The details behind catabolic cellular energetics Cellular Respiration The 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-Reduction OXIDATION 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 P

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 P P

Respiration--Glycolysis Each 3-carbon enters an Oxidation phase where ATP & NADH are formed, leaving two pyruvates 2 2 pyruvate P Pi 2 NAD+ 2 NADH P 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 P 2 NAD+ 2 NADH Pi 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 GLYCOLYSIS 4 PRODUCED 2 per pyruvate (2 pyruvates) substrate level phosphorylation* GLYCOYSIS 2 CONSUMED KREB’S CYCLE 2 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 Glucose  NADH or FADH2  ETC  chemiosmosis  ATP* PROCESS ATP GLYCOLYSIS 4 PRODUCED 2 per pyruvate (2 pyruvates) GLYCOYSIS 2 CONSUMED KREB’S CYCLE 2 PRODUCED 1 per cycle (2 rotations per glucose) Transport of NADH into Mitochondria Electron Transport Chain 34 (10 NADH x 3, 2 FADH2 x 2) TOTAL during catabolism of 1 glucose molecule +36 *Only 30% of all energy stored in glucose bonds, rest given off as heat