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Biology Chapter Notes biol1000

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BIOL 1000
David Stamos

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1 Biology Chapter Notes (chapters 4-7) Energy and Enzymes (Chp 4): Why it Matters:  In life we need enzyme  Enzyme catalyzed reactions are 10^21 times faster than ones without enzymes  Dephosphorylation with an enzyme take 0.1 seconds but without an enzyme it is estimated to take 1 trillion years  Without enzymes to speed up reactions life wouldn’t exist 4.1 Energy and the Laws of Thermodynamics:  Energy: capacity to do work  It takes energy to climb a mountain or to build a protein Energy Exists in Different Forms and States:  Energy is present in many forms such as: o Heat, chemical, electrical, and mechanical o Electromagnetic radiation (visible, infrared, and UV) is also a type of energy  Energy can be transformed from one form to another o Ex. Photosynthesis: Light -> chemical energy  All energy can be grouped into two groups: Kinetic and Potential energy  Kinetic: o Energy possessed by an object because it is in motion o Ex. Photons, it can perform work by making other objects move  Potential: o Stored energy o Ex. atoms in a glucose molecule have potential energy in the specific arrangements of energy (this is called: Chemical Potential Energy) The Laws of Thermodynamics Describe the Energy Flow in Natural Systems:  Thermodynamics: study of energy and its transformations  The object being studied is the system and everything outside the system is the surrounding  Universe is system and surrounding (Univ= Sys + Surr)  3 types of systems:  Isolated: no exchange of matter and energy b/w system and surrounding  Closed: only exchanges energy b/w system and surrounding, no matter  Open: exchanges both energy and matter b/w system and surrounding The First Law of Thermodynamics:  Energy can be transformed from one form to another or transferred from one place to another but it cannot be created or destroyed 2 The second Law of Thermodynamics:  When energy is transformed from one form to another, some of the energy is lost an is unavailable to do work  This unusable energy that is being lost is heat  Ex. Cellular respiration: 40% of the energy is turned into useable energy while the other 60% is lost through heat  The unusable energy that is produced causes an increase in the randomness of the universe  The randomness or disorder quantity is called Entropy  The second law states: o The total disorder (entropy) of a system and its surrounding always increases  Ex. Room: room keeps getting messier and the disorder of things increase ( entropy increases) and we need to do work to make it ordered   it takes energy to maintain a low entropy Life and the Second Law of Thermodynamics:  Our body contains molecules and things such as DNA or proteins that are highly order  This doesn’t follow the second law? No it does but as said before “it takes energy to maintain a low entropy”  Living cells are open systems that exchange matter and energy and use the two to create order  Therefore creating a highly ordered system in our body  The second law states that “ entropy of system and surrounding increase” the universe’s entropy increases not necessarily both variable increase o Univ= Sys + Surr, Sys -> down, then Surr-> Up and the total entropy of the Univ goes UP  inside the cells are highly ordered while the surrounding is highly disordered 4.2 Free Energy and Spontaneous Reactions:  Spontaneous reactions may proceed slowly or quickly Energy Content and Entropy Contribute to a Making a Reaction Spontaneous: 2 factors from the first and second law must be taken into account to see if a reaction is spontaneous; the change in energy content and change in entropy:  Reactions tend to be spontaneous if the products have less potential  Potential energy of a system is called the enthalpy (H)  Endothermic reactions are spontaneous since they have lower potential energy in reactants than products  Ex ice melting in a glass of water  Reactions tend to be spontaneous when the products are less ordered than the reactants  Reactions occur spontaneously if the entropy of the products is higher than the reactants  Ex. Ice melting (from solid low entropy to liquid high entropy) Change in Free Energy Indicates Whether a Reaction is Spontaneous: ☺ The energy left that does the work is called free energy  For ex, for chemical and physical work 3 ☺ The change in free energy ΔG (ΔG= Gfi– Gini) can be found from:  ΔG= ΔH + TΔS (ΔH=Enthalpy, ΔS=Entropy, T=temp in K) ☺ For a reaction to be spontaneous, ΔG must be NEGATIVE  ΔS is high (highly disordered ex. Ice melting) or ΔH is negative (combustion of methane has a large loss of potential energy therefore negative ΔH) ☺ Negative ΔG also means that there’s less free energy in the final state ☺ ALSO, systems that have high free energy (ΔG) are less stable than systems with low free energy  Ex rock at the top of a cliff (at the edge) Vs. a rock finished rolling at the bottom ☺ Systems can spontaneously change to more stable state but they don’t spontaneously change into a less stable state  Ex. Molecule spontaneously breaks down into atoms but it can’t spontaneously go back, energy must be put in ☺ This is also like a concentration gradient:  When there’s a gradient its less stable and contains more free energy than when it is equally distributed on both sides Life and Equilibrium: ♂ When a reaction reaches maximum stability it’s called at equilibrium ♂ This is the lowest point in which ΔG is ZERO ♂ As the reaction progresses (ex G1P to G6P) the free energy is being used up and becomes lower until it becomes ZERO at equilibrium where the reaction forward=reaction backwards ♂ ΔG is related to equilibrium and the more negative the ΔG is the farther the reaction will go towards completion before it reaches equilibrium ♂ In many reactions the ΔG will be zero but those are isolated systems ♂ In organism the ΔG will never be zero and its always negative since it’s an open system and there’s more reactants that keep coming in and the product of those reactions is the reactant of others ♂ Organisms reach a ΔG of zero only when they die Metabolic Pathways Consist of Exergonic and Endergonic Reactions: ♦ Exergonic: releases free energy and ΔG is negative ♦ Endergonic: Takes in free energy to form the products and ΔG is positive ♦ In metabolism there’s a series of reactions where a product is used as a reactant for another rxn ♦ Ex. Catabolic reaction releases energy (ΔG=negative) by breaking down molecules (ex. Cellular respiration) and Anabolic reaction that takes in energy (ΔG=positive) to build molecules (ex. Photosynthesis) 4.3 The Energy Currency of the Cell: ATP: Reactions involve ATP ATP Hydrolysis Releases Free Energy:  ATP contains free energy  This energy, the potential energy, is mostly in its phosphate groups since the phosphates have negative charges that repel each other 4  The breakdown of ATP is spontaneous and is also the hydrolysis of ATP  Once the phosphate is released the negative repulsion is relieved and this spontaneous reaction releases large amount of free energy  ATP + H2O  ADP + P , Piis an inorganic phosphate (ΔG= -7.9 kcal/mol)  ADP can be further broken down to AMP (monophosphate) but it won’t release as much free energy ATP and Energy Coupling: ♦ In order for ATP hydrolysis to be linked to an endergonic reaction without the energy being wasted in such forms as heat:  Energy Coupling: when ATP hydrolysis is brought in close contact with the reactant molecule of the endergonic reaction  The Enzyme Associated with this has a binding spot for the ATP and the reactant and when the hydrolysis occurs the inorganic phosphate is bonded to the reactant  This reactant is now phosphorylated and is now less stable as well  An example of this coupling is with glutamine  To get glutamine we need: Glutamic Acid + NH3  Glutamine + H2O but this reaction is not spontaneous and has a +ve ΔG therefore it occurs in 2 steps  1. ATP + Glutamic Acid  Glutamyl Phosphate + ADP ΔG= -ve  2. Glutamyl Phosphate + NH3  Glutamine + P i ΔG= -ve  These two reactions are coupled and are written as:  ATP + Glutamic Acid + NH3  Glutamine + P i+ ADP ΔG=-3.9 kcal/mol  We can also see that the difference between -7.9 and -3.9 (the ΔG of the reactions) is now in the glutamine  The endergonic reactions in biological are made possible by coupling reactions like this Regeneration of ATP:  We use ALOT of ATP but how do we regenerate it  We use foods such as carbohydrates and fats and lipids and use the energy that comes from their exergonic breakdown to recombine ADP and the inorganic phosphate to make ATP  In the cell there’s usually about 1000 more ATP than ADP and Pi and this is very far from equilibrium 4.4 The Role of Enzymes in Biological Reactions:  laws of thermodynamics can tell us if a reaction is spontaneous or not but it can tell us the speed  ***Just because a reaction is spontaneous it doesn’t mean the reaction will occur rapidly***  This is where enzymes come into play The Activation Energy Represents a Kinetic Barrier:  For a reaction to occur the reactants must become unstable and their bonds must also be strained or less stable to break  Even though a reaction can be spontaneous it needs a small energy boost to get the reactants and their bonds are unstable and ready to be broken 5  That state they reach is called Transition State and the energy required to start the reaction is called Activation Energy  An example is a rock at the top of a hill but the rock must be pushed higher before it can roll down the hill  What gives the activation energy for the reactions? Molecules are always in constant motion and they may gain enough energy for the reactant to get to the transition state  Propane torch for example can have gas coming out bus once a spark is introduced the reactants reach the transition state and react while releasing a lot of free energy into the environment (flame)  In chemistry heat is used for the reactions but in biology heat is a problem since it can damage biological parts of the cell for example proteins and the cell can die also the heat will speed up ALL the reactions not just the reactions of metabolism Enzymes Accelerate Reactions by Reducing the Activation Energy: ♦ How can reactions occur without an increase in temperature? Through catalysts ♦ The common biological catalyst is the enzyme ♦ The enzyme reduces the activation energy of the reaction and allows the reactants to reach the transition state much faster therefore the reaction occurring faster ♦ Also the enzyme can let more reactants reach the transition state faster ♦ Enzymes DON’T ALTER ΔG, they only alter Ea and reduce it by changing the path ♦ Also enzymes DO NOT provide free energy and cannot make an endergonic reaction proceed, the only REDUCE the Activation energy Enzymes Combine with Reactants and Are Released Unchanged: ♂ Enzymes combine briefly with the reactant and come out unchanged ♂ The reactant that the enzyme acts on is called the enzymes substrate ♂ Enzymes have specific molecules or groups of closely related molecules that it can act on and this is why there are over 4000 enzymes in cells ♂ The small area that the substrate binds with the enzyme is called the Active Site (like a small pocket or groove) ♂ Before this was called the lock and key but now it’s called the induced fit model since right before the substrate binds to the enzyme, the enzyme changes its shape and the active site becomes more precise in its ability to bind with the substrate ♂ The enzyme binds to the substrate forming an enzyme-substrate complex ♂ Then the enzyme converts the substrate into one or more products ♂ The enzyme doesn’t get effected so it can repeat this many, many times more in what is called the enzyme cycle ♂ The rate at which enzymes convert substrates to products depends on different things but it ranges from 100-10 mil substrate molecules per second ♂ Many enzymes need cofactors that are metals like iron zinc manganese that bind precisely to the enzyme ♂ They are essential for the catalytic activity of the enzymes ♂ Organic cofactors are similar and are called coenzymes Enzymes Reduce the Activation Energy by Inducing the Transition State: 6  Many wonder how enzymes actually reduce the activation energy  Enzymes function by bringing more reactants to the transition state  There are three ways that they can do this by: 1. By bringing the reactants closer together. In the enzyme’s active site the reactants come very close together and in the correct orientation for the reaction to occur 2. By changing the charge environments to promote catalysis. Some enzymes can have ionic groups that’s have +ve or –ve charges that can alter the substrate in a way that it favors catalysis 3. Changing the shape of the substrate. The active site distorts or strains the substrate into a different shape that mimics the transition state  All in all the enzymes causes the reactants to get to the transitions state  The way the rxn is sped up is that more molecules reach the transition state faster 4.5 Conditions and Factors that Affect Enzyme Activity: ☺ Certain changes in the environment can affect enzyme activity The influence of Enzyme and Substrate Concentrations on the Rate of Catalysis:  As the enzyme concentration increases with an excess of substrate, the graph of rate of reaction vs. enzyme is linear  As the enzyme concentration is remained the same with an excess of substrates, the graph of rate of reaction vs. substrate concentration is a decreasing curve in which a saturation level is reached and the rate of reaction will be the same since ALL of the enzymes are working Enzyme Inhibitors Have Characteristic Effects on Enzyme Activity:  The rate at which enzymes can catalyze a reaction is affected or slowed down by enzyme inhibitors  There are two types of inhibitors: competitive and non-competitive  Competitive inhibitors have similar shape to the substrate and compete with the substrate to bind with the active site and if there’s a high enough concentration of inhibitors then the reactions can stop completely  Non-competitive inhibitors bind to another area of the enzyme called the allosteric site that causes the enzyme to change and the substrate won’t be able to bind with the active site properly  Some inhibitors don’t tightly bond with the enzyme and the effect can be easily reversed and this is called reversible inhibition but in irreversible inhibition the inhibitor binds extremely tightly with the enzyme by forming covalent bonds and disables the enzyme permanently  For example cyanide binds strongly to cytochrome oxidase and inhibits it and this enzyme is used in respiration therefore we could die without it  Cells overcome this irreversible inhibition by creating more of the enzyme Allosteric Control of the Enzyme:  Many enzymes are present in the cell (thousands) that are used for synthesis of a molecule and the breakdown of that molecule  If these enzymes were active at the same time then there would be a futile cycling 7  A Futile Cycle is when two metabolic pathways occur at the same time that go in opposite directions and there is no end result but there is energy wasted  Inhibition can be used to relieve the cell of the problem and the enzyme activity is regulated by inhibitors  Allosteric regulation has two forms: allosteric inhibition or allosteric activation  Allosteric inhibition changes the enzyme from high affinity to low affinity state meaning that the substrate will now very weakly or wont bind to the active site  Allosteric activation changes the enzyme from low affinity to high affinity state in which now the substrate will be able to strongly bind with the active site  Both these allosteric regulations are non-competitive  Many of the allosteric inhibitors are a product of the reaction they are inhibiting  Once there is an access of the product, the product goes and inhibits the first enzyme of the reaction so there is no waste but once there is too little of the product the inhibition stops and more products are produce  This is called feedback inhibition Temperature and PH are Key Factors Affecting Enzyme Activity: o Effects of pH Change: ☺ Enzymes have an optimal pH in which they work best in and anywhere lower or higher than the optimal the enzyme won’t work as well and the reaction slows and when it’s really far from the optimal pH the reaction won’t occur and the rate will be zero ☺ Most of the enzymes optimal pH is around 7 but some like pepsin in the stomach (more acidic pH) and trypsin in the intestine (basic pH) have a different optimal pH o Effects of Temperature Change: ☺ There is an optimal temperature in which enzymes work at without being denatured ☺ From 0-40 deg Celsius the rate of the reaction doubles every 10 deg and then it reaches the optimal temperature of most enzymes which is 40-50 deg Celsius but once the temp is higher the enzyme becomes denatured and unfolds thus losing its function and the rate of reaction becomes very steep at 55 deg Celsius and becomes 0 at around 60 deg ☺ Other enzymes have different optimal temperatures but once it is out of the optimal range, the rate of reaction is slower Membranes and Transport (Chp 5): Why it matters:  the CTFR in the lungs acts as a membrane transport protein that pumps out Cl- out into the mucus lining and a concentration gradient is formed and Na+ moves out as well then water follows through osmosis and goes into the mucus lining as well keeping the mucus lining moist  people with cystic fibrosis don’t have a properly working CTFR and this results in heavy mucus build up and coughing won’t help and this can also result in infections 5.1 An overview of the Structures of Membranes: ☺ Development of the plasma membrane was key since it is selectively permeable meaning that it can intake nutrients while excreting waste and keeping a protected environment inside the cell ☺ The organelles also allow more complexity The Fluid Mosaic Model of Membranes: 8 ♦ Fluid mosaic model isn’t rigid and nothing is fixed ♦ It is a lipid bilayer in which there’s fluid in between and the lipid molecules can move around in them o Can vibrate, move sideways o Very thin layer ♦ It is important to maintain this membrane in a fluid state ♦ The mosaic part refers to the different proteins the lipid membrane contain ♦ Some of which are for transport and attachment, some are the enzymes involved in ETC ♦ Some of the lipid and protein molecules have carbohydrate groups linked to them that form glycolipids or glycoproteins ♦ The amount of protein and lipid in a membrane depends on the membrane o Ex inner mitochondrial membrane contains more protein than lipids but myelin contains more of lipids ♦ Another characteristic of the lipid bilayer is that the proteins and components that make up one half of it are different than the other half o Called membrane asymmetry ♦ For ex. There are glycoproteins and linked carb groups on the outside while the cytoskeleton binds to proteins on the inside ♦ Receptor proteins that are located on the external side and hormones and growth factors bind to this that causes the internal membranes to change that leads to the signal travelling through the cell Experimental Evidence in Support of the Fluid Mosaic Model:  Experiments that proved the two characteristics of the fluid mosaic model  Membranes are Fluid:  David and Michael experimented with human and mouse cell membranes  They coded the human proteins with red dye and mouse protein with green dye  They then fused the two and found the colours started to mix meaning the proteins moved around in a fluid environment and after 2 hrs it was fully intermixed  The fluidity was like of oil  Membrane Asymmetry:  Cells are frozen by being dipped in nitrogen and fractured with a microscopic knife  The bilayer breaks into inner and outer side and using an electron microscope we can see the different particles embedded in the inner and outer part of the lipid bilayer  It was seen to have different sized and shaped particles 5.2 The Lipid Fabric of a membrane:  Fluidity is important Phospholipids are the Dominant Lipids in Membranes:  The dominant lipids found in the membranes are phospholipids who contain a phosphate head and two attached amino acids  The critical property that makes these phospholipids so useful to membranes is that they are amphipathic  This means that they have a hydrophilic phosphate group and a hydrophobic fatty acid chain 9  When water is added the phospholipids assemble into a bilayer  Lipid bilayer forms spontaneously as the fatty acids join together while the polar heads associate with the water Membrane Fluidity: o The fluidity of a molecule is determined by two factors: 1.The lipid molecule 2.The temperature o If the fatty acid is saturated it is straight and can fit tightly together therefore less fluidity is present but if it was unsaturated it would be more fluid since there will be kinks in the fatty acid and it won’t be able to tightly be packed o Membranes stay fluid in a wide range of temperatures but if the temperature drops low enough the lipid bilayer becomes very closely packed and becomes semi solid 1.Ex. Melted butter to solid butter o The more unsaturated the membrane the lower the gelling temperature o Most membranes contain of both unsaturated and saturated lipid molecules but if there’s more saturated then there will be more room and more fluid Organisms Can Adjust Fatty Acid Composition: ♂ Membranes need to keep their fluidity ♂ If it becomes too hard due to low temperature then permeability may be lost and items cannot go through or leave and in things such as ETC transport through the membrane is REQUIRED ♂ At high temperature it can cause membrane leakage as well causing certain ions to leak out therefore it needs to be at a correct temperature ♂ Some organisms can adjust their fatty acid composition in order to maintain fluidity ♂ For ex protists that survive in harsh temperatures can have more unsaturated than saturated so that the membrane stays fluid in extremely cold weather ♂ The enzyme desaturase is responsible for making unsaturated fatty acids as fatty acids are produced saturated and this enzymes removes two H’s and creates a C-C double bond ♂ There are different desaturase enzymes that make double bonds in specific locations ♂ Changes in transcription can cause an abundance in transcript and more desaturase enzymes can be produce therefore there will be an abundance of them and more unsaturated fatty acids could be formed ♂ Organisms can use this to maintain fluidity ♂ Sterols can also affect fluidity ♂ The most common sterol is cholesterol found in animal cells but not in plant or prokaryotes ♂ At high temperature they will help reduce fluidity by constricting movement and at low temperature they’ll disrupt fatty acids and occupy space thus slowing down the transition to gel formation 5.3 Membrane Proteins: The key Functions of Membrane Proteins: ♦ There’s four functions of membrane proteins 1.Transport 10  Many substances can’t go through the membrane and proteins provide a hydrophilic path that allows them to go through by the protein changing shape and pushing the substance through 2.Enzymatic Activity:  Some proteins are enzymes for ex in ETC 3.Signal Transduction:  The proteins on the outside membrane bind with hormone and they trigger changes on the inside membranes and through transduction a signal goes through the cell 4.Attachment/recognition :  Proteins on the inside and outer membrane of the lipid bilayer can be used for attachment such as cytoskeleton and cell to cell recognition ♦ Membrane proteins go into two categories: 1.Integral 2.Peripheral Integral Membrane Proteins:  Embedded in the phospholipid bilayer  Most integral proteins go through the bilayer and interact with both aqueous environments around the bilayer  Hydrophobic core contains regions that have nonpolar amino acids (area that is inside the membrane with the hydrophobic lipids)  These hydrophobic chains consist of about 17-20 amino acids  The integral proteins are linked together by portions of a protein (polar amino acids since its outside) Peripheral Membrane Proteins:  On the surface of the membrane  They are connected by non-covalent bonds- hydrogen and ionic bonds  They sometimes interact with the part of the integral protein that is outside or the lipid molecule  Peripheral proteins usually are on the cytoplasmic side and are parts of the cytoskeleton  Made up of polar and non-polar amino acids 5.4 Passive Membrane Transport: Some compounds such as O2 and CO2 move across the membrane freely but other molecules like sugars cannot Passive Transport Is Based on Diffusion:  Passive transport is the movement of substances across a membrane without the use of ATP/energy  Passive transport depends on diffusion  Diffusion is when molecules are constantly moving above absolute zero and become uniformly distributed  The driving force behind diffusion is entropy 11  When molecules are all concentrated on one side of the membrane and the concentration is higher on one side, they will move towards low concentration going from low entropy to high entropy as molecules become less ordered and once they are equally spread across the membrane the molecule concentrations are the same even though the molecules keep moving  The higher the concentration on one side the faster the rate of diffusion The Two Types of Passive Transports: 1. Simple Diffusion: ♦ Size and charge matters when molecules diffuse across the lipid bilayer ♦ Non polar molecules such as O2 can go through and CO2 which can dissolve in the hydrophobic interior can go through as well ♦ Hormones and drugs can also go through ♦ Very small uncharged molecules such as H2O or glycerol can go through as well ♦ Charged molecules such as Cl- cannot go through ♦ Their charge and hydration shell makes the bilayer even more impermeable to these ions and molecules 2. Facilitated Diffusion: ♦ Metabolic processes require the molecule and ions that take a very long time to passively diffuse therefore the protein complexes that span the bilayer help move them across the membrane ♦ Concentration gradient needs to be present still and if the gradient is at 0 then the diffusion won’t occur Two Groups of Transport Proteins Carry out Facilitated Diffusion:  For facilitated diffusion integral membrane proteins (or transport proteins) are used that span the membrane  There two types of these proteins  One type is the channel proteins that provide hydrophilic pathways for water and ions to move through to the other side and so they don’t have to interact with the hydrophobic part of the membrane  Other channels called gated channels are used for ions in which they can be closed, open, or intermediate and this depends on the voltage change across the membrane o Ex. In animals voltage gated ion channels are used for nerve conduction and muscle contraction  The second type is carrier proteins in which they have pathways across the membrane for a specific single solute  This is uniport transport since only one molecule is transferred  This protein goes through conformation change thus the solute moves to the other side and this property distinguish carrier proteins from channel proteins  Many transport membranes are like enzymes since they have high specificity in the molecules they can transport o Ex transport protein for glucose CANT transport fructose  The way you can differentiate between facilitated and simple diffusion is that facilitated is MUCH faster but it has a maximum due to there being a fixed number of transport proteins 12  Simple diffusion is much slower but it keeps going faster with an increase in concentration and there is no limit Osmosis: The Passive Diffusion of Water:  Osmosis: water moving across a membrane  It can go inward or outward and can cause the cell to swell or shrink  Concrete definition: the net movement of water molecules across a selectively permeable membrane through diffusion from an area of low solute concentration to high solute concentration  The membrane must ONLY allow water to pass but not the solute molecule  Osmosis occurs b/c there’s proteins and molecules in the cytoplasm that can’t move out but water can move in  Water can move across the membrane through simple diffusion or by transport protein called aquaporin in which is a very thin channel that lets a billion of water molecules to pass every second but doesn’t let anything else go through like protons  In the middle of aquaporin there are positive charges that repel the protons that want to go through therefore they can get to the other side  If there is less solute concentration outside and HIGH SOLUTE concentration inside then it’s a HYPOTONIC solution and water moves into the cell to compensate- cell swells  If there is more solute on the outside and LOW SOLUTE concentration inside then it’s a HYPERTONIC solution and water moves out of the cell to compensate- cell shrinks  If there is equal concentrations inside and out of the cell it’s an ISOTONIC solution  To keep an isotonic solution, animals need to actively transport Na+ from inside to outside of the cell or else water will move in and the cell will burst 5.5 Active Membrane Transport: Some molecule or ions need to be transported against their concentration gradient and this is where active transport comes into play Active Transport Requires Energy:  For active transport energy is needed and the energy comes from ATP  About 25% of ATP is used for active transport  There’s two times of active transport: Primary active transport and secondary active transport  Primary Active transport: o The transport protein directly hydrolyzes ATP to get the energy to pump out/in the molecule  Secondary transport: o The transport is indirectly driven by ATP meaning that they use the concentration gradient of ions that is formed by primary active transport as the energy for its active transport  This is similar to facilitated transport since it has transport proteins that are specific and can be saturated and conformation occurs as well Primary Active Transport Moves Positively Charged Ions: 13 ▬ Primary active transport moves ions across the membrane and this is essential for certain things ▬ Proton pump (H+ pump) pushes hydrogen from the cytoplasm to outside the cell and this is essential for certain things like photosynthesis and this type of pump is not very common in animals except for pushing H+ into the stomach to make it more acidic ▬ Calcium Pump (Ca 2+ pump) pushes Ca from the cytosol to the outside and this concentration gradient is necessary for things such as muscle contraction ▬ Sodium-Potassium pump (Na+/K+ pump) is one that pumps 3 Na+ out and 2 K+ in causing a more positive charge on the outside and negative charge on the inside ▬ This charge difference causes voltage across the membrane called membrane potential ▬ Therefore we have a charge difference and concentration gradient and this is called electrochemical gradient ▬ Electrochemical gradients store energy for other transport mechanism ▬ This gradient is also used for nerve impulse transmission Secondary Active Transport Moves Both Ions and Organic Molecules: o In secondary transport, the transport of the solute is always coupled with the transport of the ion that gives the driving force o Secondary transport occurs in two different mechanism: Symport and Antiport o Sy
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