The Fundamental Unit of Life Practice Quiz (59 questions)

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A cell is both the basic structural unit and the basic functional unit of living organisms. The organ distractor confuses levels of organization, while the other choices omit either structure or function.

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Hooke observed dead, honeycomb-like cells in cork using his self-designed microscope and described them in *Micrographia*. Pond-water cells are associated with Leeuwenhoek, and the nucleus with Robert Brown.

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Schleiden and Schwann formulated cell theory in 1838 and 1839, respectively. Hooke and Leeuwenhoek are associated with cell observations, while Virchow later expanded the theory and Brown discovered the nucleus.

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Cell theory states that all cells arise from pre-existing cells. Organism composition is a separate principle, and the other choices incorrectly treat cell products or reverse the direction of origin.

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Cell shape mainly depends on the specific function the cell performs, so a signal-transmitting cell may be elongated and branched. The red-blood-cell form is a different example, and organism size does not determine cell shape.

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A unicellular organism consists of one cell that performs all life processes. Multicellular organisms are made of many cells, and the separate-cell choices incorrectly assign multiple cells to this single-celled organism.

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Organism size depends on the number of cells, not the size of individual cells. Larger-cell and different-shape explanations do not fit the stated comparison, while fewer cells would not explain the larger organism.

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Safranin is added after the peel is placed flat on the slide in water; excess stain is then drained before mounting it in glycerine. Methylene blue is used for cheek-cell mounts, while glycerine and examination come later in the onion-peel procedure.

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Onion epidermal cells form regularly arranged linear or rectangular compartments with rigid walls, and the large central vacuole pushes each nucleus towards the periphery. Irregular shapes suggest a different cell appearance, while central nuclei or absence of a vacuole do not match the described onion cells.

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The cheek-cell procedure uses methylene blue, removes extra stain, adds glycerine, places a coverslip, and gently taps it to spread the cells. Safranin belongs to the onion-peel procedure, and the other sequences put stain removal or glycerine in the wrong order.

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A definite cell wall, plastids, and a well-developed vacuole characterize plant cells, whereas animal cells lack a cell wall and plastids. Classifying the cells as animal or cheek cells confuses the stated plant-cell features with animal-cell characteristics.

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The plasma membrane is the flexible boundary that encloses the contents of every living cell. A rigid plant-cell layer is the cell wall, the fluid region is cytoplasm, and genetic material is associated with the nucleus.

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The plasma membrane consists of a phospholipid bilayer and proteins, with carbohydrates making up a small fraction of its organic molecules. The alternatives misidentify the bilayer's main material or reverse which component is present in a small fraction.

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A selectively permeable plasma membrane permits nutrients and essential materials to enter and wastes to leave while regulating specific molecules. Unrestricted passage removes that regulation, reversing the movement of materials confuses their roles, and small gases can diffuse freely rather than being excluded.

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Active transport moves substances against their concentration gradient by using energy. Passive transport and diffusion move substances down a concentration gradient, while endocytosis takes bulk material into the cell.

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Diffusion spreads substances from higher to lower concentration until they are distributed uniformly. Active transport moves against the gradient using energy, osmosis is the net diffusion of water across a permeable membrane, and endocytosis brings bulk material into a cell.

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Respiration consumes oxygen inside the cell, so oxygen diffuses inward from the external medium; carbon dioxide accumulates inside, so it diffuses outward. Reversing either direction ignores the concentration difference created by respiration.

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Osmosis is the net diffusion of water across a permeable membrane toward the region with higher solute concentration. The higher-water-concentration direction is the reverse, and equal movement in both directions would not describe a net movement toward the more concentrated region.

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A hypotonic solution drives water into cells, so an animal cell swells and may burst; the plant cell does not burst because its cell wall provides support. Reversing the outcomes misassigns the protection of the cell wall, while the other choices fail to account for the difference between cell types.

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Cells make up organisms and are where an organism’s life functions reside, so they are both structural and functional units. The tissue-level, function-only, and outside-the-cell alternatives each separate a role that the unit assigns to cells.

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The cell wall is outside the plasma membrane and is freely permeable, while the plasma membrane is selectively permeable. Reversing the order swaps their permeability properties; the central vacuole is not the selectively permeable layer immediately inside the wall.

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In a hypotonic medium, water enters by osmosis and the swelling cell presses against its wall, which pushes back and helps prevent bursting. Water loss describes the opposite direction, and the wall resists pressure rather than causing water uptake or behaving like an absent animal-cell wall.

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Bacterial walls are made of peptidoglycan, plant walls of cellulose, and walls in most fungi of chitin. The alternatives misassign cellulose to bacteria, place chitin in plants, or give bacteria the fungal material.

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Plasmolysis is the shrinkage of a living plant cell’s contents away from its wall after water loss by osmosis. Turgid swelling and endosmosis involve water entering, while mechanical support is a cell-wall function rather than this state.

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In a hypertonic solution, water leaves the central vacuole by exosmosis, causing the protoplasm to separate from the wall; the cell is then plasmolysed. Endosmosis means water enters, and water loss without separation misses the defining change.

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The nucleus is a dense protoplasmic body enclosed by a double membrane, controlling cellular metabolism and containing genetic information. The nucleolus is a component within it, a single-membrane compartment describes a different structure, and freely located genetic material characterizes a prokaryotic nucleoid.

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The nucleus consists of the nuclear envelope, nucleoplasm, nucleolus, and chromatin threads. Cytoplasm lies outside the nucleus, pores are features of the envelope rather than a separate listed component, and the plasma membrane surrounds the cell.

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The nucleus controls metabolism, directs synthesis of structural proteins for growth, participates in ribosome formation, regulates the cell cycle, and carries hereditary information between generations. Ribosomes synthesize proteins, the plasma membrane bounds the cell, and the nucleolus is involved in ribosome formation rather than all these functions.

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Prokaryotes lack a nuclear membrane, and their genetic material lies freely as a nucleoid. Calling the cell eukaryotic or describing its DNA as enclosed by a nuclear envelope reverses this distinction; a cell membrane does not establish that a nuclear membrane is present.

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Cytoplasm is the fluid content inside the plasma membrane and outside the nucleus; it contains cytosol and cell organelles. The nuclear interior is nucleoplasm, cytosol alone does not include the organelles, and material outside the plasma membrane is not cytoplasm.

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Prokaryotic ribosomes are 70S, while eukaryotic ribosomes are 80S; Svedberg units indicate sedimentation coefficient and indirectly reflect density and size. The 80S value identifies eukaryotic ribosomes, and the measurement does distinguish the two types here.

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Rough endoplasmic reticulum bears ribosomes on its outer surface and is mainly composed of cisternae. Smooth ER lacks attached ribosomes and is mainly composed of vesicles and tubules, so either the smooth label or the ribosome-free description conflicts with the observed features.

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Smooth ER helps detoxify many poisons and drugs, whereas rough ER synthesizes proteins. Reversing the ER roles, assigning detoxification to ribosomes, or assigning protein synthesis to smooth ER misplaces these functions.

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The Golgi has a polarity: its convex cis face points toward the nucleus, while its concave trans face points toward the cell membrane. Reversing the faces or assigning either face to the wrong side confuses this orientation.

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The Golgi complex modifies, stores, condenses, and packages materials for cell secretion. ATP production is associated with mitochondria, digestion with lysosomes, and membrane biogenesis is not the stated set of Golgi functions.

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Mitochondria occur in eukaryotic cells except mature mammalian red blood cells, and they are absent from prokaryotes. Assuming all eukaryotes retain them ignores the red-cell exception; assigning them to bacteria confuses prokaryotes with eukaryotes.

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Mitochondria possess their own small circular chromosome, RNA, and 70S ribosomes, enabling them to make some of their own proteins. This does not mean they make every protein they need or every protein the cell requires.

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Cristae increase the mitochondrion's inner surface area and bear F1 particles, or oxysomes, involved in ATP synthesis. Outer-membrane channels serve molecule passage, while the matrix-volume claim does not describe the cristae's role.

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A lysosome is a specialized vesicle bounded by a single membrane and containing hydrolytic enzymes. The double-membrane respiratory organelle is a mitochondrion, while secretory vesicles and the nucleus have different roles and structures.

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Mitochondria are the main sites of cellular respiration, where respiratory substrates are completely oxidized into carbon dioxide and water. Chloroplasts are associated with photosynthesis, while the other choices do not identify the main site described.

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Mitochondrial enzymes enable complete food oxidation and release energy as ATP, which powers chemical synthesis and mechanical work. Pigment storage and sunlight capture are plastid-related functions, while starch formation is not the reason mitochondria are called the powerhouse.

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Plastids are semiautonomous organelles in plant and algal cells that manufacture and store important compounds, including photosynthetic pigments and starch. The respiratory description refers to mitochondria, and storage sacs describe vacuoles.

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Chlorophyll in green plant parts traps solar energy, and chloroplasts contain the enzymes required for photosynthesis. Carotene and xanthophyll are pigments associated with chromoplast coloration, while mitochondria are chiefly involved in cellular respiration.

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A vacuole is a membrane-bound storage sac containing non-living liquid or solid contents. An ATP-producing organelle is a mitochondrion, the vacuole's covering is the tonoplast, and pigment manufacture is associated with plastids.

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Mature plant cells contain a large central vacuole occupying 50–90% of cell volume, whereas animal cells have small vacuoles. The small-vacuole pattern also applies to young plant cells, and animal cells are not described as lacking vacuoles.

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Plant-cell vacuoles contain cell sap that provides turgidity and rigidity, so losing water from the vacuole can reduce firmness. ATP production is associated with mitochondria, while pigment trapping is a chlorophyll function; excretory-product storage is another vacuole role but does not explain the support described.

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Cell division forms new cells for growth, replacement of old or injured cells, and production of gametes. Fertilization joins gametes, tissue differentiation changes cell identity, and DNA replication copies genetic material.

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Mitosis forms two identical daughter cells with the same chromosome number and supports tissue growth and repair. Meiosis forms four cells with half the chromosome number, fertilization joins gametes, and differentiation changes cell specialization.

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Prokaryotes lack a nuclear membrane and nucleoli, and their genetic material lies in a nucleoid region. Eukaryotes have a true nucleus; plant and animal cells are eukaryotic cell types.

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Diffusion is the movement of molecules or ions from a region of higher concentration to one of lower concentration. Osmosis specifically describes water crossing a semipermeable membrane, while filtration and active transport involve different mechanisms.

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Osmosis is the diffusion of water through a semipermeable membrane from a dilute solution to a concentrated solution. Movement in the reverse direction reverses the concentration relationship, while descriptions focused on solute movement do not define osmosis.

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Arun Kumar Sharma developed chromosome study techniques, investigated chromosomes’ roles in plant evolution and classification, proposed ideas about plant speciation, and introduced chromosome dynamism. The other names are associated with different areas of biology or plant science.

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Cancer develops when controls on cell growth and differentiation break down, producing uncontrolled growth and a tumor. Normal tissue repair is a regulated response, programmed cell death reduces cell numbers, and metastasis is the spread of malignant cells.

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Benign tumors generally stay at their original location and tend to cause minimal harm. Malignant tumors invade surrounding tissue, metastatic tumors have spread to distant sites, and localized growth can still be a tumor.

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Metastasis is the spread of malignant tumor cells through the bloodstream to distant body parts, where they form a new tumor. Local invasion affects nearby tissue, primary growth remains at the original site, and biopsy is a diagnostic procedure.

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A biopsy detects cancer by removing suspected tissue for staining and microscopic examination by a pathologist. X-rays, CT, and MRI are imaging methods that help detect cancers inside the body.

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MRT removes the donor egg's nucleus but retains its mitochondria, then inserts the mother's nucleus and fertilizes the reconstructed egg with the father's sperm. The procedure does not replace the donor mitochondria with maternal or paternal mitochondria.

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Small organ models grown from stem cells let researchers study how organs work and test medicines. Gene editing, real-time microscopy, and regenerative treatments are separate advances in cell biology.

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Meiosis involves two consecutive divisions, producing four cells with half the mother's chromosome number; in animals, these cells are gametes. The mitosis error retains 24 chromosomes, the two-cell error overlooks the four products, and the unhalved-number error keeps 24 in each cell.