Exam 1 Notes Lecture 1 June 7 2011 We have many feedback mechanisms that allow us to adjust to changes in our internal and external environment and maintain homeostasis Negative Feedback Mechanisms Negative feedback mechanisms digress from standard and goes back to standard Right side of diagram If you have a snack of a Dr Pepper and a Snickers your glucose level will increase Average level of glucose in plasma of blood is 90 mg 100 ml of blood We are starting to digress from the standard The Beta Cells of the Islets of Langerhans in the Pancreas is designed to detect movement of glucose level away from the 90 mg mark The hormone insulin is the first messenger and is looking for a target cell receptor The target cell then absorbs glucose from blood plasma The bottom line is that the target cell s job is to solve the problem The problem is that we have too much glucose therefore the glucose goes into the target cell by a series of steps Glucose is the molecule that a cell depends on for energy and is used via cellular respiration To get the glucose in and out of cell requires a method of transport Glucose will only get into the cell if insulin allows it to Left side of diagram Later in the day you have not eaten anything Glucose level is supposed to be 90 mg 100 ml of blood but it is lower instead so you would go left on the diagram The sensor that senses that your glucose level is decreasing is the Alpha Cells of the Islets of Langerhans in the Pancreas The Alpha Cells release the hormone glucagon which looks for a target cell Glucagon attaches to the receptor and glucose is kicked out of the cell to help raise the glucose level thus returning to the standard Other examples of negative feedback include maintaining calcium levels If you have too much calcium thyrocalcitonin is released to bring the level down If you do not have enough calcium parathormone is released to bring the level up If homeostatic mechanisms do not work properly or you interrupt positive or negative feedback you can get disease If glucose is not going into the cell fat will go into the cell and cause ketosis which can lead to atherosclerosis high blood pressure and cardiovascular disease The top cause of death in diabetics is cardiovascular disorders because their bodies constantly burn fat Positive Feedback Mechanisms Positive feedback does not occur as much as negative feedback An example of positive feedback is childbirth During childbirth As the baby grows and positions itself and gets closer to coming out the uterus gets more receptors pressure receptors These pressure receptors go up to the mom s brain and say that it is time to release oxytocin Oxytocin goes down the body and starts to make things move down to get ready for birth More pressure more oxytocin More pressure more oxytocin etc Then childbirth occurs Most positive feedback mechanisms lead to something of a more disastrous nature It constantly moves away from the standard If the actual childbirth did not occur the mother would die because you keep moving from the standard no going back to it Other examples of positive feedback include cancer and blood clots The Cell Cellular Membrane Chapter 3 The cell is the basic unit of structure and function that carries out the activities of life Cells on the outside of your skin have to be really close together so nothing comes out of your body Desmosomes tight junctions make the skin cells stay close together Gap junctions have a connection so that ions can travel between cells The cell membrane is an organelle Its number one responsibility is to control what goes in and what comes out When the cell membrane can no longer do this we say it is losing its integrity and it is on its way to death One of the first signs of a cell dying is shrinking crenation or if it s poofy lysis Transport how things get in and out of the cell membrane The cell membrane is a double phospholipid membrane Out of the cell extracellular intercellular interstitial Double phospholipid layer is composed of two phosphates and two lipids Phosphates like water hydrophilic while the lipids do not like water hydrophobic Basic unit of a protein is amino acids There are 20 amino acids They are connected together by peptide bonds Integral proteins are proteins that go from the outside to the inside through the membrane itself Integral means all the way through There will be some proteins that will be on the outside or stuck on the inside and they are called peripheral proteins Three important integral proteins are 1 stretches and forms a tube or channel or passageway from the outside to the inside or from the inside to the outside 2 Makes up things such as the pumper molecule this integral protein is represented as an X 3 Enzymes and other kinds of molecules represented as curly q s Always think of a protein as the brain of the cell because they are functional and make things happen The phospholipid is structural Sometimes peripheral proteins have the job of opening or closing the channels Sometimes they turn on off enzymes Enzymes decrease the level of activation energy required and speed up the reaction Lecture 2 June 8 2011 Cellular Membrane It is up to the cell membrane to decide what ions go in and out of the cell What is the chemical part of the cell membrane that is important for structure The double phospholipid layer Proteins are the brains of the cell membrane Three types of integral proteins 1 channels or pores 2 pumper molecules 3 enzymes Attached to the inside or outside of the cell are peripheral proteins Some might be opening and closing the channels we call this acting like gates they sometimes might turn on an enzyme or they might be there to act as a receptor The most repeated unit in the membrane is the phospholipid There are good and bad types of cholesterol The cholesterol on the edges of the cell membrane support it and also help the membrane maintain a certain level of rigidity but yet fluidity We want some cholesterol in our body to keep the membrane stable so it doesn t just float off Cellular Membrane Polarity The cell membrane must be polarized in order for it to function properly When a membrane of a cell is at rest not letting things go in and out of the cell we call that a resting membrane The resting membrane has a charge difference and it is said to be polarized On the outside of the membrane it is positive and on the inside it is negative This is just along the membrane not in the cell the cell itself