Cellular RespirationThe details behind catabolic cellular energetics

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-Reduction

OXIDIZED

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 - Adenosine TriPhosphate

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

Electron carriers

•NAD+ -----> NADH

•FADH ------> FADH2

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—Oxidative Phosphorylation

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