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CSET Science - Life Sciences (215 & 217) study materials
CSET Science - Life Sciences (215 & 217) study resources

CSET Science - Life Sciences (215 & 217) 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 11Physiology

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 12Microbiology Immunology

Gram-positive bacteria differ structurally from Gram-negative bacteria in their cell wall composition. Which characteristic feature distinguishes Gram-positive bacterial cell walls upon Gram staining?

  1. Thick multi-layered peptidoglycan meshwork retaining crystal violet-iodine complex (purple) Correct answer.
  2. Thin single layer of peptidoglycan enclosed by an outer membrane containing lipopolysaccharide (LPS)
  3. Absence of peptidoglycan, composed entirely of chitin
  4. Lipid envelope derived from host plasma membrane

Explanation

Gram-positive bacteria possess a thick, multi-layered peptidoglycan (murein) cell wall rich in teichoic and lipoteichoic acids. This dense structure dehydrates during alcohol decolorization, trapping the crystal violet-iodine complex and staining purple. Gram-negative cell walls have thin peptidoglycan and an outer LPS membrane (staining pink with safranin).

Question 13Evolution

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 14Ecology

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 15Biological inquiry and interpretation of evidence

A student wants to determine whether the amount of light affects the rate of photosynthesis in elodea. Which variable should the student deliberately change between groups?

  1. The intensity of light reaching each plant Correct answer.
  2. The number of bubbles produced per minute
  3. The species of aquatic plant used
  4. The temperature of the water bath

Explanation

The variable that the experimenter deliberately manipulates is the independent variable. Here the question is whether light affects photosynthesis, so light intensity is changed between groups. Bubble count is the dependent (measured) variable, and species and temperature should be held constant.

Question 16Biological inquiry and interpretation of evidence

Which of the following best describes the purpose of a control group in a controlled experiment?

  1. To provide a baseline for comparison with the experimental treatment Correct answer.
  2. To increase the number of independent variables tested
  3. To guarantee that the hypothesis will be supported
  4. To eliminate the need to repeat the experiment

Explanation

A control group does not receive the experimental treatment and provides a baseline against which the treatment group is compared. This isolates the effect of the independent variable. Without a control, observed differences cannot be attributed to the treatment.

Question 17Biological inquiry and interpretation of evidence

A measurement of 0.00450 kg is recorded. How many significant figures does this value contain?

  1. Three Correct answer.
  2. Two
  3. Four
  4. Five

Explanation

Leading zeros are never significant, while trailing zeros after a decimal point are significant. In 0.00450, the digits 4, 5, and the trailing 0 are significant, giving three significant figures. The leading zeros only set the decimal place.

Question 18Biological inquiry and interpretation of evidence

Which statement best characterizes a scientific theory, such as the theory of evolution?

  1. A well-substantiated explanation supported by a large body of evidence Correct answer.
  2. An untested guess about how something works
  3. A statement that can never be revised
  4. A fact that requires no supporting evidence

Explanation

In science, a theory is a broad, well-supported explanation of natural phenomena backed by extensive evidence from multiple sources. It is not a mere guess, and although robust, it can be refined as new evidence emerges.

Question 19Biological inquiry and interpretation of evidence

Which laboratory safety practice is most important when heating a liquid in a test tube over a flame?

  1. Point the open end of the tube away from yourself and others Correct answer.
  2. Seal the tube tightly before heating
  3. Hold the tube directly with your fingers
  4. Heat the very bottom continuously without moving the tube

Explanation

When heating a liquid in a test tube, always point the open end away from people because superheated liquid can suddenly erupt (bump out). The tube should never be sealed, should be held with a holder, and should be moved gently in the flame to heat evenly.

Question 20Biological inquiry and interpretation of evidence

An engineering design team is solving a problem under a strict cost limit and a weight limit. In engineering terms, these limits are best described as which of the following?

  1. Constraints Correct answer.
  2. Criteria
  3. Prototypes
  4. Hypotheses

Explanation

In the engineering design process, constraints are the limitations a solution must operate within, such as cost, weight, materials, or time. Criteria are the desired qualities used to judge success. Recognizing constraints versus criteria is part of the NGSS engineering design emphasis on the CSET.

Question 21Biological inquiry and interpretation of evidence

Which best describes the relationship between structure and function as a crosscutting concept in the life sciences?

  1. The shape and arrangement of a biological structure often determine how it functions Correct answer.
  2. Structure and function are unrelated in living systems
  3. Function determines structure but never the reverse
  4. Only nonliving systems show structure-function relationships

Explanation

Structure and function are tightly linked across biological scales: the shape of an enzyme's active site, the surface area of alveoli, and the form of a bone all reflect and enable their functions. This crosscutting concept is emphasized throughout the NGSS-aligned framework.

Question 22Biological inquiry and interpretation of evidence

A teacher wants students to model the flow of energy in an ecosystem. Which representation would best illustrate that energy decreases at each successive trophic level?

  1. An energy pyramid Correct answer.
  2. A Punnett square
  3. A pedigree chart
  4. A periodic table

Explanation

An energy pyramid visually represents the decreasing amount of energy available at each higher trophic level, with producers at the wide base and top predators at the narrow apex. This makes the roughly 10 percent energy transfer concept clear to students.

Question 23Chemistry

Which subatomic particle determines the identity (element) of an atom?

  1. The number of protons Correct answer.
  2. The number of neutrons
  3. The number of electrons
  4. The total atomic mass

Explanation

An element is defined by its atomic number, which equals the number of protons in the nucleus. Changing the proton count changes the element. Neutron number creates isotopes, and electron number creates ions, but neither changes the element's identity.

Question 24Chemistry

When table salt (NaCl) forms, a sodium atom transfers an electron to a chlorine atom. What type of bond results?

  1. Ionic bond Correct answer.
  2. Nonpolar covalent bond
  3. Hydrogen bond
  4. Metallic bond

Explanation

When electrons are transferred from a metal to a nonmetal, oppositely charged ions form and attract each other in an ionic bond. Sodium becomes Na+ and chlorine becomes Cl-. Covalent bonds, by contrast, involve sharing electrons rather than transferring them.

Question 25Chemistry

Which of the following is an example of a chemical change rather than a physical change?

  1. Iron rusting when exposed to oxygen and water Correct answer.
  2. Ice melting into liquid water
  3. Salt dissolving in water
  4. A copper wire being bent into a coil

Explanation

A chemical change produces a new substance with different properties. Rusting forms iron oxide, a new compound. Melting, dissolving, and bending are physical changes that alter form or state without producing a new substance.

Question 26Chemistry

On the pH scale, a solution with a pH of 3 is

  1. Acidic, with a higher concentration of hydrogen ions than a neutral solution Correct answer.
  2. Basic, with more hydroxide ions than hydrogen ions
  3. Neutral, with equal hydrogen and hydroxide ions
  4. Impossible because pH cannot be below 7

Explanation

The pH scale runs from 0 to 14; values below 7 are acidic and indicate a higher concentration of hydrogen ions. A pH of 3 is strongly acidic. Because the scale is logarithmic, each unit represents a tenfold change in hydrogen-ion concentration.

Question 27Physics

A cart accelerates when a constant net force is applied. According to Newton's second law, if the mass of the cart is doubled while the same force is applied, the acceleration will be

  1. Halved Correct answer.
  2. Doubled
  3. Unchanged
  4. Quadrupled

Explanation

Newton's second law states F = ma, so acceleration a = F/m. With force constant, acceleration is inversely proportional to mass. Doubling the mass therefore halves the acceleration.

Question 28Physics

Which statement best expresses the law of conservation of energy?

  1. Energy can be transformed from one form to another but is not created or destroyed Correct answer.
  2. Energy is continuously created as systems do work
  3. Energy is destroyed whenever friction is present
  4. Energy can only exist as kinetic energy

Explanation

The law of conservation of energy states that the total energy of an isolated system remains constant; energy changes form but is neither created nor destroyed. For example, friction converts kinetic energy to thermal energy rather than destroying it.

Question 29Earth Sciences

Which process is primarily responsible for the rock cycle transforming igneous rock into sedimentary rock?

  1. Weathering, erosion, deposition, and compaction Correct answer.
  2. Melting and rapid cooling of magma
  3. Heat and pressure deep within the crust without melting
  4. Radioactive decay of mineral grains

Explanation

Sedimentary rock forms when existing rock is broken down by weathering, transported by erosion, deposited in layers, and then compacted and cemented. Melting and cooling form igneous rock, while heat and pressure without melting form metamorphic rock.

Question 30Earth Sciences

The theory of plate tectonics best explains which of the following observations?

  1. The global distribution of earthquakes and volcanoes along plate boundaries Correct answer.
  2. The 24-hour day-night cycle on Earth
  3. The phases of the Moon over a month
  4. The seasonal change in daylight hours

Explanation

Plate tectonics explains how lithospheric plates move and interact, producing earthquakes, volcanoes, mountain ranges, and ocean trenches concentrated at plate boundaries. The day-night cycle, Moon phases, and seasons arise from Earth's rotation and orbital geometry, not tectonics.

Question 31Cell structure, membranes and division

Which feature of the eukaryotic cell is the primary site of aerobic cellular respiration and ATP production?

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

Explanation

The mitochondrion is the organelle where the citric acid cycle and oxidative phosphorylation occur, producing most of a cell's ATP through aerobic respiration. Its folded inner membrane (cristae) increases surface area for the electron transport chain.

Question 32Cell structure, membranes and division

Which structural feature distinguishes a prokaryotic cell from a eukaryotic cell?

  1. The absence of a membrane-bound nucleus Correct answer.
  2. The presence of a plasma membrane
  3. The presence of ribosomes
  4. The presence of DNA

Explanation

Prokaryotic cells lack a membrane-bound nucleus and membrane-bound organelles; their DNA resides in a nucleoid region. Both cell types have a plasma membrane, ribosomes, and DNA, so those features do not distinguish them.

Question 33Cell structure, membranes and division

Which sequence correctly orders the levels of biological organization in a multicellular organism from smallest to largest?

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

Explanation

In multicellular organisms, cells group into tissues, tissues form organs, and organs work together as organ systems. This hierarchy reflects the structure-function organization emphasized in the CSET life science framework.

Question 34Cell structure, membranes and division

Which of the following describes the role of the cell membrane in maintaining homeostasis?

  1. It selectively regulates the movement of substances into and out of the cell Correct answer.
  2. It synthesizes all of the cell's proteins
  3. It stores the cell's genetic information
  4. It generates ATP through respiration

Explanation

The plasma membrane is selectively permeable, controlling which substances enter and leave the cell and thereby maintaining internal homeostasis. Protein synthesis occurs at ribosomes, genetic information is stored in the nucleus, and ATP is generated in mitochondria.

Question 35Cell structure, membranes and division

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

  1. Water will leave the cell, causing it to shrink (crenate) Correct answer.
  2. Water will enter the cell, causing it to swell and burst
  3. There will be no net movement of water
  4. Salt will be actively pumped into the cell

Explanation

In a hypertonic solution, the surrounding fluid has a higher solute concentration than the cell interior, so water moves out of the cell by osmosis. A red blood cell loses water and shrinks, a process called crenation.

Question 36Cell structure, membranes and division

Which type of cellular transport requires the cell to expend energy in the form of ATP?

  1. Active transport against a concentration gradient Correct answer.
  2. Simple diffusion of oxygen across the membrane
  3. Osmosis of water through aquaporins
  4. Facilitated diffusion of glucose down its gradient

Explanation

Active transport moves substances against their concentration gradient, from low to high concentration, and therefore requires energy from ATP, as in the sodium-potassium pump. Simple diffusion, osmosis, and facilitated diffusion are passive and move substances down their gradients without ATP.

Question 37Cell structure, membranes and division

Which process produces genetically identical daughter cells for growth and repair in body tissues?

  1. Mitosis Correct answer.
  2. Meiosis
  3. Binary fission in eukaryotes
  4. Fertilization

Explanation

Mitosis divides a cell into two daughter cells with the same chromosome number and genetic content as the parent, supporting growth, tissue repair, and asexual reproduction. Meiosis produces genetically varied haploid gametes, and fertilization combines gametes.

Question 38Cell structure, membranes and division

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 centromeres split and sister chromatids are pulled apart by spindle fibers toward opposite poles, ensuring each daughter cell receives a complete chromosome set. Prophase condenses chromosomes, metaphase aligns them, and telophase reforms nuclei.

Question 39Cell structure, membranes and division

Which of the following best explains why meiosis is important for sexually reproducing organisms?

  1. It halves the chromosome number so fertilization restores the diploid number Correct answer.
  2. It doubles the chromosome number in each gamete
  3. It produces identical clones of the parent cell
  4. It eliminates all genetic variation among offspring

Explanation

Meiosis reduces the chromosome number from diploid to haploid in gametes, so that fertilization restores the normal diploid number in offspring. It also generates genetic variation through crossing over and independent assortment.

Question 40Cell structure, membranes and division

The cell theory includes all of the following principles EXCEPT:

  1. Cells arise spontaneously from nonliving matter Correct answer.
  2. All living things are composed of one or more cells
  3. The cell is the basic unit of structure and function in organisms
  4. All cells come from preexisting cells

Explanation

The cell theory states that all living things are made of cells, the cell is the basic unit of life, and all cells arise from preexisting cells. Spontaneous generation from nonliving matter was disproven and is not part of the cell theory.

Question 41Cell structure, membranes and division

Which of the following correctly distinguishes mitosis from meiosis?

  1. Mitosis produces two diploid cells; meiosis produces four haploid cells Correct answer.
  2. Mitosis produces four haploid cells; meiosis produces two diploid cells
  3. Both processes produce genetically varied gametes
  4. Both processes occur only in reproductive organs

Explanation

Mitosis produces two genetically identical diploid daughter cells used for growth and repair, while meiosis produces four genetically varied haploid cells used as gametes. Meiosis involves two divisions and includes crossing over and independent assortment.

Question 42Metabolism

During the light-dependent reactions of photosynthesis, water molecules are split. This process directly provides which of the following?

  1. Electrons and oxygen gas Correct answer.
  2. Glucose and carbon dioxide
  3. ATP from the citric acid cycle
  4. Carbon fixed into organic molecules

Explanation

In the light-dependent reactions, photolysis splits water, releasing electrons that replenish photosystem II and producing oxygen gas as a byproduct. Glucose and carbon fixation occur later in the Calvin cycle, which uses the ATP and NADPH generated by the light reactions.

Question 43Metabolism

In glycolysis, a glucose molecule is broken down in the cytoplasm. What are the direct products of glycolysis?

  1. Two pyruvate molecules, a net of two ATP, and two NADH Correct answer.
  2. Six carbon dioxide molecules and water
  3. Thirty-eight ATP and oxygen
  4. Glucose and lactic acid only

Explanation

Glycolysis splits one six-carbon glucose into two three-carbon pyruvate molecules, yielding a net gain of two ATP and two NADH in the cytoplasm. It does not require oxygen and precedes the citric acid cycle in aerobic respiration.

Question 44Metabolism

Which structure in plant cells contains chlorophyll and is the site of photosynthesis?

  1. Chloroplast Correct answer.
  2. Vacuole
  3. Nucleus
  4. Mitochondrion

Explanation

Chloroplasts contain chlorophyll, the green pigment that absorbs light energy, and are the site of photosynthesis in plant and algal cells. Vacuoles store materials, the nucleus houses DNA, and mitochondria carry out cellular respiration.

Question 45Metabolism

Which of the following correctly describes the role of ATP in cells?

  1. It serves as the primary short-term energy currency that powers cellular work Correct answer.
  2. It stores long-term genetic information
  3. It forms the structural backbone of cell membranes
  4. It directly catalyzes all metabolic reactions

Explanation

Adenosine triphosphate (ATP) is the cell's main energy currency; energy released by breaking its high-energy phosphate bonds powers active transport, muscle contraction, and biosynthesis. It is continually regenerated through cellular respiration.

Question 46Biochemistry

An enzyme lowers the activation energy of a reaction. Which statement about enzymes is correct?

  1. Enzymes are not consumed and can catalyze many reaction cycles Correct answer.
  2. Enzymes change the overall energy released by the reaction
  3. Enzymes work best at any temperature equally
  4. Enzymes permanently bind to their substrates

Explanation

Enzymes are biological catalysts that lower activation energy and are regenerated after each reaction, so a single enzyme molecule can catalyze many cycles. They do not alter the net free-energy change of the reaction, and each has an optimal temperature and pH.

Question 47Biochemistry

Which macromolecule serves as the primary structural component of plant cell walls?

  1. Cellulose, a polysaccharide Correct answer.
  2. Cholesterol, a lipid
  3. Hemoglobin, a protein
  4. Glycogen, a polysaccharide

Explanation

Plant cell walls are made primarily of cellulose, a polysaccharide of glucose units linked by beta bonds that provide rigidity and structural support. Glycogen is an animal storage carbohydrate, cholesterol is a membrane lipid, and hemoglobin is an oxygen-transport protein.

Question 48Biochemistry

Proteins are polymers built from which type of monomer?

  1. Amino acids joined by peptide bonds Correct answer.
  2. Nucleotides joined by phosphodiester bonds
  3. Monosaccharides joined by glycosidic bonds
  4. Fatty acids joined to glycerol

Explanation

Proteins are chains of amino acids linked by peptide bonds formed through dehydration synthesis. The sequence of amino acids determines the protein's folding and function. Nucleotides build nucleic acids, monosaccharides build carbohydrates, and fatty acids with glycerol form fats.

Question 49Biochemistry

Why is liquid water essential to life as it functions in living cells?

  1. It is a versatile solvent that dissolves many substances and supports biochemical reactions Correct answer.
  2. It cannot dissolve any ionic compounds
  3. It is chemically inert and never participates in reactions
  4. It exists only as a gas at biological temperatures

Explanation

Water's polarity makes it an excellent solvent for ions and polar molecules, allowing the biochemical reactions of metabolism to occur in solution. Water also participates directly in reactions such as hydrolysis and helps regulate temperature.

Question 50Physiology

In the human respiratory system, gas exchange between air and blood occurs primarily in which structures?

  1. The alveoli of the lungs Correct answer.
  2. The bronchi
  3. The trachea
  4. The diaphragm

Explanation

The alveoli are tiny air sacs surrounded by capillaries where oxygen diffuses into the blood and carbon dioxide diffuses out. Their thin walls and enormous combined surface area make them the site of gas exchange. The trachea and bronchi conduct air, and the diaphragm drives ventilation.