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94 Cards in this Set
- Front
- Back
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The Plasma Membrane |
Functions of plasma membraneSelective barrier. Things that are charged or polar can not easily go through the proteinsAllows specific transport of nutrients and waste productsAttached and communication with environment |
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The Nucleus contains DNA and Enzymes that Replicate DNA and Transcribe DNA |
DNA is complex with special proteins to form chromatin that packages DNA into ChromosomesNucleus surrounded by two membranes called Nuclear EnvelopeMolecules pass into or out of nucleus via Nuclear pore complexes |
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The Endomembrane system of membranes |
Materials are sequested from cytosolTransported around the cell and into or out of the cellVia plasma membraneTransport vesicles carry materials from one part to another |
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Lysosomes: Digestive Compartments |
A lysosomeMembranous sac of hydrolytic enzymesDigests macromoleculesLysosomal enzymes hydrolyze- ProteinsFatsPolysaccharidesNucleic adics |
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Lysosomes: Digestive Compartments (2) |
Some types of cellsENgulf another cell by phagocytosisForms a food vacuoleA lysosome Fuses with the food vacuoleDigests the molecules use enzymes to recycle the cell’s own organelles and macromoleculesProcess called autophagy |
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Mitochondria and Chloroplasts Change Energy from one Form to Another |
Mitochondria The sites of cellular respirationMetabolic process that generates ATPChloroplastsFound in plants and algaeThe sites of photosynthesisPeroxisomesOxidative organellesCatabolism of fatty acids |
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Origin of Mitochondria and Chloroplasts? |
Symbiotics relationshipMitochondria contain DNADNA related to proteobactera |
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The Cytoskeleton |
Network of fibersExtending throughout the CytoplasmComposed of three types of molecular structures:MicrotubulesMicrofilamentsIntermediate |
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Roles of the Cytoskeleton: support, Motility, and regulation |
The cytoskeleton- Helps to support the cellInteracts the motor proteinsProduce motility |
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Inside the cell, vesicles can travel along “monorails.” |
Provided by the Cytoskelton may help regulate biochemical activities |
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The Cytoskeleton(1) |
Microfilaments: Maintaining cell shapeMuscle contrationOrganelle movement Cell division |
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The Cytoskeleton(2) |
Intermediate FilamentsMaintaining Cell ShapeAnchoring NucleusNuclear Lamina |
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The Cytoskeleton(3) |
MicrotubulesCell Motility (cilia and flagella)Chromosome movementOrganelle Movement |
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Cilia and Flagella(1) |
MicrotubulesControl the beating of cilia and flagellaLocomotor appendages of some cells |
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Cilia and Flagella(2) |
Differ in their beating patternsShare a common ultrastructureA core of microtubulesSheathed by the plasma membrane |
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Cilia and Flagella(3) |
A basal body Anchors the cilium or flagellum |
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Cilia and Flagella(4) |
A motor proteinCalled dyneinDrives the bending movements of a cilium or flagellum |
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Microfilaments (Actin Filaments)(1) |
MicrofilamentsSolid rods about 7 nm in diameterBuilt as a twisted double chain of actin subunits |
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Microfilaments (Actin Filaments)(2) |
The structural role of microfilaments is to bear tensionResisting pulling forces within the cellForm a 3-D network called the cortex just inside the plasma membraneHelp support the cell’s shape |
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Microfilaments (Actin Filaments)(3) |
Bundles of microfilamentsMakes up the core of microvilli of intestinal cells |
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Microfilaments (Actin Filaments)(4) |
Microfilaments that function in cellular motility Contain the protein myosin in addition to actin |
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Microfilaments (Actin Filaments)(5) |
In muscle cellsThousands of actin filaments are arranged parallel to one another |
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Microfilaments (Actin Filaments)(6) |
Thicker filaments composed of myosinInterdigitate with the thinner actin fibers |
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The Extracellular Matrix (ECM) of Animal cells |
Animal cells lack cell wallsCovered by an elaborate extracellular matrix (ECM) |
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The Extracellular Matrix (ECM) of Animal cells(2) |
The ECMMade up glycoproteinsCollagen ProteoglycansFibronectin |
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The Extracellular Matrix (ECM) of Animal cells(3) |
ECM proteinsBind the receptor proteins in the plasma membraneCalled integrins |
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Functions of ECM |
SupportAdhesionMovement Regulation |
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Tight Junctions |
At tight JunctionsMembranes of neighboring cells are pressed togetherPreventing leakage of extracellular fluid |
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Desmosomes |
DesmosomesAnchoring junctionsFasten cells together into strong sheet |
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Gap Junctions |
Gap JunctionsCommunicating Junctions Provide cytoplasmic channels between adjacent |
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Metabolism |
The totality of an organism’s Chemical reactionAn emergent property of life that arises from interactions between molecules within the cellA metabolic pathway begins with a specific molecule and ends with a productEach step is catalyzed by a specific enzyme an organism’s metabolism transforms matter and energySubject to the laws of thermodynamics |
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Catabolic and Anabolic Pathways |
Release energy by breaking down complex molecules into simpler compounds Cellular respirationThe breakdown of glucose in the presence of oxygen |
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Anabolic pathways |
Consume energy build complex molecules from simpler onesThe synthesis of protein from amino acids is an example of anabolis |
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Bioenergetics |
The study of how organisms manage their energy resources |
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Energy |
The capacity to cause change Prerequisite for performing mechanical work |
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Energy exists in various forms |
Some of which can perform workKinetic energy Energy associated with motionHeat (thermal energy)Kinetic energy associated with random movement of atoms or molecules Potential energyEnergy that matter possesses because of its location or structure Chemical energyPotential energy available for release in a chemical reactionEnergy can be converted from one form to another |
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The Laws of Energy Transformation |
ThermodynamicsThe study of energy transformationsA close system is isolated from its surroundings Liquid in a thermosOpen system Energy and matter can be transferred between the system and its surroundingsOrganisms are open systems |
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The First Law of Thermodynamics |
According to the first law of thermodynamicsThe energy of the universe is constant Energy can be transferred and transformedBut it cannot be created or destroyed The first lawAlso called the principle of conservation of energy |
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The second law of thermodynamics |
During every transfer or transformation, some energy is usable Often lost as heatHeat - Energy transferred from one body to another by thermal interactions According to the second law of thermodynamics Every energy transfer or tranformation increases the entropy (disorder) of the universeEntropy - A measure of the thermal energy per unit temperature that is not available to do useful work |
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Spontaneous Processes |
Living cells unavoidably convert organized forms of energy to heatSpontaneous processes occur without energy inputThey can happen quickly or slowly For a process to occur without energy input:It must increase the entropy of the universe |
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Biological order and disorder |
CellsCreate ordered structures from less ordered materials Organisms Also replace ordered forms of matter and energy with less ordered forms The evolution of more complex organisms Does not violate the second law of thermodynamics Energy Flows into an ecosystem in the form of lightExists in the form of heat Entropy (disorder) may decrease in an organism But the universe’s total entropy increases Organisms are islands of low entropy in an increasingly random universe |
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Free - Energy Change, ∆G |
-Biologists Want to know which reactions occur spontaneously and which require input of energyTo do so, Biologists need to determine energy changes that occur in chemical reactions -The free - energy change of a reactionTells us whether or not the reaction occurs spontaneously -A living system’s free energyEnergy that can do work when temperature and pressure are uniformAs in a living cell∆G must have a negative value for a process to be spontaneous |
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Free Energy |
Free energy is a measure of a system’s instability Its tendency to change to a more stable state |
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Stability |
During a spontaneous changeFree energy decreases and the stability of a system increasesUnless something prevents it, each system will move toward greater stability Diver on a top platform Drop of concentrated dyeSugar molecule |
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Equilibrium is a state of maximum stability |
A process is spontaneous and can perform work only when it is moving toward equilibriumThe change in free energy(∆G) during a processRelated to the change in enthalpy, or change in total energy (∆H), change in entropy (∆S), and temperature in Kelvin (T):∆G = ∆H - T∆SOnly processes with a negative ∆G are spontaneousSpontaneous processes can be harnessed to perform work |
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More free energy ( Higher G) |
Less stableGreater workin A spontaneous change The free energy of the system decreases (∆G < 0)The system becomes more stableThe released free energy can be harnessed to do work |
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Less free energy (lower G) |
More stable Less work capacity |
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Free Energy and Metabolism |
The concept of free energy Can be applied to the chemistry of life’s processesExergonic and endergonic reactions in metabolism An exergonic reactionProceeds with a net release of free energy and is spontaneousAn endergonic reactionAbsorbs free energy from its surroundings and is nonspontaneous |
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Equilibrium and Metabolism |
Reactions in a closed systemEventually reach equilibrium and then do no workCells are not equilibrium They are open systems experiencing a constant flow of materialsA defining feature of lifeMetabolism is never at equilibriumA catabolic pathway in a cellReleases free energy in a series of reactionsA closed and open hydroelectric systems Can serve as analogies |
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ATP powers cellular work by coupling exergonic reactions to endergonic reactions A cell does three main kinds of work: |
Chemical Coupling energy from ATP (∆G < 0 ) to drive endergonic reactions ( ∆G > 0)Transport Pumping ions and molecules across membranes against concentration gradient Mechanical muscle contraction, vesicle, flagella and cilia movementTo do work, cells manage energy resources by energy couplingThe use of an exergonic process to drive an endergonic oneMost energy coupling in cells is mediated by ATPCell’s energy shuttleComposed of ribose (a sugar), adenine (a nitrogenous base), an d three phosphate groupsThe bonds between the phosphate groups of ATP’s tail can be broken by hydrolysisEnergy is released from ATP when the terminal phosphate bond is brokenThis release of energy comes from the chemical change to a state of lower free energyNot from the phosphate bonds themselves |
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Adenosine Triphosphate - ATP |
The cell’s Energy “Currency” |
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How ATP performs work |
The three types of cellular work are powered by the hydrolysis of ATPMechanicalTransportChemical |
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- In the cell |
Energy from the exergonic reaction of ATP hydrolysis- Can be used to drive an endergonic reaction Overall, the coupled reactions are exergonic |
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How ATP performs work |
ATP drives endergonic reactions by phosphorylationTransferring a phosphate group to some other molecule Such as a reactantThe recipient molecule becomes phosphorylated |
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The regeneration of ATP |
ATP is a renewable resource Regenerated by addition of a phosphate group to adenosine diphosphate (ADP)The energy to phosphorylate ADPComes from catabolic reactions in the cellThe chemical potential energyTemporarily stored in ATP drives most cellular work |
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Enzymes speed up metabolic reactions by lowering energy barriers |
A catalystA chemical agent that speeds up a reaction Without being consumed by the reactionAn enzymeA catalytic proteinHydrolysis of sucrose by the enzyme sucraseAn example of an enzyme catalyzed reaction |
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The Activation Energy Barrier |
Every chemical reaction between molecules Involved bond breaking and bond formingThe initial energy needed to start a chemical reactionActivation energy (EA)Activation energyOften supplied in the form of heat from the surroundings Enzymes catalyze reactions by lowering the EA barrierEnzymes do not affect the change in free energy (∆G)Instead, the hasten reactions that would occur eventually |
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Substrate Specificity of Enzymes |
The reactant that an enzyme acts onCalled the enzyme’s substrate The enzyme binds to its substrateForming an enzyme-substrate complexThe active siteThe region on the enzyme where the substrate bindsInduced fit of a substrateBrings chemical groups of the active site into positions enhance their ability to catalyze the reaction |
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Catalysis in the Enzyme’s Active Site |
In an enzymatic reactionSubstrate binds to the active site of the enzymeThe active site can lower EA barrier byOrienting substrates correctlyStraining substrate bondsProviding a favorable microenvironmentCovalently bonding to the substrate |
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Effects of local conditions on enzyme activity |
An enzyme’s activity can be affected by General environmental factors, such as temperature and PHChemicals that specifically influence the enzymeEffects of temperature and pHEach enzyme has an optimal temperature in which it can functionEach enzyme has an optimal pH in which it can function |
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Cofactors |
Cofactors are nonprotein enzyme helpersMay be inorganic metal in ionic formMay be organiccoenzyme |
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Coenzymes include vitamins |
Vitamin CAscorbic acid ScurvyRequired for the synthesis of collagen Bleeding from mucous membranes, spot on skin |
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Enzyme Inhibitors |
Competitive inhibitorsBind to the active site of an enzymeCompeting with the substrate |
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Noncompetitive inhibitors |
Bind to another part of an enzymeCausing the enzyme to change shapeMaking the active site less effective |
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Regulation of enzyme activity helps control metabolism |
Chemical chaosResult if a cell’s metabolic pathways were not tightly regulatte |
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- Regulation of a cell |
- Switching on or off the genes that encode specific enzymes- Regulating the activity of enzymes |
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- Allosteric regulation |
- May either inhibit or stimulate an enzyme’s activity- Occurs when a regulatory molecule binds to a protein at one site and affects the protein’s function at another site -Most allosterically regulated enzymes are made from polypeptide subunits - Each enzyme has active and inactive forms - The binding of an activator stabilizes the active form of the enzyme - The binding of an inhibitor stabilizes the inactive form of the enzyme |
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Regulation of enzyme activity helps control metabolism |
CooperativityA form of allosteric regulation that can amplify enzyme activityBinding by a substrate to one active siteStabilizes favorable conformational changes at all other subunits |
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Feedback Inhibition |
The end product of a metabolic pathwayShuts down the pathwayPrevents a cell from wasting chemical resourcesBy synthesizing more product than is needed |
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Cellular Membranes |
Cellular Membranes are Fluid Mosaics of Lipids and ProteinsMembranes have been chemically analyzed Found to be made of proteins and lipidsScientists studying the plasma membraneReasoned that it must be a phospholipid bilayer |
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Phospholipids |
The most abundant lipid in the plasma membrane Amphipathic molecules Containing hydrophobic and hydrophilic regions |
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Fluid mosaic model |
A membrane is a fluid structureWith a “mosaic” of various proteins embedded in it |
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Freeze-Fracture |
Freeze-fractureSpecialized preparation techniqueSplits a membrane along the middle of the phospholipid bilayer Freeze-fracture studies of the plasma membrane Supported the fluid mosaic model |
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The Fluidity of membranes |
Phospholipids in the plasma membraneCan move within the bilayerMost of the lipids, and some proteins, drift laterally Rarely does a molecule flip-flop tansversely across the membrane |
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The Fluidity of Membranes |
As temperatures coolMembranes switch from a fluid state to a solid state The temperature at which a membrane solidifiesDepends on the types of lipidsMembranes rich in unsaturated fatty acidsMore fluid that those rich in saturated fatty acidsMembranes must be fluid at work properlyUsually about as fluid as salad oilCholesterol within animal cellsHas different effects on the membrane fluidity at different temperaturesReduces membrane fluidity at moderate temperatures (37 C)Hinders solidification at low temperatures Preventing tight packing |
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Membrane |
Collage of different proteinsEmbedded in the fluid matrix of the lipid bilayer |
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Proteins |
Determine most of the membrane’s specific functions |
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Peripheral Proteins |
Bound to the surface of the membrane |
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Integral Proteins |
Penetrate the hydrophobic core |
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Transmembrane proteins |
Integral proteins that span the membrane |
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The hydrophobic regions of an integral protein |
Consist of one or more stretches of nonpolar amino acidsOften coiled into alpha helices |
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Six Major Functions of Membrane Proteins |
Transport Enzymatic activitySignal transductionCell-cell recognitionIntercellular joiningAttachment to the cytoskeleton and extracellular matrix (ECM) |
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The Role of Membrane Carbohydrates in the Cell-Cell recognition |
Cells recognize each each otherBy binding to surface molecules on the plasma membrane Often carbohydrates |
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Membrane carbohydrates |
May be covalently bonded to lipids or proteinsForming glycolipidsForming glycoproteins |
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Carbohydrates on the external side of the plasma membrane |
Vary among species, individuals, and even cell types in an individual |
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Synthesis and sidedness of Membranes |
MembranesHave distinct inside and outside facesAsymmetrical distribution of proteins, lipids, and associated carbohyrdates in the plasma membraneDetermined when the membrane is built by the ER and Golgi apparatus |
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Membrane Structure Results in Selective Permeability |
A cell must exchange materials with its surroundingsProcess controlled by the plasma membranePlasma membranes are selectively permeableRegulate the cell’s molecular trafficPermeability of the lipid bilayerHydrophobic (nonpolar) moleculesHydrocarbonsCan dissolve in the lipid bilayer and pass through the membrane rapidlyPolar molecules Such as sugars Does not cross the membrane easily |
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Transport Proteins |
Allow passage of hydrophilic substances across the membraneSpecific for the substance it moves |
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Channel proteins |
Transport proteinsHave a hydrophilic channelCertain molecules or ions can use a tunnel |
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Aquaporins |
Channel proteinsFacilitate the passage of water |
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Carrier Proteins |
Transport ProteinBind to moleculesChange shape to shuttle them across the membrane |
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Diffusion |
The tendency for molecules to spread out evenly into the available space. Diffusion of a population of molecules may exhibit a net movement in one directionAlthough each molecule moves randomely |
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Dynamic equilibrium |
As many molecules across one way as cross in the other direction |
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Substances diffusion diffuse down their concentration gradient |
The difference in concentration of a substance from one area to another No work must be done to move substances down the concentration gradientThe diffusion of a substances across a biological membrane is passive transport It requires no energy from the cell to make it happen |
