BIO SCI 93 Chapter Notes - Chapter 8: Ribose, Nitrogenous Base, Exergonic Reaction
29 Mar 2018
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Lecture 10 Reading Guide
Bio Sci 93 Summer 2017
Reading Guide for Lecture 10
Chapter 8, pages 142 – 157
Complete this reading guide as you read the textbook pages listed above. You might not have
to read every word on every page, rather pay close attention to the questions in this guide and
answer them as you work through the textbook. Also pay close attention to the terms that are
underlined: these are key terms that you should know the definitions of and be able to apply in
new situations.
Define metabolism and metabolic pathways. How are catabolic pathways and anabolic
pathways different? Give an example of each.
Metabolism: the totality of an organism’s chemical reactions; emergent property of life that
arises from orderly interactions between molecules
Metabolic pathways: begins with a specific molecule, which is then altered in a series of defined
steps which result in a certain product
Each step of the pathway is catalyzed by a specific enzyme
Catabolic pathways aka breakdown pathways release energy by breaking down complex
molecules to simper compounds
Major pathway is cellular respiration, where glucose is broken down with oxygen into
CO2 and water
Anabolic pathways consume energy to build complicated molecules from simpler ones;
sometimes called biosynthetic pathways
Define and give examples of the following types of energy (the capacity to cause change):
Kinetic energy: energy associated with the relative motion of objects
Thermal energy: kinetic energy associated with the random movements of atoms or molecules
Heat: thermal energy in transfer from one object to another
Potential energy: the energy that matter possesses because of its location or structure
Chemical energy: potential energy available for release in a chemical reaction
Skip to page 145 (concept 8.2)
What is Gibb’s free energy (G)?
The portion of a system’s energy that can perform work when temperature and pressure are
uniform throughout the system
Explain how free energy can change (G) as a function of temperature.
ΔG = ΔH - T ΔS
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What does it mean for chemical reactions if G is positive (greater than zero)? If G is negative
(less than zero)?
Positive = nonspontaneous
Negative = spontaneous
What is the relationship between G and stability? In other words, are systems (or molecules)
more or less stable when G is high? When G is low? See Figure 8.5 for examples of how free
energy influences stability.
Free energy can be a measure of a system’s instability – its tendency to change to a more
stable state. Higher G means an unstable system and they tend to change in a way to become
more stable.
Describe what it means for a chemical reaction to be at equilibrium.
Maximum stability. Reverse and forward reactions are occurring at the same rate. No net
change in relative concentration of products and reactants. No work is done. A process is
spontaneous and can perform work only when it is moving toward equilibrium.
If you want a review of chemical reactions, go back to pages 40 – 41 (concept 2.4)
What is the difference between an exergonic reaction and an endergonic reaction? Do these
reactions require or release energy? Are these reactions spontaneous or non-spontaneous? Is
G positive or negative for each reaction? Examine Figure 8.6 for a graphical interpretation of
these types of reactions.
An exergonic reaction proceeds with a net release of free energy; spontaneous; chemical
mixture loses free energy; G decreases; G is negative. The magnitude of G represents the
maximum amount of work the reaction can perform.
**the breaking of bonds does not release energy – it needs energy
An endergonic reaction absorbs free energy from its surroundings; G increases, G is positive,
nonspontaneous; magnitude of G is the quantity of energy required to drive the reaction.
If the conversion of water and carbon dioxide to glucose is an endergonic reaction, how do
plants power photosynthesis?
Plants get the required energy from the environment – sunlight! The light energy is converted to
chemical energy.
What happens when G = 0?
Equilibrium
Are living cells in equilibrium? What would happen if a cell was in equilibrium?
No, there is a constant flow of materials in and out of the cell and that keeps the metabolic
pathways from ever reaching equilibrium so the cell is able to do work throughout its whole life.
Answer concept check 8.2 question 3 on page 148 in the space below.
Exergonic because the light that is given off is light energy.
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BIO SCI 93 Full Course Notes
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Document Summary
Each step of the pathway is catalyzed by a specific enzyme. Major pathway is cellular respiration, where glucose is broken down with oxygen into. Complete this reading guide as you read the textbook pages listed above. You might not have to read every word on every page, rather pay close attention to the questions in this guide and answer them as you work through the textbook. Also pay close attention to the terms that are underlined: these are key terms that you should know the definitions of and be able to apply in new situations. Metabolism: the totality of an organism"s chemical reactions; emergent property of life that arises from orderly interactions between molecules. Metabolic pathways: begins with a specific molecule, which is then altered in a series of defined steps which result in a certain product. Catabolic pathways aka breakdown pathways release energy by breaking down complex molecules to simper compounds.
