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Energy
ability to do work/move matter
Kinetic energy
energy of motion (sound, light, contracting muscles)
Potential energy
stored available energy (energy bar, chemical bonds, chemical gradient)
Thermal energy
energy from heat and light
chemical energy
energy stored in chemical bonds
first law of thermodynamics
energy is never created nor destroyed
second law of thermodynamics
entropy of the universe is always increasing over time since heat is lost at each step of the energy cycle
entropy
amount of disorder or randomness of heat energy
entropy in universe increases when molecules are formed (dehydration synthesis)
Chemical reactions
rearrange atoms - energy is either put in or released
Endergonic
rxn that requires energy to forms bonds
dehydration synthesis (joining molecules)
reduction
powered by ATP
exergonic
rxn that releases energy when breaking bonds
hydrolysis
oxidation
power ATP synthase
energy coupling
energy produced by one rxn is used to drive another rxn
oxidation-reduction rxn
most energy transformations in organisms where electrons are transferred from donor to acceptor
Oxidation
atom/molecule donates electron releasing energy that was stored in electrons (exergonic)
reduction
gain of electrons by atom/molecule which gains energy from released electrons (endergonic)
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
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
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
Cofactors
bind to enzyme to help catalyze - increase enzyme activity
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)
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)
selective permeability
solutes enter/exit cells depending on concentration gradient (high → low), polarity, charge and size
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)
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
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
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
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)
electromagnetic spectrum
wavelength: short wavelength = high energy
visible light: wavelength that appear as color
photons: packets of light energy - captured by photosynthesizers in pigment
Pigment
molecules that capture energy from light
chlorophyll a: blue-green (most pop)
chlorophyll b: yellow - green
carotenoids: red, orange, yellow
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
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)
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
aerobic cellular respiration
C6H12O6 + O2 → CO2 + H2O + ATP
1 glucose produces 36 ATP
glycolysis, krebs (calvin) cycle, ETC
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
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
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
Anaerobic respiration
occurs in many prokaryotes
different e- acceptors than O2 (nitrate, sulfate, CO2)
less ATP production
includes fermentation
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)