TMJC Cell Communication Notes

Page 1 of 30 Tampines Meridian Junior College JC2 H2/9744 Biology 2024 Core Idea 3B 12. Energy and Equilibrium – Communication in Multicellular Organisms SYLLABUS OVERVIEW No. Overarching Idea Topics 1 Core Idea 1 The Cell and Biomolecules of Life Cell – The Basic Unit of Life 2 Biomolecules of Life and Cellular Transport 3 Core Idea 3 Energy and Equilibrium Transformation of Energy – Photosynthesis and Cellular Respiration 4 Core Idea 2 Genetics and Inheritance Genetics and Inheritance (I) – The Cell Cycle 5 Genetics and Inheritance (II) – DNA Replication and Gene Expression 6 Genetics and Inheritance (III) – DNA Mutations and their Consequences 7 Genetics and Inheritance (IV) – Molecular Techniques in DNA Analysis 8 Genetics and Inheritance (V) – Organization of Genome & Control of Gene Expression in Eukaryotes [Includes Core Idea 1D: Stem Cells] 9 Genetics and Inheritance (VI) – Organization and Inheritance of Viral Genomes 10 Genetics and Inheritance (VII) – Organization of Genome & Control of Gene Expression in Prokaryotes 11 Genetics and Inheritance (VIII) - Inheritance 12 Core Idea 3 Energy and Equilibrium Communication and Equilibrium in Multicellular Organisms 13 Core Idea 4 Biological Evolution Biological Evolution 14 Extension Topic A Infectious Diseases Immunity and Infectious Diseases 15 Extension Topic B Impact of Climate Change on Animals & Plants Climate Change – Causes and Impacts on Animals and Plants

Page 2 of 30 What’s the Big Picture? The following question should help students frame their learning: • How do organisms respond to internal and external changes? Communication is needed for organisms to respond to the environment and maintain equilibrium Organisms should be able to detect changes both from the surrounding environment and within themselves so that they are able to respond to these changes to maintain a constant internal environment. This ability to respond to changes is made possible due to coordination across the various biological systems as well as communication between cells. Communication between cells can take the form of electrical or chemical transmission via the nervous or endocrine system respectively. The endocrine system facilitates communication between different cells through the release of hormones into the bloodstream. Binding of hormones to receptors on or within target cells initiates signal transduction and eventually results in a change in gene expression to bring about certain physiological changes. Defects in any part of the signalling pathway often lead to detrimental conditions such as metabolic diseases and cancer. Core Idea 3: Energy and Equilibrium Topic B: Communication and Equilibrium in Organisms The emphasis of this section is on how cell signalling processes can cause a physiological response in an organism. The circulatory system transports hormones from where they are secreted to the target cells. Hormones bind to specific binding sites – receptors found on the cell surface membrane or within the cell – to initiate the process of cell signalling. Cell signalling comprises the following stages: ligand-receptor interaction, signal transduction and amplification, and cellular response. Various molecules such as second messengers, kinases and transcription factors mediate the processes of converting information from the signal molecule (hormone) into a cellular response. Insulin and glucagon are examples of hormones that trigger cell signalling pathways to bring about responses to regulate blood glucose level. It is important to appreciate the complexity and inter -connectedness of how the communication systems within and between cells interact to achieve the required response. The maintenance of blood glucose levels will be used to illustrate how physiological responses are regulated by controlling gene expression . Sufficient glucose in the blood is necessary to provide cells with respiratory substrates. The pancreas detects the level of blood glucose and secretes either insulin or glucagon to maintain a stable level of glucose in blood. These hormones trigger cellular responses in liver, muscle and adipose cells when the hormones bind to receptors . Signal transduction occurs through various proteins and molecules to amplify and transduce the signal and eventually, elicit a cellular response . Thus, cell signalling and communication result in a relatively stable internal environment for cells in an organism to function optimally.

Page 3 of 30 LEARNING OUTCOMES Core Idea 3B: Communication and Equilibrium in Organisms Candidates should be able to: a) Outline the main stages of cell signalling: i. ligand-receptor interaction, ii. signal transduction (phosphorylation cascade and signal amplification) iii. cellular response (change in gene expression). (Knowledge of intracellular receptors is not required.) b) Explain the roles and nature of second messengers (including cyclic AMP). c) Explain the role of kinases and phosphatases in signal amplification. d) Outline how insulin and glucagon regulate the concentration of blood glucose level through the respective tyrosine kinase receptor and G -protein linked receptor. (The outline should be limited to describing how the ligand induces a conformational change in membrane-bound receptor to trigger downstream signalling pathways that elicit physiological changes in blood glucose level. Details of different second messengers and specific kinases activated in the pathway are not required). Use the knowledge gained in this section in new situations or to solve related problems. LECTURE OUTLINE 1. Overview 1.1 Why is Communication within the Multicellular Organism Important? 1.2 Types of Signal Molecules / Chemical Messengers 1.3 Types of Cell Signalling 1.4 Cell Signaling - How do cells receive and communicate signals? 2. Signal Reception 2.1 G Protein-Linked Receptor Signaling 2.2 Tyrosine Kinase Receptor Signaling 2.3 Ion Channel Receptor Signaling 2.4 Intracellular Receptor Signaling 3. Signal Transduction 3.1 Important Features 3.2 Transduction by Protein Phosphorylation and Dephosphorylation 3.3 Transduction by Second Messengers 4. Cellular Responses to Signals 4.1 Nature of Cellular Responses to Signals 4.2 Termination of Signal 5. Advantages and Significance of Cell Signaling Systems in Multicellular Organisms 6. Achieving Equilibrium in the Internal Environment of Multicellular Organisms 6.1 Overview 6.2 Regulation of Blood Glucose Concentration (A) Regulation of Blood Glucose Concentration by Insulin (B) Regulation of Blood Glucose Concentration by Glucagon

Page 4 of 30 REFERENCES 1. Reece, J., et al. (2014) Campbell Biology. Pearson Education, Inc., San Francisco, Tenth Edition. Pages 232 – 248. 2. Animations: Introduction to cell signalling https://www.youtube.com/watch?v=-dbRterutHY Common cell signalling pathways (good overview!) https://www.youtube.com/watch?v=9sF_h-bAnIE Signal transduction https://www.dnatube.com/video/1162/Signal-transduction G protein coupled receptor https://www.youtube.com/watch?v=xT0mAQ4726s https://www.youtube.com/watch?v=kLOwGKEvZF0 Second messengers: cAMP https://www.youtube.com/watch?v=re2dNETlvw0 Signal amplification https://www.youtube.com/watch?v=wo_fXINA9U0 https://www.youtube.com/watch?v=PQxQ1joKd1o

Page 5 of 30 Step 1: Signal Reception Binding of signal molecules (ligands / first messengers) with a shape complementary to the binding site of receptors forms the ligand-receptor complex → receptor protein undergoes conformation change and is activated Step 2: Signal Transduction Multi-step, cascaded pathways that amplify and relay the signal received. Step 3: Cellular Response Various types of cellular responses (e.g. gene expression