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Energy Concepts
Study Objectives:
1. Define energy
2.Describe the 1st law of thermodynamics
Compare kinetic and potential energy, be able to give or recognize examples of
each
3. Describe the major forms of energy and explain how energy flows from one
type to another: radiant, electrical, mechanical, chemical, and heat (2nd
law of thermodynamics)
4. Describe the structure of ATP and explain the role of ATP in the body. How is it
recycled? What organelle produces ATP?
5. Define the following terms: metabolism, catabolism, anabolism, synthetic reactions,
decomposition reactions, reversible reactions
6. Describe the characteristics and function of enzymes. How do they work?
7. Describe the various factors that effect enzyme activity: concentrations, temperature,
pH, inhibition, and allosteric regulation
Muma
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Energy Concepts Outline
I.
Energy -the ability to do work or to put matter into motion
A. 1st Law of Thermodynamics - conservation of energy
i. Energy is not created or destroyed, it is only converted from one
form to another
B. Types of energy
i. Kinetic- energy doing work, energy of motion
ii. Potential- inactive or stored energy
C. Forms of Energy
i. Radiant - travels in waves
Example: Light waves are essential for photosynthetic
organisms; vision in animals
ii. Electrical - flow of charged particles
Example: Nerve impulses are created by the
movement of Na+ and K+ ions
iii. Mechanical - directly involved in moving matter
Example: Muscle contraction
iv. Chemical – potential energy stored in chemical bonds and is
released when bonds are broken
1. Found in food, fuel, ATP
II. Types of Reactions
A. Synthesis reaction (A+BAB)
i. Atoms or molecules combine to form larger molecules
ii. Endergonic – reaction absorbs energy into the chemical bonds
B. Decomposition reaction (ABA+B)
i. Larger molecule is broken down into smaller molecules
ii. Exergonic - chemical energy is released
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C. Reversible reaction: (A + B  C + D)
i. Chemical reaction that can proceed in either direction
ii. Direction of the reaction will shift depends on the concentration of
the reactants and products
III. Energy Conversions
A. 2nd Law of Thermodynamics - Heat is a product of all energy
conversions
i. Heat= the kinetic energy contained in the random motion of
molecules
ii. Entropy = measure of disorder or randomness
1. Therefore, all energy transformations increase the entropy
of the universe.
2. Living things are organized, therefore they have low
entropy
3.
To maintain low entropy, constant input of energy is
needed
4. Where do we get this energy???
IV. ATP and Cellular Work
A. The chemical energy in food is released in cellular respiration to make
ATP in the mitochondria
B. ATP is used to drive different types of cell work:
i. active transport
ii. muscle contraction
iii. impulse conduction
iv. we use 10 million ATP molecules per second
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C. The Structure of ATP
i. ATP (adenosine triphosphate) - chemical energy used by all cells
ii. Consists of adenosine plus a tail of three phosphate groups
iii. Energy is released by breaking high energy phosphate bond (-7.3
kcal/mol)
D. ATP is always recycled…
i. ATP  ADP + P + Energy
ii. Cellular work uses (spends) ATP so more must be made
iii. ATP is recycled from ADP and phosphate through cellular
respiration
V. Metabolism - the sum of all the chemical reactions that occur in the body
A. Two types of metabolic reactions
i. Catabolic – breaking down molecules, releases energy which is
captured in the bonds of ATP
ii. Anabolic – uses energy from ATP to synthesize large molecules
B. Enzymes
i. Few metabolic reactions occur without the assistance of specialize
proteins called enzymes
ii. Enzymes are protein molecules that speed up the rate of chemical
reactions (biological catalyst)
iii. Enzymes lower the activation energy for chemical reactions
1. Activation energy is the energy required to trigger a
chemical reaction
iv. Characteristics of Enzymes
1. Each enzyme is very selective – it catalyzes specific
reactions
2. Each enzyme recognizes a specific substrate
3. Enzymes can function over and over again (can be reused)
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v. How an enzyme works
1. Each enzyme binds a specific reactant molecule (substrate)
at its active site.
2. After the reactants are converted, the products are released
and the enzyme remains unchanged.
3. Enzyme + Substrate  Enzyme-substrate complex 
Product + Enzyme
vi. Factors Affecting Enzyme Activity
1. Concentration
a. Increase in substrate or enzyme concentration will
increase the rate
b. At some substrate concentrations, the active sites on
all enzymes are engaged and has reached saturation
2. Temperature
a. Increase in temperature, increases the rate of
enzymatic reactions by increasing kinetic energy of
molecules
b. However, at a point the rate will drop off sharply
due to denaturing of the enzyme at high
temperatures
3. pH – enzymes work best at an optimal pH
a. If it is more acidic or basic than the optimal pH the
rate of enzymatic activity will decrease
4. Enzyme inhibitors or activators- can inhibit or activate a
metabolic reaction
a. Competitive inhibition - binds to the active site, as
substrate impostors
i. Can be reversible or irreversible
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b. Noncompetitive - bind at a different site
(allosteric), changing the shape of the enzyme’s
active site
5. Allosteric Regulation
a. Feedback inhibition – the accumulation of the end
product turns off the metabolic pathway
b. Most allosterically regulated enzymes are
constructed of two or more polypeptide chains.
c. The whole protein oscillates between two
conformational shapes, one active, and one inactive.
d. Binding of regulatory molecules can either inhibit
or stimulate enzyme activity.
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Post – Lecture Practice
1. Review Energy Concepts PowerPoint slides #1-10. Describe in your own words in a
short paragraph what is happening in the diagram below. Include the specific types of
energy and how the First and Second Law of Thermodynamics apply. (Act like I don’t
know anything about this drawing and you are teaching me about the flow of energy )
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2. Explain how ATP is used as a source of energy for cellular processes. You can draw
and describe a diagram OR use words to get your point across. Include in your answer:
a. the general structure of ATP
b. how is it used and recycled during cellular processes
c. give examples of two specific mechanisms that you have learned about so far
that use ATP
3. Describe the role enzymes play in living organisms. Include in your answer:
a. Define enzyme, substrate, and product
b. Describe the characteristics of an enzyme
c. Give an example of two variables that can affect the activity of an enzyme and
explain why these variables change the course of an enzymatic reaction.
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