Exam 4 Review Chapters 11 45 Cell Communication and Chemical Signals Motivation Cells can coordinate their actions through communication chemicals such as hormones are one mechanism for communication within a cell between and among cells nearby or distant in a complex organism and between individual organisms Note that we discuss chemical communication and other forms of communication e g electrical and mechanical in many other parts of this course Objectives signaling A Describe the three main stages of cell signaling including hormonal a Stage 1 Reception a signaling molecule binds to a receptor protein causing it to change shape b Stage 2 Transduction cascades of molecular interactions relay signals from receptors to target molecules in the cell c Stage 3 Response same chemical signal can trigger different responses in different types of cell i All in the forms of light heat odor and touch d Hormonal Signaling long distance signaling An endocrine hormone usually is carried by the blood from its site of release to its target i Animals the circulatory system transports hormones throughout the body to reach target cells with appropriate receptors ii Plant plant hormones are signal molecules produced within the plant and occur in extremely low concentrations hormones regulate cellular processes in targeted cells locally and when moved to other locations in other locations of the plant iii Endocrine Signaling signaling molecules called hormones act on target cells distant from their site of synthesis by cells of endocrine organs In animals an endocrine hormone usually is carried by the blood from its site of release to its target e Paracrine Signaling local signaling the signaling molecules released by a cell only affect target cells in close proximity to it it affects other cells i Ex Two neurons would be an example of paracrine signaling growth factor and clotting factors are paracrine signaling agents f Synaptic Signaling local signaling Electrical signal triggers release of neurotransmitter Neurotransmitter diffuses across synapse hormonal signaling to the target cell B Describe how phosphorylation propagates and amplifies signal information describe the advantages of using a multistep pathway in the transduction stage of cell signaling a Phosphorylation i Propagates Amplifies because phosphorylation is a sequence of events where one enzyme phosphorylates another causing a chain reaction leading to the phosphorylation of thousands of proteins 1 Can be seen in signal transduction of hormone b Advantages of multistep pathway messages i Amplification feedback on the pathway increased redundancy in case there is a defect somewhere in the system easier to regulate or shut off the system since there are more targets C Define the term second messenger Briefly describe the role of these molecules in signaling pathways a Second Messenger intracellular mediator in many hormone sensitive systems the systemic hormone does not enter the target cell but binds to a receptor and indirectly affects the production of another molecule within the cell b Roles these molecules diffuse intracellularly to the target enzymes or intracellular receptor to produce the response D Describe how cyclic AMP cAMP is formed and how it propagates signal information a Formed after the epinephrine bound on its receptor in liver or muscle the G protein will be activated and thus it will in turn activate the Adenyl cyclase thus cAMP will be produced cAMP will trigger the protein kinase A thus glucose is released from glucogen in liver or muscle cell b Propagates Signal Epinephrine is the signaling molecule in the cAMP activity it will only be produced when there is less glucose concentration E Describe how the cytoplasmic concentration of calcium ion Ca2 can be altered and how this increased pool of Ca2 is involved with signal transduction a In addition to voltage sesitive Ca2 channels voltage sensitive Na Ca exchange can also contribute to the increase in Ca2 ion depolarization b The increased pool of Ca2 is involved with signal transduction because signal transduction occurs when extracellular signaling molecule activates a cell surface receptor In turn this receptor alters intracellular molecules creating a response F Describe how signal information is transduced into cellular responses in the cytoplasm and in the nucleus a Pathway of reactions one protein binds to another which binds to another and so on until it reaches its target organization of a stimulus receptor control center efferent G Describe the loop in an endocrine pathway involved in homeostasis H Discuss how and why different target cells exposed to the same signaling effector in a simple endocrine pathway describe an example of a signal and negative feedback molecule hormone may respond in different ways Local chemical signaling Autocrine Paracrine synaptic signaling nervous system neuro muscular junction Chapter 40 Regulating the Internal Environment Bioenergetics and Regulation of Body Temperature Motivation The environment provides many challenges to survival of living organisms in addition to the infectious agents controlled by the immune system Variations in temperature see Introduction of Animal Physiology lecture availability of water and solute concentrations in water are just a few of these challenges A Describe the basic sources of chemical energy and their fate in animal cells a Harvest chemical energy from food b Chemical energy fuels metabolism and activity c Food digested by enzymatic hydrolysis nutrients are absorbed by d Energy containing molecules are used to generate ATP e Remaining molecules are used in biosynthesis once energetic needs f ATP generates heat most of which the animal gives off to its body cells are met surroundings B Define Homeostasis Describe three functional components of a homeostatic control system negative feedback system a Homeostasis maintaining a constant internal environment b Three Functional Components 1 Senses the variable 2 Responds to stimulus by sending information to the i Receptor control center ii Control Center 1 Determines set point for the variable 2 Receives information from the receptor on afferent pathway 3 Analyzes information 4 Determines response based on set point 5 Sends information the effector on efferent pathway iii Effector 1 Means of control of the variable 2 Receives information from the control center 3 Acts to decrease of increase the variable C Distinguish between regulators
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