Topic 13 Mitochondria and Energy Generation

Energy generation

cellular respiration, substrate level phosphorylation, oxidative phosphorylation

Cellular respiration

breakdown of suger to release energy

Substrate level phosphorylation

energetically favourable breakdown, coupled unfavourable addition of phosphate to ADP, glycoysis and TCA

Oxidative phosphorylation

energy from activated carriers, ETC and Chemiosmosis, proton motive force, drive ATP synthesis

Stages of Catabolism

Digestion, glycolsis, intermediate, citric acid cycle

Digestion

large polymers into monomers, in intestines and lysosomes

Glycolysis

1 glucose (6C) into 2 pyruvate (3C), generates 2 NADH and 2ATP, substrate level phosphorylation, in cytosol, 2 phase (investement 4ATP and payoff 2ATP), 10 reactions

Intermediate step

pyruvate into CO2 and acetyl CoA (2C), in mitochondrial matrix, 3 enzymes, makes CO2/NADH/Acetyl-CoA

Cirtic Acid cycle

Acetyl CoA is oxidized to CO2, generates 2CO2/3NADH/FADH2/GTP(converted to ATP), 8 chemical reaction, Acetyl CoA + oxaloacetate = Citric Acid, Oxygen for CO2 from water splitting

Kinase

enzyme, addition of phosphate group, energy costing

Isomerase

rearrangement of bonds in molecule, no gain or loss, same formula but different arrangement

Dehydrogenase

oxidation of molecule, removal of hydrogen atom and electron, redoxreaction, removal of high energy electron to give to activated carrier (NAD+/FAD+), energy releasing

Mutase

shifts chemical group from one position to another, within a molecule

Coupling Oxidation to Activated Carriers

Step 6 oxidation (energy releasing) coupled to making high energy molecule, consumption of high energy molecule fuels attachment of phosphate to ADP in step 7 (generate ATP), free energy change of -12.5KJ/mole

Fermentation

breakdown of sugar in absence of O2, anaerobic microganisms (pathogens+deep soil/water - alcohol) and some animal cells (Muscles-lactate), regeneration of NAD+ to continue glycolysis

Anaerobic respiration

molecules other than O2 as terminal electron acceptor, almost identical to aerobic respiration, in obligate anaerobic bacteria

Coenzyme A

organic molecule that helps enzyme function (adding Acetyl-CoA to Oxaloacetate, from vitamin B, redox reaction

Generation of acetyl-CoA

Fatty acid broken down into - cuts 2C at terminal carboxyl end and makes NADH/FADH2 (redox), Amino acid converted into (smaller 2C AA)

Citric Acid Cycle products per 1 Acetyl-CoA

2 CO2, 1 GTP, 3 NADH, 1 FADH2

Citric Acid Cycle products per 1 Glucose

4 CO2, 2 GTP, 6 NADH, 2 FADH2

Biosynthesis pathways

use intermediates from glycolysis and TCA, anabolic pathways (building)

Metabolism regulation

one substrate in many pathways, control mechanisms, enhancing or inhibiting enzymes

Control Mechanisms

regulate/coordinate activity of enzymes, enhance or inhibit enzymes

Gluconeogensis

glucose synthesis, reverse of glycolysis, builds glucose from pyruvate, consumes 4ATP/2GTP, most enzymes work in reverse but need different to bypass irreversible reactions

irreversible reaction

steps that heavily favoured one reaction over another, controlled by feedback regulation

example of irreversible steps in glycolysis/glucongenesis

phosphofructokinase in glycolyis and bisphosphatase in gluconegenesis, controlled by feedback of ATP (favours glucogenesis) and ADP/AMP/Phosphate (favours glycolysis)

Electron Transport Chain

high energy electon transferred through series of carriers, in inner mitochondrial membrane, release energy to power pumps (H+ across) that generates electrochemical gradient, consumes O2 (terminal acceptor)

Chemiosmotic coipling/ Chemiosmosis

proton flow down electrochemical gradient, through ATP synthase, synthesize high amount of ATP (from ADP and phosphate)

Mitochondria

adjust location/shape/number depending needs (can make elongated tubular networks), outer membrane has many porins (beta barrels), inner membrane mostly impermeable(transport proteins for pyruvate/ATP/ETC/H) and highly folded (Cristae), Electron transport chain in inner mebrane

Electron Transport Chain

40 proteins in respiratory enzyme complexs, 4 complexs grouped in super complex (enhance efficiency), 3 transmembrane complexes (pump H+ across) and 1 peripheral (complex II), NADH DeHase complex (oxidizes NAD+/4H), Cyt c reductase (reduce cyt c/4H), Cyt c oxidase (oxidize cyt c/2H), complex contain metal ion (Fe/Mg) and chemical groups as steps, terminal acceptor is oxygen

NADH through ETC

deposit at complex 1, generates 2.5 ATP

FADH2 through ETC

deposit at complex 2, generates 1.5 ATP (associated with ubiquinone)

H+ gradient

pH gradient (matrix 7.9/intermembrane 7.2), Voltage gradient (Matrixnegative/intermembrane positive), proton motive forces pulls H+ back

ATP synthase

multi-subunit proteins, in inner mitochondrial membrane, carrier and stalk spin when H+ pass, rubbing stationary head cause conformation change, catalyze formation ATP, 3 ATP/revolution or 100ATP/sec, reversible

FLow of H+

flow through ATP synthase coupled transport other molecules, pyruvate/ADP/phosphate into matrix, ATP out of matrix