BIOL130 Chapter Notes - Chapter 4: Nicotinamide Adenine Dinucleotide Phosphate, Oxidative Phosphorylation, Mitochondrial Matrix

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5 Aug 2016
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Chapter 4: Energy
Energy obtained from chemical bond energy stored in ‘food’ and stored/transported in high
energy bonds of carrier molecules (ATP and NADH)
 most important source is carbohydrate (sugar)
 sugars oxized to CO2 and H2O
Macromolecule, nucleic acids, synthesis requires ATP
Energy stored in:
 phosphate group in ATP
 electrons and hydrogens in NADH, NADPH, FADH2
 acetyl group in acetyl CoA
Coenzymes that carry electrons from one reaction to another: accepts a hydride atom (H-, 2
electrons and a proton) and donates it
 key players in harvesting energy during oxidation of glucose
NAD+ = nicotinamide adenine dinucleotide (vitamin B3)
FAD = flavin adenine dinucleotide (vitamin B2)
NADP+ = nicotinamide adenine dinucleotide phosphate
Catabolism: breakdown of complex molecules into simpler ones (by enzymes)
Anabolism: build molecules from simpler ones, also called biosynthetic pathway
in cells, energy is released due to the breaking of six C-G bonds
if you burn glucose all at once, all the energy is released as heat
oxidation of sugar in cells in STEPS: smaller activation energies overcome by body temperatures,
generation of ATP and activated molecules (i.e. NADH) provides energy for cells to do work
Three ways to make ATP
1) substrate level phosphorylation: generate a few ATP during glycolysis (initial
breakdown/rearrangement of glucose)
2) oxidative phosphorylation (aerobic respiration): energy stored in high-energy electrons of
NADH and FADH2 are used to produce ATP
 electrons from organic fuel molecules in redox reactions are used to pump H+ across a
membrane (proton pump) occurs in the mitochondrial membrane
 protons want to get back into the mitochondrial matrix; they go back through the ATP
synthase protein
3) Photophosphorylation: occurs in chloroplasts SLIDE 17
 cyclic and non-cyclic phosphorylation
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 in cyclic: uses only photosystem I and no NADPH is produced
 in non-cyclic: uses both PS I and II, goes through all energy carriers until it reaches the final
electron acceptor which is NADPH. Therefore NADPH is produced
Extracting energy from food occurs in three stages (CELLULAR RESPIRATION):
1) digestion: outside of cells (intestine) or in lysosome
2) glycolysis: takes place in cytoplasm
3) TCA (tricarboxylic acid cycle) and oxidative phosphorylation (electron transport chain): occurs in the
mitochondria
Energy harvesting is converting one form of energy to another form
Digestion: digestive enzymes reduce macromolecules into their monomeric subunits
proteins  amino acids
polysaccharides  simple sugars
fats  fatty acids and glycerol
 small organic molecules make their way to the cytosol where oxidation process for generation
of ATP begins
Cellular respiration
 energy harvested at each step by removing H atoms from glucose, transferring electrons from
molecule to molecule
 each time electrons are moved, some energy is lost as heat, and some is captured via ATP
(direct/substrate level phosphorylation) or by making reduced energy carriers (NADH/FADH2)
By the end of cellular respiration, ‘depleted’ electrons are transferred to final electron acceptor
to regenerate oxidized carriers (NAD+/FAD) which allows the cycle to continue
oxygen  aerobic respiration
some other organic molecule  fermentation
Reduction-oxidation (Redox) Reactions
Electrons: most important source of chemical potential energy in cells
 mobile: each molecule has potential to donate and accept electrons from another molecule
Redox reactions: gain or loss of an electron. (LEO says GER)
 always coupled
reducing power: organisms are able to store energy in molecules by transferring electrons to
them
Reduction and Oxidation of the Coenzyme NAD+
High energy molecule binds to the enzyme at the same time NAD+ does
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