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General Biology: Cell Structure and Function

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  • What are the four basic features shared by all cells?

    Plasma membrane, cytosol, chromosomes, and ribosomes.

  • State the three principles of Cell Theory.

    1. All living organisms are composed of one or more cells.
    2. The cell is the basic unit of structure and organization.
    3. Cells arise only from pre-existing cells.

  • Why are most cells small in size?

    Smaller cells have a higher surface-area-to-volume ratio, allowing efficient exchange of nutrients and wastes across the plasma membrane.

  • Compare prokaryotic and eukaryotic cells in terms of nucleus and organelles.

    Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have a nucleus and membrane-bound organelles like ER and mitochondria.

  • What structures are unique to plant cells compared to animal cells?

    Cell wall (cellulose), chloroplasts, and a large central vacuole.

  • Describe the plasma membrane's structure and function.

    A phospholipid bilayer with embedded proteins that controls entry and exit of substances, maintaining the cell's internal environment.

  • What is the function of the nucleus in eukaryotic cells?

    Houses DNA, controls gene expression, and is the site of ribosomal RNA synthesis in the nucleolus.

  • Differentiate between free and bound ribosomes.

    Free ribosomes synthesize proteins for cytosol; bound ribosomes make proteins for secretion or membranes.

  • Why do eukaryotic cells have membrane-bound organelles?

    Compartmentalization allows incompatible reactions to occur simultaneously and increases efficiency by concentrating enzymes.

  • Name the main components of the endomembrane system.

    Nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and plasma membrane.

  • Compare smooth ER and rough ER functions.

    Smooth ER synthesizes lipids and detoxifies; rough ER has ribosomes and synthesizes secretory and membrane proteins.

  • What roles does the Golgi apparatus perform?

    Modifies, sorts, packages proteins and lipids from the ER for transport to their destinations.

  • Outline the path of a protein from synthesis to secretion.

    Ribosome → Rough ER → Transport vesicle → Golgi apparatus → Vesicle → Destination (membrane, secretion, lysosome).

  • What happens if the Golgi apparatus is lost or nonfunctional?

    Proteins are not modified, sorted, or packaged, leading to misdirected or nonfunctional proteins.

  • Describe the function of lysosomes.

    Contain hydrolytic enzymes to digest macromolecules and recycle damaged organelles via autophagy.

  • What is the endosymbiont theory?

    Mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.

  • Describe the structure and function of mitochondria.

    Double membrane organelle with cristae; site of cellular respiration and ATP production.

  • What are chloroplasts and their key structures?

    Plant plastids containing chlorophyll; have thylakoids stacked into grana and stroma fluid for photosynthesis.

  • What are peroxisomes and their function?

    Single membrane organelles that oxidize fatty acids and detoxify harmful substances, producing hydrogen peroxide.

  • List the three main types of cytoskeletal fibers and their functions.

    Microtubules (shape, organelle movement, chromosome separation), microfilaments (cell shape, motility), intermediate filaments (structural support).

  • How does the cytoskeleton interact with the extracellular matrix (ECM)?

    ECM glycoproteins bind cell integrins, which connect to cytoskeletal microfilaments, linking external environment to internal structure.

  • What are plasmodesmata?

    Channels connecting adjacent plant cells allowing passage of water, solutes, and some molecules.

  • Name and describe the three types of animal cell junctions.

    Tight junctions (seal cells), desmosomes (anchor cells), gap junctions (cytoplasmic channels for communication).

  • Predict the effect of losing mitochondria in a cell.

    ATP production stops, energy-dependent processes fail, and the cell cannot survive.

  • What occurs if rough ER ribosomes are lost?

    Secretory and membrane proteins are not synthesized properly, disrupting secretion and membrane growth.

  • What is the role of the central vacuole in plant cells?

    Storage of water, ions, and nutrients; maintains turgor pressure for cell rigidity and growth.