NADH and FADH2 donate electrons to the series of electron carriers in the ETC • The final electron acceptor is Oxygen. creating water as a by product of cell resp.[r]
(1)(2)Catabolic Pathways
• Recall this is breaking down of complex molecules
• types of pathways:
– Fermentation – partial pathway requires no oxygen
(3)(4)(5)(6)Cellular Respiration
• Cellular respiration is the process of
oxidizing food molecules, like glucose, to carbon dioxide and water
• The energy released is trapped in the form of ATP for use by all the
(7)Remembering ATP
• hydrolysis of the terminal phosphate of ATP yields between 11 and 13 kcal/mole of usable energy, depending on the
(8)(9)NAD+ and FAD
• Each metabolic reaction in cellular respiration is catalyzed by its own enzyme
As a metabolite is oxidized, NAD+ accepts two electrons and a hydrogen ion (H+);
results in NADH + H+
(10)(11)Respiration has four distinct
stages:
• Glycolysis • Krebs cycle
(12)Glycolysis
• Glycolysis is the anaerobic catabolism of glucose
• It occurs in virtually all cells
• In eukaryotes, it occurs in the cytosol • C6H12O6 + 2NAD+ -> 2C3H4O3 +
(13)Glycolysis is enzyme driven
• Shockwave – observe the step by step process as you look at your book as well as the animation
http://instruct1.cit.cornell.edu/courses/biom i290/ASM/glycolysis.dcr
(14)Summary of yield
• The net yield from each glucose
molecule is NADH, 2ATP and molecules of pyruvate
(15)(16)(17)Mitochondria
• Mitochondria are membrane-enclosed
organelles distributed through the cytosol of most eukaryotic cells
• Their main function is the conversion of
(18)Mitochondria have:
• an outer membrane that encloses the entire structure
• an inner membrane that encloses a fluid-filled
matrix
• between the two is the intermembrane space
• the inner membrane is elaborately folded with shelflike cristae projecting into the matrix
(19)(20)(21)• Prior to entering the Krebs Cycle, pyruvate must be converted into acetyl CoA
• This is achieved by removing a CO2 molecule from pyruvate and then removing an electron to reduce an NAD+ into NADH
(22)(23)• We are now back at the beginning of the Krebs Cycle Because glycolysis produces two pyruvate molecules from one glucose, each glucose is processes through the
kreb cycle twice
• For each molecule of glucose, six
(24)To review
(25)Points to remember
• Each NADH made in the mitochondria yields ATP
• NADH made in outside mitochondria yields ATP
• FADH yields ATP
(26)Electron transport chain overview
• Krebstca (if can’t open go to bio home (27)Harvesting the nrg
• So far we have from glycolysis and the Kreb’s cycle: (per molecule of glucose) ATP by substrate phosphorylation
NADH and FADH2 – (which account for most of the nrg stored from the
(28)Electron Transport Chain
• A collection of
molecules found in the inner
(29)Key points
• Protons are translocated across the membrane, from the matrix to the intermembrane space
• Electrons are transported along the membrane, through a series of protein carriers
• Oxygen is the terminal electron acceptor, combining with electrons and H+ ions to produce water
• As NADH delivers more H+ and electrons into the ETS, the proton gradient increases, with H+ building up
(30)• http://www.wiley.com/legacy/college/boyer
/0470003790/animations/electron_transport /electron_transport.swf
• (follow electron transport )
• respiration info (go to electron transport chain)
(31)Key Points to remember
• NADH and FADH2 donate electrons to the series of electron carriers in the ETC • The final electron acceptor is Oxygen
(32)Points cont
• Electron transport is coupled to ATP by chemiosmosis
(33)Points cont
• At certain steps along the chain, electron transfer causes electron carrying protein complexes to move Hydrogen ions from the matrix to the intermembrane space storing energy as a proton-motive force (hydrogen gradient)
(34)Points continued
• As hydrogen diffuses back into the matrix through ATP synthase, its exergonic
passage drives the endergonic phosphorylation of ADP
• Electron transport system:
(35)Related Metabolic Pathways
• Without oxygen electronegetive oxygen to pull the electrons down the transport
chain, oxidative phosphorylation ceases • Fermentation provides another avenue for
(36)Fermentation
• The oxidizing agent of glycolysis is NAD+ , not oxygen
• But glycolysis generates ATP by oxidative phosphorylation
• Fermentation regenerates ATP by
(37)(38)Process of alcohol fermentation
• Fermentation consists of glycolysis plus reduction of pyruvate to either lactate or alcohol and CO2
• NADH passes its electrons to pyruvate
instead of to an electron transport system; • NAD+ is then free to return and pick up
(39)Alcohol fermentation
• pyruvate is first
decarboxylated to yield a 2-carbon substance
acetaldehyde
Acetaldehyde is then reduced as hydrogens are transferred from
(40)lactic acid fermentation
• pyruvate is used as thedirect acceptor of the hydrogens removed from NADH The end product is a molecule of lactic acid Lactic acid [or lactate] is a
(41)Advantage of Fermentation
• provides quick burst of ATP energy for (42)Disadvantage of Ferm.
• lactate is toxic to cellslactate changes pH and causes muscles to fatigue lactate is sent to liver, converted into pyruvate; then respired or converted into glucose
(43)(44)(45)(46)