Oxidation-Reduction
•OIL RIG vs LEO says GER•Can’t have oxidation without reduction
▫One atom/element’s loss is another’s gain
C6H12O6 + 6O2 6CO2 + 6H2O + energy
•OXIDIZED—loses e- to O2
•REDUCED—gains e- from glucose (protons follow to form water)
Oxidation-Reduction
•The reduced form of the molecule has MORE potential energy than the oxidized form
•The electrons that are being transferred are carrying energy with them
•Looking at the half-reactions for respiration helps to see exactly what is oxidized and what is reduced
Oxidation-ReductionOXIDATION REDUCTION
Loss of electrons Gain of electrons
Gain of oxygen Loss of oxygen
Loss of hydrogen Gain of hydrogen
Results in many C—O bonds Results in many C—H bonds
Results in a compound with lower potential energy
Results in a compound with higher potential energy
Respiration•Step 1: Glycolysis
▫No oxygen needed
▫Occurs in the cytosol of the cell
▫3 main stages:
▫Phosphorylation
▫Lysis
▫Oxidation
Respiration--Glycolysis
•Phosphorylation uses TWO (2) ATPs to add a phosphate to each end of a glucose molecule
2 ATP
2 ADP
ATP is “spring-loaded”
•The phosphates have a negative charge –repel each other
•This means potential energy is stored in the bonds
What happens to the ATP when the spring is released?
•A phosphate is removed
•Energy is released•It becomes ADP (adenosine Diphosphate)
Respiration--Glycolysis•Lysis occurs when the phosphorylated 6-
carbon compound splits into TWO 3-carbon molecules
Respiration--Glycolysis•Each 3-carbon enters an Oxidation phase
where ATP & NADH are formed, leaving two pyruvates
2
2
2 pyruvate
2 NAD+
2 NADH
4 ADP
4ATP
Respiration--Glycolysis• SUMMARY:
▫ 2 ATPs needed, 4 produced, NET GAIN 2 ATP
▫ 2 NADH formed
▫ 2 Pyruvate formed
▫ Lysis
▫ SUBSTRATE level phosphorylation
▫ Oxidation
▫ ATP Formation
▫ Occurs in cytoplasm
▫ Controlled by enzymes *High ATP levels feedback inhibition stops glycolysis
2 NAD+
2 NADH
4 ADP
4ATP
Respiration after glycolysis
•O2 + mitochondrion = continued respiration
•Before you can get to the mitochondria, a link reaction must take place
Respiration after glycolysis•Substrate most often discussed during
respiration is glucose
•But! Acetyl CoA can be produced using most carbohydrates and lipids/fats
•If ATP levels are high, acetyl CoA synthesized into lipids for energy storage
•If ATP levels are low acetyl CoA enters Kreb’s cycle in the matrix of mitochondria
Respiration after glycolysis•DO NOT need
to know all of the names of the intermediates in the Kreb’s cycle, just the overall process
Respiration—Kreb’s Cycle
•Kreb’s cycle happens 2x for EACH glucose
•SUMMARY
▫2 ATPS (from GTP)
▫6 NADH*
▫2 FADH2*
▫4 CO2 released* Transfers e- to ETC
Respiration—ATP scoreboard
PROCESS ATP
GLYCOLYSIS4 PRODUCED
2 per pyruvate (2 pyruvates) substrate level phosphorylation*
GLYCOYSIS 2 CONSUMED
KREB’S CYCLE2 PRODUCED
1 per cycle (2 rotations per glucose)
TOTAL through Kreb’s +4
*Understand difference between this and oxidative phosphorylation
Respiration—Electron Transport Chain
• Main energy producer of respiration
• Oxygen needed for the first time
• Occurs inside the mitochondrial inner membrane
• Embedded within the membrane of the cristae are molecules that are easily oxidized and reduced
• Called carrier molecules b/c the carry electrons/energy
• Physically close to each other, pass e- from one to the next, based on differences in electronegativity
Respiration—Electron Transport Chain
•Electrons come from NADH and FADH2 generated in earlier steps
▫1 NADH 3 ATPs
▫2 FADH2 2 ATPs
•End result, OXYGEN final electron acceptor, gets reduced, water is produced
•ATP produced in large scale by oxidative phosphorylation
Respiration—Electron Transport Chain
•Oxidative phosphorylation occurs as a result of an energy gradient
•Gradient established as H+ ions (protons) get pushed into the intermembrane space of the mitochondria
•This process is called CHEMIOSMOSIS
•As H+ ions come back into matrix via ATP Synthase energy used to reduce oxygen and covert ADP to ATP (oxidative phosphorylation)
Goal – making ATP!•Substrate level
phosphorylation – enzyme transfers a P to ADP from a substrate (glucose parts)
•Oxidative phosphorylation – powered by redox reactions in ETC (ATP synthase turns)
Respiration—ATP scoreboard
PROCESS ATP
GLYCOLYSIS4 PRODUCED
2 per pyruvate (2 pyruvates)
GLYCOYSIS 2 CONSUMED
KREB’S CYCLE2 PRODUCED
1 per cycle (2 rotations per glucose)
Transport of NADH into Mitochondria
2 CONSUMED
Electron Transport Chain34
(10 NADH x 3, 2 FADH2 x 2)
TOTAL during catabolism of 1 glucose molecule +36
Glucose NADH or FADH2 ETC chemiosmosis ATP*
*Only 30% of all energy stored in glucose bonds, rest given off as heat