Individuals with advantageous heritable traits leave more offspring, shifting the population's traits over generations.

Question 12Ecology

In an energy pyramid, only about 10 percent of the energy at one trophic level is transferred to the next. Most of the remaining energy is

  1. Converted directly into new biomass at the next level
  2. Lost as heat, largely through cellular respiration and metabolic processes Correct answer.
  3. Stored permanently in the soil
  4. Recycled back to producers as light energy

Explanation

At each trophic level, organisms use most of the energy they consume for metabolism and lose much of it as heat through cellular respiration. Only about 10 percent is stored as biomass available to the next level, which limits food chain length.

Question 13Physiology

Which feature allows a steroid hormone to pass directly through the plasma membrane?

  1. Its lipid (hydrophobic) nature lets it dissolve through the phospholipid bilayer Correct answer.
  2. Its large size lets it push proteins aside
  3. Its negative charge attracts it to the membrane interior
  4. Its attachment to a carbohydrate tag opens a channel

Explanation

Steroid hormones are lipid-soluble (hydrophobic), so they can dissolve through the hydrophobic interior of the phospholipid bilayer without a transport protein. Once inside, they typically bind intracellular receptors that act on the DNA to regulate gene expression.

Question 14Biotechnology

The polymerase chain reaction, or PCR, is mainly used to do what?

  1. Amplify a selected DNA sequence Correct answer.
  2. Destroy all proteins in a sample
  3. Make plant roots bend downward
  4. Measure animal breathing rate directly

Explanation

PCR uses primers, DNA polymerase, nucleotides, and temperature cycling to make many copies of a target DNA region. It is widely used in testing and research.

Question 15Cell structure, membranes and division

Which property of water most directly helps stabilize temperature inside living cells?

  1. High specific heat capacity Correct answer.
  2. Low surface tension
  3. Ability to dissolve all lipids
  4. Permanent peptide bonding

Explanation

Water has a high specific heat capacity because hydrogen bonds absorb energy before water temperature changes much. This buffers cells and tissues against rapid temperature shifts.

Question 16Cell structure, membranes and division

A bacterial cell differs from a plant cell because the bacterial cell normally lacks which structure?

  1. Cell membrane
  2. Ribosomes
  3. A membrane-bound nucleus Correct answer.
  4. DNA

Explanation

Bacteria are prokaryotes, so their DNA is not enclosed in a membrane-bound nucleus. They still have a cell membrane, ribosomes, and genetic material.

Question 17Cell structure, membranes and division

Which cell structure is directly responsible for linking amino acids during protein synthesis?

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

Explanation

Ribosomes read mRNA and catalyze peptide-bond formation between amino acids. This is the central step of translation.

Question 18Cell structure, membranes and division

In an actively respiring root cell, which organelle produces most of the ATP by aerobic respiration?

  1. Chloroplast
  2. Mitochondrion Correct answer.
  3. Cell wall
  4. Nucleolus

Explanation

Mitochondria carry out the citric acid cycle and oxidative phosphorylation, which produce most ATP in aerobic respiration. Root cells may not contain functional chloroplasts.

Question 19Cell structure, membranes and division

The selective permeability of the plasma membrane is mainly explained by which feature?

  1. A rigid cellulose layer
  2. A phospholipid bilayer with embedded proteins Correct answer.
  3. A double helix of nucleotides
  4. A lattice of calcium carbonate

Explanation

The hydrophobic interior of the phospholipid bilayer restricts many polar substances, while membrane proteins provide specific transport routes. Together they create selective permeability.

Question 20Cell structure, membranes and division

Why does heating most enzymes far above their optimum temperature reduce reaction rate?

  1. The enzyme is denatured and its active site changes shape Correct answer.
  2. The enzyme is converted into DNA
  3. The substrate becomes an enzyme
  4. The reaction changes from catalyzed to photosynthetic

Explanation

High temperature disrupts bonds that maintain protein shape. When the active site changes, the substrate no longer binds effectively and catalytic rate falls.

Question 21Cell structure, membranes and division

A small nonpolar molecule moves directly through a membrane from high concentration to low concentration. Which transport process is this?

  1. Simple diffusion Correct answer.
  2. Active transport
  3. Endocytosis
  4. Exocytosis

Explanation

Simple diffusion moves substances down their concentration gradient without ATP or a transport vesicle. Small nonpolar molecules can pass through the lipid bilayer this way.

Question 22Cell structure, membranes and division

During the light reactions of photosynthesis in plants, the oxygen released mainly comes from which molecule?

  1. Water Correct answer.
  2. Carbon dioxide
  3. Glucose
  4. NADPH

Explanation

Photosystem II splits water, releasing electrons, protons, and oxygen gas. The oxygen atoms in released O2 therefore come from water.

Question 23Cell structure, membranes and division

In eukaryotic cells, glycolysis occurs mainly in which location?

  1. Cytoplasm Correct answer.
  2. Mitochondrial matrix
  3. Thylakoid lumen
  4. Nuclear envelope

Explanation

Glycolysis is the cytoplasmic pathway that breaks glucose into pyruvate and produces a small amount of ATP and NADH. Later aerobic steps occur in mitochondria.

Question 24Cell structure, membranes and division

What is the usual genetic result of mitosis in an animal somatic cell?

  1. Four haploid cells with recombined chromosomes
  2. Two genetically identical diploid daughter cells Correct answer.
  3. One diploid cell and one haploid cell
  4. Gametes with half the chromosome number

Explanation

Mitosis separates duplicated sister chromatids to form two daughter cells with the same chromosome number and genetic information as the parent cell. It supports growth and tissue repair.

Question 25Cell structure, membranes and division

A plant epidermal cell is placed in a strongly hypertonic solution. What is the most likely visible change under a microscope?

  1. The protoplast shrinks away from the cell wall Correct answer.
  2. The cell wall dissolves immediately
  3. The nucleus divides twice
  4. The chloroplasts become mitochondria

Explanation

In a hypertonic solution, water leaves the plant cell by osmosis. The plasma membrane and cytoplasm pull away from the wall, a process called plasmolysis.

Question 26Cell structure, membranes and division

The sodium-potassium pump moves Na+ out of animal cells and K+ into cells against their gradients. Which statement best describes this process?

  1. It is active transport powered by ATP Correct answer.
  2. It is simple diffusion through the lipid bilayer
  3. It is osmosis through aquaporins
  4. It is photosynthetic carbon fixation

Explanation

Moving ions against electrochemical gradients requires energy. The sodium-potassium pump is an ATP-driven membrane protein.

Question 27Cell structure, membranes and division

In a chloroplast, where does the Calvin cycle directly fix carbon dioxide into organic molecules?

  1. Stroma Correct answer.
  2. Thylakoid lumen
  3. Outer mitochondrial membrane
  4. Cell wall

Explanation

The Calvin cycle occurs in the chloroplast stroma, where enzymes use ATP and NADPH to reduce CO2. The thylakoid membranes carry out the light reactions.

Question 28Cell structure, membranes and division

Maize often maintains high photosynthesis under hot, bright, dry conditions better than rice. Which feature of C4 photosynthesis helps explain this?

  1. CO2 is concentrated near Rubisco, reducing photorespiration Correct answer.
  2. Water is produced directly from carbon dioxide in bundle sheath cells
  3. All stomata remain permanently open at night
  4. ATP is no longer required for sugar formation

Explanation

C4 plants first fix CO2 into four-carbon compounds and deliver CO2 to bundle sheath cells. This raises CO2 near Rubisco and reduces photorespiration in hot conditions.

Question 29Cell structure, membranes and division

A competitive inhibitor is added to an enzyme reaction. If enough substrate is added, which outcome is most likely?

  1. The maximum reaction rate can still be reached Correct answer.
  2. The enzyme becomes a carbohydrate
  3. The inhibitor permanently destroys every enzyme molecule
  4. The reaction no longer depends on enzyme-substrate binding

Explanation

Competitive inhibitors bind the active site and compete with substrate. High substrate concentration can outcompete the inhibitor, so Vmax can still be reached although more substrate is needed.

Question 30Cell structure, membranes and division

Why are cell-cycle checkpoints important before DNA replication and mitosis?

  1. They help detect DNA damage or incomplete replication before division proceeds Correct answer.
  2. They guarantee that all cells become gametes
  3. They prevent any use of ATP in the cell
  4. They replace chromosomes with cell walls

Explanation

Checkpoints pause the cycle when DNA is damaged or replication is incomplete. This reduces the chance of passing severe genetic errors to daughter cells.

Question 31Cell structure, membranes and division

In sealed dough, yeast can continue producing ATP without oxygen. Which products are characteristic of alcoholic fermentation?

  1. Ethanol and carbon dioxide Correct answer.
  2. Lactose and oxygen
  3. Starch and nitrogen gas
  4. DNA and cellulose

Explanation

Yeast alcoholic fermentation regenerates NAD+ and produces ethanol and CO2. The CO2 helps dough rise.

Question 32Cell structure, membranes and division

An inhibitor lowers the maximum rate of an enzyme reaction, and adding more substrate does not restore the original maximum rate. Which type of inhibition is most consistent?

  1. Noncompetitive inhibition Correct answer.
  2. Competitive inhibition only
  3. No inhibition
  4. A change in product color only

Explanation

A noncompetitive inhibitor reduces the amount of functional enzyme or catalytic efficiency, lowering Vmax. Extra substrate cannot fully overcome this because the inhibitor does not simply compete for the active site.

Question 33Genetics, inheritance and molecular information

Which base-pairing rule is correct for double-stranded DNA?

  1. A pairs with U, and G pairs with C
  2. A pairs with T, and G pairs with C Correct answer.
  3. A pairs with G, and T pairs with C
  4. A pairs with C, and G pairs with T

Explanation

In DNA, adenine pairs with thymine and guanine pairs with cytosine through complementary hydrogen bonding. This complementarity supports accurate replication.

Question 34Genetics, inheritance and molecular information

In modern genetics, a gene is best described as which of the following?

  1. Any visible chromosome
  2. A DNA sequence that produces a functional RNA or protein product Correct answer.
  3. A complete cell nucleus
  4. A sugar molecule in the cytoplasm

Explanation

A gene is a sequence of nucleic acid information that can be expressed as a functional RNA or translated product. It is not the same as an entire chromosome or nucleus.

Question 35Genetics, inheritance and molecular information

Mendel's law of segregation explains which event during gamete formation?

  1. Allele pairs separate so each gamete receives one allele Correct answer.
  2. All genes on one chromosome always stay together
  3. Dominant alleles disappear in meiosis
  4. DNA bases pair randomly

Explanation

The law of segregation states that the two alleles of a gene separate during gamete formation. Each gamete receives one allele for that gene.

Question 36Genetics, inheritance and molecular information

Translation of genetic information into a polypeptide occurs at which structure?

  1. Ribosome Correct answer.
  2. Centromere
  3. Cell wall
  4. Spindle fiber

Explanation

Translation occurs at ribosomes, where mRNA codons are matched with tRNAs and amino acids are joined. This process produces polypeptides.

Question 37Genetics, inheritance and molecular information

Which statement best explains why mutation is important for evolution?

  1. It always makes organisms better adapted
  2. It creates new genetic variation that selection or drift can act on Correct answer.
  3. It prevents reproduction in every affected organism
  4. It stops DNA replication completely

Explanation

Mutations introduce new alleles into populations. Their effects can be beneficial, harmful, or neutral, and evolutionary processes change their frequencies over generations.

Question 38Genetics, inheritance and molecular information

Crossing over in meiosis usually occurs during which stage and has what genetic effect?

  1. Prophase I; it creates new combinations of alleles on homologous chromosomes Correct answer.
  2. Anaphase II; it duplicates the whole genome
  3. Telophase I; it eliminates all dominant alleles
  4. Interphase after meiosis; it prevents fertilization

Explanation

During prophase I, homologous chromosomes pair and exchange corresponding segments. This recombination creates new allele combinations in gametes.

Question 39Genetics, inheritance and molecular information

If nondisjunction occurs during meiosis I, what kind of gametes can be produced?

  1. Gametes with one extra or one missing chromosome Correct answer.
  2. Only genetically identical diploid body cells
  3. Gametes with no DNA at all
  4. Only normal gametes with exactly one chromosome from each pair

Explanation

Nondisjunction means homologous chromosomes fail to separate properly. This can produce gametes with abnormal chromosome numbers, leading to aneuploid zygotes after fertilization.

Question 40Genetics, inheritance and molecular information

In a flower species, red petals and white petals show incomplete dominance, and heterozygotes are pink. If two pink plants are crossed, what phenotypic ratio is expected?

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

Explanation

With incomplete dominance, pink plants are heterozygous. A heterozygote by heterozygote cross gives a 1:2:1 genotype ratio that also appears as 1 red:2 pink:1 white.

Question 41Genetics, inheritance and molecular information

An AaBb plant is test-crossed with an aabb plant. If the genes assort independently, what offspring phenotypic ratio is expected?

  1. 1:1:1:1 Correct answer.
  2. 9:3:3:1
  3. 3:1
  4. 1:2:1

Explanation

The AaBb parent produces AB, Ab, aB, and ab gametes in equal proportions if the genes assort independently. The aabb parent contributes only ab, giving four offspring classes in a 1:1:1:1 ratio.

Question 42Genetics, inheritance and molecular information

A testcross gives 8 percent recombinant offspring for two linked genes. What is the approximate map distance between the genes?

  1. 8 centimorgans Correct answer.
  2. 16 centimorgans
  3. 50 centimorgans
  4. 92 centimorgans

Explanation

For linked genes, 1 percent recombination is approximately 1 map unit or centimorgan. An 8 percent recombinant frequency suggests about 8 cM between the genes.

Question 43Genetics, inheritance and molecular information

A recessive allele causing a disorder is on the X chromosome. Why are males more often affected by such X-linked recessive disorders?

  1. Males have only one X chromosome, so one recessive allele can be expressed Correct answer.
  2. Males have two copies of every X-linked gene
  3. X-linked alleles are never inherited by females
  4. The Y chromosome always carries a matching dominant allele

Explanation

A typical male has one X chromosome and one Y chromosome. If his single X carries a recessive disease allele, there is no second X allele to mask it.

Question 44Genetics, inheritance and molecular information

DNA replication is described as semiconservative because each new DNA molecule contains what?

  1. One original strand and one newly synthesized strand Correct answer.
  2. Two completely original strands
  3. Two completely unrelated RNA strands
  4. Only proteins and no nucleotides

Explanation

In semiconservative replication, each parental strand serves as a template for a new complementary strand. Each daughter DNA molecule therefore has one old and one new strand.

Question 45Genetics, inheritance and molecular information

During transcription in a eukaryotic cell, what is the direct role of RNA polymerase?

  1. It synthesizes RNA using a DNA template Correct answer.
  2. It joins amino acids into a protein
  3. It separates homologous chromosomes
  4. It digests all introns before transcription begins

Explanation

RNA polymerase binds DNA at a gene region and builds an RNA strand complementary to the template strand. In eukaryotes, the primary transcript may later be processed.

Question 46Genetics, inheritance and molecular information

In the lac operon model, what happens when lactose is absent and glucose conditions are not considered?

  1. The repressor binds the operator and transcription is low Correct answer.
  2. The repressor is permanently destroyed and transcription is maximal
  3. RNA polymerase translates lactose into protein
  4. The operator becomes a ribosome

Explanation

Without lactose, the lac repressor remains active and binds the operator. This blocks efficient transcription of lac structural genes.

Question 47Genetics, inheritance and molecular information

A single-base substitution changes a DNA codon but the amino acid in the protein remains the same. What type of mutation is this?

  1. Silent mutation Correct answer.
  2. Frameshift mutation
  3. Chromosome nondisjunction
  4. Whole-genome duplication

Explanation

A silent mutation changes the nucleotide sequence without changing the amino acid sequence, often because the genetic code is redundant. The protein sequence is unchanged.

Question 48Genetics, inheritance and molecular information

A pedigree shows an affected person in every generation, and affected males and females can transmit the trait to sons and daughters. Which inheritance pattern is most consistent?

  1. Autosomal dominant Correct answer.
  2. Y-linked
  3. Mitochondrial only
  4. Recessive trait appearing only after skipped generations

Explanation

Autosomal dominant traits often appear in successive generations and affect both sexes. Transmission from affected fathers to sons also rules out simple X-linked inheritance.

Question 49Genetics, inheritance and molecular information

A parent with blood genotype AO and a parent with genotype BO have a child. Which blood phenotype is possible among their children?

  1. A, B, AB, or O Correct answer.
  2. Only AB
  3. Only O
  4. Only A or B, never AB or O

Explanation

The AO parent can produce A or O gametes, and the BO parent can produce B or O gametes. The possible offspring genotypes are AB, AO, BO, and OO.

Question 50Genetics, inheritance and molecular information

In a plant, allele B gives black pigment and allele b gives brown pigment, but pigment appears only when at least one C allele is present. Plants with cc are white. If BbCc is crossed with BbCc, what phenotypic ratio is expected?

  1. 9 black : 3 brown : 4 white Correct answer.
  2. 9 black : 6 brown : 1 white
  3. 12 black : 3 brown : 1 white
  4. 1 black : 2 brown : 1 white

Explanation

Among the 16 genotype combinations, B_C_ gives black, bbC_ gives brown, and all cc genotypes are white. This recessive epistasis pattern gives 9:3:4.