Download + Energy

Energy and Metabolism
KEY WORDS:
Energy
Free Energy (ΔG)
Potential energy
Kinetic energy
Enzyme
Substrate
Activation energy
Exergonic reaction
Endergonic reaction
Catalyst
ATP/ ADP
Energy
•The capacity to do work
•Move matter
Types of energy
•Kinetic
•Potential
Question: __________ is an example of kinetic energy,
and __________ is an example of potential energy.
1.
2.
3.
4.
5.
Fire; a piece of wood
A loaded gun; a flying bullet
A rock on top of a hill; a rock rolling down the hill
None of these are correct.
All of these are correct.
Chemical Energy
•Stored in chemical bonds -high energy electrons
•Some molecules
store a lot of energy
Carbos, lipids
•Some molecules
store much less
Carbon dioxide,
water
Chemical Energy
•Energy can be
transferred/transformed
Sugar + oxygen  carbon dioxide + water + heat
C6H12O6 + O2  CO2 + H2O + Energy
First Law of Thermodynamics:
Energy: neither created nor destroyed
• Converted from one form to another
• Exchanged between substances
Second Law of Thermodynamics:
All exchanges of energy increase the entropy of
the universe
Entropy:
•Disorder or randomness of a system
•Heat is most disorganized form of energy
•Reactions that ↑ entropy happen
spontaneously & release energy
Two laws of thermodynamics
Energy Transformed
Exergonic Reactions
•Release energy
•“Spontaneous”
•Usually breakdown of complex molecules
Endergonic Reactions
•Usually involve synthesis
of complex molecules
•Not “Spontaneous”
6CO2 + 6H2O + Energy
•Require energy
C6H12O6 + 6O2
Question: Which of the following reactions
is endergonic?
1.
2.
3.
4.
CO2 and H2O
Glucose
Amino acids
Proteins
Triglycerides
Fatty acids
Ions moving across membrane from an
area of high concentration to an area of
low concentration.
Question:
Which of the following reactions releases energy?
1.
2.
3.
4.
CO2 and H2O
Glucose
Amino acids
Proteins
Triglycerides
Fatty acids
Ions moving across membrane from an area of
high concentration to an area of low
concentration.
Coupled Reactions
Exergonic provides energy for the endergonic
Exergonic
glucose
Energy
CO2 + H2O
Endergonic
Energy
Amino acids
Protein
Living organisms
Metabolism
•All chemical reactions in an organism
Anabolism
Catabolism
Living organisms
•Capture energy to drive chemical reactions.
•Convert “raw” energy into usable form
ATP
•Sunlight, food
Energy
Energy
The structure and hydrolysis of ATP
ATP: the Cell’s Rechargeable Battery
• ATP
energy
ADP
charged battery
dead battery
• This energy can then be used to run an
energy requiring reaction.
The ATP cycle
According to the first law of
thermodynamics, energy
1. is never lost or gained, but is only transformed
2. always requires an ultimate source such as
the sun
3. can never be gained, but can be lost
4. can never really be harnessed
5. can never be transformed
Each time there is a chemical reaction, some
energy is exchanged. According to the
second law of thermodynamics, with each
exchange
1.
2.
3.
4.
5.
Some energy is lost, but other energy is created.
Some energy must come from the sun.
Some energy is transformed into heat.
Energy is gained for future use.
Some energy is permanently and completely
destroyed.
ATP stores energy in the form of
1.
2.
3.
4.
5.
mechanical energy
heat
complex carbohydrates
chemical bond energy
amino acids
The complexity of metabolism
Equation: Gibb’s Free Energy
ΔG = ΔH – TΔS
Energy
available
for work
All
energy
Energy
NOT
available
for work
The relationship of free energy to stability, work capacity, and spontaneous change
Energy changes in exergonic and endergonic reactions
Energy profile of an exergonic reaction
Disequilibrium and work in closed and open systems
Is ΔG for an exergonic reaction positive
or negative?
What is the difference between:
Anabolism
Catabolism
Metabolism
From an energy perspective, when is
equilibrium reached?
Enzymes
KEY WORDS:
Enzyme
Activation energy
Catalyst
Substrate
Active site
Induced fit
Coenzyme
Allosteric site
Competitive inhibitor
Noncompetitive inhibitor
Feedback inhibition
Enzymes and Shape
Active Site
Induced fit: “Handshake” between substrate and enzyme
Activation Energy
Activation
Energy
Net Energy
Released
Enzymes
•Proteins that speed up chemical reactions
(catalysts)
•Lower activation energy for a reaction
Enzyme reactions can be simplified as:
E+S
ES
E +P
• S = Substrates (reactants) enter reaction.
• P = Product (what you get at the end) result
• E = Enzymes mediate specific steps
sucrase
sucrose + H2O
glucose + fructose
The catalytic cycle of an enzyme
Enzymes
Key Points:
•Catalyze reactions
•Don’t change reactions
•Same net release/use of energy
•Enzymes are not changed by reaction
•Each enzyme catalyzes a specific
chemical reaction
Enzymes lower the barrier of activation energy
Which of the following will lower the
activation energy of a reaction in a cell?
1.
2.
3.
4.
5.
lowering the temperature
lowering the pressure
using an enzyme
changing the amount of the reactants
supplying ATP
Which of the following will lower the
activation energy of a reaction in a cell?
1.
2.
3.
4.
5.
lowering the temperature
lowering the pressure
using an enzyme
changing the amount of the reactants
supplying ATP
Enzymes
1. accelerate specific chemical reactions
2. are not chemically altered by binding with a
substrate
3. lower the activation energy of specific chemical
reactions
4. all of the above
5. a and c only
4 Things that Affect Enzyme Activity
1. Substrate concentration
2. Enzyme concentration
3. pH
4. Temperature
Shape of enzyme
(Protein denatured)
Environmental factors affecting enzyme activity
Enzyme Regulation
• Enzymes can be turned on and off
• Regulated by other molecules in the cell
• Examples:
– Allosteric regulation
– Feedback inhibition
– Inhibitors
Inhibition of enzyme activity
Allosteric regulation of enzyme activity
Feedback inhibition
If an enzyme solution is saturated with
substrate, the most effective way to
obtain an even faster yield of products is:
a)
b)
c)
d)
e)
Add more enzyme
Heat the solution
Add more substrate
Add an allosteric inhibitor
Add a noncompetitive inhibitor
An enzyme accelerates a metabolic
reaction by
a) Altering the overall free energy change for the
reaction
b) Making an endergonic reaction occur
spontaneously
c) Lowering the activation energy
d) Pushing the reaction away from equilibrium
e) Making the substrate molecule more stable
Some bacteria are metabolically
active in hot springs because
a) They are able to maintain a cooler internal
temperature
b) High temperature facilitates active
metabolism w/o need of catalysis
c) Enzymes have high optimal temperatures
d) Enzymes are insensitive to temperature
Glycolysis is a metabolic pathway that helps
living things extract energy from food. From
this we know that glycolysis
1.
2.
3.
4.
consists of a series of chemical reactions
uses a number of enzymes
involves the modification of a series of substrates
proceeds by means of each enzyme leaving a
succeeding reaction to a different enzyme
5. all of the above