Cell Signalling
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Questions and Answers

What role do signaling molecules play in cell communication?

  • They act as receptor proteins on the cell surface.
  • They inhibit the communication between different cell types.
  • They are responsible for energy production within the cell.
  • They are released by signaling cells and elicit a specific response in target cells. (correct)

    • What can result from a change in the structure of a ligand or its binding site?

  • Loss of function in the receptor. (correct)
  • Improvement in cellular growth and differentiation.
  • Enhanced receptor sensitivity.
  • Increased efficiency of signal transduction.

    • Which of the following best defines a drug?

  • A biological molecule produced by the body to regulate functions.
  • A chemical substance intended to affect the structure or function of the body. (correct)
  • A signaling molecule that only affects neurotransmitter release.
  • A nutrient required for cellular metabolism.

    • How are drugs classified in relation to their biological response?

    <p>As agonists or antagonists depending on whether they enhance or inhibit a response.</p> Signup and view all the answers

    What is the significance of receptors in the process of signal transduction?

    <p>They provide a means for cells to communicate effectively.</p> Signup and view all the answers

    What type of drug is Salbutamol classified as?

    <p>β-adrenoceptor agonist</p> Signup and view all the answers

    What is the role of Nifedipine in medical treatment?

    <p>Ca2+ Channel blocker</p> Signup and view all the answers

    Which drug acts as a local anesthetic and blocks Na+ channels?

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

    What is the effect of Ca2+ in cellular processes?

    <p>Contraction of muscle, hormone secretion, and transmitter release</p> Signup and view all the answers

    What mechanism does Cimetidine utilize in the treatment of ulcers?

    <p>Histamine antagonist</p> Signup and view all the answers

    What distinguishes Atracurium as a drug?

    <p>It serves as a muscle relaxant</p> Signup and view all the answers

    What is the primary use of Angiotensin Converting Enzyme inhibitors such as Captopril?

    <p>Treatment of hypertension</p> Signup and view all the answers

    Which drug is known to open K+ channels for vasodilation?

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

    How does Viagra aid in erectile dysfunction treatment?

    <p>Inhibits cyclic GMP breakdown</p> Signup and view all the answers

    Which drug increases the force of cardiac contraction and is used for congestive heart failure?

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

    What property describes a drug's ability to bind to specific receptors?

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

    Which of the following drugs is used as a Na+ channel blocker and is known for its toxicity?

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

    Which drug is specifically categorized as a β-adrenoceptor agonist?

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

    What is the primary function of G-Protein Coupled Receptors (GPCRs)?

    <p>To sense and respond to external environmental signals</p> Signup and view all the answers

    Which substance is NOT involved in activating GPCRs?

    <p>RNA molecules</p> Signup and view all the answers

    What is the role of the Gα subunit in the G-Protein complex?

    <p>To display GTPase activity and undergo a conformational change</p> Signup and view all the answers

    How many GPCRs can a single ligand bind to, as exemplified by adrenaline?

    <p>9</p> Signup and view all the answers

    Which option describes the end result when G-Proteins are activated?

    <p>The initiation of two potential signaling components</p> Signup and view all the answers

    What terminates the activation of a G-Protein?

    <p>Hydrolysis of GTP into GDP</p> Signup and view all the answers

    What is the composition of a heterotrimeric G-Protein?

    <p>One Gα, one Gβ, and one Gγ subunit</p> Signup and view all the answers

    Which type of signals can activate GPCRs?

    <p>Neuropeptides and small biogenic amines</p> Signup and view all the answers

    What is the primary function of a protein kinase?

    <p>To phosphorylate tyrosine amino acids</p> Signup and view all the answers

    Which amino acids are commonly phosphorylated by kinases?

    <p>Serine, Threonine, Tyrosine</p> Signup and view all the answers

    What is the role of protein phosphatases in cellular signaling?

    <p>To catalyze the removal of phosphate groups from proteins</p> Signup and view all the answers

    How does Protein Kinase A (PKA) get activated?

    <p>By cyclic-AMP (cAMP)</p> Signup and view all the answers

    What does the hydrolysis reaction catalyzed by protein phosphatases result in?

    <p>Release of inorganic phosphate (Pi)</p> Signup and view all the answers

    Which component is required for the activity of kinases during phosphorylation?

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

    What enables the reversible regulation of proteins phosphorylated by kinases?

    <p>Action of protein phosphatases</p> Signup and view all the answers

    Which of the following statements is true regarding protein kinases and phosphatases?

    <p>Protein kinases and phosphatases both help in signal amplification.</p> Signup and view all the answers

    What is the role of the first messenger in signal transduction?

    <p>It binds to a receptor, initiating the signal relay.</p> Signup and view all the answers

    Which of the following accurately describes second messengers?

    <p>They change concentration in response to extracellular hormone binding.</p> Signup and view all the answers

    What is meant by the amplification of a signal in signal transduction?

    <p>It means that each activated protein can activate more target proteins.</p> Signup and view all the answers

    Why is specificity important in signal transduction pathways?

    <p>It prevents all cells from responding to the same hormone.</p> Signup and view all the answers

    Which molecules are included as examples of second messengers?

    <p>cAMP, cGMP, DAG, IP3, and Ca2+</p> Signup and view all the answers

    What role do relay proteins play in the process of signal transduction?

    <p>They amplify the signal by activating effector proteins.</p> Signup and view all the answers

    What is a potential effect of inefficient signal transduction within a cell?

    <p>Inaccurate cell responses and impaired functions</p> Signup and view all the answers

    Which best describes the final stages of a signal transduction pathway?

    <p>It leads to changes in protein synthesis or enzyme activity.</p> Signup and view all the answers

    What effect does adrenaline have on glycogen metabolism?

    <p>Inhibits glycogen synthesis and stimulates breakdown.</p> Signup and view all the answers

    How does PKA influence glycogen synthase?

    <p>It phosphorylates glycogen synthase and inactivates it.</p> Signup and view all the answers

    Which enzyme is responsible for degrading cAMP to AMP?

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

    What is the role of the CREB-binding protein (CBP) in cAMP signaling?

    <p>It acts as a co-activator for gene expression regulation.</p> Signup and view all the answers

    Which receptor is linked to an increased heart contraction through PKA activation?

    <p>β1 receptor via Gs protein</p> Signup and view all the answers

    What is a consequence of Gi protein activation on heart function?

    <p>Decreased cAMP levels leading to reduced heart rate</p> Signup and view all the answers

    What is the immediate effect of increased cAMP levels in muscle cells after adrenaline binds to its receptor?

    <p>Promotion of glycogen breakdown.</p> Signup and view all the answers

    How does the βγ subunit of Gi protein contribute to cardiac function?

    <p>Inhibits ion channels to slow heart conduction.</p> Signup and view all the answers

    What happens to the Gα subunit when it binds GTP?

    <p>It releases the Gβγ complex.</p> Signup and view all the answers

    What role does adenylate cyclase play in cellular signaling?

    <p>It synthesizes cAMP from ATP.</p> Signup and view all the answers

    Which statement correctly describes the function of cyclic AMP (cAMP) in cells?

    <p>cAMP mediates cellular responses primarily through PKA.</p> Signup and view all the answers

    What initiates the activation of the G-protein coupled receptor (GPCR)?

    <p>Receptor binding of a ligand.</p> Signup and view all the answers

    What is the role of Gβγ subunits in G protein signaling?

    <p>They can couple with specific targets for downstream signaling.</p> Signup and view all the answers

    How is the activation of adenylate cyclase by G proteins regulated?

    <p>By the dissociation of Gα-GTP from Gβγ.</p> Signup and view all the answers

    What is the end product when adenylate cyclase acts on ATP?

    <p>cAMP.</p> Signup and view all the answers

    Which molecule serves as the second messenger in the cAMP signaling pathway?

    <p>cAMP.</p> Signup and view all the answers

    What is the primary function of tyrosine kinase receptors?

    <p>Phosphorylating specific tyrosine residues</p> Signup and view all the answers

    What process occurs immediately after PDGF receptors dimerize?

    <p>They phosphorylate each other</p> Signup and view all the answers

    Which of the following is NOT a consequence of phosphorylation by tyrosine kinase?

    <p>Inhibition of RNA polymerase</p> Signup and view all the answers

    What role do MAPKs play in PDGF signal transduction?

    <p>They phosphorylate multiple target proteins</p> Signup and view all the answers

    What is a major consequence of receptor phosphorylation during desensitization?

    <p>Receptor internalization</p> Signup and view all the answers

    Which component is essential for the action of protein kinases during phosphorylation?

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

    How does receptor dimerization affect tyrosine kinase activity?

    <p>It enhances receptor phosphorylation</p> Signup and view all the answers

    What is the effect of phosphorylation on a protein's function?

    <p>It can alter enzyme activity and gene expression</p> Signup and view all the answers

    What is the primary role of IP3 in calcium signaling mechanisms?

    <p>To release Ca2+ from the endoplasmic reticulum</p> Signup and view all the answers

    What triggers the activation of protein kinase C (PKC)?

    <p>Binding of DAG and Ca2+</p> Signup and view all the answers

    Which of the following statements about calcium (Ca2+) signaling is accurate?

    <p>Ca2+ binds non-covalently, causing structural changes in target proteins.</p> Signup and view all the answers

    How does IP3 influence the concentration of Ca2+ in the cytosol?

    <p>By facilitating the release of Ca2+ from specific receptors in the endoplasmic reticulum.</p> Signup and view all the answers

    What process terminates the calcium response initiated by IP3?

    <p>IP3 hydrolysis to form IP4</p> Signup and view all the answers

    Which of the following correctly describes a characteristic of protein kinase C (PKC)?

    <p>PKC is dependent on DAG and Ca2+ for activation and is found in the membrane.</p> Signup and view all the answers

    What is a consequence of increased intracellular Ca2+ levels?

    <p>Activation of certain ion channels in the plasma membrane</p> Signup and view all the answers

    Which messenger is produced by phospholipase C during the activation of the inositol phospholipid signaling pathway?

    <p>IP3</p> Signup and view all the answers

    What mechanism occurs when Ca2+ levels are disrupted by okadaic acid in shellfish poisoning?

    <p>Prolonged activation of phosphorylated proteins by inhibition of phosphatases</p> Signup and view all the answers

    What is the sequence of events starting with Gα binding GTP after receptor activation?

    <p>Gα binds to PLC after exchanging GDP for GTP.</p> Signup and view all the answers

    How does IP3 influence calcium signaling within the cell?

    <p>By releasing Ca2+ from the endoplasmic reticulum.</p> Signup and view all the answers

    What role does Protein Kinase C (PKC) play in signal transduction?

    <p>It phosphorylates cellular proteins, altering their activity.</p> Signup and view all the answers

    What effect does the activation of phospholipase C have on membrane-derived signaling?

    <p>It leads to the hydrolysis of PIP2.</p> Signup and view all the answers

    Which type of G protein is primarily linked to the activation of phospholipase C?

    <p>Gq protein</p> Signup and view all the answers

    Which statement correctly describes the change in the G protein subunits following GDP-GTP exchange?

    <p>Gα dissociates from both β and γ subunits.</p> Signup and view all the answers

    Which components participate in the two-limbed signal transduction pathway activated by G proteins?

    <p>IP3 and DAG</p> Signup and view all the answers

    What is a full agonist in pharmacology?

    <p>A substance that binds and activates the receptor to produce a maximum response</p> Signup and view all the answers

    What distinguishes a partial agonist from a full agonist?

    <p>It binds to receptors but never elicits a maximum response</p> Signup and view all the answers

    What does the term 'in vitro' refer to in pharmacology studies?

    <p>Studies where tissue is isolated and tested outside of a living organism</p> Signup and view all the answers

    Which measurement is crucial for determining the effectiveness of a drug in pharmacology?

    <p>Measuring drug binding to receptors or physiological responses</p> Signup and view all the answers

    What is the overall effect of agonist binding to a receptor?

    <p>Activation of the receptor leading to a cellular response</p> Signup and view all the answers

    What is an inverse agonist's role in pharmacology?

    <p>It occupies the receptor and reduces its activity below baseline levels</p> Signup and view all the answers

    In vivo studies in pharmacology are characterized by what feature?

    <p>Drugs applied to the entire living organism</p> Signup and view all the answers

    What is the main characteristic of competitive antagonism?

    <p>Both agonist and antagonist compete for the same binding site.</p> Signup and view all the answers

    Which factor complicates in vivo pharmacological studies?

    <p>Interaction between distribution, metabolism, and different systems</p> Signup and view all the answers

    Which of the following best describes non-competitive antagonism?

    <p>It blocks the response by inhibiting the agonist at a different site.</p> Signup and view all the answers

    What effect does increasing the agonist concentration have in reversible competitive antagonism?

    <p>It can reverse the effects of the antagonist.</p> Signup and view all the answers

    Which of the following is NOT a type of drug antagonism?

    <p>Non-reversible antagonism</p> Signup and view all the answers

    What is the main function of chemical antagonism?

    <p>To inactivate the agonist through chemical reaction.</p> Signup and view all the answers

    What occurs during irreversible binding in drug antagonism?

    <p>Antagonist binding permanently inhibits the agonist's effect.</p> Signup and view all the answers

    Which substance is mentioned as an example of non-competitive antagonism?

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

    What does NOT describe a characteristic of competitive antagonism?

    <p>Totally disables the receptor, making it unavailable.</p> Signup and view all the answers

    What is the primary substance that is converted to nitric oxide (NO) in the presence of oxygen?

    <p>L-arginine</p> Signup and view all the answers

    Which form of nitric oxide synthase (NOS) produces significantly more nitric oxide compared to the others?

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

    How does intracellular calcium influence the production of nitric oxide?

    <p>By activating NOS activity</p> Signup and view all the answers

    What is the primary role of nitric oxide as a signaling molecule?

    <p>To induce relaxation of vascular smooth muscle</p> Signup and view all the answers

    Which of the following substances is classified as an endothelium-derived contracting factor (EDCF)?

    <p>Thromboxane A2 (TxA2)</p> Signup and view all the answers

    What must occur for an action potential to be triggered in a neuron?

    <p>Depolarization must exceed the threshold potential</p> Signup and view all the answers

    What is the primary function of voltage-gated Na+ channels during an action potential?

    <p>To temporarily allow Na+ influx at the stimulation site</p> Signup and view all the answers

    What mechanism prevents the weakening of signals transmitted in long-distance neuronal communication?

    <p>The generation of action potentials</p> Signup and view all the answers

    Why is passive spread of signals insufficient for long-distance transmission in neurons?

    <p>It suffers from rapid signal attenuation with distance</p> Signup and view all the answers

    What distance can an action potential effectively transmit information without weakening?

    <p>Greater than 1 meter</p> Signup and view all the answers

    What is the primary reason for the rapid depolarization of a neuron's membrane potential during an action potential?

    <p>Na+ channels opening</p> Signup and view all the answers

    What initiates the release of neurotransmitters at the nerve terminal?

    <p>Ca2+ channel activation</p> Signup and view all the answers

    Which statement best describes the 'all or nothing' nature of action potentials?

    <p>Once generated, all action potentials are the same magnitude.</p> Signup and view all the answers

    During the action potential's peak, what is the state of Na+ channels?

    <p>Inactivated and cannot reopen immediately</p> Signup and view all the answers

    What occurs when K+ channels open during an action potential?

    <p>Membrane potential becomes more negative</p> Signup and view all the answers

    What is the effect of the refractory period on the propagation of action potentials?

    <p>It prevents successive action potentials from occurring too quickly.</p> Signup and view all the answers

    What role do synaptic vesicles play in neurotransmission?

    <p>They package and transport neurotransmitters to the presynaptic membrane.</p> Signup and view all the answers

    What triggers the process of exocytosis for neurotransmitter release?

    <p>Influx of Ca2+ ions</p> Signup and view all the answers

    Which of the following statements accurately describes the synaptic cleft?

    <p>It separates pre and post synaptic cells.</p> Signup and view all the answers

    What primarily governs the movement of Na+ into a neuron during depolarization?

    <p>Electrochemical gradient</p> Signup and view all the answers

    What is pharmacodynamics primarily concerned with?

    <p>The effects of drugs on the body</p> Signup and view all the answers

    What does pharmacokinetics specifically describe?

    <p>The time course of drug movement in the body</p> Signup and view all the answers

    Which mechanism does NOT facilitate the movement of drugs across membranes?

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

    How does induction of P-glycoproteins affect drug absorption?

    <p>It decreases drug absorption</p> Signup and view all the answers

    What is one role of P-glycoproteins in the body?

    <p>Serving as a defense mechanism against foreign substances</p> Signup and view all the answers

    Which factor does NOT influence the absorption of a drug?

    <p>The patient's age</p> Signup and view all the answers

    What effect does inhibiting P-glycoproteins have on drug absorption?

    <p>Increases drug absorption?</p> Signup and view all the answers

    Why is it important to understand pharmacokinetic data of a drug?

    <p>To establish the optimal dosage regimen</p> Signup and view all the answers

    What is the term used to describe the percentage of the administered dose that reaches systemic circulation?

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

    Which factor is NOT typically considered when assessing drug distribution in the body?

    <p>Patient's vitamin levels</p> Signup and view all the answers

    How do the concentrations of certain drugs in breast milk compare to their concentrations in blood?

    <p>They can be significantly higher.</p> Signup and view all the answers

    Which physiological condition can influence the distribution of drugs in the body?

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

    What is the primary process through which drug metabolism occurs?

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

    What is a common outcome of biotransformation of drugs in the body?

    <p>Drugs are transformed into hydrophilic compounds.</p> Signup and view all the answers

    Which of the following drugs is known for causing permanent staining of infant teeth when ingested during breastfeeding?

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

    What effect does the 'first pass effect' have on drug bioavailability?

    <p>It decreases the amount that reaches systemic circulation.</p> Signup and view all the answers

    What triggers the myosin head shape change during the actin-myosin cycle?

    <p>Binding of ATP to myosin</p> Signup and view all the answers

    What is the primary role of myosin-I in muscle contraction?

    <p>Moving vesicles along microfilaments</p> Signup and view all the answers

    Which type of muscle relies primarily on myosin-II interactions for contraction?

    <p>Skeletal muscle</p> Signup and view all the answers

    How do tropomyosin and other actin-binding proteins affect muscle contraction?

    <p>They bind to actin, preventing contraction</p> Signup and view all the answers

    Which function is NOT associated with myosin-II during muscle contraction?

    <p>Transporting vesicles</p> Signup and view all the answers

    What prevents myosin binding during muscle relaxation?

    <p>The movement of troponin and tropomyosin to their original positions</p> Signup and view all the answers

    How is the contraction in smooth muscle initiated?

    <p>By Ca2+ binding to calmodulin</p> Signup and view all the answers

    What role do L-Type Ca2+ channels play in cardiac muscle contraction?

    <p>They facilitate calcium-induced calcium release from the sarcoplasmic reticulum</p> Signup and view all the answers

    What is the primary function of myosin light chain kinase (MLCK) in smooth muscle contraction?

    <p>To phosphorylate myosin light chains, enabling actin binding</p> Signup and view all the answers

    What physiological change occurs when calcium concentration in the cytosol increases?

    <p>Activation of the contraction cycle through binding to troponin</p> Signup and view all the answers

    What occurs when ATP binds to the myosin head during the actin-myosin cycle?

    <p>The actin is released as the myosin head undergoes a shape change.</p> Signup and view all the answers

    Which molecules act as a regulatory mechanism for muscle contraction?

    <p>Calcium ions and troponin</p> Signup and view all the answers

    In which state does the myosin head remain locked to the actin filament?

    <p>Attached state without ATP</p> Signup and view all the answers

    What is the effect of increased intracellular calcium ion concentration on muscle contraction?

    <p>It facilitates a shift of tropomyosin allowing actin-myosin interaction.</p> Signup and view all the answers

    What occurs during the power stroke of the myosin head?

    <p>The myosin head regains its original shape while losing ADP.</p> Signup and view all the answers

    How do drugs impact muscle contraction?

    <p>They can modify calcium ion levels affecting contractile strength.</p> Signup and view all the answers

    What distinguishes skeletal muscle fibers from cardiac muscle fibers?

    <p>Skeletal muscles are striated and voluntary, while cardiac muscles are striated and involuntary.</p> Signup and view all the answers

    What is the primary role of tropomyosin in muscle contraction?

    <p>To prevent myosin heads from binding to actin when Ca2+ is low.</p> Signup and view all the answers

    What mechanism primarily initiates contraction in skeletal muscles?

    <p>Increase in intracellular calcium concentration</p> Signup and view all the answers

    Which type of muscle is involuntary and found in the walls of internal organs?

    <p>Smooth muscle</p> Signup and view all the answers

    What is a defining characteristic of cardiac muscle tissue?

    <p>It contracts slowly and does not fatigue easily.</p> Signup and view all the answers

    In skeletal muscle, which structure is primarily responsible for the release of calcium ions during contraction?

    <p>Sarcoplasmic reticulum</p> Signup and view all the answers

    What characterizes smooth muscle tissue compared to skeletal muscle?

    <p>Single nucleus per cell</p> Signup and view all the answers

    What links the depolarization of T-tubules to calcium release in skeletal muscle contraction?

    <p>Dihydropyridine receptors</p> Signup and view all the answers

    Which of the following proteins are primarily involved in muscle contraction?

    <p>Myosin and actin</p> Signup and view all the answers

    What is the key role of calcium ions in muscle contraction?

    <p>Regulate the interaction between actin and myosin</p> Signup and view all the answers

    What initiates the contraction process in smooth muscle cells?

    <p>Phosphorylation of myosin light chains</p> Signup and view all the answers

    Which of the following statements accurately describes the structure of cardiac muscle?

    <p>Cardiac muscle fibers contain intercalated discs for synchronized contraction.</p> Signup and view all the answers

    What role does myosin phosphatase play in smooth muscle contraction?

    <p>It reverses the phosphorylation of myosin light chains, promoting relaxation.</p> Signup and view all the answers

    How do gap junctions affect the contraction of smooth muscle in the gut?

    <p>They allow direct electrical and metabolic communication between cells for synchronized contraction.</p> Signup and view all the answers

    Which mechanism is specifically utilized by smooth muscle to initiate contraction?

    <p>Calcium binding to calmodulin.</p> Signup and view all the answers

    What differentiates fast-twitch muscle fibers from slow-twitch muscle fibers?

    <p>Fast-twitch fibers have a lower myoglobin content than slow-twitch fibers.</p> Signup and view all the answers

    What is the primary purpose of the intercalated discs in cardiac muscle?

    <p>To facilitate synchronized contraction through gap junctions.</p> Signup and view all the answers

    What immediate effect does an increase in cytosolic Ca2+ have in smooth muscle cells?

    <p>Causes contraction by phosphorylating myosin light chains.</p> Signup and view all the answers

    How does nitric oxide (NO) contribute to smooth muscle relaxation?

    <p>By activating guanylate cyclase, leading to cGMP production</p> Signup and view all the answers

    In the context of the nervous system, what role does neuroglia primarily play?

    <p>Providing structural support and protection for neurons</p> Signup and view all the answers

    What is a key property that differentiates cardiac muscle from skeletal muscle?

    <p>Cardiac muscle exhibits involuntary contractions</p> Signup and view all the answers

    What is the primary function of calmodulin in the smooth muscle contraction mechanism?

    <p>It activates myosin light chain kinase in response to calcium</p> Signup and view all the answers

    Which of the following is NOT a function of nitric oxide in the cardiovascular system?

    <p>Directly promoting platelet aggregation</p> Signup and view all the answers

    Which tissue type forms the protective outer layer of the body and internal organs?

    <p>Epithelial tissue</p> Signup and view all the answers

    Which of the following best describes the role of guanylate cyclase activated by NO?

    <p>It catalyzes the conversion of GTP to cGMP</p> Signup and view all the answers

    What is the primary role of protein kinase G in smooth muscle cells?

    <p>To mediate relaxation by reducing calcium levels</p> Signup and view all the answers

    Study Notes

    Cell Signaling

    • Cells communicate with each other.
    • Yeast and multicellular organisms use communication for growth, differentiation, and metabolism.
    • Cells send and receive information through signaling molecules (e.g., neurotransmitters) and receptors (GPCRs).
    • Information is processed within the cells to produce a response (signal transduction).

    Signaling Molecules

    • Signaling cells release molecules that produce specific responses in target cells with receptors for them.
    • Examples: Hormones, pheromones, neurotransmitters, and growth factors.

    Signaling Pathways

    • Signaling pathways can be complex. (A visual representation is shown.)

    Receptors and Disease

    • Changes in ligand or ligand-binding sites result in loss of function.
    • Intracellular receptor sites are specific. Changes in amino acid sequences can cause amplification, reduction, or loss of signal transduction.

    Types of Receptors

    • G protein-coupled receptors (GPCRs): (Diagram shown)
      • Ligand binds to receptor.
      • Receptor activates an intracellular G protein.
      • G protein activates other enzymes (e.g., adenyl cyclase, phospholipase C).
      • These enzymes produce second messengers (e.g., cAMP, inositol triphosphate).
    • Ion-channel receptors: (Diagram shown)
      • Ligand binding alters ion channel opening/closing.
      • Ions flow across membrane.
    • Receptors with intrinsic enzymatic activity: (Diagram shown)
      • Tyrosine kinase activity.
      • Ligand binding activates intrinsic enzymatic activity (like tyrosine kinase).
      • This phosphorylates other proteins, leading to other cellular responses.

    What is a Drug?

    • A chemical substance used for diagnosing, curing, mitigating, treating, or preventing disease.
    • A substance, other than food, designed to affect body structure or function.

    Drugs

    • Image of various drugs (prescription pills, cigarettes, marijuana, alcohol).

    How Drugs Work

    • Drugs produce their effects via specific sites and mechanisms.
    • Drugs can be classified as agonists or antagonists based on their effect (biological response).

    Asthma

    • Image showing normal and inflamed airways with mucus.

    Drug Treatment of Asthma

    • Salbutamol is a β-adrenoceptor agonist. (Chemical structure shown).

    Drugs Blocking Ion Channels

    • (Diagram shown)
    • Drugs can block ion channels. This prevents ion flow.

    Drugs Blocking Ca2+ Channels

    • Nifedipine is a Ca2+ channel blocker used for hypertension. (Chemical structure shown).

    Drugs Blocking Na+ Channels

    • Lignocaine is a Na+ channel blocker, used as a local anesthetic. (Chemical structure shown).

    Effect of a Drug

    • Affinity: Ability to bind to a specific receptor.
    • Efficacy: Ability to modify cell activity.
    • Specificity: Range of receptors a drug can bind to.

    Drugs Inhibiting Enzymes

    • Drugs can inhibit enzymes.
    • Angiotensin-converting enzyme (ACE) inhibitors are used in hypertension. (Example diagram shown).
    • Digitoxin is used in congestive heart failure. (Example diagram shown).
    • Viagra inhibits an enzyme that prevents cAMP production. (Chemical structure shown and mechanism for erectile dysfunction).

    Therapeutics

    • Use of drugs for disease treatment.
    • Drug therapy balances efficacy and safety.

    Drugs Blocking Nicotinic Receptors

    • Example: Atracurium. (Chemical structure shown.) Used in surgical procedures to relax muscles.

    Ulcer

    • Duodenal and gastric ulcers are shown with the diseased stomach parts.

    Drug Treatment of an Ulcer

    • Cimetidine is a histamine antagonist. (Chemical structure shown).
    • It reduces acid production in the stomach.

    Channels in Cells

    • Channels allow ions to flow in or out of cells. (Diagram shown.)

    Calcium in Cells

    • Ca2+ is essential for many cellular functions.
    • Functions include muscle contraction, transmitter release, hormone secretion, and fertilization.

    Ca2+ Regulation in Cells

    • Intracellular Ca2+ concentration is kept low, while extracellular concentration is much higher. (Diagram shown).
    • Calcium pumps maintain this differential.

    Drugs Opening Ion Channels

    • (Diagram shows channels opening or closing.)
    • Drugs can open ion channels.

    Drugs Opening K Channels

    • Nicorandil opens K+ channels. (Mechanism shown).
    • This results in vasodilation.

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