The document provides an overview of key concepts in metabolism. It defines the first and second laws of thermodynamics, and discusses how cells use ATP to do work through energy coupling. Enzymes lower the activation energy of reactions and work with specificity on substrates. Regulation allows cells to control metabolic pathways and switch enzyme activity on and off through mechanisms like feedback inhibition and allosteric regulation.

1. CH. 8 WARM-UP
1.
2.
What are the 1st and 2nd laws of
thermodynamics?
Give the definition and an example of:
A. Catabolic reaction
B. Anabolic reaction

2. CHAPTER 8
An Introduction to
Metabolism

3. WHAT YOU NEED TO KNOW:
 Examples
of endergonic and exergonic reactions.
 The key role of ATP in energy coupling.
 That enzymes work by lowering the energy of
activation.
 The catalytic cycle of an enzyme that results in
the production of a final product.
 The factors that influence enzyme activity.

4. Metabolism is the totality of an organism’s
chemical reactions
Manage the materials and energy resources
of a cell

5. METABOLIC
PATHWAYS
pathways release energy by
breaking down complex molecules into
simpler compounds
Eg. digestive enzymes break down food
 release energy
 Catabolic
pathways consume energy to
build complex molecules from simpler
ones
Eg. amino acids link to form muscle
protein
 Anabolic

6. ENERGY = CAPACITY TO DO
WORK
energy (KE): energy associated
with motion
Heat (thermal energy) is KE associated
with random movement of atoms or
molecules
 Kinetic
energy (PE): stored energy as a
result of its position or structure
 Potential
energy is PE available for release
in a chemical reaction
Chemical
 Energy
can be converted from one form to
another
Eg.
chemical  mechanical  electrical

8. THERMODYNAMICS IS THE STUDY
OF ENERGY TRANSFORMATIONS
THAT OCCUR IN NATURE
A
closed system, such as liquid in a thermos, is
isolated from its surroundings
 In an open system, energy and matter can be
transferred between the system and its
surroundings
 Organisms are open systems

9. THE FIRST LAW OF
THERMODYNAMICS

The energy of the universe is constant
Energy can be transferred and
transformed
Energy cannot be created or destroyed
 Also
called the principle of Conservation
of Energy

10. THE SECOND LAW OF
THERMODYNAMICS

Every energy transfer or transformation
increases the entropy (disorder) of the universe
 During
every energy transfer or transformation,
some energy is unusable, often lost as heat

11. A
cell does three main kinds of work:
Mechanical
Transport
Chemical
 To
do work, cells manage energy resources by
energy coupling, the use of an:
exergonic (energy releasing) process to drive an
endergonic (energy absorbing) one

12. (adenosine triphosphate) is the cell’s
main energy source in energy coupling
 Modified nucleotide
 ATP = adenine + ribose + 3 phosphates
 ATP

13.  When
the bonds between the phosphate groups
are broken by hydrolysis  energy is released
 This release of energy comes from the chemical
change to a state of lower free energy, not in the
energy
phosphate bonds themselves

14. HOW ATP PERFORMS WORK
 Exergonic
release of Pi is used to do the
endergonic work of cell
 When ATP is hydrolyzed, it becomes ADP
(adenosine diphosphate)

15. LE 8-11
Pi
P
Motor protein
Protein moved
Mechanical work: ATP phosphorylates motor proteins
Membrane
protein
ADP
+
Pi
ATP
Pi
P
Solute transported
Solute
Transport work: ATP phosphorylates transport proteins
P
Glu +
NH2
NH3
+
Glu
Pi
Reactants: Glutamic acid Product (glutamine)
and ammonia
made
Chemical work: ATP phosphorylates key reactants

16.  Catalyst:
Catalyst
substance that can change the rate of a
reaction without being altered in the process; not
consumed
 Enzyme = biological catalyst; highly specific;
named for reaction they catalyze
 Speeds up metabolic reactions by lowering the
activation energy (energy needed to start
reaction)

18. SUBSTRATE SPECIFICITY OF
ENZYMES
 The
reactant that an enzyme acts on is called
the enzyme’s substrate
 The enzyme binds to its substrate, forming an
enzyme-substrate complex
 The active site is the region on the enzyme
where the substrate binds

22. INDUCED FIT: ENZYME FITS SNUGLY
AROUND SUBSTRATE, “CLASPING
HANDSHAKE”

23. An enzyme’s
activity can be
affected by:
temperature
pH
Salinity
Enzyme conc
Substrate conc
Activators
Inhibitors

24. ENZYME CONCENTRATION

25. ENZYME/SUBSTRATE
CONCENTRATION
 Enzyme
Concentration
As
↑ enzyme = ↑ reaction rate
Reaction rate levels off when substrate
becomes limiting factor. Not all enzyme
molecules can find substrate.
 Substrate
As
Concentration
↑ substrate = ↑ reaction rate
Reaction rate levels off when all enzyme
have active site engaged. Enzyme is
saturated. Max rate of reaction

26. COFACTORS
 Cofactors
are nonprotein enzyme helpers such as
minerals (eg. Zn, Fe, Cu)
 Coenzymes are organic cofactors (eg. vitamins)
Enzyme Inhibitors
 Competitive inhibitors bind to the active site of
an enzyme, competing with the substrate
 Noncompetitive inhibitors bind to another part of
an enzyme, causing the enzyme to change shape
and making the active site nonfunctional

27. INHIBITION OF ENZYME
ACTIVITY

28. REGULATION OF ENZYME
ACTIVITY
 To
regulate metabolic pathways, the cell
switches on/off the genes that encode specific
enzymes
 Allosteric regulation: protein’s function at
one site is affected by binding of a regulatory
molecule to a separate site (allosteric site)
Activator – stabilizes active site
Inhibitor – stabilizes inactive form
Cooperativity – one substrate triggers
shape change in other active sites 
increase catalytic activity

31. FEEDBACK INHIBITION
 End
product of an metabolic pathway shuts
down pathway by binding to the allosteric site of
an enzyme
 Prevent wasting chemical resources, increase
efficiency of cell

32. FEEDBACK
INHIBITION