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NY Regents Life Science: Biology study materials
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NY Regents Life Science: Biology practice questions

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Question 1Structure and Function of Cells and Organisms

A student observes a cell under a microscope and notes a rigid outer layer that provides shape and support. Which structure is being described?

  1. Nuclear envelope
  2. Cell membrane
  3. Cell wall Correct answer.
  4. Golgi apparatus

Explanation

The cell wall is a rigid structure outside the plasma membrane that gives shape, support, and protection, and is found in plant cells, fungi, and many bacteria. The other listed structures are membranes or organelles that do not provide rigid structural support.

Question 2Structure and Function of Cells and Organisms

Which organelle is the primary site of ATP production in a typical eukaryotic cell?

  1. Ribosome
  2. Lysosome
  3. Smooth endoplasmic reticulum
  4. Mitochondrion Correct answer.

Explanation

Mitochondria carry out cellular respiration, using the electron transport chain and chemiosmosis to produce most of the cell's ATP. Ribosomes build proteins, lysosomes digest materials, and smooth ER synthesizes lipids.

Question 3Structure and Function of Cells and Organisms

A plant cell is placed in a hypotonic solution. Which observation best reflects the expected water movement and its consequence?

  1. Water moves equally in both directions, and the cell becomes flaccid.
  2. Water leaves the central vacuole, and the cell shrinks away from the wall.
  3. Water enters the cell, and the cell membrane ruptures immediately.
  4. Water enters the cell, and turgor pressure increases against the cell wall. Correct answer.

Explanation

In a hypotonic solution, water moves by osmosis into the cell down its concentration gradient. In plant cells, the rigid cell wall resists expansion, so turgor pressure rises and the cell becomes turgid rather than bursting.

Question 4Structure and Function of Cells and Organisms

Which statement best describes the function of the cell membrane in maintaining homeostasis?

  1. It permanently fuses with the nucleus to share genetic material.
  2. It selectively controls the movement of materials into and out of the cell. Correct answer.
  3. It permits all dissolved substances to cross freely at equal rates.
  4. It synthesizes ATP for active transport using embedded ribosomes.

Explanation

The plasma membrane is selectively permeable, using phospholipids, channels, pumps, and carriers to regulate which substances enter or leave. This regulation keeps internal conditions stable relative to the environment.

Question 5Structure and Function of Cells and Organisms

A researcher treats a cell with a drug that blocks ATP synthesis. Which transport process would be affected most directly?

  1. Osmosis of water through aquaporins
  2. Sodium-potassium pump moving ions against their gradient Correct answer.
  3. Facilitated diffusion of glucose down its concentration gradient
  4. Simple diffusion of oxygen across the bilayer

Explanation

The sodium-potassium pump is active transport, which requires ATP hydrolysis to move ions against their concentration gradient. Diffusion, osmosis, and facilitated diffusion are passive and do not directly require ATP.

Question 6Structure and Function of Cells and Organisms

Which pair of organelles is most directly involved in the production and secretion of a digestive enzyme from a pancreatic cell?

  1. Smooth endoplasmic reticulum and peroxisome
  2. Nucleus and lysosome
  3. Mitochondrion and central vacuole
  4. Rough endoplasmic reticulum and Golgi apparatus Correct answer.

Explanation

Secretory proteins are synthesized on ribosomes attached to the rough ER, then modified, sorted, and packaged in the Golgi apparatus before being released in vesicles. This pathway is the standard secretory route.

Question 7Structure and Function of Cells and Organisms

In a laboratory simulation, a cell with a solute concentration of 2% is placed in a solution with a solute concentration of 8%. Which prediction is most accurate?

  1. Solutes move into the cell until concentrations equalize.
  2. No net movement occurs because the cell is isotonic to the solution.
  3. Water enters the cell, causing it to swell.
  4. Water leaves the cell, causing it to shrink. Correct answer.

Explanation

The surrounding solution has a higher solute concentration, making it hypertonic to the cell. Water moves by osmosis from the lower-solute interior to the higher-solute exterior, so the cell loses water and shrinks.

Question 8Structure and Function of Cells and Organisms

Which level of biological organization is correctly ordered from simplest to most complex?

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

Explanation

In multicellular organisms, similar cells form tissues, tissues form organs, and organs work together in organ systems. This hierarchy reflects increasing complexity.

Question 9Structure and Function of Cells and Organisms

Which feature distinguishes prokaryotic cells from eukaryotic cells?

  1. Prokaryotic cells lack a plasma membrane.
  2. Prokaryotic cells lack a membrane-bound nucleus. Correct answer.
  3. Prokaryotic cells contain no ribosomes.
  4. Prokaryotic cells contain multiple linear chromosomes.

Explanation

Prokaryotes keep their genetic material in a nucleoid region without a membrane-bound nucleus, while eukaryotes enclose DNA in a nucleus. Both cell types have a plasma membrane and ribosomes.

Question 10Structure and Function of Cells and Organisms

A cell is exposed to a poison that prevents the formation of vesicles from the Golgi apparatus. Which outcome is most likely?

  1. DNA replication would stop immediately.
  2. ATP production in mitochondria would increase sharply.
  3. Proteins would be synthesized but not efficiently delivered to their destinations. Correct answer.
  4. The cell membrane would dissolve completely.

Explanation

Golgi-derived vesicles carry modified proteins to the plasma membrane or other destinations. If vesicle formation is blocked, proteins can still be made but cannot be properly transported and delivered.

Question 11Structure and Function of Cells and Organisms

Which molecule serves as the main structural component of the cell membrane's bilayer?

  1. Glycogen
  2. Phospholipid Correct answer.
  3. Nucleic acid
  4. Starch

Explanation

Phospholipids arrange in a bilayer with hydrophilic heads facing the aqueous environments and hydrophobic tails facing inward. This organization forms the basic framework of the membrane.

Question 12Structure and Function of Cells and Organisms

A freshwater paramecium lives in a hypotonic environment and must continuously remove excess water. Which structure performs this function?

  1. Contractile vacuole Correct answer.
  2. Nucleolus
  3. Cell wall
  4. Chloroplast

Explanation

The contractile vacuole collects excess water entering by osmosis and expels it, preventing the cell from bursting. This osmoregulation is common in freshwater protists.

Question 13Structure and Function of Cells and Organisms

Which statement correctly describes the relationship between surface area and volume in cell size?

  1. As a cell grows larger, its surface area-to-volume ratio decreases, limiting efficient exchange. Correct answer.
  2. As a cell grows larger, its surface area-to-volume ratio increases, improving exchange.
  3. Surface area and volume increase at the same rate as cells grow.
  4. Cell size has no relationship to the efficiency of material exchange.

Explanation

Volume increases faster than surface area as a cell enlarges, so the surface area-to-volume ratio falls. A lower ratio limits the membrane's ability to supply the interior with nutrients and remove wastes efficiently.

Question 14Structure and Function of Cells and Organisms

Which organelle contains hydrolytic enzymes and functions in the digestion of worn-out organelles?

  1. Mitochondrion
  2. Lysosome Correct answer.
  3. Ribosome
  4. Nucleus

Explanation

Lysosomes are acidic vesicles containing hydrolytic enzymes that break down macromolecules and recycle damaged organelles through autophagy. They function as the cell's digestive and recycling centers.

Question 15Structure and Function of Cells and Organisms

A student examines tissue from a plant leaf and finds cells with many chloroplasts. Which function is most directly supported by this observation?

  1. Active transport of sodium ions
  2. Rapid breakdown of hydrogen peroxide
  3. Synthesis of steroid hormones
  4. Conversion of light energy into chemical energy Correct answer.

Explanation

Chloroplasts contain chlorophyll and carry out photosynthesis, converting light energy into chemical energy stored in glucose. A high chloroplast number reflects a strong photosynthetic role.

Question 16Structure and Function of Cells and Organisms

In a controlled experiment, red blood cells are placed in distilled water and in a 0.9% salt solution. Which result is expected?

  1. Cells remain unchanged in both solutions.
  2. Cells swell and may burst in distilled water; cells remain normal in 0.9% salt solution. Correct answer.
  3. Cells burst in both solutions.
  4. Cells shrink in distilled water; cells swell in 0.9% salt solution.

Explanation

Distilled water is hypotonic to red blood cells, so water enters and the cells swell and may lyse. The 0.9% salt solution is isotonic to blood cells, so water movement is balanced and cells keep their normal shape.

Question 17Structure and Function of Cells and Organisms

Which structure allows materials to pass between adjacent plant cells through pores in their cell walls?

  1. Plasmodesmata Correct answer.
  2. Cilia
  3. Tight junctions
  4. Desmosomes

Explanation

Plasmodesmata are channels that pass through plant cell walls and connect the cytoplasm of neighboring cells, enabling transport and communication. Desmosomes and tight junctions are animal cell junctions.

Question 18Structure and Function of Cells and Organisms

A mutation prevents a carrier protein from changing shape. Which type of transport is most likely disrupted?

  1. Facilitated diffusion of ions through the carrier Correct answer.
  2. Movement of gases across the membrane
  3. Simple diffusion of small nonpolar molecules
  4. Osmosis of water through the lipid bilayer

Explanation

Carrier proteins must change shape to move their specific solutes across the membrane, so a shape-change defect blocks carrier-mediated transport such as facilitated diffusion. Simple diffusion and osmosis through the bilayer do not depend on carrier shape changes.

Question 19Structure and Function of Cells and Organisms

Which statement best explains why enzymes are described as biological catalysts?

  1. They lower the activation energy of a reaction without being consumed. Correct answer.
  2. They increase the activation energy so reactions proceed more slowly.
  3. They are permanently altered after each reaction they catalyze.
  4. They provide energy directly to reactants to force reactions.

Explanation

Enzymes speed up reactions by lowering the activation energy required, and they are not consumed or permanently altered in the process. They do not supply energy to reactants.

Question 20Structure and Function of Cells and Organisms

At high temperatures, an enzyme's reaction rate decreases sharply. Which explanation best accounts for this observation?

  1. The activation energy of the reaction increases permanently.
  2. The enzyme becomes more specific and binds more substrates.
  3. The substrate concentration increases, slowing the reaction.
  4. The enzyme denatures, changing its active site shape so substrates no longer bind. Correct answer.

Explanation

High temperatures disrupt hydrogen bonds and other interactions that maintain an enzyme's tertiary structure. Denaturation distorts the active site, preventing substrate binding and lowering reaction rate.

Question 21Structure and Function of Cells and Organisms

A cell is placed in a solution containing a substance that dissolves easily in lipids. Which route will this substance most likely take across the membrane?

  1. Endocytosis through vesicle formation
  2. Facilitated diffusion through a large protein channel
  3. Direct diffusion through the phospholipid bilayer Correct answer.
  4. Active transport by a sodium-potassium pump

Explanation

Small nonpolar and lipid-soluble molecules can dissolve in and diffuse directly through the hydrophobic core of the phospholipid bilayer. They do not require pumps or channels.

Question 22Structure and Function of Cells and Organisms

Which comparison of plant and animal cells is accurate?

  1. Animal cells contain chloroplasts; plant cells lack chloroplasts.
  2. Plant cells have a large central vacuole and chloroplasts; animal cells typically lack these structures. Correct answer.
  3. Plant cells lack mitochondria; animal cells contain mitochondria.
  4. Animal cells have cell walls; plant cells lack cell walls.

Explanation

Mature plant cells typically have a large central vacuole and chloroplasts, which animal cells lack. Both cell types have mitochondria, and only plant cells have cell walls.

Question 23Structure and Function of Cells and Organisms

A scientist measures the rate of diffusion of a dye through a gel at different temperatures. The rate increases as temperature rises. Which explanation is most consistent with these results?

  1. Higher temperature reduces molecular collisions, allowing faster spreading.
  2. Higher temperature increases molecular kinetic energy, so particles move and spread faster. Correct answer.
  3. Higher temperature increases the gel's resistance, speeding particle movement.
  4. Higher temperature decreases the concentration gradient, driving faster diffusion.

Explanation

Diffusion depends on the random motion of particles; raising temperature increases kinetic energy and collision frequency, so net spreading occurs faster. The concentration gradient itself is not created by temperature.

Question 24Structure and Function of Cells and Organisms

Which process allows a white blood cell to engulf a bacterium and bring it into the cell?

  1. Phagocytosis Correct answer.
  2. Simple diffusion
  3. Osmosis
  4. Exocytosis

Explanation

Phagocytosis is a form of endocytosis in which the cell membrane extends around a particle and encloses it in a vesicle. White blood cells use this to ingest and destroy bacteria.

Question 25Structure and Function of Cells and Organisms

A cell's mitochondria are damaged and cannot carry out oxidative phosphorylation. Which process would be most severely affected?

  1. Packaging of proteins in the Golgi apparatus
  2. Replication of DNA in the nucleus
  3. Movement of water through aquaporins
  4. Production of most ATP needed for active transport Correct answer.

Explanation

Oxidative phosphorylation in mitochondria produces most of the ATP used for energy-requiring processes such as active transport. Without it, ATP supply falls and those processes suffer most.

Question 26Structure and Function of Cells and Organisms

A student views a wet-mount slide of onion epidermis and a slide of human cheek cells under the same microscope. Which structure would be visible in the onion cells but absent in the cheek cells?

  1. Cytoplasm
  2. Nucleus
  3. Cell membrane
  4. Rigid cell wall Correct answer.

Explanation

Plant cells secrete a rigid cellulose cell wall outside the plasma membrane, which gives the onion cells their boxlike shape. Cheek cells are animal cells, so they lack a cell wall while still possessing a membrane, nucleus, and cytoplasm.

Question 27Structure and Function of Cells and Organisms

A cell biologist treats a specimen with a stain that binds specifically to DNA. Which organelle would be most strongly labeled in a eukaryotic cell?

  1. Golgi apparatus
  2. Lysosome
  3. Smooth endoplasmic reticulum
  4. Nucleus Correct answer.

Explanation

The nucleus houses the cell's chromosomal DNA, so a DNA-binding stain concentrates there. The Golgi apparatus, lysosomes, and smooth ER are membrane-bound organelles that do not store the genetic material.

Question 28Structure and Function of Cells and Organisms

Which structure controls which substances enter and leave a cell while also serving as the site of many metabolic reactions?

  1. Nuclear envelope
  2. Cell membrane Correct answer.
  3. Vacuole
  4. Ribosome

Explanation

The cell membrane is selectively permeable and regulates transport into and out of the cell. Embedded proteins also carry out reactions such as electron transport and signal reception, making it metabolically active.

Question 29Structure and Function of Cells and Organisms

A muscle cell has a very high demand for ATP during contraction. Which organelle would be most abundant in the cytoplasm of this cell?

  1. Mitochondrion Correct answer.
  2. Central vacuole
  3. Chloroplast
  4. Cell wall

Explanation

Mitochondria carry out aerobic respiration and produce most of the ATP used for muscle contraction. Chloroplasts, central vacuoles, and cell walls are plant structures not responsible for ATP supply in muscle.

Question 30Structure and Function of Cells and Organisms

Which statement describes the role of ribosomes in a cell?

  1. They assemble amino acids into polypeptide chains. Correct answer.
  2. They copy DNA into messenger RNA.
  3. They package proteins into vesicles for export.
  4. They break down fatty acids for energy.

Explanation

Ribosomes translate messenger RNA and join amino acids into polypeptides. Packaging into vesicles is a Golgi function, fatty acid breakdown occurs in mitochondria and peroxisomes, and transcription to mRNA happens in the nucleus.

Question 31Structure and Function of Cells and Organisms

A single-celled organism is observed moving and capturing food using extensions of its cytoplasm. Which structure is responsible for this movement?

  1. Cilia
  2. Pseudopods Correct answer.
  3. Microvilli
  4. Flagella

Explanation

Pseudopods are temporary projections of cytoplasm used by amoebas for locomotion and engulfing food. Cilia and flagella are whip-like appendages, and microvilli increase surface area for absorption rather than movement.

Question 32Structure and Function of Cells and Organisms

Which process allows a cell to take in large particles by folding its membrane around the material and forming a vesicle?

  1. Exocytosis
  2. Osmosis
  3. Endocytosis Correct answer.
  4. Facilitated diffusion

Explanation

Endocytosis engulfs material when the plasma membrane invaginates and pinches off a vesicle. Exocytosis releases material, while osmosis and facilitated diffusion move individual molecules or water across the membrane without vesicles.

Question 33Structure and Function of Cells and Organisms

Which body system is primarily responsible for exchanging oxygen and carbon dioxide between the blood and the environment?

  1. Digestive system
  2. Skeletal system
  3. Respiratory system Correct answer.
  4. Endocrine system

Explanation

The respiratory system provides surfaces where gases diffuse between air and blood across thin, moist membranes. The digestive, endocrine, and skeletal systems handle nutrient absorption, chemical signaling, and support respectively.

Question 34Structure and Function of Cells and Organisms

A plant wilts on a hot day because water is lost from its cells faster than it is replaced. Which organelle's shrinking most directly accounts for the loss of stiffness in the cells?

  1. Central vacuole Correct answer.
  2. Ribosome
  3. Golgi apparatus
  4. Nucleus

Explanation

The central vacuole stores water and presses outward against the cell wall, producing turgor pressure that keeps plant tissue firm. When water is lost, the vacuole shrinks and turgor pressure falls, causing wilting.

Question 35Structure and Function of Cells and Organisms

An epithelial cell lining the small intestine has thousands of microscopic folds on its surface. Which function do these folds most directly enhance?

  1. Absorption of nutrients Correct answer.
  2. Synthesis of DNA
  3. Storage of water
  4. Production of ATP

Explanation

Folds such as microvilli increase the surface area of the membrane, allowing more nutrients to be absorbed across it. DNA synthesis, water storage, and ATP production depend on the nucleus, vacuoles, and mitochondria rather than on surface folding.

Question 36Structure and Function of Cells and Organisms

A drug prevents the sodium-potassium pump from hydrolyzing ATP. Which immediate effect would this have on the cell?

  1. Water would no longer cross the membrane by osmosis.
  2. Active transport of sodium and potassium ions would stop. Correct answer.
  3. Glucose would be unable to enter by facilitated diffusion.
  4. Simple diffusion of oxygen would stop.

Explanation

The sodium-potassium pump is an active transport protein that uses ATP energy to move ions against their concentration gradients. Without ATP hydrolysis, this pumping stops, but passive processes such as oxygen diffusion, osmosis, and facilitated diffusion continue.

Question 37Structure and Function of Cells and Organisms

A cell is placed in a hypertonic solution. Which prediction about water movement is most accurate?

  1. Water will leave the cell, causing it to shrink. Correct answer.
  2. Water will move equally in both directions.
  3. Water will stop moving across the membrane.
  4. Water will enter the cell, causing it to swell.

Explanation

In a hypertonic solution the solute concentration outside is higher, so water diffuses outward by osmosis. The net loss of water reduces cell volume and causes shrinking.

Question 38Structure and Function of Cells and Organisms

An enzyme that normally functions in the stomach has an optimal pH near 2. If the enzyme is moved to a solution at pH 7, what is the most likely result?

  1. The enzyme begins to synthesize ATP.
  2. The enzyme's shape changes and its activity decreases. Correct answer.
  3. The enzyme's activity increases sharply.
  4. The enzyme permanently becomes a substrate.

Explanation

Each enzyme has an optimal pH, and extreme shifts alter the ionization of amino acids in the active site, changing shape and reducing activity. A stomach enzyme moved to neutral pH is outside its optimum and loses efficiency.

Question 39Structure and Function of Cells and Organisms

In a reaction, a molecule that closely resembles the substrate binds to the enzyme's active site but is not converted to product. What effect does this molecule have?

  1. It raises the activation energy of the reaction.
  2. It permanently denatures the enzyme.
  3. It competes with the substrate and slows the reaction. Correct answer.
  4. It increases the concentration of the substrate.

Explanation

A molecule resembling the substrate can occupy the active site and block the real substrate from binding, which is competitive inhibition. This reduces the reaction rate without denaturing the enzyme or changing substrate concentration.

Question 40Structure and Function of Cells and Organisms

A scientist measures the rate of an enzyme-catalyzed reaction while increasing substrate concentration. The rate rises and then levels off. What best explains the plateau?

  1. The temperature of the reaction has fallen to zero.
  2. All active sites of the enzyme are occupied. Correct answer.
  3. The substrate has become a competitive inhibitor.
  4. The enzyme has been completely used up.

Explanation

At high substrate concentration every enzyme active site is saturated, so adding more substrate cannot increase the number of reactions per unit time. The plateau reflects enzyme saturation, not enzyme consumption.

Question 41Structure and Function of Cells and Organisms

A cell is treated with a chemical that blocks the function of the rough endoplasmic reticulum. Which process would be most directly impaired?

  1. Replication of chromosomal DNA
  2. Production of proteins destined for secretion Correct answer.
  3. Breakdown of hydrogen peroxide
  4. Formation of the spindle apparatus

Explanation

The rough ER has ribosomes on its surface and folds and modifies proteins that will be secreted or sent to other organelles. DNA replication, peroxide breakdown, and spindle formation occur in the nucleus, peroxisomes, and centrosomes respectively.

Question 42Structure and Function of Cells and Organisms

A mutation changes a channel protein so that it stays permanently open. Which consequence is most likely for the cell?

  1. Ions will pass through the membrane without regulation. Correct answer.
  2. The cell wall will thicken in response to the change.
  3. The membrane will become completely impermeable to water.
  4. The cell will lose its ability to make proteins.

Explanation

Channel proteins normally open and close to control ion movement; a permanently open channel allows ions to flow uncontrolled and disrupts gradients. Protein synthesis and water permeability are governed by other structures.

Question 43Structure and Function of Cells and Organisms

A researcher compares a prokaryotic cell and a eukaryotic cell. Which feature would be found in both?

  1. Endoplasmic reticulum
  2. Nuclear envelope
  3. Ribosomes Correct answer.
  4. Membrane-bound mitochondria

Explanation

Ribosomes are present in all cells because both prokaryotes and eukaryotes must translate mRNA into proteins. A nuclear envelope, mitochondria, and endoplasmic reticulum are membrane-bound features limited to eukaryotes.

Question 44Structure and Function of Cells and Organisms

A cell that secretes large amounts of a protein hormone would be expected to contain an especially extensive network of which organelle?

  1. Lysosome
  2. Peroxisome
  3. Rough endoplasmic reticulum Correct answer.
  4. Smooth endoplasmic reticulum

Explanation

Cells that export proteins need abundant rough ER, where ribosomes synthesize the protein and the membrane folds it for transport. Lysosomes, smooth ER, and peroxisomes handle digestion, lipid metabolism, and detoxification rather than protein export.

Question 45Structure and Function of Cells and Organisms

A single-celled freshwater organism with a contractile vacuole is placed in a solution that is isotonic to its cytoplasm. What happens to the activity of the contractile vacuole?

  1. It decreases because water no longer enters the cell by net osmosis. Correct answer.
  2. It stops permanently because the vacuole is destroyed.
  3. It increases because the cell is now losing water rapidly.
  4. It reverses direction and begins taking in water.

Explanation

In a hypotonic environment water enters continuously and the contractile vacuole must pump it out. In an isotonic solution there is no net water influx, so the vacuole's pumping activity declines.

Question 46Structure and Function of Cells and Organisms

Two cells have the same volume, but cell A is spherical and cell B is long and thin. Which statement best predicts their relative efficiency of diffusion?

  1. Cell A exchanges materials more efficiently because its shape is more compact.
  2. Cell B exchanges materials more efficiently because it has a greater surface area to volume ratio. Correct answer.
  3. Both cells exchange materials at identical rates because their volumes are equal.
  4. Neither cell can exchange materials because diffusion requires a flat surface.

Explanation

Exchange efficiency depends on the ratio of surface area to volume. An elongated, thin shape provides more membrane surface relative to its volume than a compact sphere of the same volume, so diffusion meets the cell's needs more easily.

Question 47Structure and Function of Cells and Organisms

A toxin inserts into the inner mitochondrial membrane and makes it freely permeable to protons. What is the most direct consequence for ATP production?

  1. Glycolysis can no longer occur in the cytoplasm.
  2. The cell's DNA can no longer be replicated.
  3. The proton gradient is lost, so ATP synthesis decreases. Correct answer.
  4. The Krebs cycle stops producing carbon dioxide.

Explanation

ATP synthase relies on a proton gradient across the inner mitochondrial membrane to generate ATP. If protons leak through the membrane, the gradient dissipates and oxidative phosphorylation produces far less ATP.

Question 48Structure and Function of Cells and Organisms

An enzyme is exposed to a heavy-metal ion that binds to a site away from the active site and changes the enzyme's overall shape. Which description best fits this effect?

  1. Increased enzyme activity due to a cofactor
  2. Reversible denaturation caused by high temperature
  3. Competitive inhibition that blocks the active site directly
  4. Noncompetitive inhibition that alters the active site indirectly Correct answer.

Explanation

Binding at a site other than the active site changes the enzyme's conformation so the substrate no longer fits well, which is noncompetitive inhibition. Competitive inhibitors instead occupy the active site itself.

Question 49Structure and Function of Cells and Organisms

A cell is engineered so that its lysosomes cannot fuse with vesicles carrying engulfed bacteria. What outcome is most likely?

  1. Digestion of the engulfed bacteria will be impaired. Correct answer.
  2. The cell membrane will lose its selective permeability.
  3. The bacteria will be exported from the cell by exocytosis.
  4. The cell will begin producing chloroplasts.

Explanation

After endocytosis, a vesicle containing the bacterium must fuse with a lysosome so hydrolytic enzymes can digest it. If fusion is blocked, the bacteria remain undigested inside the cell.

Question 50Structure and Function of Cells and Organisms

A plant cell is placed in a strongly hypertonic solution. Which description best predicts what happens to the membrane and vacuole?

  1. The cell wall dissolves and the cell loses its shape.
  2. The cell absorbs solutes until it becomes turgid again.
  3. The vacuole shrinks and the membrane pulls away from the cell wall. Correct answer.
  4. The vacuole swells and presses the membrane tightly against the wall.

Explanation

In a hypertonic solution water leaves the vacuole by osmosis, so the vacuole shrinks and the plasma membrane detaches from the cell wall in a process called plasmolysis. Swelling and turgor occur in hypotonic conditions.