1. Biochemical Energy Production

2. Metabolism
Sum of all the chemical activities taking place in an organism
Catabolism
Larger molecules broken down into smaller ones
Stages 1-4 (Digestion; Formation of Acetyl CoA; Citric Acid Cycle; Electron Transport Chain & Oxidative Phosphorylation)
Releases energy (may be stored temporarily as ATP)
Anabolism
Complex molecules synthesized from simpler substances
Absorbs energy & stores it as chemical bonds
Metabolism = all of the chemical pathways in a living organism (or single cell)
Catabolism (oxidation reaction) - The breakdown of larger molecules into smaller ones through the removal of electrons.
e.g. digestion
Anabolism (reduction reaction) - The synthesis of larger molecules from smaller ones through the addition of electrons (and accompanying protons or H+ ions).
e.g. protein synthesis
These metabolic pathways are able to occur at normal temperatures because of the catalytic interaction of a group of chemicals called enzymes. Enzymes help lower the activation energy needed for the reactions to occur.

3. Enzymes play a key role in metabolic pathways
Series of small reactions are run with help of enzymes
Free energy differences between reactants & products is low
Concentration differences keep enzyme-run reactions going in one direction
How?
Products are constantly removed so no build up at the end. Concentration stays low for products

4. Enzymes catalyze oxidation via series of small steps –
the controlled stepwise oxidation of sugar in a cell, compared with ordinary burning. In the cell, enzymes catalyze oxidation via a series of small steps in which free energy is transferred in conveniently sized packets to carrier molecules, most often ATP and NADH. At each step, an enzyme controls the reaction by reducing the activation energy barrier that has to be surmounted before the specific reaction can occur. The total free energy released is exactly the same in (A) and (B).
Enzymes catalyze oxidation via series of small steps –
Free E transferred to carrier molecules (e.g. ATP & NADH). Enzymes (∆G) reduce activation energy barrier.
Total free energy released is the same in (A) and (B).

5. Eukaryotic cell with organelles

6. In eukaryotic cells, the mighty mitochondrion
is where the majority of our energy is grabbed from our food molecules in
a process called aerobic cellular respiration

7. All are exergonic (occur spontaneously) Use a lot of coupled reactions
Cellular respiration
Anaerobic respiration
Fermentation
Does not require oxygen
Aerobic respiration
Requires molecular oxygen
Includes redox reactions
Cellular Respiration
Cellular respiration - Process by which cells convert the energy of fuel molecules
(eg. glucose) into usable bond energy in ATP. (Break the $100 dollar bill into small change)
Anaerobic respiration - Cellular respiration in the absence of oxygen.
Aerobic respiration - Cellular respiration which uses oxygen to completely
oxidize fuel molecules.
All are exergonic (occur spontaneously)
Use a lot of coupled reactions

8. A pyramid of production reveals the flow of energy from producers to primary consumers and to higher trophic levels
Tertiary consumers
10 kcal
Secondary consumers
100 kcal
Primary consumers
1,000 kcal
Producers
10,000 kcal
1,000,000 kcal of sunlight

9. Most biochemical pathways involve coupled reactions
ATP is the most common “energy carrier”
This is why examinations of metabolic products focus on ATP production
Other molecules can also act as exergonic energy carriers to help drive an endergonic biochemical reaction
Examples: NADH and FADH2 will become familiar to you as energy carriers
GTP, UTP, etc.

10. Reaction Coupling: released energy drives an endergonic reaction
1) ATP Hydrolysis reaction: Exergonic (spontaneous)
ATP + H2O  ADP + Pi + H ∆G = ~ -30 kJ
2) Phosphorylation of Glucose reaction: Endergonic (nonspontaneous)
Glucose + Pi + H+  Glucose-Phosphate + H2O
∆G = ~ +14 kJ
3) Coupled Reaction (showing just the key reactants & products):
Glucose + ATP  Glucose-Phosphate + ADP
net ∆G = ~ -16 kJ
In cells, an exergonic reaction is “coupled” to an endergonic reaction to give it free energy to drive the reaction. Note: energy is measured in kilojoules (kJ) or kilocalories (kcal).
Example of Reaction Coupling and ATP Hydrolysis
1) ATP Hydrolysis reaction:
ATP + H2O ADP + Pi + H+
DG = ~ -30 kJ Exergonic (spontaneous)
2) Phosphorylation of Glucose reaction:
Glucose + Pi + H Glucose Phosphate + H2O
DG = ~ +14 kJ Endergonic (needs energy to be supplied)
3) Coupled Reaction:
Glucose + ATP Glucose Phosphate + ADP
DG = ~ -16 kJ Coupled reaction has a net Exergonic effect,
so will occur “spontaneously”
Coupled reaction has a net Exergonic effect,
so will occur “spontaneously”

11. Structural relationships among AMP, ADP, and ATP molecules.

12. ATP links exergonic and
endergonic reactions

13. High Energy Phosphate Compounds
High energy compounds have greater free energies of hydrolysis than typical compounds
They contain very reactive (strained) bonds - represented by a squiggle (~)

14. Redox reactions (oxidation/reduction)
oxidized species can gain O or lose H. Substance that becomes oxidized gives up energy
reduced species can gain H or lose O. Substance that becomes reduced receives energy
Essential part of cellular respiration
Many metabolic pathways use
a series of small Redox reactions
to minimize energy loss.
Energy is transferred in the form of electrons (e-)

15. Summary of RedOx Reactions
FAD + 2H+ + 2e- <==> FADH2
NAD+ + 2H+ + 2e- <==> NADH + H+

16. energy transfer agent: In reduced state has more free energy;
Nicotinamide adenine dinucleotide. Notice the N becoming reduced in charge as it takes an electron, and the other H atom hooking to the carbon.
Electrons and their energy eventually used to produce ATP. NADP+ turns into NADPH doesn’t make ATP but actually supplies energy directly for some reactions (photosyn). Flavin adenine dinucleotide (FAD) accepts H atoms and when reduced turns into FADH2. Cytochromes are another set of iron containing proteins that accept e- from H atoms and transfers them to some other compound. All of these together are called electron transfer agents. In their reduced state they have more free energy, and less in their oxidized state.
energy transfer agent:
In reduced state has more
free energy;
less in its oxidized state.

17. Structural formula for coenzyme A
The active portion of CoA is the sulfhydryl group
An acetyl group bonds to CoA through a thioester bond

18. Classification of metabolic intermediate compounds according to function

19. Four stages of aerobic respiration
Reaction Types in Cellular Respiration
1. Dehydrogenation - Hydrogens transferred to a coenzyme.
2. Decarboxylations - Carboxyl groups removed from substrates as
carbon dioxide.
3. Preparation reactions - Molecules are rearranged in preparation
for dehydrogenation or decarboxylation.
Note location of each stage & amount of ATP formed
Product of one stage becomes reactant of next stage

20. the Four Stages of Biochemical Energy Production

21. Stages 1 & 2 Both stages are specific to the type of food
Related to metabolism of:
Carbohydrates
Lipids
Proteins