65 terms

ch 7

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autotrophs
photosynthetic, generates O2 organic molecules
heterotrophs
ingest organic cmpds, fuled by O2 and organic molecules
digestion
hydrolysis via enzymes, organic molecule breakdown is exergonic
dehydrogenation
lost electrons are accompanied by hydrogen, one hydrogen atom (1e, 1p) is lost
reduction
gain of e by molecule
oxidation
loss of electrons
reducing agent
electron donor
oxidizing agent
electron acceptor
e/energy carrier
transports e and H+ as glucose and other organic cmpds are broken down
obtaining energy from glucose
e are passed along carriers to a final e acceptor
aerobic respiration
energy must be released in small steps, final e receptor is O2 (obtaining energy from glucose) if O2 is available as the final e acceptor pyruvate is oxidized to acetyl-CoA which enters the Krebs cycle (recycling NADH to NAD+)
anaerobic respiration (obtaining energy from glucose)
(obtaining energy from glucose) final e receptor is an inorganic molecule (not O2) (recycling NADH to NAD+) an organic molecule (not O2) is the final e acceptor pyruvate is reduced in order to oxidize NADH back to NAD+
methanogens
archaea, use CO2 as e acceptor reduce to CH4
sulfur bacteria
reduce SO4- to H2S
fermentation
final e acceptor is an organic molecule, alcohol or lactic acid fermentation, uses substrate-level phosphorylation instead of ETC to generate ATP
breakdown
12 kcal/mole in a cell
glycolysis
breaks down glucose into 2 molecules of pyruvate
pyruvate oxidation an citric acid cell
completes the breakdown of glucose
oxidative phosphorylation
accounts for most of the ATP synthesis
substrate level phosphorylation (making ATP SLP)
less common method of making ATP involves 2 enzymes, 1st step: oxidation, 2nd step: uses energy to attach P to ADP
chemiosmotic generation (making ATP)
most ATP is made this way, proton pumps receive energy from NADH, e powers the H+ pump, H+ are pumped into the inter membrane space, proton motive force is generated, high concentration of H+ and charge, potential energy, ATP synthases, if ADP is present H+ powers the coupling of ADP and P
pyruvate
2 molecules are formed
NADIT
2 are made
recycling NADH to NAD+
must happen for glycolysis to continue, aerobic respiration, anaerobic respiration
oxidation of pyruvate to produce Acetyl CoA
if fermentation doesn't occur pyruvate diffuses into mitochondria, in mitochondrial membrane catalyst is pyruvate dehydrogenase complex (enzymes), rxns occur in matrix, oxidation yields (acetyl CoA 2c goes into next stage, 2 NADH, release of CO2)
after pyruvate is oxidized CAC completes
energy-yielding oxidation of organic molecules
citric acid cycle
AKA krebs cycle, 8 rxns in mitochondria (in eukaryotes), rxns occur in matrix, cycle occurs twice
reaction 1 condensation
occurs if ATP is low in cell, if lot actyl CoA is turned into fat, actyl CoA plus oxaloacetate => citrate, this rxn can shut down pathway,
reaction 2 isomerization
OH of citrate is moved from C3 to C4
reaction 3 1st oxidation
isocitrate is oxidized, e picked up by NAD+, NADH forms, CO2 is released, alpha ketoglutarate (5c product)
reaction 4 2nd oxidation
alpha ketoglutarate is oxidized to form succinyl, high energy bond, CO2 and e are released, NADH forms
reaction 5 SLP
ATP forms, high energy bond in succinyl CoA is broken, energy does to GDP to form, guanine triphosphate, succinate (4c)
guanine triphosphate
transfer P to ADP -> ATP(SLP)
reaction 6 3rd oxidation
fumarate (4C) from oxidation of succinate -less energy is released, flavin adenine dinucleotide: reduce to form FADH2 -bound to membrance
reaction 7 regeneration of oxaloacetate
malate (4C) = fumarate (4C) + H2O
reaction 8 regeneration of oxaloacetate
oxaloacetate forms from oxidation, NADH is produced from release of e
chemiosmosis (during oxidative phosphorylation)
couples electron transport to ATP synthesis
NADH and FADH2
these electron carriers donate electrons to the ETC and account for most of the energy extracted from food
electron transport chain (ETC)
powers ATP synthesis via oxidative phosphorylation
electron transport chain (ETC) and chemiosmosis
protein complexes are bound to the cristae or pm (in pk), rxns occur in inner mitochondrial membrane
NADH dehydrogenase
complex in mem, receives e from NADH ,proton pump
ubiquinone (Q)
nonpolar and e carrier, mobile and in interior of mem, receives e from FADH2
bc1 complex
protein-cytochrome complex, proton pump
cytochrome c
peripheral protein, passes e to
cytochrome oxidase
uses 4 e to reduce O2, proton pump
reduction of O2
allows it to react with H+ forming H2O
theortical yield
from NADH: 3 ATP from each molecule, 10 NADH total x 3 ATP each = 30 ATP
from FADH2: 2 ATP, 2 total FADH2 x 2 ATP each = 4 ATP
add 2 ATP from glycolysis and 2 from Krebs
for bacteria: 38 ATP per glucose
for ek: 36 ATP per glucose
2 NADH moved to mitochondria by active transport, uses 2 ATP
actual energy yield
mitochondrial mem is leaky, protons diffuse out, other uses of proton gradient, diffusion of pyruvate into mitochondrion, 30 ATP per glucose for ek
feedback inhibition
if ATP is plentiful rxns are inhibited
allosteric inhibitors
ATP and citrat from krebs
krebs cycle
pyrubate dehydrogenase: committed step
inhibitor is NADH
inhibitor: high levels of ATP inhibit citrate synthetase, stops krebs
fermentation and anaerobic
respiration enable cells to produce ATP without the use of oxygen
most cellular respiration requires O2 to produce ATP
without O2 the ETC will cease to operate, in that case glycolysis couples with fermntation or anaerobic respiration to produce ATP
anaerobic respiration uses an ETC
with a final e acceptor other than O2 (ex sulfate)
fermentation consists of
glycolysis plus reactions that regenerate NAD+ which can b reused by glycolysis
alcohol fermentation
type of fermentation pyruvate is converted to ethanol in 2 steps
1) releases CO2 from pyruvate
2) reduces acetaldehyde to ethanol
used in brewing, winemaking, and baking
lactic acid fermentation
pyruvate is reduced by NADH, forms lactate as end product, no release of CO2, LAF by some fungi and bacteria is usd to make cheese and yogurt, human muscle clls use LAF to generate ATP when O2 is scarce
comparing fermntation and aerobic respiration
use glycolysis (net ATP = 2) to oxidize glucose and harvest chemical energy of food, NAD+ is oxidizing agent that accepts e during glycolysis,
have diff final e acceptors: organic molecule in fermentation and O2 in cellular respiration
cellular respiration produces 30 ATP per glucose molecule, fermentation produces 2 ATP per glucose molecule
ATP gain in fermentation refers to ATP from glycolysis
obligate anaerobes, facultative anaerobes
obligate anaerobes
carry out only fermentation or anaerobic respiration and cannot survive in presence of O2
yeast and many bacteria are
facultative anarobes
facultative anarobes
can only survive using either fermentation or cellular respiration, pyruvate is fork in metabolic road that leads to 2 alternative catabolic routes
glycolysis and CAC
major intersections to various catabolic and anabolic pathways
protein deamination
enter glycolysis and CAC, alanine is converted to pyruvate, aspartate is converted to oxaloacetate
fatty acid catabolism
fatty acids are converted to acetyl groups by oxidation, acetyl groups enter krebs, glycerol enters glycolytic pathway, 6C fatty acid yields 20% more energy than glucose
anabolic interconversions
catabolic pathways can be reversed, glyconeogenesis, products of glycolysis and CAC can be used to make glucose
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