Ch. 8 – Metabolism
Metabolism is the totality of an organism’s
chemical reactions
Slide 4
An Introduction to Metabolism
I. Thermodynamics: The study of energy exchanges (transformations)
A. First Law of Thermodynamics: Energy can not be created or destroyed.
Energy is constant but can be transformed from one form to another
B. Second Law of Thermodynamics: Any transfer of energy results in a
loss of useable energy (heat/entropy/increasing disorder)
Potential Energy
Entropy
“Energy always flows downhill”
Kinetic Energy
Energy Exchanges can be expressed by the equation:
G =
(Delta)
H - T
Slide 1
S
= (Final State) - (Initial State)
G = Free Energy Exchange/capacity to do work
H = Amount of total energy available in the system
T = Temperature
S = Amount of Entropy (disorder / stability)
Initial State:
1.
More Free Energy in System (H)
2.
Less stable / Lower Entropy (S)
3.
Greater Work Capacity (G)
Gravitational
Motion
Diffusion
Molecular Motion
Chemical
Reactions
+
G
-
G
-
S
Spontaneous Change
1.
Free Energy Decreases
2.
Increasing stability
3.
Free energy released to do work
Final State:
1.
Less Free Energy in System (H)
2.
More Stable / Higher Entropy (S)
3.
Less Work Capacity (G)
+ S
Bioenergetics: Energy Exchanges in Living Organisms
1. Energy Exchanges always involve interactions of Electrons
2. Energy is used/released as electrons rearrange in “new” shells
AB + CD
Metabolism Vocab
Endergonic
Exergonic
AC + BD
Spontaneous
AC + BD
AB + CD
Non-spontaneous
AB + CD
AB + CD
Energy
Output
AC + BD
Energy
Input
AC + BD
+
G
-
G
Increasing
Entropy
Decreasing
Entropy
Anabolic
1.
Exergonic
1. Endergonic
2.
Spontaneous
2. Non-Spontaneous
3.
-
3. +
4.
Increasing Entropy
4. Decreasing Entropy
5.
Catabolic
5. Anabolic
6.
Energy Released
6. Energy Required
Cell Respiration
7.
Cell Respiration
7. Photosynthesis
Photosynthesis
G
G
Catabolic
Energy Released
Energy Required
Energy Coupling - The Link between Anabolism and Catabolism; using an
exergonic process to drive an endergonic process
1. ATP is the “energy coupler”
2. The structure of ATP allows the transfer of a phosphate
that will increase the energy level of molecules through
the process of phosphorylation.
P
ADP
ATP
P - AC + BD
AB + CD
AC + BD
Energy
Required
AB + CD
Energy
Required
Place the words below on the appropriate side of the ATP   ADP cycle
Phosphate Added
Exergonic
Synthesis work
Phosphate removed
Transport work
Anabolic
+
-
G
Hydrolysis
Kinetic Energy
Energy Poor
Endergonic
Chemical work
Catabolic
G
Dehydration Synthesis
Increasing Entropy
Decreasing Entropy
Potential Energy
Energy Rich
ADP Phosphorylated Other molecule phosphorylated
ATP
Phosphate Added
Potential Energy
Phosphate Removed
Kinetic Energy
Endergonic
Anabolic
Exergonic
Energy Rich
Energy Poor
Catabolic
ENERGY
ENERGY
Other Molecules Phosphorylated
+
G
ADP Phosphorylated
Transport Work
-
Dehydration synthesis
G
ADP
Decreasing Entropy
Hydrolysis
Chemical Work
Synthesis Work
Increasing Entropy
Examples of how ATP drives
Transport and Mechanical Work
ATP
ADP
Motor protein
Slide 7
Enzymes: Proteins that make life possible
1. All chemical reactions need an energy push to start the reaction
2. Enzymes unique structure lowers the energy of activation
Energy required
without enzyme
AB + CD
Energy required
with enzyme
Total energy
given off by
reaction
AC + BD
Important Enzyme Concepts
Substrate: The substance(s)
Sucrase
Substrate
that is acted on by the enzyme
(Sucrose)
Product: The substance(s) that
results from enzyme activity
(Glucose + Fructose)
Active Site: The part of the enzyme that
Sucrose
Enzyme- Substrate
Complex
bonds to the substrate
Lock and Key Substrate and enzyme fit
perfectly together
H2O
Induced Fit
Important Enzyme Concepts
Active
Site
1. Enzymes are not used up in the reaction
2. Enzymes are specific for their substrates
3. Enzymes can be catabolic or anabolic
Glucose
4. Enzymes are proteins. Their active sites
can be denatured and be non-functional. (pH
and temperature)
Products
Fructose
5. As Proteins, enzymes are coded by the
DNA. Gene traits are due to the enzymes an
organism makes
Enzyme Inhibitors
Normal Interaction
Substrate
Active Site
Enzyme
Competitive Inhibition
Inhibitor fits into active site and
“competes” with the real substrate
[influenced by concentration of
substrate]
Inhibitor
Non-Competitive Inhibition
Inhibitor bonds to enzyme away
from the active site; changes
shape of active site (can be part of
feedback inhibition) [not
influenced by concentration of
substrate]
Inhibitor
(Negative) Feedback Inhibition:
End product switches off its own production
Initial Substrate
Active site no longer
bonds to threonine
Isoleucine fits
in allosteric
site or noncompetitive
site
(threonine)
Intermediate A
Enzyme 2
Intermediate B
Enzyme 3
Intermediate C
Enzyme 4
Intermediate D
Enzyme 5
End Product
Feedback Inhibition
(isoleucine)
*Many normal enzymes need non-protein
‘helpers’ to become active and function
Cofactors – Bind to place other than active
site; inorganic like zinc, iron,
copper
Coenzymes – Cofactors that are organic;
vitamins like C, D, E
Allosteric Enzymes:
Contain allosteric sites that affect enzyme activity. Molecules bonding to
the allosteric sites can activate or inhibit. Many allosteric enzymes are
involved in negative feedback pathways
Activator
Inhibitor
Active sites
Active Form
Inactive Form
Cooperativity:
As a substrate binds to an enzyme, the enzyme changes shape (induced fit)
allowing other active sites to bind to the substrate
Substrate
Active site with
greatest affinity
to substrate
New active sites are
made available
Inactive form
Active form
How Phosphorylation Transfers Energy
Slide 5
The Structure and Function of ATP
Structure
Function
Slide 5
1st Law of Thermodynamics
100 Energy Units
Transformation #2
Transformation #1
Transformations
aaa
100 Energy
Units
Slide 1
2nd Law of Thermodynamics
50 units 25 units
100 units
50 units
25 units
Slide 1
A spontaneous chemical reaction will
occur…but how long will it take?
Sucrose
(C12H22O11)
Slide 9
Space-filling model of Active Site
Slide 10
Environmental factors affecting enzyme activity
Slide 10