1. Metabolism
The sum total of all chemical reactions & physical workings occurring in a cell

2. 2 types of metabolism Anabolism - biosynthesis
building complex molecules from simple ones
requires energy (ATP)
See condensation or dehydration synthesis below
Catabolism - degradation
breaking down complex molecules into simple ones
generates energy (ATP)
See hydrolysis below

4. RNA enzymes - ribozymes

5. Activation Energy
For a reaction to occur, an energy barrier must be surmounted
Enzymes make the energy barrier smaller
activation energy
without enzyme
starting
substance
activation energy
with enzyme
energy
released
by the
reaction
Figure 6.12a Page 105
products

6. Figure 6.8 Activation Energy Initiates Reactions
Figures\Chapter06\High-Res\life7e-fig jpg

7. Figure 6.9 Over the Energy Barrier
Figures\Chapter06\High-Res\life7e-fig jpg

8. Transition State Unstable at highest energy level
(substrate + activation energy)
Point when a reaction can easily run in either direction, to product or back to a reactant
Substrate is bound most tightly to an enzyme in this state

9. Would take so long that it practically does not happen

10. Enzyme structure Simple enzymes – consist of protein alone
Conjugated enzymes or holoenzymes – contain protein and nonprotein molecules
apoenzyme –protein portion (core)
cofactors – nonprotein portion
metallic cofactors – iron, copper, magnesium
coenzymes -organic molecules - vitamins

12. Enzyme-substrate interactions Lock and key vs Induced Fit model

13. Enzyme-substrate interactions Lock and key vs Induced Fit model

14. Synthesis or condensation reactions – anabolic reactions to form covalent bonds between smaller substrate molecules, require ATP, release one molecule of water for each bond
Hydrolysis reactions– catabolic reactions that break down substrates into small molecules, requires the input of water

16. Transfer reactions by enzymes
Oxidation-reduction reactions – transfer of electrons
Aminotransferases – convert one type of amino acid to another by transferring an amino group
Phosphorylatoin– transfer phosphate groups, involved in energy transfer
Photophosphorylation
Substrate level phosphorylation
Oxidative phosphorylation

17. Metabolic pathways

18. Control of enzyme activity
Control of enzyme activity directly
Control of enzyme activity by regulating enzyme synthesis

19. Control of enzyme activity directly
Competitive inhibition – substance that resembles normal substrate competes with substrate for active site
Noncompetitive inhibiot – substance that binds to the cofactor and distorts the shape of the active site
Feedback inhibition – concentration of product at the end of a pathway blocks the action of a key enzyme

20. Competitive inhibition

21. Control of enzyme synthesis
Constitutive enzymes – always present, always produced in equal amounts or at equal rates, regardless of amount of substrate; enzymes involved in glucose metabolism
Induced enzymes – not constantly present, produced only when substrate is present, prevents cell from wasting resources
Represible enzymes – Enzymes not produced when the end product of the pathway is present

22. Exoenzymes – transported extracellularly, where they break down large food molecules or harmful chemicals; cellulase, amylase, penicillinase
Endoenzymes – retained intracellularly & function there