Cellular Respiration: Harvesting Chemical Energy - PowerPoint Presentation

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Cellular Respiration: Harvesting Chemical Energy

Cellular Respiration

Cells harvest chemical energy stored in molecules and use this to generate ATP.

Organic compounds store energy in their arrangements of atoms.

Catabolic (releases energy)

Exergonic

(- G, products store less energy than reactants)

Occurs mostly in the mitochondria (but first step is in cytosol)C6H12O6 + 6O2

 6CO

2 + 6H2O + energy (ATP and heat)

Redox Reaction Recap

Involves the transfer of electrons

LEO (loss of electrons)

 oxidation (less -)GER (gain of electrons)  reduction (more -)

Electron donor (reducing agent

) the atom that becomes less negative (positive)

Electron acceptor (oxidizing agent) the atom that becomes more negative

Sodium and Chlorine (think of the Bohr Models)

Which atom is the electron donor? Acceptor/

Which atom is the reducing agent? Oxidizing agent?

Three Processes in Cell

Resp

Glycolysis

The Kreb Cycle (Citric Cycle)

Electron Transport Chain (Chemiosmosis and oxidative phosphorylation)

Glycolysis(

“splitting of sugar”)

Glucose is split into two, three carbon sugars called

pyruvate

Catabolic pathway (breakdown)

Occurs in the

cytosol

Two major phases

Energy investment (puts in 2 ATP)

Energy payoff (creates 4 ATP)

Produces 2

molecules of usable

ATP (4 total but we have to put in 2 ATP, so only 2 left for cell use)

Produces 2 molecules of NADH

Can

occur without the presence of oxygen

glycolysis

Oxidizing Glucose

The oxidation of glucose allows energy to be taken out of storage and make energy available to make ATP.

Glucose is broken down

gradually in a series of steps catalyzed by an enzyme: dehydrogenaseHydrogen atoms are stripped from glucose and passed to a coenzyme: NAD + (oxidizing agent)

The dehydrogenase removes two hydrogen atoms from the glucose (2 p+ and 2e-)

NAD+ traps 2e- and 1p+ from glucose break down = NADH

NADH stores

energy ready and will pass on electrons to make ATP when e- complete their journey to oxygen.

Overview of Cellular Respiration

Step by step process that releases energy along the way (does not release all energy at once)

Hydrogen atoms are stripped away from glucose

Hydrogen atoms ultimate destination is the oxygen moleculeFirst they are transferred to a coenzyme NAD+

NAD + wants to gain electrons

(to be neutral)

NAD + traps electrons from glucose using dehydrogenase (enzyme) which removes a pair of hydrogen atoms from glucose

STOP and THINK of a Bohr model for hydrogen: How many electrons? How many protons?

So if we removed two hydrogen atoms, that means we remove two electrons and two protons

C

6

H12O6

Enzyme gives two electrons and one proton to its coenzyme NAD +

forming NADH

The other proton (left over) is released into the surrounding environment

Is NAD+ an electron acceptor or donor?Is NAD+ an oxidizing agent or a reducing agent?**NAD+ is the most versatile electron acceptor in cell resp.

Little potential energy is lost when e- are transferred from glucose (food) to NAD+

NADH molecules represent stored energy that can be used to make ATP when e- complete their “fall” to oxygen

An electron transport chain is used to break the fall of electrons to oxygen

Produces several energy releasing steps NOT one big explosion of energy

Pathway of Electrons

Electrons (from glucose in the form of hydrogen atoms) move to

 NAD+  NADH  oxygen (final electron acceptor)

Cell Respiration Terms

Phosphorylation

:

the transfer of a phosphate molecule

the production of ATP

(adenosine

triphosphate)ADP + P i  ATP

Oxygen is very

electronegative

(i.e. it wants electrons ...think of its Bohr

model)