Biochemical Energy Production

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

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 – 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. Cellular respiration Anaerobic respiration • Fermentation • Does not require oxygen • Aerobic respiration • Requires molecular oxygen • Includes redox reactions 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 Tertiaryconsumers 10 kcal Secondaryconsumers 100 kcal Primaryconsumers 1,000kcal 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 Coupled reaction has a netExergonic 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; less in its oxidized state.

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

18. Classification of metabolic intermediate compounds according to function

19. Four stages of aerobic respiration 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