Cellular Glycolytic Pathways

Lecture Presented by:

Dr. Ozair Chaudhry, Ph.D.,CP Ag. (USA)., MOCT ( Canada)

Albert Campbell Collegiate Institute (NS) Con.Ed. Toronto, Ontario

August, 2008

© Reserved copyright 2008. Users advised to quote author’ reference

Introduction (Key Idea)

Energy is a driving force for any physical /biological activity

How Cell produce energy from food (Macromolecules)

Energy can neither be created nor destroyed; however,

It transforms one form to another Sun /radiant energy is the sole

source in universe.

Key Terms Metabolism is building and breaking of molecules Metabolism is sum of Anabolism & Catabolism Glucose metabolism is series of reactions In Eukaryote these reactions occur at special

locations: Cytoplasm & Mitochondria (special Enz.) Free E transferred to e- carriers: NAD, FAD, ATP

Energy Transfer Two mechanisms: 1) Substrate level Phosphorylation (forming

ATP in enzyme-catalyzed reaction ) E.g.

ADP+ PEP+ Enz. ATP +Pyruvate (31 kJ Pot. En. Transferred to one ATP).

2) Oxidative Phosphorylation. (form ATP after series of Redox Rxn, O2 final e- acceptor E.g.

NAD+ removes 2 H+ (2 protons & 2 e-) from a portion of glucose

GLUCOSE METABOLISM ( 4 stages of Catabolism)

1. (Glycolysis & Fermentation) Anaerobic Respiration is 10 step Rxn in cytosol 6-C Glucose splices in 2 (3C ) mol. Called

Pyruvate (pathway details on Overhead / handout) In ist 4 reactions 2 mol ATP used, (priming

Glucose by adding P) After reaction # 5 both molecules of

Glyceraldehyde-3-P undergo Rxn step 6-10 Net: 4 ATP Prod - 2 ATP used= 2 ATP

Note: 2 NADH proceed for ATP later

Glucose priming

G

L

y

c

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y

s

I

s

ATP

Glucose ----> 2 Pyruvic Acid (or pyruvate) + 2 net ATP + 4 hydrogens (2 NADH2)

Fermentation In many cells, if oxygen is not present, pyruvate is

metabolized in a process called fermentation. Fermentation complements glycolysis by producing ATP

continually in the absence of oxygen. By oxidizing the NADH produced in glycolysis,

fermentation regenerates NAD+, which can take part in glycolysis once again to produce more ATP.

1. Pyruvate 3-C Lactic acid

2. Pyruvate 2-C Ethanol

Anaerobic Fermentation

2. Pyruvate Oxidation Aerobic Respiration (Mitochondria Matrix) 2 mol. (3-C pyruvate) 2Acetyl COA (Fig next)

Low E (COOH) is removed as Co2 catalyzed by decarboxylase forming Acetate

S-containing Co-Enzyme attaches with Acetate forming Acetyl-COA (unstable bond)

Acetyl-COA enters in Kreb Cycle for further redox reactions if body needs ATP energy/ OR follows other path ways for fat and store.

Pyruvate Oxidation In Mitochondrial Matrix (Aerobic Respiration) 2x (NADH) produced

3. Kreb Cycle 8-step cyclic Rxn from oxaloacetate (overhead/handout)

Glucose consumed completely hence 6-Co2 released as cell waste, E is saved in molecules.

Summary (Fate of Glucose): CCCCCC 2(CCC) 2(CC+Co2)---

(Glucose) (Pyruvate) acetylCOA & 2Co2

4(Co2) waste,

Free Eng: ATP, Co Enz: NADH, FADH2 transformed to ATP in 4th stage ETC

glycolysis Pyruvate Oxidation

Kreb cycle

Kreb

Cyc

le

NADH= 3, FADH=1, ATP= 1

Goal of ETC/Chemiosmosis To break down NADH and FADH2,

Pumping H+ into the outer compartment of the mitochondria

In this reaction, the ETC creates a gradient which is used to produce ATP

Electron Transport phosphorylation typically produces 32 ATP's

Goal of ETC/ Chemiosmosis

4. ETC & Chemiosmosis Electrons in H atoms of (NADH, FADH2) transferred to

proteins in membrane of mitochondria called ETC-chain.

Components of ETC placed in increasing electronegativity order E.g.

Weakest e- attracting NADH-dehdrogenase first and strongest cytochrome-oxidase last in chain finally to O2.

Conted./

ETC/Chemiosmosis Conted.

As such, Electro-chemical gradient create potential difference across inner membrane.

Protons move through ATP synthase towards lower conc. of H+, Free energy stored in electrochemical gradient is consumed to make ATP

ATP ase

ADP+Pi ATP The above process is called CHEMIOSMOSIS.(Overhead display)

ETC/ Chemiosmosis conted.

In ETC Protons accumulated in the intermembrane space by 3 proteins create Electrochemical gradient: (Electrical component by increasing (+ charge) and chemical component by increasing conc.of H protons)

Free E Provided by NADH (-222 kJ/mol NADH) drives Creation of ELECTROCHEMICAL GRADIANT.

H+ being unable to diffuse through phospholipid bilayer, are forced by special channel ATP-synthase

Energy Account /Glucose MoleculePathway Substrate level NADH/FADH2/Oxid-Phosphorylation

Glycolysis 2 ATP 2 NADH cytosolic(changes to 2 FADH) 2 (2ATP) = 04 ATPwhen enters to ETC

Pyruvate Oxidation ------ 2 NADH 2 (3 ATP) = 06 ATP

Kreb Cycle 2ATP 6 NADH 6 (3ATP) = 18 ATP

2 FADH2 2 (2ATP) = 04 ATP------------------------------------------------------------------------------------------------------------------------------------Sub Total=4 ATP 32 ATP

Grand Total= -------------------------------------------------- 36 ATP

Rule: Each FADH2 generates 2 ATP, and each NADH forms 3 ATP

The End

Thank You All