Hormones and Signaling Quiz
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Questions and Answers

What defines a hormone in an organism?

  • A molecule that carries a signal to alter metabolic processes at the cellular level. (correct)
  • A protein that binds to enzymes to enhance their activity.
  • A substance that acts as a catalyst for chemical reactions.
  • A nucleotide that functions primarily in energy transfer.

    • Which type of molecule is NOT considered a second messenger?

  • cAMP
  • Diacylglycerol
  • Epinephrine (correct)
  • Calcium ions (Ca2+)

    • Which hormone is classified as a peptide hormone?

  • Cortisol
  • Insulin (correct)
  • Epinephrine
  • Thyroid hormones

    • What is the primary role of receptors in hormone action?

    <p>To amplify signals through second messengers.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of amino acid-derived hormones?

    <p>They are always water-soluble.</p> Signup and view all the answers

    What primary effect does insulin have on glucose uptake in the muscle and adipose tissue?

    <p>Promotes translocation of GLUT4 to the cell membrane</p> Signup and view all the answers

    Which process following the binding of insulin to its receptor is involved in signaling transduction?

    <p>Tyr autophosphorylation and kinase activation</p> Signup and view all the answers

    What type of second messenger is involved in the protein kinase A pathway?

    <p>Cyclic AMP (cAMP)</p> Signup and view all the answers

    How do gas molecules like nitric oxide act as second messengers?

    <p>They diffuse through membranes to induce responses.</p> Signup and view all the answers

    Which long-term effect is associated with insulin action?

    <p>Increased glucose uptake</p> Signup and view all the answers

    What best describes hydrophilic second messengers?

    <p>They remain soluble in the cytosol.</p> Signup and view all the answers

    Which molecule is required for the activation of glycogen phosphorylase?

    <p>Cyclic AMP</p> Signup and view all the answers

    What triggers the activation of adenyl cyclase in liver cells?

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

    How does feedback regulation influence hormone biosynthesis?

    <p>It adjusts hormone levels based on physiological needs.</p> Signup and view all the answers

    What enzyme activity is primarily regulated by insulin to enhance glycogen synthesis?

    <p>Glycogen synthase</p> Signup and view all the answers

    Which of the following minerals is classified as a macro mineral?

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

    What is the final effect of active protein kinase A on glycogen metabolism?

    <p>Stimulates glycogen breakdown</p> Signup and view all the answers

    Which micro mineral is essential for insulin action and glucose metabolism?

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

    Which hormone requires a second messenger for its action?

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

    Which of these is not a direct effect of insulin on cellular metabolism?

    <p>Decrease in protein synthesis</p> Signup and view all the answers

    What is the role of phosphodiesterase in the cAMP pathway?

    <p>Converts cAMP to AMP</p> Signup and view all the answers

    Which protein kinase is associated with the activation of glycogen phosphorylase?

    <p>Protein kinase A</p> Signup and view all the answers

    What is the primary role of serine/threonine kinases in insulin signal transduction?

    <p>Protein phosphorylation for metabolic activation</p> Signup and view all the answers

    What happens to protein kinase A once it is activated by cAMP?

    <p>It converts glycogen phosphorylase b to a</p> Signup and view all the answers

    What does Nitric Oxide (NO) primarily activate in smooth muscle cells?

    <p>Guanylate cyclase</p> Signup and view all the answers

    What is the primary effect of cGMP in smooth muscle cells?

    <p>Activate myosin phosphatase</p> Signup and view all the answers

    What is the role of phosphodiesterases in the NO/cGMP signaling pathway?

    <p>Convert cGMP to GTP</p> Signup and view all the answers

    Which drug is best known as a phosphodiesterase inhibitor?

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

    What type of receptor is primarily involved in the tyrosine kinase pathway?

    <p>Membrane receptor</p> Signup and view all the answers

    What enzyme is responsible for synthesizing Nitric Oxide from Arginine?

    <p>Nitric oxide synthase (NOS)</p> Signup and view all the answers

    Which of the following proteins do receptor tyrosine kinases primarily phosphorylate?

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

    Which type of Nitric Oxide synthase is considered inducible?

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

    What is a key function of the cGMP produced by guanylate cyclase?

    <p>Alter gene expression</p> Signup and view all the answers

    What is the primary role of cGMP in vascular function?

    <p>To cause vasodilation</p> Signup and view all the answers

    Which growth factors are associated with the tyrosine kinase pathway?

    <p>Insulin and EGF</p> Signup and view all the answers

    What molecule does Adenyl cyclase convert to produce cAMP?

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

    Which protein kinase is activated by cAMP?

    <p>Protein kinase A</p> Signup and view all the answers

    What is the function of Protein kinase C in hormone secretion?

    <p>Facilitates exocytosis of hormones</p> Signup and view all the answers

    Which of the following is a product of the action of nitric oxide synthase?

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

    Which substance does Phospholipase C convert to generate IP3 and DAG?

    <p>PIP2</p> Signup and view all the answers

    What is the primary action of PLC in relation to PIP2?

    <p>It hydrolyzes PIP2 to form DAG and IP3.</p> Signup and view all the answers

    What role does IP3 play in cellular signaling?

    <p>It stimulates the release of Ca2+ from the endoplasmic reticulum.</p> Signup and view all the answers

    How does Ca2+ contribute to exocytosis?

    <p>It facilitates the fusion of secretory granules with the plasma membrane.</p> Signup and view all the answers

    What does GnRH primarily regulate?

    <p>The secretion of FSH and LH.</p> Signup and view all the answers

    What is required for the activation of PKC?

    <p>The availability of DAG.</p> Signup and view all the answers

    What is the role of Ca2+ in the context of GnRH signaling?

    <p>It promotes exocytosis of secretory granules.</p> Signup and view all the answers

    Which of the following correctly describes the sequence of events following the binding of IP3?

    <p>IP3 stimulates the intracellular release of Ca2+ leading to exocytosis.</p> Signup and view all the answers

    What occurs after PLC hydrolyzes PIP2?

    <p>DAG and IP3 are released, activating different signaling pathways.</p> Signup and view all the answers

    Study Notes

    Signal Transduction I: Cell Surface Receptor

    • This lecture covers the definition of hormones and their differentiation from enzymes.
    • It discusses hormones' classification based on chemical structure.
    • Different hormones are discussed based on biosynthesis, storage, secretion, and transportation.
    • It examines the feedback mechanism regulating hormone biosynthesis.
    • The role of receptors in hormone action is explained.
    • Mechanisms of action producing metabolic and physiological responses are detailed.

    What are Hormones?

    • Substances in an organism that carry a signal to cause metabolic changes at the cellular level.
    • Hormones are also known as first messengers.
    • Hormones interact with specific receptors to amplify signals through second messengers.
    • Various types of second messengers exist within the cytosol and membrane-associated receptors

    Three basic types of second messengers

    • Hydrophilic molecules: water-soluble (e.g., cAMP, cGMP, IP3, and Ca2+), located within the cytosol.
    • Hydrophobic molecules: water-insoluble (e.g., diacylglycerol, phosphatidylinositols), membrane-associated, and diffusing from the plasma membrane.
    • Gas molecules: gases (e.g., nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H2S)) that can diffuse through both cytoplasm and cellular membranes.

    Classification of Hormones

    • Peptide hormones: insulin, glucagon, growth hormone, hCG, FSH, ACTH, LH, etc.
    • Amino acid-derived hormones: epinephrine, norepinephrine, thyroid hormones, TSH.
    • Steroid hormones: aldosterone, cortisol, testosterone, estrogen.

    Hormone Interaction With Receptor

    • Receptors on plasma membranes for peptide hormones and amino acid-derived hormones.
    • Intracellular receptors for some steroid hormones and thyroid hormones.

    Mechanism of Second Messenger Synthesis

    • Agonist activates membrane-bound receptor.
    • G-protein is activated and produces effector.
    • Effector stimulates second messenger synthesis.
    • Second messenger activates intercellular processes through a cascade reaction.

    General Mechanism of Signal Transduction Across Cell Membrane

    • Hormone binds to cell surface receptor.
    • Conformational changes enable association with a G-protein.
    • Activated G-protein causes enzyme activation.
    • Enzyme synthesizes intracellular second messenger.

    Specificity & Regulation of Receptor

    • Receptors have a high degree of specificity (e.g., b1 and b2-adrenergic receptors).
    • High affinity (e.g., 10⁹-10¹¹ M⁻¹).
    • Receptors can be regulated (e.g., phosphorylated receptors binding to arrestin).
    • Hormone-receptor complexes can be internalized (endocytosis).

    G Protein

    • G-proteins (also called transducer proteins) transmit external stimuli to effector enzymes.
    • Composed of three subunits (α, β, γ).
    • GTPase activity: hydrolyzes GTP to GDP.
    • Inactive state: GDP-bound, active state: GTP-bound.
    • Subunits (αs, αi) affect adenylate cyclase activity.

    Hormone-Receptor Interaction: Adenylyl Cyclase Signaling Pathway

    • Resting state: receptor, G-protein, and enzyme do not interact.
    • Hormone binding to receptor.
    • Conformational change exposing site for G-protein attachment.
    • G-protein activation via GTP exchange.
    • α-GTP disassociates from βγ-complex and activates effector enzyme.

    cAMP - Protein Kinase A Pathway

    • cAMP is synthesized from ATP by adenylate cyclase.
    • cAMP activates protein kinase A (PKA)
    • PKA phosphorylates proteins, altering cellular function.

    Role of cAMP in the breakdown of Glycogen

    • Glucagon and epinephrine trigger glycogen breakdown via PKA.
    • PKA phosphorylates glycogen phosphorylase kinase, activating glycogen phosphorylase, leading to glucose release.

    Role of cAMP in the action of hormones

    • Glucagon and epinephrine stimulate glycogen breakdown (glycogenolysis) and increase blood glucose via PKA activation.
    • Insulin regulates glycogen synthesis.

    Regulation of glycogen degradation

    • Hormones like epinephrine and glucagon increase glycogen breakdown by activating glycogen phosphorylase.

    Second Messengers

    • Any compound acting intracellularly in response to an extracellular signal.
    • Hormones need a second messenger to enter a cell as they cannot directly cross the cell membrane themselves.
    • Various types of second messengers exist: cyclic AMP (cAMP), inositol trisphosphate (IP₃), diacylglycerol (DAG), Ca²⁺, cyclic GMP (cGMP), and tyrosine kinase pathways.

    Inositol trisphosphate (IP3), Diacylglycerol (DAG) & Ca2+ - protein kinase C pathway

    • Phospholipase C (PLC) cleaves PIP2 to form DAG and IP3.
    • IP3 triggers Ca2+ release from intracellular stores.
    • DAG and Ca2+ activate protein kinase C (PKC).
    • PKC phosphorylates target proteins
    • Cellular response

    IP3 and Calcium as Second Messengers

    • Hormone binds to receptor (Gq protein mediated).
    • Gq-protein releases GDP and binds GTP.
    • Phospholipase C (PLC) activated.
    • IP3 and DAG created.
    • IP₃ binds to receptor releasing Ca²⁺.
    • This Ca²⁺ activates proteins & mediates cellular response

    Protein Kinase C (PKC) Pathway

    • Hormone binding to receptor.
    • Activation of phospholipase C (PLC).
    • Breakdown of PIP2 into DAG and IP3.
    • IP3 causes release of Ca²⁺ from endoplasmic reticulum.
    • PKC activation by Ca²⁺ and DAG.
    • Phosphorylation of proteins.
    • Intracellular effects like enzyme activation and modulation of other proteins

    Mode of action of GnRH in the release of FSH and LH

    • GnRH activation of gonadotropic cells.
    • GnRH binds to cell surface receptors, causing activation of phospholipase C (PLC).
    • PLC hydrolysis of PIP2 to DAG and IP3.
    • Increase in cytosolic Ca2+ and PKC activation.
    • Exocytosis of LH and FSH hormones from cells.

    NO as a 2nd Messenger

    • NO is synthesized from arginine by nitric oxide synthase (NOS).
    • Endothelial forms of NOS (e.g., eNOS) and neural forms (nNOS) exist.
    • NO stimulates the production of Cyclic GMP (cGMP).

    (iii) Nitric Oxide can stimulate production of cGMP

    • Nitric oxide interacts with the heme group of soluble guanylyl cyclase (sGC).
    • The interaction converts GTP to cGMP.
    • cGMP activates protein kinase G (PKG).

    Role Of cAMP, DAG, cGMP

    • Adenyl cyclase converts ATP to Cyclic AMP (cAMP) which activates Protein Kinase A.
    • Phospholipase C converts PIP2 to IP3 and DAG which activates Protein Kinase C.
    • Nitric Oxide activates guanylate cyclase to convert GTP to cyclic GMP (cGMP) which activates Protein Kinase G

    (iv) Tyrosine Kinase Pathway

    • Protein kinase system involves tyrosine phosphorylation within the cytoplasm.
    • Important for growth factor receptors like insulin, EGF, PDGF, NGF, VEGF, and certain oncogenes.

    Hypothetical scheme for signal transduction in insulin action

    • Insulin binding to receptor triggers tyrosine autophosphorylation.
    • Tyrosine phosphorylation regulates essential cellular processes.
    • Metabolism reactions involve GLUT4 translocation and glucose uptake, glycogen synthesis and lipid synthesis, cell growth and death or apoptosis

    Specific Reading Materials

    • Devlin's Textbook of Biochemistry with Clinical Correlations, pp 925-931, 943-953.
    • Lippincott Illustrated Review of Biochemistry, pp 79-85.
    • Harpers Review of Biochemistry, 25th edition, Chapter 44 (Cell-surface and Intracellular Receptors).

    Signal Transduction II: Intracellular Receptors

    • This lecture covers intracellular receptors, focusing on the cytoplasmic receptors and nuclear receptors.
    • Hormones that bind intracellular receptors are non-polar steroids, that can diffuse across the cell membrane.
    • Intracellular receptors are located within the cell (cytoplasm or nucleus).

    Summary of Signal Transduction I

    • Peptide hormones cannot penetrate the plasma membrane.
    • Receptors are located on the plasma membrane.
    • Second messengers are generated.
    • Existing enzymes are covalently modified.
    • Protein phosphorylation affects gene expression.
    • Effects happen faster than steroid hormones.

    Hormone Interaction With The Cognate Receptor

    • Receptors are either on the cell surface (plasma membrane) or intracellular receptors.
    • Steroid hormones (and thyroid hormones) bind with intracellular receptors
    • The hormone-receptor complex moves into the nucleus.
    • The activated complex binds to specific DNA sequences called Hormone Response Elements (HREs).
    • Genes are activated or repressed.

    Hormone Receptor Interaction

    • Free steroids enter cytoplasm and interact with their receptor.
    • Receptor-ligand complex dissociates heat shock protein and translocates to the nucleus.
    • The complex acts as a transcription factor to either augment or suppress gene transcription on DNA.

    Two classes of Nuclear Receptors

    • Type I receptors have HSP, present in the cytoplasm and translocate to the nucleus after binding to ligand.
    • Type II receptors lack HSP are located directly in the nucleus.

    Steroid hormone mechanism of action

    • Steroid hormones pass through the cell membrane and bind to intracellular receptors.
    • The hormone receptor complex moves to the nucleus.
    • Complex binds to specific DNA sequences.
    • mRNA production is regulated, leading to protein synthesis.

    Steroid Hormone Response

    • Steroid hormones bind to receptors in the cytoplasm or nucleus.
    • The hormone-receptor complex translocates to the nucleus.
    • Complex binds to specific DNA regulatory sites (HREs).
    • Transcription of target genes is regulated, leading to protein production.

    Steroid Receptors

    • Steroid receptors are transcription factors.
    • They may be located in the cytoplasm or the nucleus depending on the receptor-type.
    • They bind to the response element (HRE) on the DNA.
    • Heat shock proteins (HSPs) can bind to the receptor and regulate its activity until the specific hormone is present

    Steroid Receptor has 3 Functional Domains

    • Ligand/hormone-binding domain: Binding of ligand, heat shock proteins inactivation and translocating to the nucleus
    • DNA-binding domain: Interacting with DNA, until ligand is bound.
    • Variable (immunogenic domain): Modulates transcriptional activation

    Steroid Receptor has 4 Functional Domains

    • Variable domain: Most variable domain between various receptors.
    • DNA binding domain (DBD): Highly conserved and involved in DNA binding to the response element (HRE, part of the promoter).
    • Hinge region: Involved in receptor movement into the nucleus, and interacts with chaperones (e.g., HSP90 and HSP56).
    • Hormone binding domain (LBD): Modulating the magnitude of the response, with cytoplasmic conformation and homo/heterodimer formation

    General Model of Steroid Hormone Action

    • Hormone dissociates from binding protein.
    • Diffuses into cytosol or nucleus.
    • Binds to an intracellular receptor.
    • Hormone-receptor complex is activated.
    • Complex moves into nucleus and binds to HRE on DNA.
    • Gene expression is affected.
    • Synthesis of new proteins.
    • Alteration of cell phenotype or metabolic activity

    Features of the hormone response element (HRE)

    • Specific segments of chromosomal enhancers,
    • Binding elements for different steroid hormone receptors (glucocorticoids, mineralocorticoids, progesterone, and androgens).
    • Extent of expression determines hormone sensitivity in a cell type

    Steroid Hormone Receptors and their Response Elements

    • Steroid hormone receptors are proteins with binding sites for specific steroid molecules.
    • Receptor complexes bind to specific DNA sequences (response elements) within promoters of target genes.
    • Gene activation or repression is mediated by the binding of receptor complexes to HREs.
    • The presence of the hormone's receptor in a cell determines if the cell responds to the hormone.

    How a steroid hormone regulates gene transcription

    • Hormone binds to specific receptors.
    • Hormone-receptor complex forms a dimer.
    • The complex travels to the nucleus.
    • The complex binds to a DNA region called response element.
    • Gene transcription is affected.

    Positive and Negative Response Elements

    • Some glucocorticoid response elements activate gene transcription when bound by the hormone receptor complex.
    • Others inhibit gene transcription.
    • Examples: cortisol binding to positive response elements activating gluconeogenesis and to negative response elements diminishing insulin synthesis.

    Evidence to say that Not all cells have receptors for a specific hormone

    • Endometrial cells concentrated radioactivity after progesterone/estrogen administration; it's specific for hormones.
    • Other cells do not concentrate the hormone.
    • Hormone localization to a certain target cells. Cells without hormone receptors do not have the same response.

    Usually hormone exert → positive effect i.e. induction of gene expression.

    • Hormone exerts positive effect → induction of gene expression
    • Hormone exerts negative effect → repression.
    • Receptor acts as homodimer or heterodimer.
    • Ligand-activated transcription factors - modulate gene expression.

    General Model of Steroid Hormone Action

    • Overview of steroid hormone binding to specific intracellular protein receptors.
    • Preformed steroid hormones diffuse into target cells, binding to intracellular receptors.
    • Hormone receptor complex translocates to the nucleus and activates specific genes.

    Specific Reading Materials

    • Devlin's Textbook of Biochemistry with Clinical Correlations, pp 925-931, 943-953.
    • Lippincott Illustrated Review of Biochemistry, pp 79–85
    • Harpers Review of Biochemistry, 25th edition, Chapter 44

    Minerals

    • Inorganic substances essential for various bodily functions.
    • Classified as macro or micro minerals based on daily requirement.
    • Provide structural support, regulate fluid balance and enzyme activity.
    • Insufficient intake leads to potential deficiency while excessive intake might prove toxic.

    Requirement of Calcium

    • Calcium is critical for bone health, muscle contraction, nerve function, and blood clotting.
    • Sources: milk, dairy products, and plant-based foods
    • Deficiency symptoms: rickets, osteomalacia, osteoporosis

    Requirement of Magnesium

    • Essential mineral necessary for various enzymatic reactions.
    • Stored in bones and soft tissues, including muscles.
    • Crucial for neuromuscular function, energy metabolism, and nucleic acid synthesis.
    • Deficiency symptoms: muscle weakness and other symptoms

    Body Requirement of Macrominerals

    • Describes various macrominerals (e.g., sodium, potassium, chlorine, phosphorus, sulfur).
    • Includes their major sources, daily intake, functions, and deficiency symptoms.
    • Focuses on the importance of maintaining the balance of these elements within the body.

    Requirement of Iron

    • Iron exists in ferrous (Fe²⁺) and ferric (Fe³⁺) forms; only Fe²⁺ is readily absorbed.
    • Essential for hemoglobin and myoglobin (oxygen transport).
    • Deficiency in iron leads to anemia.
    • Sources of iron include: meat, liver, eggs, vegetables, and potatoes.

    Requirement of Cobalt

    • Cobalamin (vitamin B₁₂) is an essential compound containing cobalt.
    • Essential for red blood cell development.
    • Deficiency symptoms include anemia.

    Requirement of Manganese

    • Manganese is a cofactor for enzymes involved in antioxidant systems (e.g., manganese superoxide dismutase), bone formation and various metabolic pathways.
    • Deficiency symptoms could include impaired growth.

    Requirement of Zinc

    • Zinc is involved in many metabolic pathways, including enzyme function and synthesis of proteins.
    • Deficiency symptoms include impaired wound.
    • Important for normal growth in children.
    • Source: meat, liver and cereals

    Requirement of Selenium

    • Selenium is involved in antioxidant enzyme function, particularly in glutathione peroxidase.
    • Deficiency symptoms include rare cases of cardiac muscle damage.

    Requirement of Chromium

    • Chromium plays a regulatory role in hormone action and metabolism (e.g., regulating glucose tolerance; insulin sensitivity).
    • Deficiency symptoms may include glucose intolerance.
    • Sources include: liver, oysters, cheeses, and asparagus.

    Body Requirement of Microminerals

    • Lists microminerals like copper (Cu), molybdenum (Mo), iodine (I), vanadium (V).
    • Details their daily requirements, sources and functions in various processes (e.g., metabolism of carbohydrates and lipids).
    • Explains any potential deficiencies or symptoms.

    Summary of Mineral Metabolism

    • Inorganic mineral elements that have a bodily function must be received from the diet.
    • Two main groups: macrominerals and microelements (trace elements).
    • Insufficient intake can lead to deficiencies; excessive intake, toxicity.
    • Sodium: Extracellular cation, potassium: Major intracellular cation.
    • Only ferrous form of iron is absorbed.
    • Selenium is crucial for antioxidant enzymes.

    Biochemistry Water Soluble Vitamins

    • Distinguishes between water-soluble and fat-soluble vitamins.
    • Explains the sources, synthesis, and functions of various water-soluble vitamins in humans.
    • Discusses avitaminosis as a deficiency syndrome.

    Classification of Vitamins

    • Categorizes vitamins as water-soluble or fat-soluble.
    • Further classifies water-soluble vitamins into Non-B-Complex, B-Complex, and Other categories, based on their functions (energy-releasing, hematopoietic, etc.)

    Importance of Ascorbic Acid (Vit. C)

    • Reducing agent: reducing O2, nitrate, and various cytochromes.
    • Involved in iron absorption and enzyme action e.g. collagen synthesis.
    • Antioxidant: directly removing peroxyl radicals; indirectly restoring the antioxidant properties of fat-soluble vitamin E.
    • Deficiency of this vitamin causes scurvy.

    Importance of Thiamine (Vit. B₁)

    • Thiamine pyrophosphate (TPP) is a crucial coenzyme in oxidative decarboxylation reactions.
    • Plays a key role in carbohydrate metabolism (especially in the Krebs cycle).
    • Deficiency leads to beriberi, causing polyneuropathy, muscle wasting, and cardiac failure.

    Importance of Riboflavin (Vit. B₂)

    • Riboflavin converts into flavin adenine dinucleotide (FAD) and flavin adenine mononucleotide (FMN).
    • FAD & FMN are important electron carriers in redox reactions in Kreb's cycle.
    • Deficiency symptoms: angular stomatitis, glossitis

    Importance of Niacin (Vit. B₃)

    • Niacin is essential for the biosynthesis of nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+).
    • NAD+ & NADP+ are crucial coenzymes for many redox reactions, including those in the Krebs cycle.
    • Deficiency leads to pellagra, exhibiting symptoms of diarrhea, dermatitis, and dementia.

    Importance of Pantothenic Acid (Vit. B₅)

    • Pantothenic acid is essential for Coenzyme-A (CoA) synthesis, a crucial carrier for acyl groups.
    • CoA plays vital roles in many metabolic processes, including the formation of acetyl-CoA, fatty acid synthesis, and the Krebs cycle.

    Importance of Vitamin B₆

    • Pyridoxal Phosphate (PLP) is an essential coenzyme involved in amino acid metabolism (especially transamination and decarboxylation).
    • PLP is essential for the formation of neurotransmitter and haem synthesis.
    • Deficiency could cause anaemia and nerve function problems.

    Importance of Cobalamin (Vit. B₁₂)

    • Cobalamin is exclusively synthesized by microorganisms.
    • Must be consumed via diet.
    • Plays a role in the metabolism of amino acids and fatty acids.
    • Needed for converting methylmalonyl-CoA to succinyl-CoA and for methyl group transfer reactions. Very important in DNA & RNA development.
    • Deficiency can cause pernicious anemia

    Importance of Folate (Folic Acid)

    • Folate derivatives are carriers of single carbon units, essential for nucleotide synthesis.
    • Essential for DNA synthesis in dividing cells.
    • Folate deficiency: macrocytic anemias, neural tube defects in developing fetuses

    Importance of Biotin

    • Biotin is a coenzyme for carboxylation reactions,
    • Crucial for gluconeogenesis and fatty acid synthesis.
    • Deficiency is rare and usually linked to an overly cooked egg rich diet
    • Intestinal flora may have a role in generating this vitamin.

    Carbohydrate Metabolism: Glycolysis

    • Describes Glycolysis as a set of reactions oxidising glucose to pyruvate or lactate depending on the presence or absence of oxygen.
    • Takes place in the cytosol of cells and involves ten reactions.
    • Glycolysis has two main stages: priming and energy-yielding.
    • Summarizes the overall reaction occurring in aerobic and anaerobic conditions and the energy yield from each of the conditions.

    Active Transport

    • Transport method where energy is required to move substances against their concentration gradient.
    • This is usually done through carrier/transporter proteins.
    • The mechanisms include: endocytosis, phagocytosis and pinocytosis.
    • Exocytosis as another form of active transport.
    • The Na+/K+ pump as an important method.

    Cell Surface Receptors

    • Integral proteins that span the plasma membrane.
    • Recognize and bind with external ligands, such as hormones and neurotransmitters.
    • Trigger a series of intracellular events (signal transduction) to create an intracellular response, often involving cascades of second messenger molecules.
    • Three main categories of receptors: ion channels, G-protein coupled receptors, and enzyme linked receptors.

    Transmembrane Signaling

    • Recognition of extracellular signals by integral membrane receptors leads to the generation of intracellular signals that are propagated across the cell.
    • Transmembrane proteins have both an extracellular domain which bind to a specific molecule and an intracellular domain which triggers a reaction within the cell.

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    Signal Transduction I: Cell Surface Receptor PDF

    Description

    Test your knowledge on hormones and their roles in signaling pathways. This quiz covers various aspects of hormone action, including peptide hormones, second messengers, and insulin's effects on glucose uptake. Understand the complex interactions that govern hormonal regulation in organisms.

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