11 - Cell Communication
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سلولها می‌توانند به یکدیگر سیگنال بدهند و سیگنالهایی را که از سلولهای دیگر و محیط دریافت می کنند، تفسیر کنند. سیگنالها ممکن است شامل نور و یا بر اثر تماس باشند، اما اغلب مواد شیمیایی هستند. در این جلسه، ما بر مکانیسم های اصلی انتقال پیام متمرکز می‌شویم که سلولها سیگنال‌های شیمیایی ارسال شده از سلولهای دیگر را دریافت، پردازش و پاسخ می‌دهند. --------------------------------------------------------------------------------- Cells can signal to each other and interpret the signals they receive from other cells and the environment. The signals may include light and touch, but are most often chemicals. In this session, we focus on the main mechanisms by which cells receive, process, and respond to chemical signals sent from other cells.
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cardiac ion channels and channelopathies
The document discusses ion channels and their role in generating cardiac action potentials. It begins by defining ion channels as pore-forming proteins that gate the flow of ions across cell membranes. It then describes the key properties of ion channels including selectivity, gating, and their role in establishing membrane potentials. The remainder of the document details the specific ion channels involved in each phase of the cardiac action potential, including the fast sodium current underlying the upstroke in Phase 0, the potassium and chloride currents producing Phase 1 repolarization, the calcium and potassium currents maintaining the Phase 2 plateau, and the currents responsible for Phase 3 repolarization. Pacemaker cell action potentials are also discussed, noting their unique pacemaker potential in Phase 4 and lack of Phase
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Ion channelopathy
The document discusses ion channelopathies and provides details on the cardiac action potential and the ion channels involved in each phase. It describes the major ion channels that generate the cardiac action potential, including sodium channels, transient outward potassium current, ultra-rapidly activating delayed outward rectifying current, and rapidly activating delayed outward rectifying current. It also discusses channelopathies associated with these ion channels like Brugada syndrome and long QT syndrome.
Signal transduction sm
This is a Powerpoint made by a myself for the PG seminar in front of Professors. For the preparation standard books were followed and guidance from expertise was taken. This will be helpful for UG and PG students of Medical and life science students.
Ion channels
Ion channels are pore-forming membrane proteins that regulate the flow of ions across cell membranes. There are several types of ion channels classified by their gating mechanism and selectivity for specific ions like potassium, sodium, calcium, and chloride. Voltage-gated ion channels open or close in response to changes in membrane potential, while ligand-gated channels are activated by binding of neurotransmitters or other ligands. Ion channels play crucial roles in generating electrical signals in excitable cells and regulating various cellular processes. Diseases caused by mutations in ion channel genes are known as channelopathies.
Ion channels
Ion channels are membrane proteins that allow ions to pass through their pore, regulating ion flow and electrical signals. There are two main types of gated ion channels: ligand-gated channels, which open when neurotransmitters bind, and voltage-gated channels, which open in response to changes in membrane potential. Ligand-gated channels allow sodium influx upon acetylcholine binding, depolarizing the membrane and triggering action potentials. Voltage-gated channels maintain the resting potential and enable action potential propagation along axons by selectively transporting sodium, potassium, calcium, and chloride ions in response to changes in voltage.
Translation in eukaryotes
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cardiac ion channels and channelopathies
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The document discusses ion channelopathies and provides details on the cardiac action potential and the ion channels involved in each phase. It describes the major ion channels that generate the cardiac action potential, including sodium channels, transient outward potassium current, ultra-rapidly activating delayed outward rectifying current, and rapidly activating delayed outward rectifying current. It also discusses channelopathies associated with these ion channels like Brugada syndrome and long QT syndrome.
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Ion channels
Ion channels are pore-forming membrane proteins that regulate the flow of ions across cell membranes. There are several types of ion channels classified by their gating mechanism and selectivity for specific ions like potassium, sodium, calcium, and chloride. Voltage-gated ion channels open or close in response to changes in membrane potential, while ligand-gated channels are activated by binding of neurotransmitters or other ligands. Ion channels play crucial roles in generating electrical signals in excitable cells and regulating various cellular processes. Diseases caused by mutations in ion channel genes are known as channelopathies.
Ion channels
Ion channels are membrane proteins that allow ions to pass through their pore, regulating ion flow and electrical signals. There are two main types of gated ion channels: ligand-gated channels, which open when neurotransmitters bind, and voltage-gated channels, which open in response to changes in membrane potential. Ligand-gated channels allow sodium influx upon acetylcholine binding, depolarizing the membrane and triggering action potentials. Voltage-gated channels maintain the resting potential and enable action potential propagation along axons by selectively transporting sodium, potassium, calcium, and chloride ions in response to changes in voltage.
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Cell signaling involves three main stages - reception, transduction, and response. Reception involves signaling molecules binding to membrane receptors, which leads to conformational changes. Transduction refers to the activation of intracellular signaling pathways through second messengers. Response occurs when downstream effectors are activated, bringing about cellular responses like metabolism, gene expression, and cell differentiation. Precise regulation of cell signaling pathways is essential for normal cell function, and defects can lead to diseases.
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Cell Signalling.pptx
Cell signaling involves three main stages - reception, transduction, and response. In reception, signal molecules bind to receptor proteins on the cell surface. Transduction then involves a cascade of intracellular molecular interactions that relay the signal, often using phosphorylation or second messengers like cAMP or calcium ions. This ultimately leads to the response stage, where the signal regulates gene transcription or cytoplasmic activities, resulting in changes in the cell. Signaling pathways allow cells to communicate both locally and over long distances to coordinate functions in multicellular organisms.
Signal tranduction
1) Signal transduction is the process by which extracellular signals are converted into intracellular responses through receptors and signaling pathways.
2) Ligands bind to membrane receptors, triggering intracellular signaling cascades that often involve secondary messengers like cAMP, IP3, DAG, Ca2+, or nitric oxide.
3) These secondary messengers activate intracellular effector molecules like protein kinases that phosphorylate target proteins and regulate cellular processes or gene expression.
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Cell signalling
This document summarizes cell signaling and signal transduction. It discusses extracellular signaling molecules that transmit information to target cells via paracrine, autocrine, endocrine, or direct contact signaling. Signal transduction involves reception of signals by cell surface or intracellular receptors, transduction through a signal cascade, and cellular response. Secondary messengers like cAMP, cGMP, IP3, DAG, and calcium ions amplify and carry intracellular signals.
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This document summarizes the process of translation in prokaryotes. It begins with an introduction to translation occurring in the cytoplasm where ribosomes synthesize proteins using messenger RNA (mRNA). The three main stages of translation are then described in detail: initiation, elongation, and termination. Initiation involves assembly of the ribosome and initiation factors on the mRNA start codon. Elongation is the process of adding amino acids to the growing polypeptide chain through binding of transfer RNA (tRNA) and the actions of elongation factors. Termination occurs when a stop codon is reached and release factors trigger hydrolysis and release of the completed protein. Key components of translation like ribosomes, mRNA, tRNA, and their functions are
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Calcium channels play a key role in many cellular functions by regulating intracellular calcium levels. There are several types of calcium channels that influence calcium influx and release from intracellular stores. Voltage-dependent calcium channels include L-type, N-type, P/Q-type, R-type, and T-type channels that are involved in processes like muscle contraction, neurotransmitter release, and pacemaking. Dysfunctions in calcium channels can lead to channelopathies like hypokalemic periodic paralysis or malignant hyperthermia. Calcium channels are also important therapeutic targets, with calcium channel blockers and other drugs influencing channels to treat conditions like hypertension, angina, epilepsy, and migraines.
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Cell signaling transduction mechanisms
1. Cell signaling involves the synthesis, release, and transport of signaling molecules like neurotransmitters and hormones that bind to receptors on target cells.
2. This triggers signal transduction pathways inside the cell that cause changes in cell behavior.
3. The cell then responds accordingly through actions like releasing other molecules or changing its activity level.
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The document discusses cell membranes and various mechanisms of transport across membranes. It explains that cell membranes are made up of a lipid bilayer with embedded proteins. Transport can occur passively via diffusion or facilitated transport, or actively via pumps requiring ATP. Active transport is exemplified by the sodium-potassium pump which maintains electrochemical gradients. Other topics covered include endocytosis, receptor-mediated endocytosis, signal transduction pathways using secondary messengers like cAMP and calcium ions, and voltage-gated ion channels.
cell signalling & communication of cells.ppt
The presentation illustrates the basic modes of cell signalling pathways for undergraduate students. It mentions variety of examples of cell signalling with different receptors, ligands and target molecules
overview signaltransductionpathways
1. The document discusses cell signaling and communication between cells through signaling molecules. It describes different types of cell signaling including paracrine, autocrine, and synaptic signaling.
2. Key components of cell signaling pathways are described such as receptors, ligands, second messengers, and protein phosphorylation. Different classes of receptors - intracellular receptors, ligand-gated ion channels, G-protein coupled receptors, and receptor tyrosine kinases - are summarized.
3. Common second messengers like calcium ions, cyclic AMP, and inositol phosphates are explained. The roles and mechanisms of hormone receptors and different types of ligands are also outlined.
Physiology retina
The retinal pigment epithelium (RPE) performs several important functions to support photoreceptor cells in the retina. It acts as a barrier between the retina and choroid, transports nutrients between the retina and blood vessels, regulates the subretinal space ion concentration, engages in the visual cycle to regenerate photopigments, and phagocytoses shed photoreceptor outer segments. Phototransduction is the process where photons are converted to electrical signals in the photoreceptor cells. It involves photoisomerization of rhodopsin triggering a biochemical cascade that modulates cyclic GMP levels and closes cation channels, ultimately leading to hyperpolarization.
Cell signaling
This document summarizes an evaluation seminar on cell signaling and signal transduction pathways presented by Mrutyunjay B Bellad of the Department of Pharmacology at H.S.K. College of Pharmacy in Bagalkot. The seminar covered various topics related to cell signaling including introduction, types of cell signaling, signal molecules and their actions, signaling through different receptor types, second messengers, G-protein coupled receptors, and signal transduction pathways. References included standard pharmacology textbooks.
Cell Signaling through GCPRs and intracellular receptors.pptx
Cell- Cell communication
Cell surface receptors
GPCRs
Intracellular signaling mechanisms
Second messenger system
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Cell signaling, regulating mechanism and structure
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Cell Signaling through GCPRs and intracellular receptors.pptx
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More from Ahmad V.Kashani
16 - From DNA To Protein - Part II
The process of DNA expression, or more widely known as gene expression is the synthesis of proteins using RNA molecules from genes. In other words, proteins are the link between genotype and phenotype. Gene expression is the process by which DNA directs the synthesis of proteins (or, in some cases, just RNAs). The last step of the expression of genes that code for proteins is translation.
فرآیند بیان DNA، یا بیشتر به عنوان بیان ژن شناخته میشود، سنتز پروتئینها با استفاده از مولکولهای RNA از ژنهاست. به عبارت دیگر، پروتئینها رابط بین ژنوتیپ و فنوتیپ هستند. بیان ژن فرآیندی است که در آن DNA سنتز پروتئینها (یا در برخی موارد فقط RNAها) را هدایت میکند. آخرین مرحله بیان ژنهایی که پروتئینها را کد میکنند، ترجمه است.
15 - From DNA to Protein - Part I
The inherited DNA of an organism contains specific traits that dictate the synthesis of proteins through the RNA molecules involved in protein synthesis. In other words, proteins are the link between genotype and phenotype. Gene expression is the process by which DNA directs the synthesis of proteins (or, in some cases, just RNAs). The expression of genes that code for proteins includes two stages: transcription and translation. In this slide, we are going to take a look into the processes of replication and transcription.
DNA ارثی یک ارگانیسم حاوی صفات خاصی است که سنتز پروتئینها را از طریق مولکولهای RNA درگیر در سنتز پروتئین دیکته میکند. به عبارت دیگر، پروتئینها رابط بین ژنوتیپ و فنوتیپ هستند. بیان ژن فرآیندی است که در آن DNA سنتز پروتئینها (یا در برخی موارد فقط RNA ها( را هدایت میکند. بیان ژنهایی که برای پروتئینها کد میکنند شامل دو مرحله است: رونویسی و ترجمه. در این اسلاید قصد داریم نگاهی به فرآیندهای همانندسازی و رونویسی بیاندازیم.
14 - The Chromosomal Basis of Inheritance
When chromosomes are duplicated, each chromosome has two copies of the allele, one on each sister chromatid. However, Gregor Mendel’s “hereditary factors” were purely an abstract concept when he proposed their existence in 1860. Using improved techniques of microscopy, cytology and genetics were converged as biologists began to see parallels between the behavior of Mendel’s proposed hereditary factors during sexual life cycles and the behavior of chromosomes which later began to be developed into “the chromosome theory of inheritance”. According to this theory, Mendelian genes have specific loci (positions) along chromosomes, and it is the chromosomes that undergo segregation and independent assortment.
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وقتی کروموزومها کپی میشوند، هر کروموزوم دارای دو نسخه از یک آلل است که هر کدام بر روی هر کروماتید خواهری قرار دارد. با این حال، اصل "عوامل وراثتی" مندل، هنگامی که وی در سال 1860 وجود آنها را مطرح کرد، یک مفهوم کاملاً انتزاعی بود. با استفاده از تکنیکهای بهبود یافته میکروسکوپی، سیتولوژی و ژنتیک همگرا شدند، زیرا زیست شناسان رفتارهای موازی بین عوامل وراثتی مندل در طول چرخههای جنسی را مشاهده کردند که بعدها این رفتارهای کروموزومی به "نظریه کروموزومی وراثت " تبدیل شد. براساس این نظریه، ژنهای مندلی دارای موقعیتهای (موقعیت) خاصی در امتداد کروموزومها هستند و این کروموزومها هستند که تحت جداسازی و طبقه بندی مستقل قرار میگیرند.
13 - Mendel and the Gene Idea
توضیح وراثت به طور کلی و گسترده در دهه 1800، و به طور مشخص فرضیه "مخلوط شدن" مورد پسند دانشمندان و زیست شناسان عصر خود بود. براساس این ایده، مواد ژنتیکی توسط والدین و درست همان طور که رنگ های آبی و زرد برای تبدیل شدن به رنگ سبز ترکیب میشوند، مخلوط میشدند. البته این فرضیه توضیح نمیداد که چگونه صفات پس از کنار رفتن یک نسل دوباره در نسل بعدی ظاهر میشوند. یک گزینه جایگزین برای مدل مخلوط شدن مواد ژنتیکی، فرضیه وراثت "ذرات معلق" است یا همان ایده ژن. در این مدل، والدین واحدهای موروثی به نام ژنها را که هویت جداگانه خود را در فرزندان حفظ می کنند، منتقل میکنند. گریگور مندل راهبی بود كه سازوكار ذرهای این نوع وارثت را با استفاده از گیاه نخود فرنگی به اثبات رساند.
The explanation of heredity most widely in favor during the 1800s was the “blending” hypothesis, the idea that genetic material contributed by the two parents, mixes just as blue and yellow paints blend to make green. The blending hypothesis failed to explain how traits can reappear after they’ve skipped a generation. An alternative to the blending model is a “particulate” hypothesis of inheritance: the gene idea. In this model, parents pass on discrete heritable units—genes— that retain their separate identities in offspring. Gregor Mendel was the monk who documented a particulate mechanism for this form of inheritance using pea plants.
12 - The Cell Division Cycle
The ability of organisms to produce more of their own kind is the one characteristic that best distinguishes living things from nonliving matter. This unique capacity to procreate, like all biological functions, has a cellular basis. The continuity of life is based on the reproduction of cells, or cell division. Cell division plays several important roles which are giving rise to a new organism, enabling development, renewing and repairing and also replacing damaged tissue is multicellular organisms.
توانایی موجودات زنده در تولید بیشتر از نوع خود یکی از ویژگیهایی است که موجودات زنده را از مواد غیر زنده به بهترین وجه متمایز می کند. این ظرفیت منحصر به فرد برای تولید مثل، مانند همه عملکردهای بیولوژیک، دارای پایه سلولی است. تداوم زندگی براساس تولید مثل سلولها یا تقسیم سلولی است. تقسیم سلولی چندین نقش مهم را ایفا میکند که نه تنها باعث ایجاد یک ارگانیسم جدید میشود، همچنین امکان رشد، تجدید و ترمیم و همچنین جایگزینی بافت آسیب دیده موجودات چند سلولی را نیز فراهم می کند.
10 - Photosynthesis
انرژی روی زمین توسط خورشید تأمین می شود. گیاهان و ارگانیسمهای خاص از طریق فرآیندی که فتوسنتز نامیده میشود، انرژی خورشید را توسط اندامکهای سلولی ویژهای به نام کلروپلاست به مولکول های آلی تبدیل می کنند. در این فصل ، من در مورد این روند به طور مفصل صحبت خواهم کرد.
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Life on earth is powered by sun. Plants and specific organisms convert the energy of the sun by specialized cellular organelles called chloroplasts into organic molecules through a process which is called photosynthesis. In this chapter, I will talk about this process in details.
9 - Metabolism and Transfering Energy - Part Two
سلولهای زنده برای انجام بسیاری از وظایف خود به انتقال انرژی از منابع خارجی نیاز دارند. همه ارگانیسمها باید از طریق فتوسنتز و تنفس سلولی این انرژی را از مولکول های آلی موجود درغذا بدست آورند. تنفس با استفاده از اکسیژن و تولید ATP، باعث شکستن این سوخت میشود. مواد زائد این نوع تنفس، دی اکسید کربن و آب، مواد اولیه فتوسنتز هستند. در این اسلاید، من سعی می کنم چگونگی برداشت سلولها از انرژی ذخیره شده در مولکولهای آلی و استفاده از آن برای تولید ATP از طریق تنفس سلولی را توضیح دهم.
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Living cells require transfusions of energy from outside sources to perform their many tasks. All organism need to obtain this energy from organic molecules of food through photosynthesis and cellular respiration. Respiration breaks this fuel down, using oxygen and generating ATP. The waste products of this type of respiration, carbon dioxide and water, are the raw materials for photosynthesis. In this slide, I try to explain how cells harvest this energy stored in organic molecules and used it to generate ATP through cellular respiration.
8 - Metabolism and Transfering Energy - Part One
Metabolism involves the chemical reactions that take place in organisms to sustain life. These reactions occur along metabolic pathways and either break down molecules through catabolism to release energy, or build molecules through anabolism by consuming energy. Adenosine triphosphate (ATP) is used to power cellular work by storing and transferring energy from exergonic reactions through its phosphate bonds. Enzymes regulate metabolic reactions by lowering their activation energy and increasing reaction rates in their active sites. Environmental factors and feedback inhibition regulate enzymatic activity and metabolic pathways.
7 - Membrane Structue and Function
در زیست شناسی کمپبل با صراحت و روشنی ذکر شده است: "غشای پلاسمایی که سلول را احاطه کرده است را میتوان به عنوان لبه حیات دانست، مرزی که سلول زنده را از محیط اطراف خود جدا میکند." در این اسلاید، ما سعی میکنیم یاد بگیریم که چگونه غشای سلولی، عبور مواد مختلف را با اندازهها و ماهیت مختلف کنترل میکند.
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It is neatly mentioned in Campbell Biology: “The plasma membrane that surrounds the cell can be considered the edge of life, the boundary that separates a living cell from its surroundings.” In this slide, we try to learn how cellular membrane controls the passage of different substances of different size and nature.
6 - A tour of the cell - Part Three
دیواره سلولی، شکل ویژهای از ماتریس خارج سلولی است که هر سلول گیاه را احاطه کرده است. دیواره سلولی مسئول بسیاری از خصوصیاتی است که سلولهای گیاهی را از سلولهای حیوانی متمایز میکند. در سلولهای حیوانی داستان متفاوت است! بافتهای مختلف دارای اجزا و سازمان منحصر به فرد و تخصصی ماتریس خارج سلولی (ECM) هستند، که هر ECM را قادر میسازند تا نقشهای خاص بافتی، از جمله پشتیبانی ساختاری، انتقال نیروها و فیلتراسیون ماکرومولکولی را انجام دهد.
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Cell wall, specialized form of extracellular matrix that surrounds every cell of a plant. The cell wall is responsible for many of the characteristics that distinguish plant cells from animal cells. In animal cells, the story is different! Different tissues have unique and specialized Extracellular Matrix (ECM) components and organization, which enables each ECM to carry out tissue-specific roles, including structural support, the transmission of forces and macromolecular filtration.
5 - A tour of the cell - Part Two
در روزهای اولیه میکروسکوپ الکترونی، زیست شناسان تصور میکردند که اندامک سلول یوکاریوتی آزادانه در سیتوزول شناور است. اما پیشرفت های انجام شده در تکنولوژی ساخت میکروسکوپهای نوری و الکترونی نشان داده است که شبکهای از فیبرها در سراسر سیتوپلاسم گسترش یافته است و آنها آن را اسکلت سلولی نامیده اند.
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In the early days of electron microscopy, biologists thought that the organelles of a eukaryotic cell floated freely in the cytosol. But improvements in both light microscopy and electron microscopy have revealed that a network of fibers is extended throughout the cytoplasm and they named it the cytoskeleton.
4 - A tour of the cell - Part One
سلولها به همان اندازه اتمها در شیمی، برای سیستمهای زنده اساسی هستند. هم اکنون انواع مختلفی از سلول ها در بدن ما کار میکنند. در طول تکامل، سلولها به روشهای مختلف اصلاح شدهاند. اگرچه سلولها می‌توانند تفاوت اساسی با یکدیگر داشته باشند، اما ویژگیهای مشترکی دارند. در این اسلاید و 2 مورد بعدی، ما سفری به درون یک سلول خواهیم داشت و با اجزای سازنده آن آشنا خواهیم شد.
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Cells are as fundamental to the living systems of biology as the atom is to chemistry. Many different types of cells are working in our body right now. During the evolution, cells have been modified in many different ways. Although cells can differ substantially from one another, they share common features. In this slide and the next 2 ones, we’ll take a tour inside a cell and become acquainted with its components.
3 - Chemical Composition of the Cell - Part 2
The document outlines the key biomolecules - lipids, proteins, and nucleic acids. It describes how lipids such as fats, phospholipids, and steroids are made up of nonpolar tails and polar heads that allow them to perform structural and energy storage functions. Proteins are composed of amino acid polymers that fold into primary, secondary, tertiary, and sometimes quaternary structures to enable their diverse catalytic, defensive, and structural roles. Nucleic acids DNA and RNA are made of nucleotides with pentose sugars, nitrogenous bases, and phosphate groups that encode genes and genetic information.
2 - Chemical Composition of the Cell - part 1
This slide tries to show how elements can turn into molecules and then complex structures and further develop into organs for building a living organism.
This slide is adapted from "Campbell Biology" and for further studies, you can refer to the second chapter of the book.
The slide is prepared for freshman Bachelor's students.
1 - variety of life
This slide is the first one of a series of slides adapted from the "Campbell Biology" for Bachelor student of science and medicine. In this Slide I have tried to briefly talk about taxonomy and the classification of organisms.
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Immersive Learning That Works: Research Grounding and Paths Forward
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The binding of cosmological structures by massless topological defects
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
waterlessdyeingtechnolgyusing carbon dioxide chemicalspdf
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
Direct Seeded Rice - Climate Smart Agriculture
Direct Seeded Rice - Climate Smart AgricultureInternational Food Policy Research Institute- South Asia Office
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
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11 - Cell Communication
- 1. Cell Communication UNIVERSITY OF TEHRAN Ahmad V.Kashani, PhD
- 2. Outlines • The nature of signaling • The elements of signaling • Types of signaling • Stages of signaling • Reception: A signaling molecule binds to a receptor protein • Plasma membrane receptors • G protein-coupled receptors • Receptor Tyrosine Kinases • Ion channel receptors • Intracellular receptors • Transduction • Response
- 3. The Elements of Signaling • Signaling pathway is composed of different elements: • Signaling cell • Signal • Target cell • Signal transduction: is the conversion of one form of signal to another • Cell signaling: is receiving and transducing signals
- 4. Types of signaling • The released signal may carry out its effect on: • Local cells (local signaling) • Distant cells (long-distant signaling) • In both animal and plant: • Cell junctions • Cell-cell recognition • AKA Contact-dependent
- 5. Types of signaling Local Signaling Long-distance Signaling
- 6. Stages of signaling • There are 3 stage: • Reception: Reception is the target cell’s detection of a signaling molecule coming from outside the cell. • A chemical signal is “detected” when the signaling molecule binds to a receptor protein located at the cell’s surface • Transduction: converts the signal to a form that can bring about a specific cellular response. • Response: the transduced signal finally triggers a specific cellular response.
- 7. Reception
- 8. Reception • Main elements of this system are: • Receptor protein molecule • Ligand molecule • Ligand binding generally causes a receptor protein to undergo a change in shape. • 3 types of receptors are involved in this stage: • G protein-coupled receptors (GPCR) • Receptor Tyrosine Kinases (RTKs) • Ion channel receptors
- 9. Reception – G protein receptors • A G protein-coupled receptor (GPCR) is a cell-surface transmembrane receptor that works with the help of a G protein, a protein that binds the energy-rich molecule GTP.
- 10. Reception – G protein receptors
- 11. Reception – RTKs • Receptor tyrosine kinases (RTKs) belong to a major class of plasma membrane receptors characterized by having enzymatic activity.
- 13. Reception – Ion channel Receptors • A ligand-gated ion channel is a type of membrane channel receptor containing a region that can act as a “gate,” opening or closing the channel when the receptor changes shape. • When a signaling molecule binds as a ligand to the channel receptor, the channel opens or closes, allowing or blocking the flow of specific ions, such as Na+ or Ca2+.
- 16. Transduction
- 17. Transduction • Signal transduction pathway is the chain of molecular interactions that leads to a particular response within the cell. • Like dominos, it resembles a series of activations • Transduction molecules: • Proteins • Phosphorylation/ Dephosphorylating • Small Molecules and Second Messengers • Cyclic AMP (cAMP) • Calcium ion and Inositol Triphosphate (IP3)
- 18. Transduction Proteins • Protein Phosphorylation and Dephosphorylation • Protein Kinase: • An enzyme that transfers phosphate groups from ATP to a protein • Protein Phosphatase: • An enzymes that can rapidly remove phosphate groups from proteins
- 19. Signaling – Transduction Small Molecules • Cyclic AMP • The second messenger cyclic AMP (cAMP) is made from ATP by Adenylyl Cyclase • This enzyme is embedded in the plasma membrane. • The phosphate group in cAMP is attached to both the 5’ and the 3’ carbons; this cyclic arrangement is the basis for the molecule’s name. • Cyclic AMP is inactivated by phosphodiesterase • This enzyme converts it to AMP.
- 20. Signaling – Transduction Small Molecules • Cyclic AMP • Epinephrine and many other signaling molecules lead to activation of adenylyl cyclase by G proteins and formation of cAMP • The immediate effect of an elevation in cAMP levels is usually the activation of a serine/threonine kinase called protein kinase A.
- 21. Transduction Small Molecules • Calcium Ions and Inositol Trisphosphate (IP3 ) • In animals many signaling molecules induce responses their target cells via increasing the cytosolic concentration of calcium ions (Ca2+): • Neurotransmitters • Growth factors • Some hormones
- 22. Transduction Small Molecules • The Ca2+ concentration in the cytosol is usually much lower than in the extracellular fluid and ER. • Protein pumps in the plasma membrane and the ER membrane, driven by ATP, move Ca2+ from the cytosol into the extracellular fluid and into the lumen of the ER. • Mitochondrial pumps, driven by chemiosmosis, move Ca2+ into mitochondria when the calcium level in the cytosol rises significantly.
- 23. Transduction Small Molecules • If the cytosolic Ca2+ level is low, in response to a signal relayed by a signal transduction pathway, the cytosolic calcium level may rise, usually by a mechanism that releases Ca2+ from the cell’s ER. • The pathways leading to calcium release involve two other second messengers: • Inositol trisphosphate (IP3) • Diacylglycerol (DAG). • Scientists use the term second messenger for all small, non- protein components of signal transduction pathways.
- 24. Response
- 25. Response • The response at the end of the pathway may occur: • In the nucleus: Many signaling pathways ultimately regulate protein synthesis, usually by turning specific genes on or off in the nucleus. Like an activated steroid receptor, the final activated molecule in a signaling pathway may function as a transcription factor. • In the cytoplasm: Sometimes a signaling pathway may regulate the activity of proteins rather than causing their synthesis by activating gene expression. This directly affects proteins that function outside the nucleus
- 26. Summary • The nature of signaling • The elements of signaling • Types of signaling • Stages of signaling • Reception: A signaling molecule binds to a receptor protein • Plasma membrane receptors • G protein-coupled receptors • Receptor Tyrosine Kinases • Ion channel receptors • Intracellular receptors • Transduction • Primary element: Proteins • Secondary elements: • Small molecules: cAMP • Ions: Ca2+ • Response • In the nucleus • In the cytoplasm