Metabolism

The sum total of the chemical processes that occur in living organisms, resulting in growth, production of energy, elimination of waste material, etc.

• Anabolism- build up of complex molecules

• Catabolism- break down of complex molecules

Metabolism

Fates of Organic Building Blocks in

ATP Metabolis

m

ORGANIC BUILDING BLOCK MOLECULESMonosaccharides

Amino acidsAcetates

Nucleotide bases

Polymers &

other energy

rich molecules

CO2

&H2O

anabolic processes

catabolic processes

ATP

ADP+Pi

energyenergy

Cellular RespirationC6H12O6 + 6O2 + 36ADP + 36Pi

6CO2 + 6H2O + 36ATP

Basic Steps Involved

Glycolysis

Krebs Cycle

Electron Transport System

Acetyl CoA Formation

1

2

3

4

Overview of Glycolysis

Other Other Metabolic Metabolic PathwaysPathways

FatsFats GlycogenGlycogen ProteinProtein

Glycolysis

Net:•2 ATP•2 NADH•2 Pyruvate molecules

2 pyruvate

Glucose

Cystol

NADH

NADH

ATP

ATP

ATP

ATP

ATPATP

NAD+

NAD+

P

P

ADP

ADP

ADP

ADP

ADP

ADP

P

P

P

P

H

H

Balance Sheet for Glycolysis

Input1 Glucose

4 ADP + Pi

2ATP

2 NAD+

Output2 Pyruvate

2 net ATP

2 NADH

NAD+ NAD+

ADPP ADPP

ATP ATP

NADH NADH

ATP ATP

Transition ReactionTransition Reaction

CO2

CoA

NADH+

NADH+H+

2 Acetyl CoA’s

2 pyruvates

3NAD+ +3H

Krebs Krebs CycleCycle

Transition ReactionTransition Reaction2 Acetyl CoA’s

2CO2

CoA

ATP

FADH2

FAD

3ADP+Pi

NADHNADHNADH

Krebs Cycle (Citric Acid Cycle)Krebs Cycle (Citric Acid Cycle)

Balance Sheet for the Balance Sheet for the Transition Reaction and Transition Reaction and

Krebs CycleKrebs CycleInput

2 Pyruvate2 ADP + 2 Pi

8 NAD+

2 FAD

Output6 CO2

2 ATP8 NADH2 FADH2

Krebs Cycle

Handles other substrates

Intermediate molecules used: proteins and lipids

Replenishment of intermediates necessary

Hans Krebs (1937): paper originally rejected

Krebs Cycle

Takes 2 complete cycles

8 steps, each with an enzyme

Krebs Cycle 3

Oxidative PhosphorylationOxidative Phosphorylation

ChemiosmosisElectrons are transferred from complex to complex and some of their energy is used to pump protons (H+) into the intermembrane space, creating a proton gradient.

ATP synthesis is powered by the flow of H+ back across the inner mitochondrial membrane through ATP synthase.

Each Glucose Molecule

CO2 6

NADH 10

FADH2 2

ATP 4

Electron Transport System

CO2 6

NADH 10

FADH2 2

ATP 4

used to make ATPused to make ATP

Electron Transport System 4

Electron Transport System

+Pi

Electron Transport Chain and Oxidative Phosphorylation

• Electrons are delivered to O, forming O–

• O– attracts H+ to form H2O

Figure 24.9

Glycolysis Krebscycle

Electron trans-port chain and oxidativephosphorylation

EnzymeComplex I

EnzymeComplex III

EnzymeComplex IV

EnzymeComplex II

NADH+H+

FADH2

Fre

e e

nerg

y r

ela

tive t

o O

2 (

kcal/

mol)

Electronic Energy Gradient

• Transfer of energy from NADH + H+ and FADH2 to oxygen releases large amounts of energy

• This energy is released in a stepwise manner through the electron transport chain

ATP Synthase

• Two major parts connected by a rod 1. Rotor in the inner mitochondrial

membrane

2. Knob in the matrix

• Works like an ion pump in reverse

Figure 24.11

Mitochondrial matrix

Intermembrane space

ADP+

A stator anchored in the membrane holds the knob stationary.

As the rotor spins, a rod connecting the cylindrical rotor and knob also spins.

The protruding, stationary knob contains three catalytic sites that join inorganic phosphate to ADP to make ATP when the rod is spinning.

A rotor in the membrane spins clockwise when H+

flows through it down the H+ gradient.

Net ATP Yield

34 to 36 molecules ATP for every glucose molecule

about 40% efficiencyabout 40% efficiency

ATP

Transition cycle

Overall ATP Production

Electron Transport System 34Citric Acid Cycle 2Glycolysis 2SUBTOTAL 38NADH Transport into Mitochondrion* -2TOTAL 36

Fermentation (Anaerobic Respiration)

Lactic Acid Fermentation

C

Glucose 2 Pyruvate 2 Lactic Acid

NAD+

NADH

NAD+

NADH

(Glycolysis) (Lactic acid fermentation)

C C C C C C C C C C C

Glucose

Pyruvateno

O2 O

2

Acetyl CoAEthanol or

LactateKrebs Cycle

Anaerobic Respiration

Aerobic Respiration

INQUIRY1. What is the end product in glycolysis?2. What substance is produced by the

oxidation of pyruvate and feeds into the citric acid cycle?

3. Name a product of fermentation.4. What role does O2 play in aerobic

respiration?5. What stage during cellular respiration is the

most ATP synthesized?6. What is chemiosmosis?7. When NAD+ and FAD+ are reduced what

do they form?8. What are they used for?