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Cell Test 2 notes

by: Michael Notetaker

Cell Test 2 notes CELL-1010-01

Michael Notetaker
Intro to Cell & Molec Biology
Vijayaraghavan, Meenakshi

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Cell test 2 notes
Intro to Cell & Molec Biology
Vijayaraghavan, Meenakshi
Study Guide
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This 36 page Study Guide was uploaded by Michael Notetaker on Friday October 2, 2015. The Study Guide belongs to CELL-1010-01 at Tulane University taught by Vijayaraghavan, Meenakshi in Fall 2012. Since its upload, it has received 27 views. For similar materials see Intro to Cell & Molec Biology in Business at Tulane University.

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Date Created: 10/02/15
Test 2 Chap 4 Motor Proteins Category of cellular proteins that use ATP as a source of energy to promote movement Three domains called the head hinge and tail Walking analogy 0 Ground is a cytoskeletal lament your leg is the head of the motor protein and your hip is the hinge Three different kinds of movements 0 Motor protein moves the cargo from one location to another along the xed lament Motor protein can remain in place and cause the lament to move Motor protein attempting to walk both the motor protein and lament restricted in their movement exerts a force that causes the lament to bend REREAD AND OUTLINE MICROTUBLES THROUGH MOTOR PROTENS O O Flagella and cilia Prokaryotes have ag Human have cilia sperm however have ag Some lower euks have it like algae Microtubles and motor proteins interact to facilitate cilia and agella movement The type of movement associated with cilia and agella movement is when the motor proteinand liment are restricted in their movement and when the motor protein attempts to walk it exerts a force on the liament that causes the lament to bend Flagella usually longer than cilia and present singly or in pairs Cilia are often shorter than agella and tend to cover all or part of the surface of a cell 0 Ex protists like paramecia have cilia Share the same internal structure arrangement of microtubules motor protein dynein and linking proteins like nexin Dynein moves stuff toward nuc Microtubles have 9 2 array each of the two central microtubles consist of a single microtuble while the outer nine are doublet microtubles two merged microtubles Microtubles in cilia and agella eminate from basal bodies o Basal bodies are anchored to the cytoplasmic side of the plasma membrane 0 Basal bodies provide a site for microtubles to grow Just like the crentrosome in animal cells Microtubules dynein and axoneme Movement involves the propagation of a bend which begins at the base of the structure and proceeds toward the tip 0 Motor protein dynein is activated to walk toward the basal bodies of the mcirotubles ATP hydrolysis is required 0 Because of the linking proteins the microtubules and the motor protein dynein are not free to move relative to each other The motor proteins exert a force that bends the microtubule o Dyneins at the base activated rst ATP hydrolysis followed by ones progressively closer to the tip Motor protein interaction with actin Cytoskelyton liment actin and its motor protein myosine responcible for movement in muscle cells Ex protists like amoeba with pseudopodia Actin liments capable of d i and polymerizes formed at the leading edge and create a lamellipodium Myosine tugs on actin laments and moves the cell Sheetz and Spudich Show That Myosin Walks Along Actin Filaments Early researchers proposed the sliding lament model based on work with living cells in vivo actin laments slide past thicker laments composed of myosine indicated myosine and actin were nes for muscle movement 1983 Michael Sheetz and James Spudich devised an approach to study myosin in vitro to see how the muscle contraction worked on a molecular level Is dif cult to est function of any one protein So they isolated and puri ed cellular components and studied their function outside the cell Nitella cells were used as a source of actin laments Puri ed actin becomes tangled Myosin was puri ed and attached to a uorescently labeled bead Nitella cells cut open and plasma membrane where the parallel array of actin laments were and pined it down thus exposed the laments Rest of cellular components besides choloplast were washed away Cytoplasmic streaming Floresent myosone added done with and Mo atp and with NEM which should have which was thought to bind to myosine and inhibit its function With atp present myosine moved along actin lament and did not when NEM was there Con rmed that myosin is a motor protein that uses ATP to walk along actin laments And not actin as the motor protein on myosine o All that is needed for movement are actin myosin and ATP Endomembrane system Organels that have membs inside cystplams Cytosol is everything iside cytopllams outside the membrane bond organells As well as the plasma membrane Small amount of genetic material also found in chloroplasts and mitochondria Network of membranes enclosing the nucleus endoplasmic reticulum Golgi apparatus lysosomes and vacuoles Also includes plasma membrane bc the pm is involved in secretion May be directly connected to each other or pass materials via vesicles small membrane enclosed spheres Endomembrane system forms a dynamic integrated network of membranes that requires constant sorting to maintain the functional properies of each organelle Nuclear envelope 1020 of cell Doublemembrane structure enclosing nucleus called nuclear envelope Outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum membrane Nuclear pores provide passageways for molecules and macromolecules are located where the outer mem meets the inner mem Materials within the nucleus are not part of the endomembrane system Inside the nucleus is chromosomes and lamentius network of proteins called nuclear matrix part of endomembrane system Nuc encloses a matrix made of scaffold protein of irregular length called 0 Each chromosome is composed of genetic material mainly DNa and proteins that allow the chromosome to compact itself and t inside the nucleus This combination is called the chromatin Chromosomes located in chromosome territories Nuclear matrix consists of two parts 0 Nuclear lamina made of intermediate laments that line inner nuclear membrane 0 Internal nuclear matrix connected to lamina and lls interior of nucleus 0 nuc matrix in inner part of nuc mem o lining inner nuc membrane are intermediate proteins Very stable provide support Called nuclear lamina supports the iner nuc mem Gate keeper proteins make sure that only proteins that bind to nucleic acids come inside and only certain proteins like rna come out 0 Inside nuc is chromosomes forms by ass of dna and hystone and other proteins 0 Nuc matrix maintain chromosomes in their territory 0 Materials within the nucleus are not part of the endomembrane system Nucleus involves the protection organization and expression of genetic materials Nucleus Another important function of nucleus is ribolsome assembly Nucleolus prominent region in the nucleus of non dividing cells site of rib asymbly is a colectoin of genes involved in synth of rib nra Genes that incode these rna molecules are located there Dense struc in nuc Rna molecules that are components of ribs are made at the nucleolus bc of this Composed of two subunits one small and one large Each subunits contain one or more rna molecules and several types of proteins 0 When rib is going to be formed rib is complexes on which prot synth takes place formed by some protein and mostly rib rna rib rna assymbled in nuc protein part of rib be made in cytosol protein moves in through nuc pore and orgs with rib rna molecules to form ribosomal subunits Units then exit through the pores into the cytosol where they are need for protein synthesis Endoplasmic reticulum Network of membranes that form attened uid lled tubules or cisternae ER membrane encloses a single compartment called the ER lumen O O O O 0 Rough endoplasmic reticulum rough ER Studded with ribosome s Ribosome s actively synthesize proteins through the ER membrane Involved in protein synthesis and sorting of proteins destined for the ER gogi apparatus lysosomes vacuoles plasma membrane or outside the cell Protein must rst be directed through the ER membrane bf it can go to any of these other places Allows certain protein to bind to the membrane insertion of newly made proteins into the membrane Glycocylation third imp function of rough er attahment of proteins to carbohydrates and lipids Smooth endoplasmic reticulum smooth ER 0 O O Lacks ribosome s Bc of large network of smooth er increased surface area for key enzymes that play key metabolic roles Enzymes in Smooth involved in detox of alcholhol smooth increase Converts hydrophobic acl to hydrophilic metabolites and leaves out the kidney bc they are easily exreeted Detoxi cation carbohydrate metabolism calcium balance synthesis and modi cation of lipids Glycogen associated with the smooth Glycos broken into active glucose Carbohydrate met Liver cells of animal sstore energy in form of glycogen polymerof glucose glycogen are in cytosol neer smooth er When chemical energy is needed enzymes break down glycogen into glucose 6 phosphate Smooth has enzyme called glucose 6 phofatase converts glucose 6 phosphate into glucose only in form of glucose can it move out of liver into blood stream Function accumulation of Ca ions S er has Ca pumps that transport Ca2 into the er loomen The regulated release of Ca2 ions into the cytosol is involved I many vital cellular processes like muscle contractions 0 Plasma storage stores plasma ions they are in voleved in signaling Help in contractinon in muscle 0 Involved with lipids involved in formation of hormones enzymes in the smooth er are critical in the synthesis and modi cation of lipids 0 Synthesis of phospholipids the main lipid component of euk cell membranes Golgi apparatus 0 O 0 Also called the Golgi body Golgi complex or simply Golgi Stacks of attened membrane each atterned membrane encloses a single compartment Associated with endoplasm rect Sis golgi near ER the medial then trans near the plasma membrane Packageing and traport center of cell Receives all glycociated and lipids form endoplasm rec and processes them and send sthem to dif organels 7777777777777777777 Stack of attened membranebounded compartments which are not continuous with the ER Vesicles transport materials between stacks that bud with one compartment in the golgi and fuse with another Three overlapping functions 0 Secretion processing and protein sorting Material packed by golgi into sectretory vesicles that later fuse with the plasma membrane thus releasing their contents outside the cell Proteins destined for secretion ar synthesized in the ER travel to golgi then the plasma membrane secretory way Enzymes in golgi process or modify certin proteins and lipids Glycosilation continues in golgi o Proteinlipid transported from the ER via vesicle to the yto the cis Most glycosilation occurs in medial Proteolysis enzyme call proteolase cuts enzymes int smaller polypeptides Protein sorting is function of the golgi 0 Once protein enters the golgi from the er is directed to one of six locations Stay in golgi Transported via vesicle to er Lysosome vacuole plasma mem exterior of cell Lysosomes Involved in degrading macromolecules they can lyse macromolecules O 0 Contain acid hydrolases that perform hydrolysis hydroytic enzymes use a water mol to break a covalent bond Primary ys rich in acid hydrolasis does not come in comtact with anything so does not do function of hydrolysis doent degrade anothing Absorbes protons so ph is lowered Ph is initially not low Now is called secondary ys w ph of 48 that is whenit can prefrm its function of break down Many different types of acid hydrolases to break down proteins carbohydrates nucleic acids and lipids One other function of ysosome is digestion of substances that are taken up from outside the cell endocytosis 0 Recycling of wornout organelles through endocytosis Autophagy digest intracellular materials 0 Cellular material ssuch as worn out organells are engulfed in a double membrane now called and autophagosome fuses with a ysosome the material inside the autophagosome is digested the small molecules that are released from this digestion are recycled back into the cytosol Vacuoles 0 Functions of vacuoles are extremely varied and they differ among cell types and even environmental conditions they function in storage regulation of cell volume and degradation Can contain uid and sometimes solid substances Made from the fusion of many smaller membrane vesicles Central vacuoles in plants for storage and support membrane of this is called tonoplast 0 Store water enzymes inorg ions like Ca also proteins and pigments o preforms a space lling function exerts pressure called turgor pressure on cell wall Wilting occurs when this pressure is lost due to the dehydration of the plant Contractile vacuoles in protists for expelling excess water necessary to remove excess water that enters the cell by diffusing across the plama membrane Phagocytic vacuoles in protists and white blood cells for degradation 0 Contain enzymes to break down the macromolecules within the food o Exist in animals cells as storage vesicles and temporarily store materials or transport substances 0 Vacuoles can exist in animals Plasma membrane 0 Boundary between the cell and the extracellular environment 0 Proteins in the plasma membrane play important roles that affect the activity inside the cell 0 Some of these proteins involved in membrane transport Transport essential nutrients or ions into the cell while others export o Membrane transport in and out of cell 0 Selectively permeable allows only certain substances in or out 0 Cell signaling using receptors 0 Cells must be able to sence change in their environment cells of muticellular organisms need to communicate with each other to coordinate their activities 0 Contains receptors that recognize signaling molecules environmental agents or molecules secreted by other cells 0 Signaling molecule binds t a receptor elicits a series of steps called signal cascade 0 Cell adhesion in animal cells proteins in the plasma membrane of adjacent cells bind to each other to promotes cell to cell adhegon Semiautonomous organelles in euk Can grow and divide to reproduce themselves but they are not completely autonomous because they depend on other parts of the cell for their internal components they depend on dna present in nuc to send dignal to them to divide Semiauto bc they have their own dna and ribosome s Mitochondria chloroplasts and peroxisomes Mitochondria supply cells with most of their atp Cells with heavy energy demand have more 0 Some proteins are absorbed from the plasma mem that are nec for the making of atp the energy currency of the cell 0 Outer and inner membrane 0 lntermembrane space separates them 0 Inner mem invaginated and forms projections clled cristae lnvaginations increase surface area of inner mem site where atp is made encloses mitochondrial matrix 0 Involved in formatin of hormones 0 Primary role is to make ATP not create energy 0 Converts chemical energy stored in the covalent bonds of org molecules sugars fats amino acids into a form the cells can use the breakdown of these molecules releases energy used to make atp Also involved in the synthesis modi cation and breakdown of several types of cellular molecules 0 Can also generate heat in brown fat cells groups of these cells serve as heating pads revive hibernating animals protection from cold Instead of producing atp they generate heat Chloroplasts not in pro bc they don39t have mem bound orgs o Photosynthesis certain pigment can convert radiant enrgy into usable energy 0 capture light energy and use some of that energy to synthesize organic molecules such as glucose 0 Found in nearly all species of plants and algae Outer and inner membrane with an intermembrane space 0 Third membrane the thylakoid membrane forms attened tubules that enclose a single convoluted conpartment stack to form a granum plural grana ln thy mem nd pigments embedded chlorophyll o Stroma inside inner mem outside thylakoid within this carbohydrates are produced Has enzymes to produce ba rbohydrates o Thylakoid lumen enclosed in thy mem Chloroplasts are specialized versions of plant organelles called plastids various types distinguished by their synthetic abilities and the types of pigments they contain 0 Types of plastids a Chloroplasts are involved in photosynthesis and give plants their green color have green pigment chlorophyll b Chromoplasts function in synthesizing and storing yellow orange and red pigments typically found in fruit and owers Nec for pollination and seed dispersal colors attract birds and insects c Amyloplasts are colorless plastids that synthesizes and stores starch energy inroots Are types of leucoplasts Proplastids give rise to plastids Peroxisomes Relatively small organelles found in all eukaryotic cells Single membrane that encloses uidfilled lumen Peroxisomal proteins are imported into the peroxisome in a manner similar to the targeting of proteins to the mitochondria and chloroplasts New peroxisomes are creaed by the devision of preexisting peroxisomes Origin remains controversial General function to catalyze certain chemical reactions typically those that break down molecules by removing hydrogen or adding oxygen involved in maintain the ph Leads to an accumulation of hydrogen peroxide Toxic molecules are broken down in liver Reaction byproduct is hydrogen peroxide H202 peroxisomes break this dangerous by product down Catalase enzyme in peroxisome breaks down H202 to water and oxygen Contain enzymes involved in the metabolism of fats and amino acids 0 Plant seeds contain organelles similar to peroxisomes called glyoxysomes Contains enzymes to convert fats to sugars Activated when a seed germinates Involved l betaoxidation of fatty acids into carbs Involved in detoxi cation Both peroxisomes and glyoxysomes are under name of microbodies MEM BRANE STRUCTURE AND TRANSPORT CHAPTER 5 Biological Membranes One of the key functions of a biomembrane is to regulate the traffic of substances into and out of the cell and its organelles Structure determines function 0 The structure of cellular membranes enables them to compartmentalize the cell while selectively importing and exporting vital substances Lipids form the basic matrix of a membrane 0 Proteins are embedded in the membrane or loosly attached to its surface 0 o Carbohydrates can be attached to membrane lipids and proteins 0 Basic framework of the membrane is the phospholipid biayer consists of two layers of lipids Phospholipids are amphipathic molecules Hydrophobic tails waterfearing region faces in fatty acyl tails Hydrophilic waterloving region faces out phosphate polar heads Membranes also contain proteins and carbohydrates Relative amount of each vary 0 Typical membrane might have 50 protein by mass remainder is lipids and some carbohydrates 0 Lipids are less massive than proteins so they outnumber the proteins 50 to 1 Fluidmosaic model Membrane is considered a mosaic of lipid protein and carbohydrate molecules Membrane exhibits properties that resemble a uid because lipids and proteins can move relative to each other within the membrane Half of the phospholipid biayer is termed a lea et Are highly asymmetrical Asymmetry occurs mostly with glycolipids lipids with carbohydrates attached are primarily in the extracellular lea et so that the carbohydrate portion of the glycolipid protrudes into the extracellular medium Proteins bound to membranes membrane proteins are attached to or embedded in the phospholipid biayer While the lipid biayer is the basic foundation of the cell membrane the proteins carry out most of the functions 0 Proteins can bind to membranes in three different ways 0 Integral membrane proteins intrinsic membrane proteins 0 Transmembrane proteins 0 One or more regions that are physically embedded in the hydrophobic region of the phospholipid biayer o The regions area the fransmembrane segments are stretches of hydrophobic amino acids that span the lipid biayer from one lea et to another 0 Segment is folded into an dhelix structure stabilized by hydrogen bonds Segment is stable because the non polar amino acids interact with the hydrophobic fatty acyl tail of the lipid molecules 0 Lipid anchors covalent attachment of a lipid to an amino acid side chain of a protein Fatty acyl tails of the lipid keep the protein bond to the membrane 0 Integral membrane proteins cannot be released from the membrane unless membranes are dissolved with organic solvent or detergent Peripheral membrane proteins Noncovaenty bound to regions of integral membrane proteins that project out from the membrane or they are bound to the polar head groups of phospholipids bound by hydrogen or ionic bonds thus can be removed by exposing the membrane to high salt concentrations Approximately 25 of All Genes Encode Membrane Proteins Membrane proteins participate in 0 Transport energy transduction cell signaling secretion cell recognition cell to cell contact 0 cell devote large amount of energy and metabolic machinery to synthesis of these membrane proteins 0 70 of medication produce their effects by binding to membrane proteins Membranes are important biologically and medically Computer programs can be used to predict the number of membrane proteins 0 Estimated percentage of membrane proteins is substantial 20 30 of all genes may encode membrane proteins 0 This trend is found throughout all domains of life including archaea bacteria and eukaryotes Function of many genes unknown study may provide better understanding and better treatments OOOOO Membranes are semi uid Fluidity biomembranes exhibit this individual molecules remain in close association yet have the ability to readily move within the membrane Semi uid most lipids can rotate freely around their long axes and move laterally within the membrane lea et 2d movement that occurs within the plane of the membrane 0 ln uid substances molecules can rotate in 3d 0 Rotational and lateral movement is energetically favorable bc it keeps the fatty acyl tails within the hydrophobic interior of the bHayeh quotFlip op of lipids from one lea et to the opposite lea et does not occur spontaneously energetically unfavorable bc the polar phospholipid head must be transported through the hydrophobic interior of the membrane 0 this transport requires ipasse uses energy from hydrolysis of atp Fippase requires ATP to transport lipids from one lea et to another Factors affecting uidity biochemical properties of phospholipids have effects on uidity of phospho bilayers 0 Length of fatty acyl tails Shorter acyl tails are less likely to interact which makes the membrane more uid 0 Presence of double bonds in the acyl tails 0 Therefore is unsaturated with respect to the number of hydrogen bonds that can be bound to the carbon atom Double bond creates a kink in the fatty acyl tail making it more difficult for neighboring tails to interact and making the bilayer more uid 0 Presence of cholesterol produced by animal cells Cholesterol tends to stabilize membranes Effects depend on temperature at higher temps cholesterol makes membranes less uid and visa versa to prevent freezing high temps to uid leakage At lower temps functioning of mem proteins may be inhibited Cell alter lipid comp of their membranes to adapt to these things Ex low temp more cholesterole high temp longer fatty acyl tails and fewer double bonds shorter tails intract less more uid longer tails enteract more less movement double bonds less interaction more uid therefore less hydrogen bonds will increase the interaction of the neighboring lipids therefore less movement Like lipids integral mem proteins may rotate and lat move throughout the plane of membrane They are large than the lipids so they move through the membranes slower Flip op of the mem proteins does not occur bc very energetically unfav the proteins contain hydrophilic regions projecting out from the phospholipid heads Energet unfav for the hydrophilic regions of the mem ros to pass through the hydrophobic bilayer portion Experiments on lateral transport 0 Larry Frye and Michael Edidin conducted an experiment that veri ed the lateral movement of membrane proteins 0 Mouse and human cells were fused picture 12 of fused cell with the green H2 mouse proteins and the other 12 with red proteins of the human cell 0 Temperature treatment 0 C or 37 C before being recooled Mouse membrane protein H2 uorescently labeled 0 C cells label stays on mouse side bc the low temp prevented movement 37 C cells label moves over entire cell bc higher temp enabled movement FRAP Watt Webb and colleagues used fluorescence recovery after photobleaching FRAP Proteins on the surface of a cell were covalently labeled with a uorescent chemical Small area of cell photobleached leaving white spot the previous color caused by the orecent molecules was removed 0 Over time bleached molecules within the white spot spread outward and the white region lled in with red uorescent molecules 0 Indicates that proteins can laterally move in the membrane Not all integral membrane proteins can move 0 Depending on the cell type 10 70 of membrane proteins may be restricted in their movement Integral membrane proteins may be bound to components of the cytoskeleton which restricts the proteins from moving laterally Also membrane proteins may be attached to molecules that are outside the cell such as the interconnected network of proteins that forms the extracellular matrix Glycosylation Process of covalently attaching a carbohydrate to a protein or lipid Glycolipid carbohydrate to lipid Glycoprotein carbohydrate to protein the carbohydrates that are attached have well de ned structures which serve as 0 Can serve as recognition signals for other cellular proteins 0 Proteins that are destined for a certain area of the cell can be glycocylated a sugar is added on a carb the carbsugar is then recognized by by other proteins which guide the protein to the area Often play a role in cell surface recognition 0 Protective effects Cell coat or glycocalyx carbohydraterich zone on the cell surface shielding cell from damage carb rich portion protects them from the harsh conditions of the extracellular environ and degredation from cellular protease enzyme that digests proteins Electron microscopy Transmission electron microscopy TEM uses a biological sample that is thin sectioned and stained with heavymetal dyes Dye binds tightly to the polar head groups of phospholipids but it does not bind well to the fatty acyl tails Stained membranes resemble a railroad track Stained polar head groups separated by a uniform light space about 2 nm thick FFEM specialized form of TEM Freeze fracture electron microscopy Specialized form of TEM can be used to analyze the interiors of phospholipid bilayers Sample is frozen in liquid nitrogen and fractured with a knife Due to the weakness of the central membrane region the lea ets separate into a P face the protoplasmic face that was next to the cytosol and the E face the extracellular face most transmembrane proteins do not break in half they remain embedded in one of the lea ets usually the p face sprayed with a heavy medal that coats sample and receals arch features within each lea et can provide signi cant threedimensional detail about membrane protein form and shape Selectively permeable Membrane transport If the plasma mem was only a phospho bilayer would not permit the uptake of most nutrients and the export of waste products It is however selectively permeable Allows things like amino acids and glucose to enter metabolic intermidiates remain within and waste leaves allows cells to maintain favorable internal environment Transport proteins are embedded within the phospho bilayer they allow membranes to be selectively permeable by providing a passageway for the movement of some but not all substances across the membrane Plasma membs of different cell types have diff trans pros to allow only certain ions and molecules to cross Essential molecules enter Metabolic intermediates remain Waste products exit Phospholipid bilayer is a barrier to the diffusion of hydrophilic substances Hydrophobic interior makes formidable barrier to movement of ions and hydrophilic molecules 0 Diffusion Movement of solute from an area of higher concentration to an area of lower concentration Passive diffusion when diffusion occurs through a membrane without the aid of a transport protein 0 Rates of passive diff deps on the chemistry and concentration of solute Solutes vary in their rates of penetration ions and larger polar molecules rate of diff is slower proteins and large carbs do not readily cross Gasses and some small uncharged polar molecules can paaivly diffuse arcoss the bilayer For rates of passive diffusion greatest variation occurs in the ability of solutes to enter the hydrophobic region of the bilayer o Diethylurea is more hydrophobic than urea bc it has 2 non polar ethyl groups thus it can more easily pass through the hydrophobic region of the bilayer rate of passive diff is 50 times faster than urea Cells maintain gradients Phospho bilayers are very impermeable to ions and most hydrophilic mols Cell maintain a rel const int enviorn This involves establishing gradients of solutes across the plasma memb and organellar membs Transmembrane gradient consentration of a solute is greater on one side of a memb than the other after you eat con of glucose is greater on the outside of cells than on the inside Concentration of a solute is higher on one side of a membrane than the other gradients involving ions 0 Ion electrochemical gradient dual grad that hasboth electrical grad and chemical grad 0 Ex Na electrical grad might exist where the amount of net positive charge outside a cell is greater than inside chemical grad in which the con of Na outside is greater than inside Both an electrical gradient and chemical gradient transmemb grads of ions and solutes are feature of all cells Passive transport one way to view transport of solutes across membanes is to consider how the transport process affects the pre existing gradients across membs Passive transport diff of solute across mem in a process that does not require an input of energy energetically favorable o 2 types Passive diffusion o Diffusion of a solute directly through the phospho bilayer to move across the memb without transport protein not common for most solutes Faciitated diffusion o Diffusion of a solute through a membrane with the aid of a transport protein Carries transport ions and other solutes across plasma membrane transport proteins facilitate the movement of various nutrients even sometimes water across the memb o Facilitate movement by physically binding molecules on one side of the membrane and releasing then on the other 0 Essential characteristics saturation of transprt through carries Specific Passive Saturates Tonicity Because many cells have transmembrane gradients that exist across membranes sotonic Equa water and solute concentrations on either side of the membrane 0 Hypertonic Soute concentration is higher and water concentration lower on one side of the membrane 0 Hypotonic Soute concentration is lower and water concentration higher on one side of the membrane osmosis osmotic consentration con of all solutes in solution hyperosmotic solutions with the higher soute con hypoosmotic solution with the lower solute con isosmotic solute consentrations are equal Osmosis hypotonic hypo osmotonic Lipid bilayers are somewhat permeable to water Water diffuses through a membrane from an area with more water to an area with less water water goes from area of hypotonic solution less solute more water into the area of hypertonic solution more solute less water If the solutes cannot move across the membrane water will move and tend to balance the solute consentrations This process called osmosis water diffuses across membrane from hypotonic compartment to hypertonic compartment Movement can make the cell shrink or swell as water leaves or enters the cell Osmotic pressure the tendency for water to move into any cell the hydrostatic pressure required to stop the net ow of water across a membrane due to osmosis Animal cells must maintain a balance between extracellular and intracellular solute concentrations bc they don t have ridged cell wall to maintain their size and shape 0 To do this they have transport proteins which sence changes in cell volume this allows the necessary movements of solutes across the mem to avoid osmotic changes and maintain normal cell shape Crenation shrinking in a hypertonic solution if placed in a hypertonic solution water will exit cell which is thus hypotonic by comparison to equalize solute consentrations on both sides of the cell If placed in a hypotonic solution water will enter cell and cell may burst This is called osmotic ysis In plants causes wilting but bc of the ridged cell walls cells wont burst if placed in a hypotonic solution A cell wall prevents major changes in cell size Turgor pressure pushes plasma membrane against cell wall osmotic pressure in plant cells Maintains shape and size Plasmolysis plants wit because water leaves plant cells Some organisms contain contractile vacuole to prevent osmotic lysis Takes up water from cytosol and periodically discharges it by fusing the vacuole with the plasma membrane Agre Discovered That Osmosis Occurs More Quickly in Cells with Transport Proteins That Allow the Facilitated Diffusion of Water Water may passively diffuses across plasma membranes Certain cell types allow water to move across the plasma membrane at a much faster rate than would be predicted by passive diffusion Water moves very quickly across the membrane of red blood cells which causes them to shrink and swell in response to changes in extracellular solute consentratoins Speculated that certain cell types might have proteins in their plasma mem that permit the rapid movement of water One approach used to characterize a new protein id a protein based on its relative abundance in a particular cell type then attempt to determine its function Peter Agre and his colleagues rst identi ed a protein that was abundant in red blood cells and kidney cells but not found in many other cell types Didn t know its function but its structure was similar to other proteins know to function as transport proteins CHIP28 Identi ed the gene that encodes it and made many copies of it then added enzyme to transcribe the gene into mRNA that encodes the CHIP28 protein mRNA was injected into frog oocytes which lacked the preeisting proteins in their plasma mem that allowed rapid water movement mRNA was expected to be translated into the protein which would inset into the plasma membrane It and controle group of frog oocytes placed in hypotonic medium Striking difference was observed between frog oocytes that expressed CHIP28 versus the control the chip ones enlagered much quicker and even some burst Aquaporins example of a channel Agre was awarded the Nobel Prize in 2003 for this work Transport proteins cause biological membranes to be selectively permeable Phosopho bilayer is physical barrier to passive diffusion of ions and most hydrophilic molecules They have transport proteins to take up nutrients from the environment and export waste products Transport proteins transmembrane proteins that provide a passage for the movement of ions and hydrophilic molecules across membranes they enable biological membranes to be selectively permeable 2 classes ChanneB Transporters Channels 0 Form an open passageway for the facilitated direct diffusion of ions or molecules across the membrane solutes move directly though a channel to get to the other side Aquaporins Most are gated open and close to allow diffusion Ligandgated controlled by the noncovalent binding of small molecules called ligands like hormones or neurotransmitters Alternatively Intracellular proteins may bind noncovalently to channels and controle their ability to open and close another gating mechanism involves the covalent binding of a small molecule like a phosphate group to the channel protein Regulatory proteins involved in cell signaling pathways may covalently attach phosphate to proteins as a way to regulate their function Sometimes the targets of these regulatory proteins are channels Phosphorylation channel gating can also occur by mechanisms that don t involve the direct binding of a molecule to the channel protein 0 Voltagegated channel opens and closes in response to changes in the amount of electrical charge across the membrane sodium and potassium channels in nerve cells are voltagegated Mechanosensitive channels sensitive to changes in membrane tension hearing Transporters Also known as carriers Bind their solute in a hydrophilic pocket and undergo a conformational change that switches the exposure of the pocket to the other side Slower than channels 0 Principal pathway for the uptake of organic molecules such as sugars amino acids and nucleotides In animals allow cells to take up certain hormones and neurotransmitters Key role in export waste products of cellular metabolism must be released from cells before they reach toxic levels Transporter types Uniporter Single molecule or ion Symporter cotransporter o 2 or more ions or molecules transported in same direction Antiporter 2 or more ions or molecules transported in opposite directions Pump 0 a transporter that directly couples conformational changes to an energy source such as ATP hydrolysis the conformational changes of pumps are energetically driven o ATPdriven pumps have binding sites for ATP The hydrolysis of ATP provides energy that controls the sequence of conformational changes 0 Energy obtained from the APT hydrolysis can be used to pump solutes against a gradient 0 can be uniporters symporters or antiporters 0 use energy to achieve active transport Active transport 0 Movement of a solute across a membrane against its gradient from a region of low concentration to higher concentration 0 Energetically unfavorable and requires the input of energy 0 Primary active transport Functioning of pumps that directly use energy to transport solute against a gradient pump uses ATP to transport H against a gradient can establish a large H electrochemical gradient across a membrane 0 Secondary active transport Use preexisting gradient to drive transport of solute ex Hsucrose symporter can utilize an H electrochemical gradient to move sucrose against its consentration gradient only sucrose is actively transported hydrogen ions move down with their electrochemical gradient in animal cells a pump that exports Na maintains the Nagradient across the plasma membrane symporters allow cells to act imp nutrients against a gradient Symporters use the energy stored in the electrochemical gradient of Naor H to power the uphill movement of org solutes like sugars amino acids and other solutes with symporters in plasma membs cells can get nutrients from outside cell and accumulate them to high levels within the cytoplasm ATPDriven Ion Pumps Generate Ion Electrochemical Gradients o NaKATPase ATPdriven ion pump Activey transport Na and K against their gradients by using the energy from ATP hydrolysis every time one ATP is hydrolyzed NaKATPase functions as an antiporter that pumps 3 Na out of the cell and 3 K into the cytosol Bc one cycle of pumping results in the export od one positive charge it produces an electrical gradient across the mem It is considerd an electrogenic pump bc it generates an electrical gradient 3 Na exported for 2 K imported into cell 0 Antiporter o Electrogenic pump export 1 net positive charge Reaction mechanism NaKATPase alternates bt E1 and E2 conformations ln e1 the ion binding sites are accessible from the cytosol Sodium ions bind to this while potassium have a low affinity ln e2 ion binding sites are accessible from the extracellular environment Potassium binds tighly while sodium ions have a low affinity E1 conformation 3 Na bind to the NaKATPase from the cytosol Then ATP is hydrolyzed to ADP and phosphate temporarily the phosphoate is covalently bonded to the pump This is called phosphorylation Pump then switches to E2 conformation E2 conformation sodium ions are released into the extracellular environment bc they have a lower affinity for the e2 conformation and 2 K ions bind from the outside This binding causes the release of phosphate which causes a switch to e1 E1 has a low affinity for K which are released into the cytosol The NaKATPase is now ready for another round of pumping NaKATPase is a key cellular enzyme in aminal cells bc it funcitoins as an ion pump that maintains Na and K gradients across the plasma memb Atp is commonly the source of energy to drive the ion pumps Macromolecules and large particels are transported via endocytosos and exocytosis Eukaryotic cells have two other mechanisms to transport larger molecules like proteins and polysaccharides Exocytosis Endocytosis Transport larger molecules such as proteins and polysaccharides and even very large particles 0 Exocytosis Material inside the cell which is packaged into vesicles is excreted into the extracellular medium vesicels are usually derived form the trans golgi apparatus The trans forms a bud Coat proteins depoite themselves on the bud As they are formed a specifc cargo is loaded into their interior Ex large polys are made within the lumen of the golgi and packaged within vesicles that bud from the golgi The budding process involves the formation of a protein coat around the emerging vesicle The assymbly of caot proteins on the surface of the mem causes the bud to form Bud separates from the mem to form a vesicle When the vesicle is released the protein coat is shed Vesicle fuses with the plasma mem dissolution on vesicle mem once the bud touches the plasma mem and releases its stuff Procolagen Endocytosis Pasma membrane invaginates or folds inward to form a vesicle that brings substances into the cell goes to lysosome Receptor mediated endocytosis receptor is speci c fr a given cargo When the resceptor binds to that cargo stimulates binding of coat proteins to the mem That inittiates the formation of a vesicle Receptors aggregate tpgether as a protein coat forms around the vesicle Once inside cell vesicle sheds its coat Vesicle fuses with an internal mem organell and releases its cargo Talking about speci c type of endo have plasma mems in cells with pits These pits where the receptor takes place is lined with protein called patin Coats the pits They are receptor mediated pits that help in r m endocytosis On top of the plasma mem you have receptors The tail of the receptor is embedded in the pits The recetors are proteins that are speci c for sihnal mols Once the sig mols bind to the receptors the pit get the signal to close 0 LDL attached to LDL receptor in pits Once all LDL goes into the receptors that gives the signal for the pit to close Now have patin encoated vesicle Platilin will go back Vesicle wil bud 0 7777777777 Specialized forms of endocytosis Pinocytosis taking in liquid formation of mem vesicels from the plasma mem as a way for cells to internalize the extracellular uid Allows cells to sample the extracellular solutes Particularly important with cells that are actively involved in nut absorbtion intestine cells of animals Phagocytosis extrme form of endocytosis Involves the formation of a big memb vesicle called a phagosome or phagocytic vacuole Engulfs a large particle Ex macrophages in cells of the immunes sytems of animals Kill bact via phagocytosis Once insiode cell the p fuses with lysosome and the dig enzyme within the lysosome destroy the bact Chap 7 Chapter 7 Chemical reaction Chemical reaction is a process in which one or more substances are changed into other substances Metabolism term for sum total of all chemical reactions that occur within an organism Can refer to speci c set of chemical reactions occurring at cellular level Involves breakdown or synthesis of organic molecules Ex sugar or fat metabolism Meta in living cells is very controlled Underlying theme in metabolism is remarkable control that cells possess when coordinating chemical reactions that utilize energy Energy chemical reactions and enzymes Two factors govern fate of chemical reaction 1 Direction 2 Rate aA bB ltgt cC dD A B are reactants C D are products a b c d are number of moles of reactants and products Direction depends on energy and consentration of A B C D cells use energy intermediates molecules like atp to drive chemical reactions in a desired direction Energy exists in many forms Energy ability to promote change Keneticpotential 0 Chemical energy type of potential energy Energy contained within covalent bonds The breakage of these bonds is one way cells can harness this energy to perform cellular functions Thermodynamics study of energy interconversions 2 laws governing it 0 1st law of thermodynamics energy cannot be created or destroyed Can be transformed or transferred 0 2nOI law of thermodynamics transfer or transformation of energy increases the entropy or degree of disorder of a system This increase in entropy causes some energy to become unusable Change in free energy determines the direction of a chemical reaction or any other cellular process Total energy usable energy unusable energy Some energy is unusable bc of entropy An increase in entropy is the measure of the disorder that cannot be harnessed to do work 0 Total energy H enthalpy 0 Free energy G usable energy can be used to do work 0 S unusable energy is the systems entropy H G TS T absolute temperature in kelvins G H TS Whether a process will occur spontaneously Spontaneous reaction or process will occur without an additional input of energy 0 Exergonic reaction has negative free energy change AG lt 0 free energy is released are spontaneous reaction favors formation of products Endergonic positive free energy change AG gt 0 requiring the addition of free energy form the environment not spontaneous reaction favors formation of reactants Andenosine triphosphate ATP molecule that is a common energy source for all cells Water is used to remove a phosphate group hydrolysis reaction AG is 73 kcalmol in converting one mole of ATP to one mole of ADP and Pi therefore exergonic and strongly favors the formation of products Energy that is liberated by the hydrolysis of ATP is used to drive a variety of cellular processes Even with a reaction with negative free energy not all reactants are converted into products Reaction reaches state of chemical equilibrium in which the rate of formation of products equals the rate of formation of reactants According to aA bB ltgt cC dD Keq CCDdAaBb keq is the equilibrium constant Two simplifying assumptions Consentration of water does not change during the reaction 0 pH remains constant at 7 If water is one of the reactants like in a hydrolysis reaction it is not include in the chemical equilibrium equation For example hydrolysis of ATP ATP439 H20 ltgt ADPZ39 Piz39 Keq ADPPiATP 1650000 M such large value indicates that the equilibrium greatly favors the formation of products ADP and Pi Cells use ATP to drive endergonic reactions if reaction is endergonic it requires addition of free energy and will not occur spontaneously To overcome this organisms couple endergonic reactions with exergonic reactions Endergonic reaction will proceed spontaneously if the net free energy change for the combined reactions is negative Glucose phosphate239 gtglucosephosphate239 H20 AG 33 kcalmole ATP439 H20 gt ATP 239 Piz39 AG 73 kcalmole Coupled reaction glucose ATP439 gt glucosephosphate239 ADPZ39 AG 4 kcalmole In the rst reaction phosphate is covalently attached to glucose endergonic not spontaneous Once coupled phosphate is directly transferred from ATP to glucose The transfer of phosphate from ATP to glucose is rst step to break down of glucose to smaller molecules Enzymes increase the rates of chemical reactions Thermodynamics does not control the rate of chemical reactions Catalyst is needed Catalyst agent that speeds up chemical reaction without being used up Most common catalysts are enzymes protein molecules that accelerate chemical reactions Ribozymes rna molecule that is a biological catalyst Rna molecules within ribosomes catalyze formation of bonds that link amino acids together Why are catalysts necessary to speed up a chemical reaction When a covalent bond 5 broken or formed involves the straining or contorting of one or more bonds in the starting molecules or may involve the positioning of two molecules so they can properly interact with each other Reaction where ATP is used to attach a phosphate to a glucose glucose ATP439 gt glucosephosphatez39 ADPZ39 for the reaction bt the reactants to occur they must collide in the correct orientation and possess enough energy so that chemical bonds can be changed The electron clouds of glucose and ATP repell each other In order to overcome these repelling forces initial input energy called activation energy must be used Once this energy is put in the glucose and ATP achieve a transition state in which the original bnds have stretched to their limits Once the transition state has been reached the reaction can proceed to the formation of products Activation energy is the barrier to the formation of products reason why many reactions are slow 2 ways to overcome barrier and therefore accelerate a chemical reaction reactants exposed to large amounts of heat 0 Lower the activation energy barrier o Enzymes lower the activation energy to a point where a small amount of heat can push the reactants to the transition state 0 How do enzymes lower the act energy barrier Enzymes are large proteins that bind small reactants when bound to enzymes the bonds in the reactants can be strained stretched making it easier to achieve their transition state When chemical reactions involves 2 or more reactants enzyme provides a site where the reactants are positioned very close to one another and in an orientation that facilitates the formation of new covalent bonds Summary straining the reactants and bringing them closer together are tow common ways enzymes lower the activation energy barrier o Enzymes may facilitate a chemical reaction by changing the local environment of the reactants Ex amino acids in an enzyme may have charges that affect the chemistry 0 fthe reactants o In some cases enzymes lower the activation energy by directly participating in the chemical reaction Ex enzymes that hydrolyze ATP form a covalent bond bt phosphate and an amino acid in the enzyme Is very temporary The bond is quickly broken releasing the phosphate and returning the amino acid to its original condition Example is NaK ATPase Enzymes recognize their substrates with high speci city ad undergo conformational changes Enzymes lower act energy and thus increase the rate of reaction Other features of enzymes that enable them to be effective catalysts in chemical reactions Active site is the location on an enzyme where chemical reaction takes place Substrates for an enzyme are the reactants that bind to the enzyme at the active site and participate in the chemical reaction Binding between an enzyme and a substrate produces an enzyme substrate complex Key feature of nearly all enzymes is that they bind their substrates with a high af nity or high degree of speci city Hexokinase is the enzyme whose substrates are glucose and ATP Binds glucose very weel thus has a high af nity for it Has a low af nity for other substrates like other sugars which are similar to glucose quotonly the right sized key substrate reactant will t into the key hole active site of the lock the enzyme Interaction between the substrates and enzyme involve movents or conformational changes in the enzyme These conformational changes cause the substrate to bind more tightly to the enzyme induced t Only after the conformational change does the enzyme catalyze the conversion of reactants to products Some enzymes require additional nonprotein molecules or ions to carry out their functions Prosthetic groups small molecules permentantly attached to the surface of an enzyme aids in catalysis Cofactors usually inorg ions Fe3 Zn temp bind to the surface of an enzyme and promote chemical reactions not permenantly attached Coenzymes org molecules that participate in the chemical reactions but are left unchanged after the reaction is completed not perm NAD is example Ability of enzymes to increase the rate also affected by environment 0 Temp 37 celcius 0 pH 73 Using chem Energy to drive meta autotrophs harvests sunlight and convert radiant energy into chem Energy photoautotrphps heterotrophs live off the energy produced by autotrophs 0 food energy laden chemical bonds 1 carbs 2 proteins 3 fats extraction of energy take place in several stages 0 digestion o catabolism overview of metabolism chemical reactions are often coordinated with each other occur in sequences metabolic pathway the products of 1st reaction becomes substrates of 2nd multienzyme complex Each step is catalyzed by speci c enzyme catabolic breakdown of molecules usually exergonic anabolic synthesis of molecules usually endergonic must be coupled catabolic reactions recycle organic building blocks and produce energy intermediates such as ATP and NADH one reason for breakdown of mols is to recyclemake building blocks for new macromols When protein is made incorrectly or no longer needed the peptide bonds between the amino acids are broken by protease This generates amino acids for new proteins 2nol reason for breakdown obtain energy that can be used for endergonic processes requires additional energy from the environment in the cell Covalent bonds store large amounts of energy When cells break these bonds in organic mols they do not directly use the energy released 0 This energy is stored in energy intermidiates like ATP and NADH directly used to drive endergonic reactions in cells 0 Ex break down of glucose into pyruvate involves catabolic pathway called glycolysis 0 Some energy released during the breakingof the coval bonds in glucose is harnessed ot make atp 0 Many steps glycolysis is a series of steps in which covalent bonds are broken and rearranged creates molecules that can readily donate a phosphate group to ADP creating ATP Ex phosphoenolpyruvate has a phosphate group attached to pyruvate bc of the bond arragements in phosphoenolpyruvate phosphate bond is easily broken and group can be transferred to ADP to create pyruvate and ATP Phosphoenolpyruvate ADP gt Pyruvate ATP AG 75 kcalmole is exergonic favors products Breakdown of org mol phosphpyruvate results in synthesis of energy intermediate mol ATP used by cell to drive endergonic reactions This way of synthesizing ATP is called direct substrate level phosphorylatoin when an enzyme directly transfers a phosphate from one mol to another 0 Another way to make ATP is indirect chemiosmosis Energy stored in an ion electrochemical gradient is used to make ATD from ADP and Pi Oxidation may occur during breakdown of smaller org molecules process involves removal of electrons Oxygen is frequently involved in reactions that remove electrons from molecules Reduction is the addition of electrons addition of negatively charged electrons reduces the net charge on a molecule Redox reaction reduction oxidation reaction electrons don t exist freely in solution Ae B gt A Be A has been oxidized B has been reduced Thing oxidized has less energy thing reduced has more energy During oxidation electrons are used to create energy intermediates like NADH an org mol has been oxidized and NAD has been reduced to NADH Cells use NADH 2 ways 0 Oxidation of NADH is exergonic reaction used to make ATP 0 NADH can donate electrons to other org molecules and energize them more energized molecules can more readily form covalent bonds therefore NADH is often needed in anabolic reactions that involve the synthesis of larger molecules throught the formation of covalent bonds bt smaller molecules Anabolic reactions require an input of energy to make larger molecules Anabolic reactions called biosynthetic reaction necessary to make larger molecules and macromols Cells also need to synthesize small org mols if not available form food are made by the covalent linkages bt precursor mols In such reactions an energy intermidiate is needed to drive the reaction forward like ATP orNADH Many proteins use ATP as a source of energy Proteins use ATP to drive cellular processes Breakdown of food mols release energy that allows us to make more ATP from ADP and Pi This is ATP synthesis Avg person hydrolyses 100 lbs of ATP per day but does not have 100 lbs of atp on us therefore ATP undergoes about 10000 cycles of hydrolysis and resynthesis each day Particular amino acid sequences within proteins function as ATP binding sites allows forte prediction of whether a new rotein will uses atp or not Genes that encode proteins can be analyzed to see if the encoded proteins proteins have ATP binding sites in their amino acid sequences Then can est percentage of proteins that are able to bind ATP most of these proteins will use ATP as a source of energy though some may simly bind ATP without hydrolyzing it to ADP and Pi Est that 20 of ALL proteins bind to ATP Probably underestimated bc have not been able to id all types of ATP binding sites in proteins Metabolic pathways are regulated in three different ways Reg of catabolic pathways is imp cell breaks down org molecules when energy needed conserve them when adequate supply of energy intermediates in available Reg of anabolic pathway is imp cell does not waste energy making too much of the products of such pathways Regulation occurs on genetic cellular biochemical levels Gene reg enzymes in every metabolic pathway are encoded by genes one way cells contol chemical reactions is via gene regulation 0 Ex cell not exposed ot certain sugar will turn off gene that encode enzyme that are needed to break down that sugar Cellular regulation cells integrate signals from their environment and adjust their chemical reactions to adapt to those signals 0 Ex frightened secrete hormone called epinephrine binds to surface of muscle cells stimulates intracellular pathway that leads to the phosphorylation or several intracellular proteins ie enzymes involved in carb metabolism These activated enzymes promote breakdown of carbs Give frightened person more energy When no longer frightened hormone levels drop and other enzymes called phosphatases remove phosphate group from enzymes restoring the orginial level of carb metabolism Biochemical reg binding of a molecule to an enzyme to directly regulate its function Categorized according to site where the regulatory molecule binds 2 types of regulation that involve regulatory molecules that inhibit enzyme function 0 Competitive inhibitors molecules that binds to the active site of the enzyme and inhibits the enzymes substrates from binding there The mol that binds there has a similar structure to the substrates Can be overcome by increasing the consentratoin of the substrate or decreasing the consentration of the inhibitor 0 Noncompetitive inhibitors bind to an enzyme outside the active site and inhibit the enzymes function 0 Ex feedback inhibitor product of a metabolic pathway inhibits an enzyme that acts early in the pathway preventing the overaccumulatioin of the product Inhibited enzyme has two binding sites one is the active the other enzymes controlled by feedback inhibitors have an allosteric site where a mol can bind noncovalently and effect he function of the function of the actve site Binding of a molecule to the all site causes conformaoitnal changes in the enzyme that inhibit its catalytic functions These sites are often found in enzymes that catalyze the early steps in a metabolic pathway These typically bind molecules that are products of the pathway When products bind to thee sites they inhibit the function of these enzymes and thus prevent the production of too much product 0 Which enzyme in a pathway should be controlled 0 A metabolic athway has a ratelimiting step is the slowest step in a pathway If the rate limiting step is inhibited or occurs at a faster rate such changes will have the greatest impact on the production on product of the metabolic pathway Sellualr and biochemical regultoin are often directed at the enzyme that catalyzes the rate limiting step Cellular Respiration Cellular rsp process by which living cells obtain eregry from organic molecules Aim of cellular resp make energy ints like ATP NADH Aerobic resp 02 is used 02 consumed C02 released Inhale oxygen needed for aerobic resp and exhale C02 that is the byproduct of the process Different types of organic molecules like carbs proteins and fats can be used a senergy sources to drive aerobic resp Org mols 02 gt C02 H20 Energy Main focus on use of glucose as an energy source for cellular resp C6H1206 602gt 6C02 6H20 Energy Intermediates heat WILL NOW EXAMINE METABOLIC PATHWAYS WHERE GLUCOSE IS BROKEN DOWN INTO C02 AND WATER WHICH RELEASES LARGE AMOUNTS OF ENERGY USED TO MAKE ATP 4 pathways Glycolysis o Breakdown of pyruvate Citric acid cycle oxidative phosphorylation Several metabolic pathway are involved in the breakdown of glucose to C02 focus will be on breakdown of glucose in euk cells in the presence of oxygen Covalent bonds in glucose have large amounts of chemical bond energy When glucose is broken down in C02 and water energy in the bonds is released used to make enrgy intermediates ATP NADH FADH2 Overview of the stages that occur during the breakdown of glucose 1 Glycolysis glucose 6 C compound with 6 carbon atoms broken down in cytosol to 2 pyruvate mols 3 C each net gain of 2 ATP mols via substratelevel phosphorylation and 2 NADH mols 2 Breakdown of pyruvate to an acetyl group 2 pyruvate mols nter the mitochondrion 1 is broken down into an acetyl group 2 C and 1 C02 mol For each pyruvat ebroken down 1 NADH mol is made 3 Citric acid cycle each acetyl group 2 C is broken into 2 C02 mols 1 ATP 3 NADH 1 FADH2 made in process Bc there are 2 acetyl groups total yield is 4 C02 2 ATP via substrate level phosphorylation 6 NADH and 2 FADH2 4 Oxidative phophorylation NADH and FADH2 made in the previous steps contain high energy electrons that can be readily transferred in a redox reaction to other mols Once removed these electrons released some energy which is harnessed to make 30 to 34 ATP mols via chemiosmosis Oxidative phophorylation consists of 2 components electron transprt chian and the ATP synthase Class Glycolysis Compete oxidation of org compound krebs cycle


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