1. Agenda: Thur 9/12 Due MONDAY Collect HW Biomolecules Match-Up
Start Energy, Metabolism, and Enzymes Lecture
Homework Energy, Metabolism, and Enzymes Guided Reading (Chp.2&3)
Due MONDAY

2. Energy, Metabolism, & Enzymes Notes

3. Chemical Reactions Make and/or Break Chemical Bonds
Chemical reactions are the making and breaking of chemical bonds
The starting molecules of a chemical reaction are called reactants
The final molecules of a chemical reaction are called products
Classic definitions—again “prior knowledge”

4. Example: Photosynthesis…a mighty important chemical reaction!
Sunlight powers the conversion of carbon dioxide and water to glucose and oxygen 6 CO2 + 6 H2O → C6H12O6 + 6 O2
Ask them what’s inside the “bubbles”! AND Why are the bubbles positioned where they are with respect to the leaves?

5. Metabolism/Bioenergetics
Metabolism: The totality of an organism’s chemical processes; managing the material and energy resources of the cell
Catabolic pathways: degradative process such as cellular respiration; releases energy
Anabolic pathways: building process such as protein synthesis; photosynthesis; consumes energy

6. Strategies to regulate body temp and metabolism
Endothermy = use of thermal E generated by metabolism to maintain homeostatic body temperatures
Ectothermy = use of external thermal E to help regulate and maintain body temp

7. Thermodynamics = study of E transformations
Energy (E)=capacity to do work; Kinetic energy~ energy of motion; Potential energy~ stored energy
Thermodynamics~ 1st Law: conservation of energy; E transferred/transformed, not created/destroyed
2nd Law: transformations increase entropy (disorder, randomness)
Combo: quantity of E is constant, quality is not

8. ATP: An Important Source of Energy for Cellular Processes
Adenosine triphosphate (ATP) is the primary energy-transferring molecule in the cell
ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups
They most likely know this molecule’s general structure from their Biology I course. Emphasize yet again that breaking a bond requires energy (as in removing one of those phosphates) while bond formation releases energy.

9. Energy Coupling & ATP
E coupling: use of exergonic process to drive an endergonic one
Adenosine triphosphate (ATP)
ATP tail: high negative charge
ATP hydrolysis: release of free E

10. The ATP cycle ATP synthesis from ADP + P i requires energy ATP
Energy for cellular work
(endergonic, energy-
consuming processes)
Energy from catabolism
(exergonic, energy yielding
processes)
ATP hydrolysis to
ADP + P i yields energy

11. Free energy Free energy (G) = the energy available to do work
DG = change in free energy
Order is maintained by constant free energy input into a system
Loss of order or free energy flow results in death
Remember: excess acquired free energy versus required free energy expenditure results in energy storage or growth!

13. If DG is positive then DG is endergonic (absorbs energy).
In the previous example the initial state has more energy than the final state so that DG is a negative number
If DG is a negative number, then the reaction is exergonic (releases energy)
If DG is positive then DG is endergonic (absorbs energy).

14. Rule-Things tend to go from high energy to lower energy.
During this time bonds must be broken and remade.
The energy used to do this is called the energy of activation (EA).

15. Another example ∆G = –3.9 kcal/mol NH2 NH3 ∆G = +3.4 kcal/mol Glu ADP
Endergonic reaction: ∆G is positive, reaction
is not spontaneous
∆G = +3.4 kcal/mol
Glu
∆G = –7.3 kcal/mol
ATP
H2O +
NH3
ADP
NH2
Glutamic
acid
Ammonia
Glutamine
Exergonic reaction: ∆ G is negative, reaction
is spontaneous P
Coupled reactions: Overall ∆G is negative;
together, reactions are spontaneous
∆G = –3.9 kcal/mol

16. Energy Concepts Video Clip
2 min.

17. Enzymes = proteins (catalysts) that increases the rate of biochemical reaction.
Characteristics of enzymes:
Made of proteins
b. They are very specific and only work with a certain set of reactants or substrates that fit on their active site.
This is the space filling and ribbon model of the lysozyme. The groove is the active site where the substrate attaches

18. c. When an enzyme binds with the substrate, the substrate interacts with the enzyme causing it to change shape. This change in shape will facilitate the chemical reaction to occur. This is called the induced fit
Substrate: enzyme reactant
Active site: pocket/groove on enzyme that binds to substrate

20. Example of an enzyme-catalyzed reaction: hydrolysis of sucrose by sucrase
CH2OH
CH2OH
CH2OH
CH2OH O H H O O H H H O H H
Sucrase H OH O H HO +
H2O OH H HO OH H H O HO
CH2OH HO
CH2OH H OH OH H H OH OH H
Fructose
Sucrose
Glucose
C12H22O11
C6H12O6
C6H12O6

21. d. It increases the reaction rate by lowering the energy of activation
d. It increases the reaction rate by lowering the energy of activation. They do not change D G.
e. Enzymes can be used over and over again

22. The graph represents the amount of product formed
The graph represents the amount of product formed. At first amount of product formed increases, then the rate slows down until it reaches a constant maximum. The enzyme is becoming saturated. The fastest rate of product formation is at the beginning and is called the initial velocity. If the enzyme is kept constant and there is an increase in the amount of substrate, there will be an increase in the initial velocity until a saturation point is reached.

23. The previous experiment is repeated with the same amount of enzyme but increasing amount of substrate. The initial velocities increase because there is more substrate to attach the enzyme but the eventually there is no increase in initial velocity because all the enzymes have become saturated with substrate.

24. Effects on Enzyme Activity
Temperature (denature) pH
Cofactors:
inorganic, nonprotein helpers
ex.: zinc, iron, copper
Coenzymes:
organic helpers
ex.:vitamins

25. Temperature- at first an increase in temperature will increase the reaction rate because of the kinetics of the reaction but after a certain temperature is reached, the hydrogen bonds fall apart and the enzyme will denature.

26. pH can affect the reaction rates
pH can affect the reaction rates. Most enzymes work best at a range of 6 to 8 but there are some exception such as pepsin. If the environment changes much from the optimum pH, again hydrogen bonds are affected, denaturing the enzyme.

27. Enzyme Inhibitors = Some chemicals inhibit the action of an enzyme.
Irreversible (covalent) or reversible (weak bonds)
Competitive: competes for active site (reversible); mimics the substrate
Noncompetitive: bind to another part of enzyme (allosteric site) altering its conformation (shape); poisons, antibiotics

28. A competitive inhibitor is a molecule that resembles the substrate enough that it can bind to the active site in place of the substrate. This will slow down the reaction rate

29. A noncompetitive inhibitor is one that does not bind to the receptor site but to some other place on the molecule  the allosteric site. This causes the active site to change shape so that substrate cannot bind. This also slows down
the reaction rate.

30. Allosteric Regulation- These enzymes have two or more polypeptide chains each with its own active site. This enzyme also has two conformations-one with a functional active site and the other with a nonfunctional active site. This enzyme also has a place for the binding of an activator and an inhibitor. The activator will stabilize the conformation with the functional active site and the inhibitor will stabilize the inactive form of the enzyme.

31. Feedback inhibition- Usually enzymes work in biochemical pathway in which there is a series of intermediate chemical reaction that occur in order to get from point A (reactants) to point B (products). It is not unusual for an end product to act as an inhibitor to shut down the pathway when there is sufficient product present.

32. Feedback inhibition in isoleucine synthesis
Active site available
Isoleucine used up by cell
Feedback inhibition
Isoleucine binds to allosteric site
Active site of enzyme 1 no longer binds threonine; pathway is switched off
Initial substrate (threonine)
Threonine in active site
Enzyme 1 (threonine deaminase)
Intermediate A
Intermediate B
Intermediate C
Intermediate D
Enzyme 2
Enzyme 3
Enzyme 4
Enzyme 5
End product (isoleucine)
Feedback inhibition in isoleucine synthesis

33. How Enzymes Work Video Clip
1 min.

34. After:
Enzymes & Metabolism Worksheet