1. How does the work in a cell get done? ENZYMES
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2. All chemical reactions require a certain amount of energy
Energy must be available to break bonds and form new ones
This energy is called energy of activation (EA)
Reaction
without
enzyme
EA with
Energy
Reactants
Reaction with
EA without
Net
change
in energy
(the same)
Products
Progress of the reaction
Heat could be used to initiate a reaction. However, heat would kill the cell and would not be specific for a particular reaction.
For the BLAST Animation Enzymes: Activation Energy, go to Animation and Video Files.
Student Misconceptions and Concerns
1. For students not previously familiar with activation energy, analogies can make all the difference. Activation energy can be thought of as a small input that is needed to trigger a large output. This is like (a) an irritated person who needs only a bit more frustration to explode in anger, (b) small waves that lift debris over a dam, or (c) lighting a match around lighter fluid. In each situation, the output is much greater than the input.
Teaching Tips
1. The information in DNA is used to direct the production of RNA, which in turn directs the production of proteins. However, in Chapter 3, four different types of biological molecules were noted as significant components of life. Students who think this through might wonder, and you could point out that DNA does not directly control the production of carbohydrates and lipids. So how does DNA exert its influence over the synthesis of these two chemical groups? The answer is largely by way of enzymes, proteins with the ability to promote the production of carbohydrates and lipids.
Copyright © 2009 Pearson Education, Inc.

3. Enzymes can lower the activation energy required
The cell uses catalysis to drive (speed up) biological reactions
Enzymes= proteins that function as biological catalysts
Speed up the rate of the reaction by lowering the EA
Not used up in the process
Each enzyme has a particular target molecule called the substrate
Most enzymes are proteins, but RNA enzymes, also called ribozymes, also catalyze reactions.
Student Misconceptions and Concerns
1. For students not previously familiar with activation energy, analogies can make all the difference. Activation energy can be thought of as a small input that is needed to trigger a large output. This is like (a) an irritated person who needs only a bit more frustration to explode in anger, (b) small waves that lift debris over a dam, or (c) lighting a match around lighter fluid. In each situation, the output is much greater than the input.
Teaching Tips
1. The information in DNA is used to direct the production of RNA, which in turn directs the production of proteins. However, in Chapter 3, four different types of biological molecules were noted as significant components of life. Students who think this through might wonder, and you could point out that DNA does not directly control the production of carbohydrates and lipids. So how does DNA exert its influence over the synthesis of these two chemical groups? The answer is largely by way of enzymes, proteins with the ability to promote the production of carbohydrates and lipids.
Reaction
without
enzyme
EA with
Energy
Reactants
Reaction with
EA without
Net
change
in energy
(the same)
Products
Progress of the reaction
Copyright © 2009 Pearson Education, Inc.

4. Enzyme available
with empty active
site
Active site 1
Enzyme
(sucrase)

5. Enzyme available with empty active site Active site Substrate1
Enzyme
(sucrase)
Substrate binds
to enzyme with
induced fit 2
Substrate
(sucrose)

6. Enzyme available with empty active site Active site Substrate1
Enzyme
(sucrase)
Substrate binds
to enzyme with
induced fit 2
Substrate
(sucrose)
Substrate is
converted to
products 3

7. Enzyme available with empty active site Active site Substrate1
Enzyme
(sucrase)
Substrate binds
to enzyme with
induced fit 2
Substrate
(sucrose)
Substrate is
converted to
products 3
Products are
released 4
Fructose
Glucose

8. What are the key characteristics of enzymes?
Protein structure
Not used up in reactions
Specific for one substrate (one reaction)
Reaction rates are very fast (100s to s of reactions per second!)
Certain chemicals also alter enzyme function and have been used to kill bacteria.
For the BLAST Animation Enzymes: Types and Specificity, go to Animation and Video Files.
Student Misconceptions and Concerns
1. The specific interactions of enzymes and substrates can be illustrated with simple physical models. Many students new to these concepts will benefit from several forms of explanation, including diagrams such as those in the textbook, physical models, and the opportunity to manipulate or create their own examples. Just like pitching a tent, new concepts are best constructed with many lines of support.
Teaching Tips
1. The information in DNA is used to direct the production of RNA, which in turn directs the production of proteins. However, in Chapter 3, four different types of biological molecules were noted as significant components of life. Students who think this through might wonder, and you could point out that DNA does not directly control the production of carbohydrates and lipids. So how does DNA exert its influence over the synthesis of these two chemical groups? The answer is largely by way of enzymes, proteins with the ability to promote the production of carbohydrates and lipids.
2. The text notes that the relationship between an enzyme and its substrate is like a handshake, with each hand generally conforming to the shape of the other. This induced fit is also like the change in shape of a glove when a hand is inserted. The glove’s general shape matches the hand, but the final “fit” requires some additional adjustments.
Copyright © 2009 Pearson Education, Inc.

9. What do you think affects enzyme activity??

10. Factors affecting enzyme activity
Anything that denatures a protein!
Temperature pH
Chemicals
Competitive and non-competitive inhibitors
Substrate
Enzyme
Active site
Normal binding of substrate
Competitive
inhibitor
Enzyme inhibition
Noncompetitive
Penicillin, an antibiotic, is an example of a noncompetitive inhibitor because it blocks the active site of an enzyme that some bacteria use to make their cell wall.
For the BLAST Animation Enzyme Regulation: Chemical Modification, go to Animation and Video Files.
For the BLAST Animation Enzyme Regulation: Competitive Inhibition, go to Animation and Video Files.
Student Misconceptions and Concerns
1. The specific interactions of enzymes and substrates can be illustrated with simple physical models. Many students new to these concepts will benefit from several forms of explanation, including diagrams such as those in the textbook, physical models, and the opportunity to manipulate or create their own examples. Just like pitching a tent, new concepts are best constructed with many lines of support.
Teaching Tips
1. The information in DNA is used to direct the production of RNA, which in turn directs the production of proteins. However, in Chapter 3, four different types of biological molecules were noted as significant components of life. Students who think this through might wonder, and you could point out that DNA does not directly control the production of carbohydrates and lipids. So how does DNA exert its influence over the synthesis of these two chemical groups? The answer is largely by way of enzymes, proteins with the ability to promote the production of carbohydrates and lipids.
2. Enzyme inhibitors that block the active site are like (a) a person sitting in your assigned theater seat or (b) a car parked in your parking space. Analogies for inhibitors that change the shape of the active site are more difficult to imagine. Consider challenging your students to think of such analogies. (Perhaps someone adjusting the driver seat of the car differently from your preferences and then leaving it that way when you try to use the car.)
3. Feedback inhibition relies upon the negative feedback of the accumulation of a product. Ask students in class to suggest other products of reactions that inhibit the process that made them when the product reaches high enough levels. (Gas station pumps routinely shut off when a high level of gasoline is detected. Furnaces typically turn off when enough heat has been produced.)
4. Challenge your class to identify advantages of specific enzyme inhibitors for pest control. These advantages include (a) the ability to target chemical reactions of only certain types of pest organisms and (b) the ability to target chemical reactions that are found in insects but not in humans.
Copyright © 2009 Pearson Education, Inc.

11. What do all the enzymes do in a cell? Allow the cell to perform work!

12. Cells transform energy as they perform work
Energy is the capacity to do work and cause change
Kinetic energy is the energy of motion
Potential energy is energy that an object possesses as a result of its location
Chemical energy is potential energy because of its energy available for release in a chemical reaction
Copyright © 2009 Pearson Education, Inc.

13. Two laws govern energy transformations
Energy transformations within matter are studied by individuals in the field of thermodynamics
The first law of thermodynamics—energy in the universe is constant
The second law of thermodynamics—energy conversions increase the disorder of the universe
Entropy is the measure of disorder, or randomness
Copyright © 2009 Pearson Education, Inc.

14. Energy conversion in a cell Energy for cellular work
Fuel
Gasoline
Energy conversion in a cell
Energy for cellular work
Cellular respiration
Waste products
Energy conversion
Combustion
Energy conversion in a car
Oxygen
Heat
Glucose
Water
Carbon dioxide
Kinetic energy
of movement
energy

15. Reactions that release energy
An exergonic reaction is a chemical reaction that releases energy
Example: Burning wood releases the energy in glucose, producing heat, light, carbon dioxide, and water
Reactants
Amount of
energy
released
Potential energy of molecules
Energy released
Products
Copyright © 2009 Pearson Education, Inc.

16. Reactions that store energy
An endergonic reaction requires an input of energy and yields products rich in potential energy
Example: Photosynthesis makes energy-rich sugar molecules using energy in sunlight
Reactants
Potential energy of molecules
Energy required
Products
Amount of
energy
required
Copyright © 2009 Pearson Education, Inc.

17. Metabolism couples all the exergonic and endergonic reactions
Metabolism is the total chemical reactions that break down complex molecules and build up complex molecules
Energy coupling—the use of exergonic processes to drive an endergonic one
Copyright © 2009 Pearson Education, Inc.

18. Cellular work Chemical work— e.g. driving endergonic reactions
Transport work— e.g. pumping substances across membranes
Mechanical work— e.g. beating of cilia
Cellular work
Chemical work
Solute transported
Molecule formed
Product
Reactants
Motor
protein
Membrane
Solute
Transport work
Mechanical work
Protein moved

19. $$ Cellular work Chemical work— e.g. driving endergonic reactions
Transport work— e.g. pumping substances across membranes
Mechanical work— e.g. beating of cilia
Cellular work $$
Chemical work
Solute transported
Molecule formed
Product
Reactants
Motor
protein
Membrane
Solute
Transport work
Mechanical work
Protein moved

20. ATP is the money (energy) to drive cellular work
ATP, Adenosine TriPhosphate, is the energy currency of cells.
PO4 + ADP creates ATP and stores energy
Hydrolysis of ATP releases energy by transferring its third phosphate from ATP to some other molecule
Ribose
Adenine
Triphosphate (ATP)
Adenosine
Phosphate
group
Hydrolysis
Diphosphate (ADP) +
Copyright © 2009 Pearson Education, Inc.

21. How do cells get the ATP to
drive cellular work??

22. How do cells get the ATP to (and Fermentation and Photosynthesis)
drive cellular work??
Cellular Respiration
(and Fermentation and Photosynthesis)

23. Cellular respiration in eukaryotes:
using oxygen and removing carbon dioxide
Breathing
Cellular Respiration
Muscle cells carrying out
CO2 + H2O + ATP
Lungs
Bloodstream
CO2 O2
Glucose + O2

24. from organic fuels to oxygen
Cells tap energy from electrons “falling”
from organic fuels to oxygen
Cellular respiration is the controlled breakdown of organic molecules
Energy is released in small amounts that can be captured by a biological system and stored in ATP
Copyright © 2009 Pearson Education, Inc.

25. What happens during cellular respiration?
Redox reactions

26. Specifically…
Glucose loses its hydrogen atoms and is ultimately converted to CO2
At the same time, O2 gains hydrogen atoms and is converted to H2O
Loss of electrons is called oxidation (Oxidation Is Loss)
Gain of electrons is called reduction (Reduction Is Gain)
C6H12O O2
Glucose
Loss of hydrogen atoms
(oxidation)
6 CO H2O Energy
Gain of hydrogen atoms
(reduction)
(ATP)

27. Electron carries transport electrons that eventually are used to make ATP
Electron carriers (e.g. NAD+):
Form a staircase where the electrons pass from one to the next down the staircase
These electron carriers collectively are called the electron transport chain, and as electrons are transported down the chain, ATP is generated
ATP
NAD+
NADH H+
2e–
Electron transport
chain
Controlled
release of
energy for
synthesis
of ATP + O2
H2O 1  2
Copyright © 2009 Pearson Education, Inc.

28. The 3 steps of cellular respiration
Mitochondrion
CO2
NADH
ATP
High-energy electrons
carried by NADH
CITRIC ACID
CYCLE
GLYCOLYSIS
Pyruvate
Glucose
and
FADH2
Substrate-level
phosphorylation
OXIDATIVE
PHOSPHORYLATION
(Electron Transport
and Chemiosmosis)
Oxidative
Cytoplasm
Inner
mitochondrial
membrane
Citric acid or
Krebs cycle
Electron Transport
Chain (Oxidative
Phosphorylation)
Glycolysis

29. Glycolysis
Glucose
NAD+ + 2
2 ADP
NADH P
ATP H+
2 Pyruvate
Glycolysis: a single molecule of glucose is enzymatically cut in half to produce 2 molecules of pyruvate
Additional outcomes:
2 electron carriers
2molecules of ATP are produced by substrate-level phosphorylation (S.L. ATP)

30. Substrate level phosphorylation
Phosphorylation reactions add a phosphate group to ADP
Energy used to add phosphate is found in substrate +
ADP
ATP
Substrate
Enzyme
Product P

31. Citric Acid or Krebs Cycle
Pyruvate converts to Acetyl coA (Intermediate step)
Acetyl coA enters Krebs cycle
Outcomes:
8 electron carriers
2 S.L. ATP
Release of CO2
CITRIC ACID CYCLE
NAD+
NADH
3 H+
CO2  3 2
CoA
Acetyl CoA P
ADP +
ATP
FADH2
FAD

32. Most ATP production occurs by oxidative phosphorylation
Oxidative phosphorylation involves electron transport and chemiosmosis
1. Electrons from electron carriers are passed down the electron transport chain
2. A H+ ion gradient is formed and facilitated diffusion through the ATP synthase uses this potential energy to make ATP
Aerobic respiration: Electrons and H+ reduce oxygen to make water
Copyright © 2009 Pearson Education, Inc.

33. OXIDATIVE PHOSPHORYLATION
Oxidative phosphorylation through
chemiosmosis
ATP H+
Intermembrane
space O2
H2O 2  1
Inner
mitochondrial
membrane
NAD+
Mitochondrial
matrix
Electron
flow
carrier
Protein
complex
of electron
carriers
NADH
FADH2
FAD
synthase P
ADP +
Chemiosmosis
+ 2
OXIDATIVE PHOSPHORYLATION
Electron Transport Chain

34. Summary of cellular respiration
Cytoplasm
Glucose
FADH2
Mitochondrion
Maximum per glucose:
OXIDATIVE
PHOSPHORYLATION
(Electron Transport
and Chemiosmosis)
CITRIC ACID
CYCLE
Electron shuttle
across membrane 2
NADH 6
(or 2 FADH2)
2 Acetyl
CoA
GLYCOLYSIS
Pyruvate
About
38 ATP
 about 34 ATP
by substrate-level
phosphorylation
by oxidative phosphorylation
 2 ATP
In a prokatyote… 36 in a eukaryote

35. Alternatives to respiration… fermentation
1 glucose provides only
2 ATP
Fun end products!