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General Biology: Chapters 7-8

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  • What are the four main components all cells have?
    Proteins perform most cell functions, nucleic acids store and process information, carbohydrates provide energy and identity, and the plasma membrane acts as a selectively permeable barrier.
  • What distinguishes prokaryotic cells from eukaryotic cells?
    Prokaryotes have one chromosome, ribosomes for protein synthesis, a plasma membrane, and a cell wall; they lack membrane-bound organelles found in eukaryotes.
  • What is the difference between cytoplasm and cytosol?
    Cytoplasm includes all cell contents inside the membrane, including organelles and fluid; cytosol is only the fluid portion inside the cell.
  • What is the function of the nucleus?
    The nucleus stores genetic material (DNA), is membrane-bound with pores for regulated transport, and is the site of DNA replication and RNA synthesis.
  • What roles do ribosomes play in the cell?
    Ribosomes manufacture proteins; they are complexes of proteins and RNA but are not membrane-bound organelles.
  • What are the two types of endoplasmic reticulum and their functions?
    Rough ER has ribosomes and synthesizes proteins; Smooth ER lacks ribosomes and synthesizes lipids and contains enzymes.
  • What is the role of the Golgi apparatus?
    The Golgi apparatus processes proteins from the rough ER, modifies them (e.g., glycosylation), and sorts them for transport to their destinations.
  • What is unique about lysosomes in animal cells?
    Lysosomes contain acid hydrolase enzymes that break down lipids, proteins, carbohydrates, and nucleic acids; they maintain an acidic pH (~5.0) for enzyme activity.
  • What is the endomembrane system?
    A system including the ER, Golgi apparatus, and lysosomes that manufactures, processes, and transports proteins and lipids within the cell.
  • What is the function of mitochondria?
    Mitochondria supply ATP to cells, have two membranes (outer and folded inner cristae), contain mitochondrial DNA, and power cellular activities.
  • How do proteins know where to go inside the cell?
    Proteins have amino acid signal sequences (zip codes) that direct them to specific locations, such as the nucleus or ER.
  • What is the nuclear localization signal (NLS)?
    A 17-amino-acid sequence that directs proteins to enter the nucleus through nuclear pore complexes.
  • How are proteins targeted to the endoplasmic reticulum?
    Proteins with an ER signal sequence are recognized by the Signal Recognition Particle (SRP), which directs ribosomes to the ER membrane for translation.
  • What is the pathway for protein secretion in cells?
    Proteins are synthesized in the ER, processed in the Golgi apparatus, and then transported via vesicles to the plasma membrane or lysosomes.
  • What is the role of mannose-6-phosphate in protein targeting?
    It is a molecular tag that directs proteins to lysosomes.
  • What is receptor-mediated endocytosis?
    A process where receptors on the plasma membrane bind macromolecules, forming vesicles that bring cargo into the cell for recycling or degradation.
  • What are the three major types of cytoskeleton filaments?
    Actin filaments (microfilaments), intermediate filaments, and microtubules.
  • What is metabolism?
    The sum of all chemical reactions in a cell, including making and breaking down molecules, driven by enzymes.
  • What is the difference between kinetic and potential energy?
    Kinetic energy is energy of motion (e.g., thermal energy), while potential energy is stored energy based on position or chemical bonds.
  • What is energetic coupling in cellular reactions?
    Using energy released from one reaction (exergonic) to drive another reaction that requires energy (endergonic), often via electron or phosphate transfer.
  • What are redox reactions?
    Chemical reactions involving electron transfer: oxidation is loss of electrons, reduction is gain of electrons; they always occur together.
  • What roles do NAD and FAD play in cells?
    NAD and FAD are electron carriers that accept electrons and protons to become NADH and FADH2, donating electrons in metabolic reactions.
  • How does ATP store and transfer energy?
    ATP stores energy in its phosphate bonds; hydrolysis of ATP releases energy used to power cellular processes.
  • What is phosphorylation?
    The transfer of a phosphate group to a molecule, increasing its potential energy and altering its function.
  • How do enzymes lower activation energy?
    Enzymes stabilize the transition state and strain chemical bonds, reducing the energy needed to start a reaction.