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DAT Quantitative Reasoning study materials
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DAT Quantitative Reasoning practice questions

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Question 1Survey of the Natural Sciences

A solution contains 0.20 mol of NaCl dissolved in enough water to make 500 mL of solution. What is the molarity of NaCl in the solution?

  1. 0.20 M
  2. 0.80 M
  3. 0.40 M Correct answer.
  4. 0.10 M

Explanation

Molarity equals moles of solute divided by liters of solution. Here 0.20 mol divided by 0.500 L gives 0.40 M.

Question 2Survey of the Natural Sciences

Which cellular organelle is the primary site of ATP synthesis by oxidative phosphorylation in a eukaryotic cell?

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

Explanation

The inner mitochondrial membrane houses the electron transport chain and ATP synthase, which carry out oxidative phosphorylation. Ribosomes make protein, the Golgi modifies and sorts proteins, and lysosomes degrade material.

Question 3Survey of the Natural Sciences

In a population at Hardy-Weinberg equilibrium, the frequency of the recessive allele is 0.3. What fraction of the population is expected to be heterozygous?

  1. 0.42 Correct answer.
  2. 0.21
  3. 0.49
  4. 0.09

Explanation

If q = 0.3, then p = 0.7, and the heterozygote frequency is 2pq = 2(0.7)(0.3) = 0.42. The other terms are p squared (0.49) and q squared (0.09).

Question 4Survey of the Natural Sciences

Which type of chemical bond is primarily responsible for holding the two strands of a DNA double helix together?

  1. Ionic bonds between phosphate groups
  2. Peptide bonds between amino acids
  3. Hydrogen bonds between complementary bases Correct answer.
  4. Phosphodiester bonds between nucleotides

Explanation

Complementary base pairs are joined by hydrogen bonds: two between A and T, three between G and C. Phosphodiester bonds instead link nucleotides within a single strand.

Question 5Survey of the Natural Sciences

A block slides down a frictionless incline that makes a 30-degree angle with the horizontal. If the acceleration due to gravity is 9.8 m/s squared, what is the magnitude of the block's acceleration along the incline?

  1. 9.8 m/s squared
  2. 17 m/s squared
  3. 4.9 m/s squared Correct answer.
  4. 8.5 m/s squared

Explanation

On a frictionless incline, the component of gravity along the slope is g times the sine of the angle. Sine of 30 degrees is 0.5, so the acceleration is 9.8 times 0.5, which equals 4.9 m/s squared.

Question 6Survey of the Natural Sciences

Which molecule is the final electron acceptor in the electron transport chain of aerobic cellular respiration?

  1. Oxygen Correct answer.
  2. Pyruvate
  3. Carbon dioxide
  4. NAD+

Explanation

Oxygen accepts electrons at the end of the electron transport chain and combines with protons to form water. This keeps electrons flowing and allows continued ATP production.

Question 7Survey of the Natural Sciences

An atom of an element has 17 protons, 18 neutrons, and 17 electrons. Which statement correctly describes this atom?

  1. It is an isotope with mass number 17.
  2. It is a neutral atom of chlorine-35. Correct answer.
  3. It is a cation with a +1 charge.
  4. It is an anion with a -1 charge.

Explanation

Equal numbers of protons and electrons give a neutral atom, and 17 protons identifies chlorine. The mass number is 17 protons plus 18 neutrons, which equals 35.

Question 8Survey of the Natural Sciences

Which process produces the greatest net yield of ATP per molecule of glucose in a eukaryotic cell under aerobic conditions?

  1. Glycolysis
  2. The Krebs cycle alone
  3. Oxidative phosphorylation Correct answer.
  4. Lactic acid fermentation

Explanation

Oxidative phosphorylation, driven by the electron transport chain and chemiosmosis, generates most of the ATP from glucose. Glycolysis and the Krebs cycle yield only small direct amounts of ATP.

Question 9Survey of the Natural Sciences

A gas occupies 2.0 L at 300 K. Assuming constant pressure, what volume will it occupy at 600 K?

  1. 6.0 L
  2. 2.0 L
  3. 4.0 L Correct answer.
  4. 1.0 L

Explanation

Charles's law states that volume is directly proportional to absolute temperature at constant pressure. Doubling the temperature from 300 K to 600 K doubles the volume from 2.0 L to 4.0 L.

Question 10Survey of the Natural Sciences

Which structure in the human nephron is primarily responsible for the reabsorption of glucose and amino acids from the filtrate?

  1. Collecting duct
  2. Distal convoluted tubule
  3. Descending limb of the loop of Henle
  4. Proximal convoluted tubule Correct answer.

Explanation

The proximal convoluted tubule reabsorbs nearly all filtered glucose and amino acids through cotransport with sodium. The loop of Henle mainly handles water and ion gradients.

Question 11Survey of the Natural Sciences

Which of the following describes the role of tRNA during translation?

  1. It catalyzes the formation of peptide bonds.
  2. It delivers amino acids to the ribosome in accordance with the mRNA codon. Correct answer.
  3. It carries the genetic message from DNA to the ribosome.
  4. It forms the structural core of the ribosome.

Explanation

Transfer RNA has an anticodon that pairs with the mRNA codon and carries the corresponding amino acid. Messenger RNA carries the message, and ribosomal RNA forms the ribosome core and catalyzes peptide bond formation.

Question 12Survey of the Natural Sciences

A solution has a hydrogen ion concentration of 1 x 10^-4 M. What is its pH, and is the solution acidic or basic?

  1. pH 4, acidic Correct answer.
  2. pH 4, basic
  3. pH 10, acidic
  4. pH 10, basic

Explanation

pH is the negative logarithm of the hydrogen ion concentration, so 1 x 10^-4 M gives pH 4. A pH below 7 indicates an acidic solution at standard temperature.

Question 13Survey of the Natural Sciences

In a cross between two heterozygous individuals (Aa x Aa) for a trait showing complete dominance, what is the probability that an offspring shows the recessive phenotype?

  1. 1/2
  2. 1/4 Correct answer.
  3. 3/4
  4. 0

Explanation

An Aa x Aa cross produces a 1:2:1 genotypic ratio, with only the aa genotype showing the recessive phenotype. That genotype occurs in one of four offspring, so the probability is 1/4.

Question 14Survey of the Natural Sciences

Which statement correctly distinguishes mitosis from meiosis in human cells?

  1. Mitosis produces four haploid cells, whereas meiosis produces two diploid cells.
  2. Mitosis produces two diploid cells, whereas meiosis produces four haploid cells. Correct answer.
  3. Mitosis occurs only in gametes, whereas meiosis occurs in somatic cells.
  4. Both mitosis and meiosis produce cells that are genetically identical to the parent cell.

Explanation

Mitosis yields two diploid daughter cells genetically identical to the parent, supporting growth and repair. Meiosis yields four haploid gametes with genetic variation from crossing over and independent assortment.

Question 15Survey of the Natural Sciences

Which of the following best explains why water has a relatively high boiling point compared with similar-sized nonpolar molecules?

  1. Water molecules are nonpolar and pack tightly.
  2. Water molecules are held together by strong hydrogen bonding. Correct answer.
  3. Water has a low molar mass and small molecular size.
  4. Water molecules form ionic bonds with one another.

Explanation

Each water molecule can form multiple hydrogen bonds because of its polar O-H bonds, and breaking these intermolecular attractions requires substantial energy. This raises the boiling point relative to nonpolar molecules of similar size.

Question 16Survey of the Natural Sciences

A patient's blood sample shows a hematocrit of 30 percent, well below the normal range. Which condition does this most directly suggest?

  1. Anemia Correct answer.
  2. Leukemia
  3. Polycythemia
  4. Thrombocytopenia

Explanation

Hematocrit measures the fraction of blood volume occupied by red blood cells, and a value of 30 percent is abnormally low. A reduced red cell fraction indicates anemia.

Question 17Survey of the Natural Sciences

Which of the following correctly ranks the levels of biological organization from simplest to most complex?

  1. Organ, tissue, cell, organism, organ system
  2. Cell, tissue, organ, organ system, organism Correct answer.
  3. Cell, organ, tissue, organ system, organism
  4. Tissue, cell, organ system, organ, organism

Explanation

Cells group into tissues, tissues into organs, organs into organ systems, and organ systems form the organism. This ordering reflects increasing structural and functional complexity.

Question 18Survey of the Natural Sciences

An object is placed 30 cm in front of a converging lens with a focal length of 10 cm. Where is the image formed?

  1. 15 cm on the same side as the object
  2. 30 cm on the opposite side of the lens
  3. 10 cm on the same side as the object
  4. 15 cm on the opposite side of the lens Correct answer.

Explanation

Using the thin lens equation, 1/f = 1/do + 1/di, we get 1/10 = 1/30 + 1/di, so 1/di = 1/15 and di = 15 cm. A positive image distance places a real image on the opposite side of the lens.

Question 19Survey of the Natural Sciences

Which of the following is the primary function of the sodium-potassium pump in a neuron?

  1. It maintains the resting membrane potential by moving three sodium ions out and two potassium ions in. Correct answer.
  2. It releases neurotransmitters into the synaptic cleft.
  3. It generates action potentials directly.
  4. It reabsorbs neurotransmitters after release.

Explanation

The sodium-potassium pump uses ATP to export three sodium ions and import two potassium ions, contributing to the negative resting membrane potential. Action potentials arise from ion channels, not the pump itself.

Question 20Survey of the Natural Sciences

Which type of RNA is processed in the nucleus by the addition of a 5-prime cap and a poly-A tail before export to the cytoplasm?

  1. Small nuclear RNA
  2. Ribosomal RNA
  3. Transfer RNA
  4. Messenger RNA Correct answer.

Explanation

Messenger RNA transcripts receive a 5-prime cap and a poly-A tail during processing in the nucleus, which aid stability and export. These modifications are characteristic of mRNA.

Question 21Survey of the Natural Sciences

Which of the following best describes the difference between an ionic bond and a covalent bond?

  1. Ionic bonds involve electron transfer, whereas covalent bonds involve electron sharing. Correct answer.
  2. Ionic bonds involve electron sharing, whereas covalent bonds involve electron transfer.
  3. Ionic bonds occur only between identical atoms, whereas covalent bonds occur between different atoms.
  4. Both ionic and covalent bonds involve equal sharing of electrons between atoms.

Explanation

In an ionic bond, one atom transfers electrons to another, creating oppositely charged ions that attract. In a covalent bond, atoms share electron pairs rather than transferring them.

Question 22Survey of the Natural Sciences

A population of bacteria is exposed to an antibiotic, and a small number of cells survive because they carry a resistance mutation. Over several generations, the proportion of resistant cells increases. Which mechanism does this illustrate?

  1. Genetic drift
  2. Directional selection Correct answer.
  3. Stabilizing selection
  4. Disruptive selection

Explanation

Directional selection favors one extreme phenotype, here the resistant bacteria, shifting the population toward that trait. Stabilizing and disruptive selection act differently, and drift is random rather than driven by the antibiotic.

Question 23Survey of the Natural Sciences

Which of the following correctly describes the relationship between the Calvin cycle and the light reactions of photosynthesis?

  1. The light reactions supply ATP and NADPH to the Calvin cycle, which fixes carbon dioxide. Correct answer.
  2. Both stages occur in the thylakoid membrane and produce oxygen directly.
  3. The Calvin cycle supplies ATP and NADPH to the light reactions, which fix carbon dioxide.
  4. The light reactions fix carbon dioxide, and the Calvin cycle produces oxygen.

Explanation

The light reactions in the thylakoid membrane generate ATP and NADPH, which the Calvin cycle in the stroma uses to fix carbon dioxide into sugar. Oxygen is released by the light reactions, not the Calvin cycle.

Question 24Survey of the Natural Sciences

A 1.0 kg object moving at 4.0 m/s collides with and sticks to a stationary 3.0 kg object. What is the speed of the combined object immediately after the collision?

  1. 4.0 m/s
  2. 1.0 m/s Correct answer.
  3. 1.3 m/s
  4. 2.0 m/s

Explanation

Momentum is conserved in the perfectly inelastic collision: (1.0 kg)(4.0 m/s) = (4.0 kg)(v), giving v = 1.0 m/s. The combined mass is 4.0 kg.

Question 25Survey of the Natural Sciences

Which of the following best explains why enzymes lower the activation energy of a reaction?

  1. They increase the temperature of the reaction mixture.
  2. They stabilize the transition state and provide an alternative reaction pathway. Correct answer.
  3. They are consumed during the reaction to provide energy.
  4. They change the equilibrium constant of the reaction.

Explanation

Enzymes bind substrates and stabilize the transition state, offering a lower-energy pathway to products. They do not alter the overall free-energy change or the equilibrium constant.

Question 26Survey of the Natural Sciences

A bacterial cell is placed in a solution whose solute concentration is higher than that of its cytoplasm. Which response is expected?

  1. There is no net movement of water across the membrane.
  2. Water leaves the cell, causing it to shrink and shrivel. Correct answer.
  3. Solute moves from the cell into the surrounding solution.
  4. Water enters the cell, causing it to swell and possibly lyse.

Explanation

The solution is hypertonic relative to the cytoplasm, so water moves by osmosis from the region of lower solute concentration (inside the cell) to higher solute concentration (outside). This net loss of water reduces cell volume and causes shrinking, a phenomenon called plasmolysis in walled cells.

Question 27Survey of the Natural Sciences

Which part of the human central nervous system is the primary control center for regulating body temperature, thirst, and hunger?

  1. The cerebellum
  2. The medulla oblongata
  3. The hypothalamus Correct answer.
  4. The corpus callosum

Explanation

The hypothalamus contains nuclei that monitor blood composition and temperature and trigger homeostatic responses such as sweating, shivering, and thirst. It serves as the main link between the nervous and endocrine systems via the pituitary gland.

Question 28Survey of the Natural Sciences

In the human digestive tract, most chemical digestion of proteins begins in which organ, and by the action of which enzyme?

  1. The small intestine, by lipase
  2. The stomach, by pepsin Correct answer.
  3. The mouth, by salivary amylase
  4. The large intestine, by pepsin

Explanation

Pepsin is secreted as inactive pepsinogen by gastric chief cells and is activated by the acidic environment of the stomach, where it begins breaking proteins into peptides. Salivary amylase acts on starch, and lipase acts on lipids.

Question 29Survey of the Natural Sciences

Which blood vessel type has the thinnest walls, consisting of only a single layer of endothelial cells, to permit exchange of gases and nutrients with tissues?

  1. Arterioles
  2. Capillaries Correct answer.
  3. Arteries
  4. Veins

Explanation

Capillaries are the smallest vessels and their walls are one endothelial cell thick, minimizing diffusion distance so that oxygen, carbon dioxide, and nutrients can be exchanged with surrounding tissue fluid.

Question 30Survey of the Natural Sciences

A mutation changes a DNA codon from GAG to GUG. If the original codon coded for glutamic acid, which type of mutation has occurred?

  1. A frameshift mutation
  2. A silent mutation
  3. A nonsense mutation
  4. A missense mutation Correct answer.

Explanation

A single base substitution that changes the amino acid specified by a codon is a missense mutation. Because the new codon still codes for an amino acid but a different one, it is neither silent nor nonsense.

Question 31Survey of the Natural Sciences

Which molecule serves as the immediate energy currency that powers most cellular work, being regenerated from ADP and phosphate?

  1. NADH
  2. Glucose
  3. FADH2
  4. ATP Correct answer.

Explanation

ATP is the universal energy currency of cells; hydrolysis of its terminal phosphate bond releases free energy used to drive endergonic reactions, and it is continually regenerated from ADP and inorganic phosphate.

Question 32Survey of the Natural Sciences

A population of rabbits includes individuals with thick and thin fur. In a cold climate, thick-furred rabbits survive and reproduce more often. Over many generations, the proportion of thick-furred rabbits increases. This is an example of which mechanism?

  1. Genetic drift
  2. Natural selection Correct answer.
  3. Mutation pressure
  4. Gene flow

Explanation

Natural selection occurs when heritable traits that improve survival and reproduction in a given environment become more common over generations. The cold climate acts as a selective pressure favoring thick fur.

Question 33Survey of the Natural Sciences

Which of the following correctly pairs a human organ system with its primary function?

  1. Lymphatic system - breakdown of ingested food
  2. Endocrine system - transport of oxygen to tissues
  3. Integumentary system - protection and temperature regulation Correct answer.
  4. Respiratory system - production of hormones

Explanation

The integumentary system, consisting of skin, hair, and nails, provides a physical barrier against pathogens and helps regulate body temperature through sweating and blood flow.

Question 34Survey of the Natural Sciences

During DNA replication, the enzyme that joins nucleotides into a new strand by adding them to a growing chain is which of the following?

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

Explanation

DNA polymerase catalyzes the addition of complementary nucleotides to the growing DNA strand, using the parental strand as a template. It also proofreads the newly synthesized strand.

Question 35Survey of the Natural Sciences

A cell is placed in a hypotonic solution. Which statement best explains the resulting movement of water?

  1. Water moves out of the cell because the solution has more solute.
  2. Water does not move because the membrane blocks all molecules.
  3. Water moves into the cell because the solution has a lower solute concentration than the cytoplasm. Correct answer.
  4. Solute moves into the cell to equalize concentration.

Explanation

In a hypotonic solution the solute concentration outside the cell is lower than inside, so water diffuses inward across the selectively permeable membrane. This can cause the cell to swell and, in animal cells lacking a wall, to lyse.

Question 36Survey of the Natural Sciences

Which statement accurately describes the role of the sinoatrial (SA) node in the heart?

  1. It contracts to pump blood into the aorta.
  2. It delays impulses to allow the atria to empty before ventricular contraction.
  3. It carries electrical signals from the atria to the ventricles.
  4. It acts as the pacemaker, generating electrical impulses that set the heart rate. Correct answer.

Explanation

The SA node is a cluster of self-exciting cells in the right atrium that spontaneously depolarizes, setting the rhythm of the heartbeat and acting as the primary pacemaker.

Question 37Survey of the Natural Sciences

A person's blood pH is measured at 7.30. Which statement best describes this condition and a likely compensatory response?

  1. It is alkalosis; the kidneys will excrete more bicarbonate.
  2. It is acidosis; the respiratory rate will decrease to retain carbon dioxide.
  3. It is acidosis; the respiratory rate will increase to exhale more carbon dioxide. Correct answer.
  4. It is normal; no compensation is required.

Explanation

A pH below the normal 7.35 to 7.45 range indicates acidosis. Increasing ventilation lowers blood carbon dioxide, which shifts the carbonic acid equilibrium toward less acid and helps raise pH toward normal.

Question 38Survey of the Natural Sciences

Which of the following best describes the function of the loop of Henle in the mammalian kidney?

  1. It creates a concentration gradient in the medulla that allows water reabsorption. Correct answer.
  2. It secretes hydrogen ions to regulate blood pH.
  3. It reabsorbs the majority of filtered glucose.
  4. It filters blood plasma into the renal tubule.

Explanation

The loop of Henle establishes an osmotic gradient in the renal medulla through countercurrent multiplication, enabling the collecting duct to reabsorb water and concentrate urine.

Question 39Survey of the Natural Sciences

In a dihybrid cross between two individuals heterozygous for both traits (AaBb x AaBb), assuming independent assortment, what fraction of offspring is expected to show the recessive phenotype for both traits?

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

Explanation

Each trait independently shows a 3:1 ratio, so the probability of the recessive phenotype for each trait is 1/4. Multiplying the independent probabilities gives 1/4 x 1/4 = 1/16 for both recessive traits together.

Question 40Survey of the Natural Sciences

Which of the following describes the relationship between a codon and an anticodon during translation?

  1. The codon is on mRNA and pairs with the complementary anticodon on tRNA. Correct answer.
  2. The codon is on tRNA and pairs with the anticodon on mRNA.
  3. Both are found on the same tRNA molecule.
  4. The anticodon is on mRNA and pairs with the codon on rRNA.

Explanation

During translation the mRNA codon is read by the ribosome and matched, through complementary base pairing, with the anticodon loop of a tRNA carrying the corresponding amino acid.

Question 41Survey of the Natural Sciences

Which statement best explains why a person with type O blood can donate red blood cells to recipients of any ABO type?

  1. Type O plasma contains both anti-A and anti-B antibodies.
  2. Type O red cells have Rh antigen but no ABO antigens.
  3. Type O red cells carry both A and B surface antigens.
  4. Type O red cells lack A and B surface antigens, so recipient antibodies do not target them. Correct answer.

Explanation

ABO compatibility depends on surface antigens on donor red cells. Type O cells lack A and B antigens, so antibodies in a recipient's plasma have no target on the transfused cells, making O red cells suitable for universal donation.

Question 42Survey of the Natural Sciences

A plant is kept in continuous darkness for several days. Which process will stop first because it requires light directly?

  1. Glycolysis
  2. Cellular respiration
  3. The light reactions of photosynthesis Correct answer.
  4. The Calvin cycle

Explanation

The light reactions require photons to excite electrons in photosystem pigments, so they cease immediately in darkness. The Calvin cycle can continue briefly using stored ATP and NADPH but eventually stops without their supply.

Question 43Survey of the Natural Sciences

Which property of the cell membrane is best described by the fluid mosaic model?

  1. A rigid, static layer of protein covering the cell.
  2. A solid barrier that prevents all molecular movement.
  3. A dynamic bilayer of phospholipids with embedded proteins that can move laterally. Correct answer.
  4. A single layer of phospholipids with no proteins.

Explanation

The fluid mosaic model describes the plasma membrane as a fluid phospholipid bilayer in which proteins, cholesterol, and glycolipids are embedded and can move laterally. This arrangement allows selective permeability and membrane function.

Question 44Survey of the Natural Sciences

A population of 500 organisms has 50 individuals that are homozygous recessive for a trait. Assuming Hardy-Weinberg equilibrium, what is the approximate frequency of the recessive allele?

  1. 0.32 Correct answer.
  2. 0.90
  3. 0.10
  4. 0.50

Explanation

The frequency of homozygous recessive individuals equals q squared, so q squared = 50/500 = 0.10. Taking the square root gives q, the recessive allele frequency, of about 0.316, or roughly 0.32.

Question 45Survey of the Natural Sciences

Which of the following best explains why the enzyme catalase increases the rate at which hydrogen peroxide is broken down?

  1. It raises the activation energy required for the reaction.
  2. It increases the free energy released by the reaction.
  3. It lowers the activation energy by stabilizing the transition state. Correct answer.
  4. It changes the equilibrium constant of the reaction.

Explanation

Enzymes accelerate reactions by providing a microenvironment that stabilizes the transition state, thereby lowering the activation energy barrier. They do not alter the overall free energy change or the equilibrium position.

Question 46Survey of the Natural Sciences

During which phase of mitosis do sister chromatids separate and move toward opposite poles of the cell?

  1. Anaphase Correct answer.
  2. Prophase
  3. Metaphase
  4. Telophase

Explanation

In anaphase, the cohesin proteins holding sister chromatids together are cleaved, and the chromatids are pulled to opposite poles by shortening spindle microtubules. Each chromatid then becomes an independent chromosome.

Question 47Survey of the Natural Sciences

A patient's blood test shows abnormally low levels of plasma proteins. Which change in capillary exchange is most likely to result?

  1. Increased blood pressure within the capillary bed.
  2. Decreased reabsorption of fluid, leading to fluid accumulation in tissues. Correct answer.
  3. Increased oxygen diffusion across capillary walls.
  4. Increased reabsorption of fluid into capillaries due to higher oncotic pressure.

Explanation

Plasma proteins, especially albumin, generate colloid osmotic (oncotic) pressure that draws fluid back into capillaries. When they are low, this inward pull weakens, so less fluid is reabsorbed and edema can develop.

Question 48Survey of the Natural Sciences

In a pedigree, a trait appears in every generation and affects both males and females, with affected individuals having at least one affected parent. Which mode of inheritance is most consistent with this pattern?

  1. Autosomal dominant Correct answer.
  2. Autosomal recessive
  3. X-linked recessive
  4. Y-linked

Explanation

A trait that appears in every generation and affects both sexes equally, with each affected individual having an affected parent, fits autosomal dominant inheritance. Recessive traits often skip generations, and Y-linked traits affect only males.

Question 49Survey of the Natural Sciences

A respirometer measures that a germinating seed consumes oxygen but produces very little carbon dioxide. Which explanation best accounts for this observation?

  1. The seed is performing only the light reactions of photosynthesis.
  2. The seed is performing anaerobic fermentation producing ethanol.
  3. The seed has stopped cellular respiration entirely.
  4. The seed is using oxygen as a final electron acceptor while retaining carbon in intermediate metabolites. Correct answer.

Explanation

During aerobic respiration oxygen is consumed at the end of the electron transport chain, but some carbon can be retained in biosynthetic intermediates, so oxygen uptake may exceed carbon dioxide release. This is reflected in a respiratory quotient below 1.

Question 50Survey of the Natural Sciences

Which structural feature of the small intestine most directly increases the surface area available for nutrient absorption?

  1. The presence of goblet cells that secrete mucus
  2. The villi and microvilli lining its inner wall Correct answer.
  3. The presence of a muscularis layer for peristalsis
  4. The secretion of hydrochloric acid by its lining

Explanation

Fingerlike villi and the microscopic microvilli on their epithelial cells multiply the absorptive surface area enormously. This arrangement, along with a rich capillary and lacteal network, maximizes nutrient uptake.