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Week 6 Notes

by: Kylie McLaughlin

Week 6 Notes Bio 208

Kylie McLaughlin
Fundamentals of Cell Biology
Dr. Ed Draper

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Here's week 6 notes. It covers chapter 7 and the beginning of chapter 8.
Fundamentals of Cell Biology
Dr. Ed Draper
Class Notes
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This 8 page Class Notes was uploaded by Kylie McLaughlin on Sunday October 4, 2015. The Class Notes belongs to Bio 208 at Northern Illinois University taught by Dr. Ed Draper in Fall 2015. Since its upload, it has received 5 views. For similar materials see Fundamentals of Cell Biology in Biological Sciences at Northern Illinois University.

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Date Created: 10/04/15
Week 6 Notes Chapter 7 cont The Role of Membrane Carbohydrates in CellCell Recognition ces recognize each other by binding to molecules often containing carbohydrates on the extracellular surface of the plasma membrane membrane carbohydrates may be covalently bonded to lipids forming glycolipids or more commonly to proteins forming glycoproteins sugars are added in the ER and GA carbohydrates on the external side of the plasma membrane vary among species individuals and even cell types in an individual Membrane Topology distinct inside and outside faces the asymmetrical distribution of proteins lipids and associated carbohydrates in the plasma membrane is determined when the membrane is built by the ER and golgi apparatus and can more between endomembrane organelles within NE gt ER gt GA gt PM outer or of all of these organelles as well as the cell exterior are quottypologically equivalentquot inner or of all of these organelles as well as the outer surface of the PM are quottypologically equivalentquot Six Maior Functions of Membrane Proteins Transport Enzymatic activity Signal transduction Cellcell recognition lntercellularjoining Attachment to the cytoskeleton and extracellular matrix ECM P P PP NE Diffusion the tendency for molecules to spread out evenly into the available space no energy is required net movement of solutes from HIGH to low and the concentration movement down a concentration gradient spontaneous does not require energy net solute movement occurs until an equilibrium is reached movement continues after equilibrium is reached Osmosis the diffusion of water across a selectively permeable membrane allows water but not substance in water requires no energy membrane is permeable to water but not solutes soutes quotwantquot to move from HIGH to low but cant instead water moves which tends to equalize solute concentrations on both sides of a membrane a concentration gradient can be used to do work Tonicty the ability of a surrounding solution to cause a cell to gain or lose water lsotonic solution solute concentration is the same as that inside the cell no net water movement across the plasma membrane Hypertonic solution solute concentration is greater than that inside the cell cell loses water Hypotonic solution solute concentration is less than that inside the cell cell gains water lsotonic same solute concentration on both sides during osmosis water moves from hypotonic gt hypertonic hypotonic lower solute concentration hypertonic higher solute concentration hypertonic or hypotonic environments create osmotic problems for organisms osmoreguation the control of solute concentrations and water balance is a necessary adaption for life in such environments animal cells prefer to be in isotonic solution cell walls help maintain water balance in hypotonic solution the plant cell becomes turgid expands cell cannot burst because of cell wall in an isotonic solution plant cell can survive but is not the ideal situation in hypertonic solution plant cells don39t like it and can die because the actual cell shrinks but cell wall stays the same size Passive Transport is the movement of a solute or its concentration gradient This process is exergonic it does not require and may release energy 1 Simple diffusion is transport directly through a membrane Uncommon few substances are membranepermeable 2 Facilitated diffusion requires a or protein Many types each is for the solute it transports Transport Proteins transport proteins allow passage of hydrophilic substances across the membrane some transport proteins called channel proteins have a hydrophilic channel that certain molecules or ions can use as a tunnel channe proteins called facilitate the passage of water other transport proteins called carrier proteins bind to molecules and change shape to shuttle them across the membrane a transport protein is speci c for the substance it moves Active transport is the movement of a solute I or its concentration gradient this process is it requires energy which is supplied by ATP active transport proteins are called lon Pumps Maintain Membrane Potential membrane potential is the voltage difference across a membrane votage is created by differences in the distribution of positive and negative ions across a membrane two combined forces collectively called the drive the diffusion of ions across a membrane a chemical force the ions concentration gradient an electrical force the effect of the membrane potential on the ions movement an is a transport protein that generates voltage across a membrane eectrogenic pumps help store energy that can be used for cellular work The Proton Pump the main electrogenic pump of plants fungi and bacteria is a proton pump the proton pump uses ATP energy to generate a proton gradient H gradient this gradient has chemical and electricalcharge components the cytoplasm is negative more anions a proton H gradient is used to cotransport work movement of another solute up its gradient endergonic is driven by movement of H down its gradient exergonic an H gradient is the quottransport currencyquot in plants fungi and bacteria not in animals each solute has a speci c cotransporter protein movement of the solute is in the direction as H sucrose uptake movement of the solute is in the direction as H the NaK pump sodiumpotassium pump is the main eectrogenic pump in the PM in animal cells net reaction per cycle 6 steps 3 Na out 2 K in net negative charge inside use ATP in animals a sodium gradient is the quottransport currencyquot used to drive symport and anitport of various solutes Exocvtosis and Endocvtosis movement of molecules and structures across the PM occurs in the membrane Exocytosis moving out of the cell transport vesicles migrate to the membrane fuse with it and release their contents outside the cell synthesis of luminal proteins begins at the rough ER proteins are modi ed sorted and packaged in the GA exampes of proteins that are delivered to the PM and secreted into the extracellular space antibodies into the blood digestive enzymes from the pancreas into the intestine neurotransmitters at synapses Endocytosis ce takes in macromolecules by forming vesicles from the plasma membrane endocytosis is a reversal of exocytosis involving different proteins there are three types of endocytosis 1 Phagocytosis cellular eating 2 Pinocytosis cellular drinking 3 Receptormediated endocytosis Phagocytosis ceuar eating a cell engulfs a particle in a vacuole the vacuole fuses with a lysosome to digest the particle Pinocytosis cellular drinking endocytosis of vacuoles containing bulk uids from the cell exterior soube materials are taken up but uptake is not speci c pinches off little pieces of the membrane takes uid into the cell large random molecules the hope is that these molecules can be used to make amino acids ReceptorMediated Endocvtosis in receptormediated endocytosis binding of ligands to receptors triggers vesicle formation a ligand is any molecule that binds speci cally to a receptor site of another molecule receptors are clustered into pits with the help of cytoplasmic coat proteins coated vesicles are formed receptors are made to bind to speci c things to bring into the cell materials are taken up Chapter 8 An Introduction to Metabolism use this for break down carbohydrates and plant cells use energy from light sources to make carbohydrates Metabolism is the totality of an organisms chemical reactions metaboism is an emergent property of life that arises from orderly interactions between molecules 1 Making and breaking covalent bonds 2 Getting using and changing the form 3 Reactions are catalyzed by enzymes 4 Several enzymes may be organized into a pathway starting molecule substrate goes into catalyzed reaction enzyme 1 converts substrate A to product B enzyme 2 converts substrate B to product C enzyme 3 converts substrate C to product D Forward Reaction animals aerobic respiration in mitochondria cataboic degrade to simpler forms exergonic energy released Glucose 02 C02 H20 energy Reverse Reaction plants photosynthesis in chloroplasts anaboic make complex molecules endergonic energy required for plants the energy comes from the sun Energy capacity to cause change exists in various forms some of which can perform work Kinetic energy energy associated with motion Heat thermal energy kinetic energy associated with random movement of atoms or molecules Potential energy is the energy that matter possesses because of its location or structure Chemical energy is potential energy available for release in a chemical reaction energy can be converted from one form to another First Law of Thermodvnamics according to the rst law of thermodynamics the energy of the universe is constant energy can be transferred and transformed but it cannot be created or destroyed the rst law is also called the principle of conservation of energy Second Law of Thermodvnamics during every energy transfer or transformation some energy is unusable and is often lost as heat according to the second law of thermodynamics every energy transfer or transformation increases the disorder of the universe the evolution of more complex organisms does not violate the second law of thermodynamics entropy disorder may decrease in an organism but the universes totally entropy increases Reactions Cause Disorder think of a chemical reaction occurring in a cell that has a constant temperature and volume this reaction can produce disorder in two ways 1 Changes of bond energy of the reacting molecules can cause heat to be released which disorders the environment around the cell 2 The reaction can decrease the amount of order in the cell Ex by breaking apart a long chain of molecules or by disrupting an interaction that prevents bond rotations bioogists want to know which reactions occur spontaneously and which require input of energy to do so they need to determine energy changes that occur in chemical reactions a living systems is energy that can do work when temperature and pressure are uniform as in a living cell Free enerov is relative 1 Position relative to gravity 2 Concentration gradient amount on 2 sides of a membrane 3 Relative stability of reactants and products free energy G is energy that is available to do work interested in AG the change in G between the reactants and products if AG is negative lt0 the reaction releases energy and is exergonic if AG is positive gt0 the reaction requires energy and is endergonic AG G nal state G initial state AG AH TAS AH change in enthalpy AS change in entropy T absolute temperature in K metalic equilibrium death ATP powers cellular work by coupling exergonic reactions to endergonic reactions a cell does three main kinds of work 1 Chemical 2 Transport 3 Mechanical to do work cells manage energy resources by energy coupling the use of exergonic process to drive an endergonic one most energy coupling in cells is mediated by ATP


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