Transcript Chemical reactions either release or store energy

ENERGY AND THE CELL
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Cells transform energy as they perform work
• Cells are miniature chemical factories, housing
thousands of chemical reactions.
• Some of these chemical reactions release energy,
and others require energy.
• Energy changes forms
• By definition, “Living Systems” can take in energy
and use it.
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Cool “Fires” Attract Mates and Meals
• Fireflies (family Lampyridae) use light to send
signals to potential mates instead of using
chemical signals like most other insects
The light comes from a
set of chemical
reactions that occur
in light producing
organs in its
abdomen
Females of some species produce a light pattern that
attracts males of other species, which are then eaten by
the female – Yummy!
Examples of energy
conversions:
- Chemical bonds to light
- Chemical bonds to new
chemical bonds and
movement
ENERGY AND THE CELL
Energy is the capacity to perform work
Work = defined as the capacity to cause change
• All organisms require energy to change
• “Maintain homeostasis” and stay “alive”
• Change = “work”
There two basic types
of energy forms:
Gravity can move this biker
down the mountain,
However –
How’d he get up there?
You know there is
“stored energy” in this
system, it’s just that –
You don’t know how much.
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• Kinetic energy is the energy of motion
• Potential energy is stored energy
- can be converted to kinetic energy & vice versa
Figure 5.1A–C
Cells transform energy as they perform work
Energy is the capacity to cause change or to
perform work.
There are two basic forms of energy.
1. Kinetic energy is the energy of motion.
2. Potential energy is energy that matter
possesses as a result of its location or
structure.
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Cells transform energy as they perform work
• hermal energy is a type of kinetic energy
associated with the random movement of atoms or
molecules.
• Thermal energy in transfer from one object to
another is called heat.
• Light is also a type of kinetic energy; it can be
harnessed to power photosynthesis.
Cells transform energy as they perform work
Chemical energy is the
• potential energy available for release in a chemical
reaction and
• the most important type of energy for living
organisms to power the work of the cell.
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Cells transform energy as they perform work
Thermodynamics is the study of energy
transformations that occur in a collection of matter.
• The word system is used for the matter under study.
• The word surroundings is used for everything
outside the system; the rest of the universe.
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Two laws govern energy transformations
• Thermodynamics
• Is the study of energy transformations
1st Law of Thermodynamics, and –
2nd Law of Thermodynamics
The First Law of Thermodynamics
Energy cannot be created or destroyed
The total amount of energy in the universe is constant,
However –
Energy can be changed from one form to another
So, it might look like it’s being made or destroyed, but it’s
just changing forms -
What are all the different forms of energy you see
in this room?
Which ones are stored energy or kinetic energy?
What are all the different forms of energy you see
in this room?
Second Law =
Energy transformations do not convert 100% of one
type of energy into only one other type Most of the energy is converted to other types we
cannot measure – that is, entropy
The Second Law of Thermodynamics
States that energy transformations increase disorder or
“entropy”
Some energy lost as heat that organism uses anyway
Living systems have adapted to transfer energy efficiently
Heat
Chemical reactions
+
Glucose
+
Carbon dioxide
ATP
ATP
water
Oxygen
Figure 5.2B
Energy for cellular work
Energy conversion
Fuel
Waste products
Heat
energy
Carbon dioxide
Gasoline
+
Combustion
Kinetic energy
of movement
+
Water
Oxygen
Energy conversion in a car
Heat
energy
Glucose
+
Oxygen
Cellular respiration
Carbon dioxide
ATP
ATP
Energy for cellular work
Energy conversion in a cell
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+
Water
Cells transform energy as they perform work
• Automobile engines and cells use the same basic
process to make the chemical energy of their fuel
available for work.
• In the car and cells, the waste products are carbon
dioxide and water.
• Cells use oxygen in reactions that release energy
from fuel molecules.
• In cellular respiration, the chemical energy stored
in organic molecules is used to produce ATP,
which the cell can use to perform work.
Discussion &/or Homework Assignment:
What is a “perpetual motion machine?”
The second law says that such a thing
cannot exist . . .
Cells transform energy as they perform work
Two laws govern energy transformations in
organisms.
• Per the first law of thermodynamics (also known
as the law of energy conservation), energy in the
universe is constant.
• Per the second law of thermodynamics, energy
conversions increase the disorder of the universe.
Entropy is the measure of disorder or randomness.
Chemical reactions either release or store
energy
Chemical reactions either
• release energy (exergonic reactions) or
• require an input of energy and store energy
(endergonic reactions).
Chemical reactions either release or store
energy
Exergonic reactions release energy.
• These reactions release the energy in covalent
bonds of the reactants.
• Burning wood releases the energy in glucose as
heat and light.
• Cellular respiration
• involves many steps,
• releases energy slowly, and
• uses some of the released energy to produce ATP.
Potential energy
Reactants
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Amount of
energy released
Energy
Products
Chemical reactions either release or store
energy
An endergonic reaction
• requires an input of energy and
• yields products rich in potential energy.
Endergonic reactions
• start with reactant molecules that contain relatively
little potential energy but
• end with products that contain more chemical
energy.
Potential energy
Products
Energy
Reactants
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Amount of
energy required
Chemical reactions either release or store
energy
Photosynthesis is a type of endergonic process.
In photosynthesis,
• energy-poor reactants (carbon dioxide and water)
are used,
• energy is absorbed from sunlight, and
• energy-rich sugar molecules are produced.
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Chemical reactions either release or store
energy
A living organism carries out thousands of
endergonic and exergonic chemical reactions.
• The total of an organism’s chemical reactions is
called metabolism.
A metabolic pathway is a series of chemical
reactions that either
• builds a complex molecule or
• breaks down a complex molecule into simpler
compounds.
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Chemical reactions either store or release energy
• Endergonic reactions absorb energy and yield
products rich in potential energy
• Anabolic reactions (anabolism)
Potential energy of molecules
Products
Energy required
Reactants
Amount of
energy
required
Exergonic reactions = release energy and yield
products that contain less potential energy than their
reactants = Catabolic reactions, catabolism
Potential energy of molecules
Reactants
Amount of
energy
released
Energy released
Products
Chemical reactions either release or store
energy
Energy coupling uses the energy released from
exergonic reactions to drive endergonic reactions,
typically using the energy stored in ATP molecules.
• Metabolism = The sum of all the chemical reactions
in an organism. {Cells carry out thousands of
chemical reactions}
• Energy coupling = shuttle energy from
exergonic reactions to fuel endergonic reactions
ATP couples chemical energy and drives cellular
work = Energy Exchange Molecule
• ATP powers nearly all forms of cellular work
ATP drives cellular work by coupling
exergonic and endergonic reactions
• ATP, adenosine triphosphate, powers nearly all
forms of cellular work.
• ATP consists of
• adenosine and
• a triphosphate tail of three phosphate groups.
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Triphosphate
Adenosine
P
P
P
ATP
Diphosphate
H 2O
Adenosine
ADP
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P
P
P
Phosphate
Energy
The energy in an ATP molecule is carried in the bonds
between its phosphate groups
Adenosine
Adenosine diphosphate
Triphosphate
Phosphate
groups
P
Adenine
P
P
H2O
P
Hydrolysis
Ribose
ATP
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ADP
P +
P +
Energy
– Cellular work can be sustained, because ATP is a
renewable resource that cells regenerate
– ATP Cycle:
ATP
Energy from
exergonic
reactions
Energy for
endergonic
reactions
ADP +
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P
ATP drives cellular work by coupling
exergonic and endergonic reactions
• A cell uses and regenerates ATP continuously.
• In the ATP cycle, energy released in an exergonic
reaction, such as the breakdown of glucose during
cellular respiration, is used in an endergonic
reaction to generate ATP from ADP.
ATP synthesis
is endergonic
Energy from
cellular respiration
(exergonic)
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ATP
ADP + P
ATP hydrolysis
is exergonic
Energy for
cellular work
(endergonic)
ATP drives cellular work by coupling
exergonic and endergonic reactions
There are three main types of cellular work:
1. chemical,
2. mechanical, and
3. transport.
• ATP drives all three of these types of work.
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ATP drives cellular work by coupling
exergonic and endergonic reactions
• Hydrolysis of ATP releases energy by transferring
its third phosphate from ATP to some other
molecule in a process called phosphorylation.
• Most cellular work depends on ATP energizing
molecules by phosphorylating them.
• ATP drives endergonic reactions by phosphorylation
• Transferring a phosphate group onto a molecule to
make it more reactive
Chemical work
P
ATP
P
ADP + P
Reactants
Product formed
Transport work
ATP
ADP + P
P
P
Transport protein
Solute transported
Mechanical work
ATP
P
Motor protein
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P
Protein filament moved
ADP + P
Metabolism =
all the chemical reactions in an organism
Cells need a mechanism for linking chemical reactions, by
1. Coupling energy between endergonic & exergonic
reactions.
= ATP Cycle couples anabolism to catabolism
2. Reactions need to occur fast enough to pass their
products onto the next reaction.
So – Run reactions in a series, one after another,
in Metabolic pathways
- using protein catalysts called ENZYMES: