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General Biology: Cell Structure and Enzyme Function

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  • Function of fimbriae in bacteria
    Fimbriae are important for bacterial growth on surfaces, such as teeth, by helping bacteria adhere.
  • How eukaryotic cells overcome inefficiency as they grow larger
    Eukaryotic cells have organelles that compartmentalize the cytosol, reducing fluid volume and increasing reaction efficiency.
  • Function of secretory cells with abundant rough ER and Golgi apparatus
    These cells primarily manufacture and secrete digestive enzyme proteins.
  • Role of nuclear localization signals (NLS)
    NLS are amino acid sequences that direct proteins to the nucleus by binding to receptor proteins.
  • Why small proteins might have an NLS despite diffusing through nuclear pores
    The NLS allows active import into the nucleus, minimizing cytoplasmic presence.
  • Structure that allows nucleotide monomers to move in and out of the nucleus
    Nucleotide monomers move through nuclear pores.
  • Final location of a protein with ER signal, mannose-6-phosphate tag, and NLS
    The protein is directed into the ER, processed in the Golgi, and targeted to a lysosome.
  • Sequence of secreted protein movement through the endomembrane system
    Proteins move from the ER to cis-Golgi, then trans-Golgi, and finally to vesicles.
  • How proteins are transported to correct cellular locations
    Proteins contain molecular zip codes that direct them to specific compartments.
  • Role of actin filaments in eukaryotic cells
    Actin filaments are required for cytoplasmic streaming and other dynamic processes.
  • How ATP hydrolysis powers motor protein movement
    ATP hydrolysis causes conformational changes in motor proteins, enabling movement along filaments.
  • Common feature of myosin, dynein, and kinesin
    All hydrolyze ATP to provide energy for movement.
  • Purpose of differential centrifugation
    It allows researchers to isolate cell components from each other.
  • Likely location of a protein lacking a signal sequence
    Such a protein will likely remain in the cytoplasm.
  • Difference between intermediate filaments and other cytoskeletal filaments
    Only intermediate filaments play a purely structural role.
  • Fundamental difference between plant and animal cells
    Animal cells lack chloroplasts, cell walls, and large vacuoles.
  • Organelle abundant in cells specializing in lipid synthesis
    The smooth endoplasmic reticulum is abundant in lipid-synthesizing cells.
  • Organelle malfunctioning in Tay-Sachs disease
    Malfunction of lysosomes causes accumulation of undigested lipids.
  • Effect of phosphorylation on enzyme activity
    Phosphorylation is a covalent modification that can activate or inactivate enzymes.
  • Difference between competitive and allosteric inhibition
    Competitive inhibitors bind the active site, while allosteric inhibitors bind other sites changing enzyme shape.
  • Why enzyme activity plateaus at high substrate concentration
    All enzyme molecules are saturated and working at maximal speed.
  • Effect of temperature on enzyme activity
    Activity increases with temperature until the enzyme denatures at high temperatures.
  • Role of enzyme-substrate complex
    It forms when substrate binds the enzyme's active site, enabling catalysis.
  • Function of FAD and NAD+ in metabolism
    Both act as electron carriers in metabolic pathways.
  • Why ATP hydrolysis releases free energy
    Breaking the bond between phosphate groups releases energy due to charge repulsion relief and product stabilization.
  • Definition of feedback inhibition
    The end product of a pathway inhibits an earlier enzyme to regulate the pathway.
  • What determines enzyme specificity
    The shape and structure of the enzyme's active site.
  • How enzymes speed up reactions
    By lowering activation energy required for the reaction.
  • Effect of pH on enzyme activity
    pH affects enzyme folding and reactivity by altering proton concentration.