Bio 101 Unit 2

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38 Terms

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Energy

ability to do work/move matter

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Kinetic energy

energy of motion (sound, light, contracting muscles)

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Potential energy

stored available energy (energy bar, chemical bonds, chemical gradient)

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Thermal energy

energy from heat and light

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chemical energy

energy stored in chemical bonds

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first law of thermodynamics

energy is never created nor destroyed

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second law of thermodynamics

entropy of the universe is always increasing over time since heat is lost at each step of the energy cycle

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entropy

amount of disorder or randomness of heat energy

  • entropy in universe increases when molecules are formed (dehydration synthesis)

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Chemical reactions

rearrange atoms - energy is either put in or released

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Endergonic

rxn that requires energy to forms bonds

  • dehydration synthesis (joining molecules)

  • reduction

  • powered by ATP

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exergonic

rxn that releases energy when breaking bonds

  • hydrolysis

  • oxidation

  • power ATP synthase

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energy coupling

energy produced by one rxn is used to drive another rxn

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oxidation-reduction rxn

most energy transformations in organisms where electrons are transferred from donor to acceptor

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Oxidation

atom/molecule donates electron releasing energy that was stored in electrons (exergonic)

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reduction

gain of electrons by atom/molecule which gains energy from released electrons (endergonic)

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electron transport chain

series of membrane proteins performing sequential/linked oxidation/reduction rxns

  • used in photosynthesis and cellular respiration

  • released energy is stored in cells to use in other rxns

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ATP

nucleotide that temporarily stores energy to power chemical rxns

  • removing end phosphate grp via hydrolysis releases potential energy

  • formed during cellular respiration - release energy from sugar (ADP → ATP)

  • ATP breakdown is coupled - ATP breakdown powers endergonic rxns

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Enzymes

protein that acts as a catalyst - speeds up chemical rxn and lower energy required

  • substrate binds to active site on enzyme where rxn occurs and releases product

  • some enzymes combine two substrates

  • activation energy - amt required to start rnx

  • hv optimal temperature, salt concentration and pH

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Cofactors

bind to enzyme to help catalyze - increase enzyme activity

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Enzyme inhibitors

used to prevent unneeded rxns from occurring

  • noncompetitive: binds to separate spot on enzyme to change active site shape so it cannot bind to substrate anymore

  • competitive: binds to enzyme in place of substrate (may be product of rxn binding to enzyme when numbers increase)

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feedback loops

  • negative feedback - once enough final product is produced, this product can bind to initial enzyme as inhibitor

  • positive feedback - final product binds to initial enzyme to speed up production (acts as its own cofactor)

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selective permeability

solutes enter/exit cells depending on concentration gradient (high → low), polarity, charge and size

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Passive transport

down the concentration gradient

  • simple diffusion - small nonpolar molecules move across membrane (O2 moves from lungs to red blood cells)

  • osmosis - diffusion of water accross membrane for equal solute ratio in/out of cell

  • facilitated diffusion - membrane proteins transport ions and polar substances (hydrogen ions using transport proteins produce ATP) (glucose from food moves into cells)

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Tonocity

ability of extracellular solution to make water move in/out of cell

  • hypotonic: water moves into cell - higher solute concentration inside cell

  • hypertonic: water moves out of cell - higher solute concentration outside cell

  • isotonic: water does not move - equal concentration in/out of cell

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Water balance in plants

plants keep solute higher inside cells to get water to enter cell to maintain turgor pressure. (hypertonic = loss of water = vacuole shrinks = plants wilt

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Active Transport

uses ATP to transport against concentration gradient (ions moved in/out neurons/muscle cells)

  • protein pump - sodium-potassium pump moves 3 Na+ out of cell and 2 K+ into cell

  • endocytosis: vesicles engulf large molecules into cell

  • exocytosis: vesicles to secrete large polar molecules (proteins - mammary/milk) out of cell

  • pinocytosis: cell takes in fluid via vessicles

  • Phagocytosis: cell releases water via vessicles

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Photosynthesis

converting light (kinetic) energy into chemical (potential) energy

  • 6CO2 + 6H2O + light → C6H12O6 (sugar) + 6O2

  • conducted by autotrophs (cyanobacteria in water, doesn’t include kingdom archaea)

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electromagnetic spectrum

  • wavelength: short wavelength = high energy

  • visible light: wavelength that appear as color

  • photons: packets of light energy - captured by photosynthesizers in pigment

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Pigment

molecules that capture energy from light

  • chlorophyll a: blue-green (most pop)

  • chlorophyll b: yellow - green

  • carotenoids: red, orange, yellow

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Plant structure

  • stomata: leaf pores where gas exchange occurs - contains mesophyll cells: sole purpose is photosynthesis

  • stroma: fluid inside chloroplasts

  • thylakoids: coin like membranes inside stroma

  • granum: stack of thylakoids

  • inner membrane + outmembrane + intermembrane space btwn both

  • chrorophyll: photosynthetic pigment

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Light reactions

1) light strikes Photosystem II (protein in thylakoid membrane) where chlorophyll absorbs light and transfers to e- from H2O

2) e- moves to ETC and heads to Photosystem I where chlorophyll transfers energy to e-

3) e- moves to seconds ETC

(produces NADPH and ATP which power later carbon rxns)

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Carbon reactions

Calvin cycle: occurs in stroma

1) rubisco enzyme catalyzes first rxn

2) carbon fixation: rubisco adds CO2 onto RuBP forming unstable 6 carbon org mol

3) PGAL synthesis: uses ATP+NADPH energy to convert PGA into PGAL → multiple PGALS (one from each cycle) combine to form glucose molecules)

4) RuBP regeneration: some PGAL is used to reform RuBP (5 carbon) which restarts new cycle

  • Photorespiration: occurs due to O2 buildup inside leaf to release it - decreases rate of photosynthesis

  • C3, C4, CAM plants use different pathway for carbon fixation

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aerobic cellular respiration

  • C6H12O6 + O2 → CO2 + H2O + ATP

  • 1 glucose produces 36 ATP

  • glycolysis, krebs (calvin) cycle, ETC

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glycolysis

  • occurs in cytosol in all cells

  • 1 glucose + 2ATP → 2 3C pyruvate (PGAL) → oxidation = 2 NADH → substrate level phosphorylation = 2 ATP each (x2 = 4 total ATP)

  • overall: 1 glucose, 2 NAD+, 2 ADP → 2 pyruvate, 2 NADH, 2 ATP

  • transition step: 2 pyruvate → 2 acetyl CoA, releases CO2 & NAD+ → NADH

  • probably first of 3 pathways to emerge

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Krebs Cycle

  • occurs in: prokaryotes - cytosol, eukaryotes - mitochondria

  • 2 acetyl CoA oxidized → energy transfer to e- → release 4 CO2, 2 ATP, 6 NADH, 2 FADH2

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Electron Transport Chain

  • occurs in: prokaryotes - cytosol, eukaryotes - mitochondria

  • e- potential energy used

  • NADH + FADH2 donate e-s to ETC → H+ gradient formed from e- transporting H+ into intermembrane space and into matrix into ATP synthase enzyme (chemiosmotic phosphorylation) → yeilds 34 ATP

  • extra e- donated to O2 which then bonds with H+ to form H2O

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Anaerobic respiration

  • occurs in many prokaryotes

  • different e- acceptors than O2 (nitrate, sulfate, CO2)

  • less ATP production

  • includes fermentation

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Fermentation

only glucose - continues cycles to produce 2 ATP per cycle

  • pyruvate oxidizes NADH → NAD+

  • pyruvate can be converted into alcohol or lactic acid

  • Alcoholic fermentation: NADH reduces pyruvate to ethanol creating NAD+ (carried out by microbes)

  • lactic acid fermentation: NADH reduces pyruvate to lactic acid creating NAD+ (occurs in bacteria + muscle cells)