1. An Organism’s Metabolism Transforms Matter and Energy, Subject to the Laws of Thermodynamics

2. Potential and Kinetic Energy: Cheetah at Rest and Running
Energy is lost
as heat

3. Potential and Kinetic Energy:

4.  First Law of Thermodynamics: Energy Can Neither Be Created or Destroyed Second Law of Thermodynamics: Every Energy Transfer Increases the Disorder (Entropy) of the Universe.

5. The Free Energy Change of a Reaction Tells Us Whether the
Reaction Occurs Spontaneously
∆G = G Final State – G Initial State

6. The Relationship of Free Energy to Stability, Work Capacity, and Spontaneous Change

7. Energy Changes in Exergonic (energy releasing) and Endergonic (energy storing) Reactions

8. Disequilibrium and Work in Closed and Open Systems

9. Cells in our body experience a constant flow of materials in and out, preventing metabolic pathways from reaching equilibrium
Figure 8.7
(b) An open hydroelectric system. Flowing water keeps driving the generator because intake and outflow of water keep the system from reaching equilibrium.
∆G < 0

10. A cell does three main kinds of work: Mechanical Transport Chemical
ATP powers cellular work by coupling exergonic reactions to endergonic reactions
A cell does three main kinds of work:
Mechanical
Transport
Chemical

11. The three types of cellular work are powered by the hydrolysis of ATP
(c) Chemical work: ATP phosphorylates key reactants P
Membrane
protein
Motor protein
P i
Protein moved
(a) Mechanical work: ATP phosphorylates motor proteins
ATP
(b) Transport work: ATP phosphorylates transport proteins
Solute
transported
Glu
NH3
NH2 +
Reactants: Glutamic acid
and ammonia
Product (glutamine)
made
ADP
Figure 8.11

12. The Structure and Hydrolysis of ATP

13. Energy COUPLING by Phosphate Transfer

14. The Regeneration of ATP
Catabolic pathways drive the regeneration of ATP from ADP and phosphate
ATP synthesis from
ADP + P i requires energy
ATP
ADP + P i
Energy for cellular work
(endergonic, energy-
consuming processes)
Energy from catabolism
(exergonic, energy yielding
processes)
ATP hydrolysis to
ADP + P i yields energy
Figure 8.12

15. An active cell needs millions of
molecules of ATP per second
to drive its biochemical
machinery. They’re consumed
in less than a second and an
average person produces and
hydrolyzes about 40 kg of ATP
per day!

16. Enzymes speed up metabolic reactions by lowering energy barriers

17. Enzymes
1.Proteins: most enzymes are catalytic proteins, primarily tertiary and quaternary structures.
2.Catalysts:chemical agents that accelerate a reaction without being permanently changed in the process.

18. Example of an Enzyme-Catalyzed Reaction: Hydrolysis of Sucrose

19. How Do Reactions Occur? Spontaneous reactions may occur very slowly.
All reactions require free energy of activation (EA)
Uphill portion represents the EA required to start the reaction.
Downhill portion represents the loss of free energy by the molecules in the reaction.

20. Is this reaction exergonic or endergonic?

21. How can the EA barrier be overcome?
Temperature
Temperatures that are too high denature organic molecules, so what else is there?
Enzymes lower the EA barrier so that reactions can occur at lower temperatures.

23. Enzymes Without Enzyme With Enzyme Free Energy
Progress of the reaction
Reactants
Products
Free energy of activation

24. Enzyme / Substrate Relationship:
What is the substrate?
It is the reactant upon which an enzyme reacts.
Enzymes are substrate specific.
Only the active site of the enzyme actually binds the substrate.

25. Substrate
The substance (reactant) an enzyme acts on.
Enzyme
Substrate

26. Active Site
A restricted region of an enzyme molecule which binds to the substrate.
Enzyme
Substrate
Active Site

27. Enzyme Animations

28. The Active Site
Most enzyme-substrate interactions are the result of weak bonds.
The active site may cause the enzyme to hold onto the substrate in a very specific way.
The active site may provide a micro-environment (e.g. low pH) which enhances a reaction.

30. Induced Fit
A change in the configuration of an enzyme’s active site (H and ionic bonds are involved).
Induced by the substrate.
Enzyme
Active Site
substrate
induced fit

31. Enzymatic Reaction substrate (sucrose) + enzyme (sucrase) 
enzyme-substrate complex 
and +
sucrase
glucose fructose
products enzyme

32. Enzyme Activity is Affected by:
Temperature pH
Enzyme Concentration
Substrate Concentration

35. Cofactors and Coenzymes
Inorganic substances (zinc, iron) and vitamins (respectively) are sometimes needed for proper enzymatic activity.
Example:
Iron must be present in the quaternary structure - hemoglobin in order for it to pick up oxygen.

36. Enzyme Inhibitors Two examples:
a. Competitive Inhibitors: are chemicals that resemble an enzyme’s normal substrate and compete with it for the active site.
Substrate
Enzyme
Competitive
inhibitor

37. Enzyme Inhibitors
b. Noncompetitive Inhibitors:
Inhibitors that do not enter the active site, but bind to another part of the enzyme causing the enzyme to change its shape, which in turn alters the active site.
Substrate
Enzyme
Noncompetitive
Inhibitor
active site
altered

39. Allosteric Regulation
Regulatory molecules that bind to the enzyme’s allosteric site changing the shape of the enzyme.
Allosterically regulated enzymes have a quaternary protein structure.
Each subunit of the enzyme has an active site and an allosteric site.
Allosteric activators stabilize the active site
Allosteric inhibitors deactivate the active site.

41. Feedback Inhibition A metabolic pathway is switched off
by the inhibitory
binding of its end
product to an enzyme
earlier in the pathway

42. In the amylase lab, the
amylase broke down the polysac-
charides (starches) into _______.
2) Enzymes work by lowering
the ___________ _________
required for a reaction to occur.