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56 Cards in this Set
- Front
- Back
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All cells capture and use energy
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Energy – ability to do work
Potential energy – stored energy available to do work Kinetic energy – energy being used to do work Movement, heat, light, sound Calorie used to measure energy Energy required to raise 1 g of water 1°C Kilocalorie or Calorie = 1000 calories |
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Laws of Thermodynamics
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First law – law of energy conservation
Energy cannot be created or destroyed Only converted to other forms Energy transformations sustaining life are similar in all organisms |
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Second law – all energy transformations are inefficient
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Lose some energy as heat
Entropy – tendency toward randomness Organisms must use incoming energy and matter to remain organized |
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Chemical reactions
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Metabolism – sum of all the reactions in cells
Organized in metabolic pathways Product of one reaction becomes the substrate of anothe |
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Endergonic reactions
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Require energy to proceed
Build complex molecules Photosynthesis |
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Exergonic reactions
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Release energy
Break apart large, complex molecules Cellular respiration |
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Chemical equilibrium
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Most reactions can proceed in both directions
If reactants accumulate, the reaction goes forward and vice versa At chemical equilibrium, reaction goes in both directions at the same rate Cells must remain far from equilibrium |
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Oxidation-reduction or redox reactions
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Transfer energized electrons from one molecule to another
Oxidation – lose electrons, release energy Reduction – gain electrons, requires energy If one molecule is reduced (gains electrons), then another must be oxidized (lose electrons) Electron transport chain releases small amounts of energy as electrons transferred Photosynthesis and cellular respiration |
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ATP – Adenosine triphosphate
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Temporary energy storage
Adenosine – adenine and ribose Triphosphate – 3 phosphate groups ATP hydrolysis is exergonic and releases energy ATP + H2O → ADP + P + energy ATP synthesis is endergonic and stores energy ADP + P + energy → ATP + H2O Coupled reactions – one provides energy that drives the other |
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phosphorylation
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cell uses ATP as an energy source by transferring its phosphate group to another molecule
2 effects May energize target molecule fueling endergonic reaction Can cause a protein to change shape |
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Enzymes
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Protein that catalyzes a chemical reaction without being consumed
Lowers energy of activation Amount of energy required to start a reaction Increases reaction rates a billion times |
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Active site – region where reactant (or substrate) binds
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Specific fit
Active site “hugs” reactant forming enzyme-substrate complex Reaction does not alter enzyme Cofactors are nonprotein helpers required by enzyme Coenzymes/vitamins |
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Cells precisely control reaction rates
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Pacesetter – enzyme in pathway with slowest reaction rate sets rate of entire pathway
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Negative feedback or feedback inhibition
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Excess of reaction’s product inhibits enzyme controlling formation
Thermostat example Competitive vs. noncompetitive inhibition |
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Positive feedback
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Product activates pathway, reaction proceeds faster and faster
Not as common |
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Environmental conditions
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Enzymes are very sensitive
Too hot, too high or low pH, too low or high salt concentration can alter shape and function Denature – loses shape and function Exact conditions depend on the organism and enzyme |
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Membrane transport
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Cells spend a tremendous amount of energy maintaining differences between themselves and the outside world
Concentration gradient – solute is more concentrated in one region than another Dissipates unless energy expended to maintain it All forms of membrane transport involve gradients Membranes are selectively permeable – admit some but not all molecules |
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Passive transport
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does not require cell to expend energy
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Diffusion
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spontaneous movement of a substance from a region where it is more concentrated to an area where it is less concentrated
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Diffusion-Passive transport
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Occurs because atoms are in constant, random motion
If diffusion occurs long enough, gradient disappears, traffic equal going in and out of cell Cell maintains gradients by consuming substance so it diffuses in or producing product so it diffuses out |
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Simple diffusion
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Form of passive transport not using a carrier protein
Oxygen and carbon dioxide use simple diffusion to enter and leave blood in the lungs or tissues |
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Osmosis
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Simple diffusion of water across a membrane
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tonicity
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ability of a substance to cause water movement
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Isotonic
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concentrations equal inside and outside the cell – water does not enter or leave – cell stays the same size
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hypotonic
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hypo means under – solute concentration lower inside cell – water enters – cell swells
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hypertonic
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hyper means over – solute concentration higher outside cell – water leaves cell – cell shrink
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Facilitated diffusion
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Form of passive transport in which a membrane protein assists solute movement along concentration gradient
Does not require energy Glucose uses facilitated diffusion – too hydrophilic to pass through membrane unassisted Aquaporins can enhance osmosis |
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Active transport
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Cell uses a transport protein to move a solute against its concentration gradient requiring ATP
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Sodium-potassium pump
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uses ATP to expel 3 Na+ for every 2 K+ it admits
Uses 25% of a cell’s ATP |
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Gradients
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can be used as source of potential energy – ATP synthase in photosynthesis and cellular respiration
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endocytosis
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allows a cell to engulf large molecules and fluid
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pinocytosis
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for fluids and dissolved substances
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phagocytosis
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engulfs large particles or debris
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exocytosis
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cell uses vesicles to transport fluids and large particles out of cell
Golgi apparatus produces vesicles |
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Energy
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ability to do work
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Potential energy
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stored energy available to do work
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Kinetic energy
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energy being used to do work. Movement, heat, light, sound
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Calorie used to measure energy
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Energy required to raise 1 g of water 1°C
Kilocalorie or Calorie = 1000 calories |
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First law – law of energy conservation
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Energy cannot be created or destroyed
Only converted to other forms Energy transformations sustaining life are similar in all organisms |
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Metabolism
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sum of all the reactions in cells
Organized in metabolic pathways Product of one reaction becomes the substrate of anothe |
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Oxidation
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lose electrons, release energy
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Reduction
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gain electrons, requires energy
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Adenosine
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adenine and ribose
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Triphosphate
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3 phosphate groups
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ATP hydrolysis is exergonic and releases energy
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ATP + H2O → ADP + P + energy
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ATP synthesis is endergonic and stores energy
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ADP + P + energy → ATP + H2O
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Coupled reactions
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one provides energy that drives the other
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Active site
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region where reactant (or substrate) binds
Specific fit Active site “hugs” reactant forming enzyme-substrate complex Reaction does not alter enzyme Cofactors are nonprotein helpers required by enzyme Coenzymes/vitamins |
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Pacesetter
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enzyme in pathway with slowest reaction rate sets rate of entire pathway
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Negative feedback or feedback inhibition
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Excess of reaction’s product inhibits enzyme controlling formation
Thermostat example Competitive vs. noncompetitive inhibition |
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Positive feedback
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Product activates pathway, reaction proceeds faster and faster
Not as common |
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Denature
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loses shape and function
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Passive transport
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does not require cell to expend energy
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Diffusion
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spontaneous movement of a substance from a region where it is more concentrated to an area where it is less concentrated
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Glucose uses facilitated diffusion
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too hydrophilic to pass through membrane unassisted
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Aquaporins
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can enhance osmosis
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