Cell Development and Signaling
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Questions and Answers

What distinguishes stem cells from differentiated cells?

  • Differentiated cells can express all genes present in the genome.
  • Differentiated cells give rise to stem cells.
  • Stem cells can differentiate into various cell types. (correct)
  • Stem cells do not have the ability to divide.

    • How can external signals influence stem cells?

  • By making them differentiate immediately.
  • By permanently altering their DNA.
  • By causing them to lose their ability to divide.
  • By determining their gene expression behavior. (correct)

    • What role do sterol molecules play in cell membranes?

  • They make the membrane impermeable to all substances.
  • They provide structural support only at low temperatures.
  • They act as a buffer to moderate membrane fluidity. (correct)
  • They prevent fluidity from changing in any situation.

    • What type of proteins span the entire membrane?

    <p>Integral membrane proteins</p> Signup and view all the answers

    Which statement regarding gene expression in stem cells is accurate?

    <p>Stem cells can express all genes but only differentiate if certain genes are turned off.</p> Signup and view all the answers

    How do small and nonpolar molecules interact with the cell membrane?

    <p>They can diffuse through the membrane easily.</p> Signup and view all the answers

    What happens to membrane fluidity at high temperatures?

    <p>Membrane fluidity increases, requiring more saturated fatty acids.</p> Signup and view all the answers

    Which cell type has the capability of differentiating into various specialized cells?

    <p>Stem cells</p> Signup and view all the answers

    What is the primary role of stem cells in development?

    <p>To divide, grow, and differentiate into various cell types</p> Signup and view all the answers

    What is apoptosis?

    <p>Programmed cell death</p> Signup and view all the answers

    How do cells receive signals to differentiate?

    <p>From external signals and neighboring cell communication</p> Signup and view all the answers

    What activates the MAPK pathway?

    <p>Cell division signal through Raf and MEK</p> Signup and view all the answers

    What can lead to uncontrolled cell division?

    <p>Mutations in proto-oncogenes affecting signal pathways</p> Signup and view all the answers

    What is the role of EGFR in cell signaling?

    <p>It regulates cell division and can mutate in cancers.</p> Signup and view all the answers

    What happens during endocytosis in receptor signaling?

    <p>Ligands bind and then the receptor is internalized after signaling.</p> Signup and view all the answers

    What type of signaling involves second messengers like cAMP?

    <p>Signal amplification through kinase cascades</p> Signup and view all the answers

    Which of the following statements about feedback loops is true?

    <p>A positive feedback loop maintains the activation of a pathway.</p> Signup and view all the answers

    What is the main function of transcription factors in cell signaling?

    <p>To modulate gene expression and facilitate communication</p> Signup and view all the answers

    Which pathway is essential for translating growth signals into mitotic activity?

    <p>Ras-Raf-MEK-MAPK signaling pathway</p> Signup and view all the answers

    What indicates that a receptor is permanently activated in cancer conditions?

    <p>Loss of GTPase activity in Ras protein</p> Signup and view all the answers

    How does the extracellular matrix influence cell behavior?

    <p>It provides signals for differentiation and migration.</p> Signup and view all the answers

    What is a possible outcome of reduced phosphatase activity in cells?

    <p>Increased receptor activation and prolonged signaling</p> Signup and view all the answers

    What characterizes the differentiation of specialized cells?

    <p>The capacity to perform specific functions and roles</p> Signup and view all the answers

    What is the primary role of ubiquitin in the cell?

    <p>To tag proteins for degradation</p> Signup and view all the answers

    How does the action of phosphatases affect kinases?

    <p>They deactivate kinases</p> Signup and view all the answers

    Which phase of the cell cycle is typically the longest?

    <p>Interphase</p> Signup and view all the answers

    What is the significance of checkpoints during the cell cycle?

    <p>They prevent uncontrolled cell division</p> Signup and view all the answers

    What kind of feedback loop is described by the luciferin signaling response in fireflies?

    <p>Negative feedback loop</p> Signup and view all the answers

    Which organelles are known to have their own circular DNA?

    <p>Mitochondria and chloroplasts</p> Signup and view all the answers

    What characterizes the difference between haploid and diploid cells?

    <p>Haploid cells have a single set of chromosomes.</p> Signup and view all the answers

    What must occur to chromatin for successful cell division?

    <p>It must condense into chromosomes.</p> Signup and view all the answers

    What is a possible outcome of mutations affecting cell cycle checkpoints?

    <p>Uncontrolled cell division leading to cancer</p> Signup and view all the answers

    Which of the following statements about sister chromatids is correct?

    <p>They are identical copies of a chromosome.</p> Signup and view all the answers

    What is the role of kinetochores during cell division?

    <p>To attach microtubules to chromosomes</p> Signup and view all the answers

    Which of the following is NOT a function of mitochondria?

    <p>Synthesis of proteins</p> Signup and view all the answers

    What term describes the exchanges of genetic material between homologous chromosomes during meiosis?

    <p>Crossing over</p> Signup and view all the answers

    What is one of the key characteristics that separates living cells from non-living entities?

    <p>Ability to metabolize energy</p> Signup and view all the answers

    Which statement correctly describes the nature of phospholipids in the plasma membrane?

    <p>They are amphipathic, containing both hydrophilic and hydrophobic components.</p> Signup and view all the answers

    What effect do unsaturated hydrocarbons have on membrane fluidity?

    <p>They create more double bonds, increasing the spacing between hydrocarbons.</p> Signup and view all the answers

    How do viruses differ from living organisms in terms of metabolism?

    <p>Viruses do not metabolize energy on their own.</p> Signup and view all the answers

    What role does cholesterol play in animal cell membranes?

    <p>It contributes to membrane rigidity and stability.</p> Signup and view all the answers

    Which statement accurately describes the fluidity of membranes at varying temperatures?

    <p>Membrane fluidity can increase when temperatures are too low.</p> Signup and view all the answers

    What best defines the term 'amphipathic' as it relates to phospholipids?

    <p>Phospholipids have both hydrophobic and hydrophilic regions.</p> Signup and view all the answers

    What is the structural configuration of phospholipids in water?

    <p>Hydrophilic heads interact with water while hydrophobic tails face each other.</p> Signup and view all the answers

    Which of the following statements about water transport is true?

    <p>Aquaporins are specialized transporters for water and do not require ATP.</p> Signup and view all the answers

    What characterizes secondary active transport?

    <p>It indirectly uses ATP and relies on the gradients established by primary active transport.</p> Signup and view all the answers

    Which type of transport requires carriers and channels?

    <p>Facilitated diffusion</p> Signup and view all the answers

    How does the Na-K pump function?

    <p>It uses ATP to change conformation and moves Na+ out of the cell.</p> Signup and view all the answers

    Which of the following best describes a symporter?

    <p>It transports one molecule against its concentration gradient while moving another with it.</p> Signup and view all the answers

    Study Notes

    Cell Development and Signaling

    • Cell development is orchestrated by cell signaling and modulated by gene expression. This process leads from fertilization to a fully developed organism.
    • Stem cells divide and differentiate into specialized cells.
    • Differentiated cells cannot further divide and perform specific functions (e.g., muscle cells generate force, neurons transmit signals, bone cells provide structural support).
    • Mesenchymal stem cells (MSCs) can differentiate into various cell types including fat, bone, muscle, tendon, ligament, cartilage, and skin.
    • External and internal signals (neighboring cells, cell membrane components) guide cell differentiation.
    • Apoptosis is programmed cell death.
    • Transcription factors regulate gene expression and cell communication.
    • Cell communication involves signaling molecules released by signaling cells binding to receptor proteins on responding cells, initiating signal transduction pathways.
    • The extracellular matrix and adjacent cells influence cell behavior.
    • The MAPK/ERK pathway is activated during cell division, stimulating gene expression for cell renewal; its dysregulation can lead to cancer. Raf and MEK are oncogenes within this pathway.
    • The EGF pathway, frequently mutated in cancers, regulates cell division; a constitutively active receptor can cause uncontrolled growth. Ras protein, a key component, is often affected by mutations reducing GTPase activity.
    • Signal termination mechanisms include kinase dephosphorylation by phosphatases, receptor endocytosis, and the use of inhibitors. Ubiquitin-mediated proteolysis targets proteins for degradation in the proteasome.
    • Kinases and phosphatases regulate protein activity; positive and negative feedback loops control signaling pathways. The firefly flash is an example of a negative feedback loop (oscillatory pathway).

    Cell Cycle Control, Mitosis, and Meiosis

    • The cell cycle includes interphase (G1, S, G2, G0 phases) and mitotic phases. The G0 phase is a quiescent state; cells may re-enter the cycle.
    • Chromatin condenses into chromosomes during cell division. Humans have 23 pairs of chromosomes (22 somatic pairs, 1 sex pair).
    • Haploid number refers to the number of unique chromosomes (23 in humans); diploid number refers to the total number of chromosomes (46 in humans).
    • Centromeres join sister chromatids; kinetochores are attachment sites for microtubules during cell division.
    • Uncontrolled cell division leads to cancer.

    Cell Structure and Membrane Dynamics

    • The cell theory states that all organisms are composed of cells, cells are the basic units of life, and cells come from pre-existing cells. Viruses are not considered living organisms.
    • The plasma membrane defines cells, separating them from their environment and facilitating compartmentalization (in eukaryotes) and communication.
    • Cell membranes are composed of phospholipids, which are amphipathic (both hydrophilic and hydrophobic). Phospholipids form bilayers in aqueous environments. Micelles form if the hydrophilic portion is more prominent.
    • Membrane fluidity is influenced by temperature and fatty acid composition (saturated vs. unsaturated). Cholesterol (animals), sitosterol (plants), and hopanoids (bacteria) modulate fluidity.
    • Membrane proteins are integral (span the membrane) or peripheral (attach to one side). The fluid mosaic model describes the dynamic nature of membrane components.
    • Transport across membranes can be passive (simple or facilitated diffusion, osmosis through aquaporins) or active (primary or secondary, requiring ATP). The Na+/K+ pump is an example of primary active transport.

    Organelles and Endosymbiosis

    • Mitochondria produce ATP through cellular respiration; chloroplasts (in plants) conduct photosynthesis.
    • Mitochondria and chloroplasts possess features suggesting bacterial ancestry (circular DNA, double membranes, ribosomes, independent replication), supporting the endosymbiotic theory.

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    Description

    Explore the intricate processes of cell development and signaling in this quiz. Learn how stem cells differentiate into specialized cells and the roles of external signals and transcription factors in this process. Test your knowledge on apoptosis and cell communication as you discover the fundamentals of cellular functions.

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