a classroom lecture on cell metabolism. by: dr. ozair chaudhry
DESCRIPTION
Oxidative Phosphorylation, Carbohydrate Metabolism, Glycolysis, Kreb Cycle Cellular Energy Production.Chemiosmosis, ETC Electron Transport Chain.TRANSCRIPT
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
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y
s
I
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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