IB 150 Chapter Notes -Chloroplast, Homeostasis, Glycolysis
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The Energetics of Life 09/16/2014
Week 1 Learning Objectives
1. What does it mean to be alive?
A. List the five characteristics all organisms on Earth share.
- Energy (endergonic reactions required)
- Cells (homeostasis)
- Information (genes for reproduction)
- Replication (goal of replicating oneself)
- Evolution (products of adaptation)
B. Explain why the first four are required for life.
All organisms are made of cells; it’s our basic unit:
Cells display all properties of living organisms (cell theory)
It’s also imperative that we keep our bodies out of chemical equilibrium so that’s where the necessity of
energy (endergonic reactions) come in
C. Understand how the ability to perform work is related to being alive.
It’s necessary for cells to constantly do work in order for it to stay out of chemical equilibrium – once the cell
reaches chemical equilibrium with the outside world, it’s considered dead.
Endergonic reactions are vital to life: maintaining homeostasis
The reason why we need an outside source of energy (from the sun) is because our endergonic reactions
always need an input of energy in order to occur; this is why the sun is so necessary because it’s our only
D. Predict the direction of net flow of water across a cell membrane due to osmosis given information about
solute concentrations on either side of the membrane. Explain what happens to rates of movement of water
molecules in both directions across the membrane at equilibrium.
E. Understand that net flow of molecules due to osmosis is a result of the rates of movement of particles in
both directions, NOT as a result of an inherent preference or force moving these molecules in one direction
or the other.
2. Be able to apply the First and Second Law of Thermodynamics and explain
their relevance to living processes
A. Define the First and Second Law of Thermodynamics.
First Law: conservation of energy; cannot be created or destroyed
Second Law: universe’s tendency to move towards entropy/disorder
In other words, the second law can also state that “no process is ever 100% efficient”
Entropy can be defined as “the spontaneous dispersal of energy”
Really good website: http://entropysite.oxy.edu/students_approach.html
B. Use the First Law of Thermodynamics to explain how chemical reactions transfer energy from one
molecule to another.
Because energy cannot be created or destroyed, it can only be transformed into different types of energy
(kinetic, thermal, gravitational, etc)
C. Understand how molecules store chemical potential energy.
Electrons in atoms store chemical potential energy based on their location in the orbits. The closer it is to
the nucleus, the more stable it is. The further away it is from the center, the more potential it has to be
attracted to center.
Organic molecules store their energy in the C-H bonds of macromolecules
D. Determine whether a change of a system increases or decreases in enthalpy (ΔH) and entropy (ΔS) over
the course of the reaction.
ΔS = Entropy (products) – Entropy (reactants) > 0
ΔH = Potential energy (products) – potential energy (reactants) < 0
E. Use the Second Law of Thermodynamics to predict whether a process is exergonic or endergonic
and thus will proceed spontaneously or not by qualitatively applying the equation ΔG = ΔH – T*ΔS.
S = Entropy
H = Enthalpy
Are reactions spontaneous? Anything that the ΔG releases energy and occurs spontaneously
F. Define exergonic and endergonic chemical reactions.
- Exergonic reactions release Gibbs energy for work to be done – it’s spontaneous and organisms can
couple these reactions with endergonic chemical reactions
- Endergonic reactions require an input – it needs input of work in order to work
**Overall change in G must be NEGATIVE in order for endergonic reactions to proceed
***Decreasing entropy; increasing enthalpy = endergonic
3. How do organisms control exergonic reaction rates?
A. Be able to draw a graph that illustrates activation energy in a graph of the time course of a chemical
B. Explain why raising temperature helps overcome the activation energy of a chemical reaction.
in temperature = in molecule movements; gives electrons a chance to bond/rearrange (enthalpy)
10°C Rule: 10° increase doubles reaction rate
C. Explain how adding catalysts helps overcome the activation energy of a chemical reactions
- Catalysts provide favorable chemical environments for reactions; there are enzymes and active sites
particular to certain molecules
- Activation energy has nothing to do with Gibbs’ free energy!!!
Important concept to remember:
- Enzymes STILL need an input of energy to work!
It does not make it exergonic or endergonic – reactions that involve an enzyme still require an input of
energy (whether it’s from ATP or a temperature raise). Enzymes just DECREASE the activation energy
that’s required to start the reaction
D. Be able to use these terms in context: catalyst, enzyme, active site
E. Understand why the majority of chemical reactions an organism relies on are catalyzed with enzymes.
If our bodies hate to wait for reactions to occur naturally on their own, it would take too long – enzymes help
speed the entire process along to insure reactions work at a reasonable rate
4. Explain how organisms manage to run endergonic reactions without violating
the Second Law of Thermodynamics.
A. Explain why four of life's characteristics are endergonic processes.