autotrophs
harvest sunlight and convert radiant energy into chemical energy
heterotrophs
live off the energy produced by autotrophs
how do heterotrophs extract energy
digestion and catabolism
cellular respiration reactions
oxidations, dehydrogenations
dehydrogenations
lost electrons are accompanied by hydrogen (what is actually lost is a hydrogen atom)
overall cellular energy harvest
-Dozens of redox reactions take place
-Number of electron acceptors including NAD+
-end with high-energy electrons from initial chemical bonds losing much of their energy and transferring it to a final electron acceptor
cellular respiration
cells harvest energy by breaking bonds and shifting electrons from one molecule to another
aerobic respiration
final electron acceptor is oxygen
anaerobic respiraton
final electron acceptor is inorganic molecule (not oxygen)
fermentation
final electron acceptor is an organic molecule
goal of respiration
produce ATP
what form is energy released from oxidation reactions in? Where is it converted to ATP?
electrons which are shuttled by electron carriers to the electron transport chain, that's where the energy is converted to ATP
Redox reactions
electrons release some of their energy as they pass from a donor molecule to an acceptor molecule, free energy is available for cellular work
substrate-level phosphorylation
transfer phosphate group directly to ADP during glycolysis
oxidative phosphorylation
ATP synthase uses energy from a proton gradient
electron carriers (4)
soluble, membrane-bound, move within membrane, easily oxidized and reduced, carry either just electrons or both electrons and protons
NAD+ needs what to become NADH
2 electrons and a proton
aerobic respiration free energy per mol of glucose
-686
enzyme for oxidative phosphorylation
ATP synthase
how is energy derived in oxidative phosphorylation
proton gradient formed by high energy electrons during oxidation of glucose, energy depleted electrons are then donated to oxygen
glycolysis location
cytosol
pyruvate oxidation and citric acid cycle location
mitochondrial matrix
electron transfer system location
inner mitochondrial membrane
4 stages of oxidation of glucose
glycolysis, pyruvate oxidation, kreb's cycle, electron transport chain
Glycolysis overall
breaks 6 carbon glucose into 2 molecules of 3-carbon pyruvate, 2 ATP and 2 NADH produced
glucose priming part 1 of glycolysis
cleavage and rearrangement
substrate level phosphorylation part 2 of glycolysis
oxidation, ATP generation
what reactions in glycolysis require energy
1 glucose is broken to 2 g3ps
energy releasing reactions in glycolysis
G3P to Pyruvate (produce 2 nadh and 2 atp)
How does pyruvate enter the mitochondria?
active transport
what does oxidation of 1 pyruvate generate
1 CO2, 1 acetyl-CoA, 1 NADH
What enters the citric acid cycle?
Acetyl CoA, but the coenzyme A is stripped leaving the 2 carbon acetyl
fate of pyruvate with O2
oxidized to acetyl-coA which enters krebs cycle
fate of pyruvate without O2
reduced in order to oxidize NADH to NAD+ (fermentation)
how does pyruvate become acetyl-coA
it is decarboxylated
what catalyzes the oxidation of pyruvate in the mitochondria?
a multienzyme complex called pyruvate dehydrogenase catalyzes the reaction
where does oxidation of pyruvate occur in eukaryotes vs prokaryotes?
eukaryotes- mitochondria
prokaryotes- plasma membrane
citric acid cycle products
2 CO2, 3 NADH, FADH2, ATP, oxaloacetate
for glycolysis to continue what must happen
NADH must be recycled to NAD+ by either aerobic respiration or fermentation
After the krebs cycle, what has glucose been oxidized to
6 co2, 4 ATP, 10 NADH, and 2 FADH2
feedback inhibition in glycolysis
phosphofructokinase is allosterically inhibited by ATP and / or citrate
feedback inhibition in pyruvate oxidation
pyruvate dehydrogenase inhibited by high levels of NADH,
citrate synthase inhibited by high levels of ATP
what is the feedback inhibitor for hexokinase?
glucose 6 phosphate
what are the 3 feedback regulators for phosphofructokinase?
ATP and citrate inhibit, AMP promotes
what are the feedback regulators for pyruvate kinase?
fructose-1,6 bisphosphate promotes, ATP and acetyl-coA inhibit
what are the feedback regulators for citrate synthase?
ATP and Citrate inhibit
glucose catabolism
involves a series of oxidation-reduction reactions that release energy by repositioning electrons closer to oxygen atoms- harvested from glucose using NAD+ and FAD+ as electron carriers
ETC
series of membrane bound electron carriers in inner mitochondrial membrane, electrons from NADH and FADH2 are transferred to complexes of the ETC
what does each complex in the ETC have?
a proton pump creating proton gradient
Where is the high H+ concentration?
intermembrane compartment
Where is the low H+ concentration?
matrix
what 3 major complexes serve as electron carriers
I, III, IV
where is complex II
bound to the inner mitochondrial membrane on the matrix side
where do electrons from NADH enter?
complex I
where do electrons from FADH2 enter?
complex II
what mobile electron carriers shuttle electrons between the major complexes
cytochrome c and ubiquinone (coenzyme Q)
cytochromes
proteins with a heme prosthetic group that contains an iron atom that accepts and donates electrons
how are individual electron carriers organized?
high to low free energy (NADH and FADH2 have abundant free energy and are easily oxidized while oxygen is easily reduced)
electron movement is _______ and _________ free energy
spontaneous, releases
what do complexes I, III, and IV do?
actively transport protons from matrix to intermembrane compartment
concentration of H+ in the intermembrane generates an __________ and ____________ gradient across the inner mitochondrial membrane
electrical and chemical
proton-movement force
stored energy produced by proton and voltage gradient, used for ATP synthesis and cotransport of substances to and from mitochondria
atp synthase structure
a basal unit in the inner membrane is connected by a stalk to a headpiece located in the matrix; a peripheral stator bridges the basil unit and headpiece
theoretical yield per glucose for bacteria
38 ATP
theoretical yield for eukaryotes per glucose molecule
36 ATP
theoretical yield of NADH
3 atp
theoretical yield of FADH2
2 atp
actual yield of 1 NADH
2.5
actual yield of FADH2
1.5
actual yield per glucose molecule for eukaryotes
30
why is there a reduced yield?
the proton gradient isn't only used for ATP synthesis, "leaky" inner membrane
E. Racker and W. Stockenius research
showed H+ gradient powers ATP synthesis using membrane vesicles that had a proton pump and ATP synthase; atp was synthesized in light (when protons flowed in to membrane) but not in dark
during fermentation, what supplies ATP
Glycolysis by substrate level phosphorylation
methanogens
CO2 reduced to CH4, found in cows
sulfur bacteria
inorganic sulphate is reduced to hydrogen sulfide
lactate fermentation
converts pyruvate to lactate
occurs in some bacteria, plant tissues, and skeletal muscles
alcoholic fermentation
converts pyruvate into ethyl alcohol and CO2
occurs in some plant tissues, invertebrates, protists, bacteria, and yeast
what does lactate fermentation make
milk, yogurt, dill pickles
what does alcoholic fermentation make
bread and alcoholic beverages
amino acids catabolism
deamination to a molecule that can enter glycolysis or krebs cycle
alanine deamination
pyruvate
aspartate deamination
oxaloacetate
glutamate deamination
a-ketoguterate
catabolism of fats
broken down to fatty acids and glycerol, converted to acetyl groups by beta-oxidation (OXYGEN DEPENDENT)
The respiration of a 6-carbon fatty acid yields
20% more energy than glucose
strict anaerobes
Fermentation is the only source of ATP for bacteria and fungi that lack enzymes to carry out oxidative phosphorylation
facultative anaerobes
can switch between fermentation and full oxidative pathways
examples of facultative anaerobes
e. coli, lactobacillus (used in buttermilk and yogurt), and s. cerevisiae (used in brewing, wine making, and baking), many cell types in higher organisms such as vertebrate muscle cells
strict aerobes
unable to live soley by fermentations and have an absolute requirement for oxygen
strict aerobe example
vertebrate brain cells
abnormal glycolysis
process of higher than normal rates of glycolysis that occurs in most cancer cells, generates large amounts of lactate, aka warburg effect
gloconeogenesis
when energy is not needed by the body, glucose can be synthesized from intermediates (consumes ATP)
Evolution of metabolism
1. Ability to store chemical energy in ATP
2. Evolution of glycolysis
3. Anaerobic photosynthesis using H2S
4. Use of H2O in photosynthesis
5. Evolution of nitrogen fixation
6. Aerobic respiration evolved most recently