1. Chapter 8: An Introduction to Metabolism

2. Metabolism Metabolism = Catabolism + Anabolism
Catabolic reactions are energy yielding involved in the break down of more complex molecules into simpler ones
Anabolic reactions are energy requiring
involved in the building up of simpler molecules into more-complex ones
Bioenergetics-study of how organisms use their energy resources

3. 1st & 2nd Laws of Thermodynamics
“Energy can be transferred or transformed but neither created nor destroyed.”
“Every energy transfer or transformation increases the disorder (entropy) of the universe.”
Note especially the waste heat

4. Organisms as Transformers
transform energy to new forms (1st law)
are less than 100% efficient (2nd law)
Organisms tend to use energy in a more organized fashion therefore requiring energy ( always fighting entropy)

5. Free energy change- ΔG
G-Free energy-energy that is available to perform work
H- total energy (enthalpy)
S – entropy
ΔG = ΔH - T ΔS
If ΔG = negative, reaction is spontaneous
If ΔG = positive, reaction needs energy

6. Metabolic Reactions
Exergonic reaction- releases energy so G decreases and ΔG is negative
Endergonic reaction- absorbs free energy so G increases and ΔG is positive

7. Exergonic Reactions
KNOW THIS CHART!
“Food”
Energy released

8. Endergonic Reactions
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“Work”
Energy required

9. Cells do different kinds of work
Mechanical- muscles
Transport- cell membrane
Chemical- endergonic reactions

10. Summary of Metabolic Coupling
Exergonic processes drive Endergonic processes
ATP is an agent of energy coupling
It is created by one process and is used in another!

11. Adenosine Triphosphate (ATP)

12. Cellular work is always powered by ATP
Hydrolysis releases 7.3 kcal of energy per mole ATP
Can heat the environment (keep us warm)
ATP is renewable

13. Enzymes Catalysts speed up a reaction without being consumed
An enzyme is a catalytic protein
Catalysts reduce activation energy- energy needed to get a reaction going

14. Enzymes lower activation energy
KNOW THIS CHART !!!!
Enzymes lower activation energy

15. Catalysis as Viewed in 3D
Substrate is reactant that the enzyme works on
Active site is site of catalysis

16. Induced Fit- used to be
Called “lock and key”
Enzymes and substrate brought into position for optimum interaction

17. Environmental Factors and Enzymes
Temperature- increases enzyme action until it denatures
pH 6-8 depending on environment or organ
Cofactors- non-protein helpers (minerals)
Coenzymes- vitamins

18. Each Enzyme has Opt. Temp and pH
Denatured?
Optimal pH of most enzymes fall in 6-8 range

19. Competitive Enzyme Inhibitors
resembles the substrate and bonds to active site, blocking it
Is reversible by increasing substrate concentration

20. Noncompetitive Enzyme Inhibitors
Binds to another site (allosteric site) not the active site
Changes shape of protein so it can no longer function
Toxins and Poisons- sarin, DDT

21. Negative Effects of Inhibition
Sarin (nerve gas ) attaches to acetylcholine- important nervous system enzyme
DDT
Antibiotics blocks active sites of bacterial enzymes

22. Allosteric Regulation of Enzymes
Not all inhibitors are bad.
Some are used to regulate enzyme activity
Can activate or inhibit enzyme
Example-speeding up or slowing down of ATP production

23. Feedback Inhibition Pathway is switched off by the binding of the
product to
the
allosteric site

24. ATP Feedback Inhibition