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Principles of Biology
Biology 101
Lake Tahoe Community College
Instructor: Sue Kloss
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Ch 8 - Intro to Metabolism
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I. Metabolism
A. Organizaton of life chemistry into metabolic pathways
1. metabolism
2. metabolic pathways
3. each step of the pathway is catalyzed by a specific enzyme
4. catabolism
5. Anabolic pathways
B. Forms of energy
1. energy
2. kinetic
3. potential
C. Laws of Thermodynamics - study of energy transformation
1. First Law - energy conservation
2. Second Law - inefficiency
3. Energy and biological systems
D. Chemical reactions either store or release heat
1. endergonic reactions - input of energy
2. exergonic reactions - release of energy
3. Difference in reactants and products
4. Cell metabolism is sum total of all endergonic and exergonic reactions in a cell
II. ATP shuttles energy in cells, via energy coupling; cells do 3 main types of work - mechanical work (cilia), transport
work (pumping substances across membranes against the gradient), and chemical work (pushing of endergonic
reactions, which would not occur spontaneously
A. energy coupling
B. ATP - key to energy coupling
C. usable energy of most exergonic reactions (eg breaking down glucose) can be stored in ATP
D. hydrolysis of ATP produces usable energy
E. regeneration of ATP is endergonic; not spontaneous
F. ATP cycle- moves at an astonishing pace
G. the chemical potential energy temporarily stored in ATP drives most cellular work
III. How Enzymes work.
A. Enzymes speed up cell’s chemical (metabolic) reactions
1. Enzymes are large protein molecules
a. catalysts
2. Energy barriers
3. Enzymes lower a Energy of Activation
4. Enzymes catalyze reaction w/out entering into it
B. Specific enzymes catalyze each cellular reaction
1. reactant = substrate
2. enzyme-substrate complex
3. Each enzyme binds to particular substrate
4. at end of reaction, enzyme unchanged
5. Active site
6. induced fit
7. catalytic cycle
8. an enzyme can catalyze in both directions
C. Cell environment affects enzyme action
1. temp, pH, salt
2. cofactors
3. coenzymes
D. Enzyme inhibitors
1. competitive
2. noncompetitive
3. negative feedback
E. Allosteric regulation of enzymes
CHAPTER 8
An
Introduction to Metabolism
OBJECTIVES
1. Explain the role of catabolic and anabolic pathways in cellular metabolism.
2. Distinguish between kinetic and potential energy.
3. Explain the first and second laws of thermodynamics in your own words.
4. Explain why highly ordered living organisms do not violate the second law of thermodynamics.
5. Distinguish between exergonic and endergonic reactions in terms of energy of the products.
6. List the three main kinds of cellular work. Explain in general terms how cells obtain the energy to do cellular work.
7. Describe the structure of ATP.
8. Explain how ATP performs cellular work.
9. Describe the function of enzymes in biological systems.
10. Explain why an investment of activation energy is necessary to initiate a spontaneous reaction.
11. Explain how enzyme structure determines enzyme specificity.
12. Draw a simple model of the catalytic cycle.
13. Explain the induced-fit model of enzyme function and describe the mechanisms by which enzymes lower
activation energy.
14. Explain how substrate concentration affects the rate of an enzyme-catalyzed reaction.
15. Explain how temperature, pH, cofactors, and enzyme inhibitors can affect enzyme activity.
16. Explain how the location of enzymes in a cell may help order metabolism.
17. Explain how both activators and inhibitors work in allosteric regulation of enzymes.