Download Overview of Aerobic Respiration

Ch 7-2 Aerobic Respiration
Soooo when there is oxygen in the cell’s environment, pyruvic acid undergoes aerobic respiration, releasing
almost 20x more ATP than glycolysis.
Overview of Aerobic Respiration
These
reactions
only
occur
with
OXYGEN
2 major stages: KREBS
CYCLE
o
o
o
Oxidation of glucose from glycolysis is completed
As glucose is oxidized, NAD+ is reduced to NADH
Produces smalllllll amount of ATP
& ELECTRON TRANSPORT CHAIN; (associated to chemiosmosis;{using energy released as
protons move across membrane to make ATP})
o NADH used to make ATP
o Moooost of ATP produced in aer.resp. comes from activities of
elctrontransportchain&chemiosmosis.
In PROKARYOTES – reactions of KrebsCycle & ETC. happens in the CYTOSOL
But in EUKARYOTES – reactions happen in the MITOCHONDRIA
-
The pyruvic acid diffuuuusses through the doublemembrane & into the mitochondrial matrix
o
Mit.mat: space inside the inner membrane

Contains the enzymes needed to catalyze reactions in Krebs Cycle
Krebs cycle: takes place in mitochondrial
matrix
Electron transport chain: located in inner
membrane
o
o
o
so when pyruvic acid enters the mitochondrial matrix,
it reacts with Coenzyme A (CoA) to form acetyl CoA
That carbon atom that’s lost comes out as CO2
This whole reaction reduces NAD+ to NADH
The Krebs Cycle
-
Biochemical pathway that breaks down acetyl CoA, producing CO2, hydrogen atoms, and ATP
Reactions were first identified by Hans Krebs,(1900-1981) German biochemist dude
5 STEPS: in euks, it all happens in mitochondrial matrix
1) 2 carbon molecules of
acetyl CoA combines with
4carbon compound,
oxaloacetic acid= 6carb.
Citric acid. **this reaction
regenerates coenzyme A
2)Citric acid releases CO2 and
hydrogen atom, forming
5carbon compound. Since H
atom&electron is lost, citric
acid is oxidized. (electron in H
atom is transferred to NAD+,
reducing it to NADH
3) 5carbcompound releases
CO2 and H atom = 4
carb.compound. NAD+ Is
reduced to NADH *molecule of
ATP is synthesized from ADP.
4)from the 4carbcompound we already have, It turns into another carbcompound, only a H atom is released, so
that FAD is reduced to FADH2 (((FAD is like NAD+, it accepts electrons in redox reactions)))
5) ok now ANOTHER Hydrogen atom is released, so that oxaloacetic acid is regenerated. – that’s what keeps
the Krebs cycle going.. oh and electron in the H atom reduces NAD+ to NADH
1 GLUCOSE – 2 pyruvic acid molecules – 2 molecules of acetyl CoA… the Krebs cycle breaks down one acetyl CoA
at at time….
SO TWOO TURNS of krebs cycle completely breaks down a glucose.
-
Produces: 4 CO2, 2 ATP, and hydrogen atoms that make 6 NADH and 2 FADH2 molecules.
CO2 diffuses out of cells and given off as waste, and ATP can be used for energy
-
But each glucose yields only 2 MOLECULES OF ATP- same as gylcolysis
Glycolysis – makes 2 NADH molecules…
& conversion of 2 resulting pyruvic acid to acetyl CoA makes 2 MORE NADH
Now add the 6 NADH from Krebs cycle and that’s a total of 10 NADH molecules/per oxidized glucose and 2
FADH2 ……  THEY DRIVE THE NEXT PART OF AEROBIC RESP… WHERE MOST OF GLUCOSE TO ATP OCCURSSS!
Electron Transport Chain & Chemiosis
-
-
2nd part of aerobic respiration
Electron transport chain- buncha molecules in membrane that transfer electrons from one molecule to
another
o In eukaryotes – ETC and enzyme ATP synthase are embedded next to each other in inner
membrane of mitochondrion;; in the folds called cristae.
o In prokaryotes – ETC is in the cell membrane
ATP produced by ETC when NAD+ and FADH2 release H atoms- which regenerates NAD+ and FAD.
So the electrons in
NADH and FADH2 are
at high energy level.
As electrons are
passed along ,they
lose energyyyy
1)NADH and FADH2 give electrons to the chain.*NADH does it in the beginning, FADH2 later on…. * they also give
up protons; H+ (hydrogen ions)
2)electrons are mooooving down the chain..and meanwhile losing energy.
3) that lost energy is used to pump protons from matrix, making a high concentration of protons between the
inner and outer membranes. SO A CONCENTRATION GRADIENT- across inner membrane.
**an electrical gradient is made too, since protons have a positive chargeee
4)the concentration and electrical gradient of protons drives the ATP synthesis by chemiosmosis(same thing
from photosynthesis) sooo as protons move through ATP synthase and down their gradients, ATP is made!
(from ADP + phosphate)
5) oxygen is the FINAL ACCEPTOR of electrons that were passed down the chain….it also accepts protons (that
were part of H atoms from NADH and FADH2 ) look at that equation::::::: the protons+electrons+oxygen = water.
OXYGEN IS IMPORTANTE!!
ATP is only gonna be synthesized if electrons are moving through the chain!
That last molecule has got to pass electrons on to final electron acceptor. OOR THE ETC IS GOING TO STOPPP
It’s like a bunch of cars going down a dead end street…. Eventually no more cars can come in!!
-
So if that last molecule can’t “unload” the accepted electrons…ATP synthesis is going to stoppp
EFFICENCY OF CELL RESPIRATION
-
Glycolysis & Krebs cycle each produce 2 ATP molecules.
-
Each NADH molecule that supplies ETC generates 3 ATP
molecules
-
Each FADH2 molecule generates 2 ATP
-
Soooo 10 NADH and 2 FADH2 made through glycolysis,
conversion of pyruvic acid to acetyl CoA, and the Krebs
cycle produces up to 34 ATP (by ETC and chemiosmosis)
Add the 4 ATP molecules from glycolysis & Krebs cycle
= MAX. 38 ATP PER MOLECULE OF GLUCOSE
# of ATP molecules made through cellresp. Varies from cell to cell.
In most eukaryotes, the NADH made during glycolysis can’t diffuse through inner membrane of mitochondria
It has to ACTIVELY transport through—that means ATP is consumed, to euks usually produce about
36ATP molecule per glucose.
In general:
So cell resp is up to 20 times more effective than glycolysis.
- In faccccct cell resp is more efficient than human made machines like cars
o Most of remaining energy in cars from gas is lost as heat
OKKKKKKKKKKKK SOOOOO CELL RESPIRATION: GLYCOLYSIS & AEROBIC RESPIRATION
GLYCOLYSIS; glucose converted into pyruvic
acid, a lil bit of ATP and NADH released
AEROBIC RESPIRATION: pyruvic acid converted
into CO2 and water (in presence of OXYGEN)
&lotttsa ATP produced
Complete oxidation of glucose! (in cell
respiration)
The PRODUCTS of photosynthesis are reactants in cell respiration, and
Products of cell respiration are reactants in photosynthesis , BUT CELL RESP IS NOT REVERSE OF
PHOTOSYNTHESISSSSS ( they have different biochemical pathways and occur in different places!!)
ANOTHER ROLE OF CELL RESP???
Wowie wow wow
- Cell resp provides ATP for cells to support activities of life
-
But cells also need specific organic compounds from which they build
macromolecules that compose their own sturcutres…
-
And that’s not always found in the foods heterotrophs consume
o Compounds formed during glycolysis & krebs cycle go through other biochemical pathways
where the cells make the molecules they need!!!!!
 Ex. about 10 of amino acids human body needs is made from compounds from
KREBS CYCLE WOOHOOOOO DONE.