Muhammad Fahad Ansari 12IEEM14

1. Energy and Metabolism
Muhammad Fahad Ansari 12IEEM14

2. The Energy of Life
• The living cell generates thousands of different
reactions
• Metabolism
– Is the totality of an organism’s chemical reactions
– Arises from interactions between molecules
• An organism’s metabolism transforms matter
and energy, subject to the laws of
thermodynamics

3. •
Metabolic Pathways
Biochemical pathways are the organizational units of metabolism
• Metabolism is the total of all chemical reactions carried out by an organism
• A metabolic pathway has many steps that begin with a specific molecule and
end with a product, each catalyzed by a specific enzyme
• Reactions that join small molecules together to form larger, more complex
molecules are called anabolic.
• Reactions that break large molecules down into smaller subunits are called
catabolic.
Enzyme 1 Enzyme 2 Enzyme 3
A B C D
Reaction 1 Reaction 2 Reaction 3
Starting Product
molecule

4. Metabolic Pathway
• A sequence of chemical reactions, where the product of one
reaction serves as a substrate for the next, is called a metabolic
pathway or biochemical pathway
• Most metabolic pathways take place in specific regions of the
cell.

5. Bioenergetics
• Bioenergetics is the study of how organisms
manage their energy resources via metabolic
pathways
• Catabolic pathways release energy by breaking
down complex molecules into simpler
compounds
• Anabolic pathways consume energy to build
complex molecules from simpler ones

6. Energy
• Energy is the capacity to do work or ability to
cause change. Any change in the universe
requires energy. Energy comes in 2 forms:
– Potential energy is stored energy. No change is
currently taking place
– Kinetic energy is currently causing change. This
always involves some type of motion.

7. Forms of Energy
• Kinetic energy is the energy On the platform, a diver
has more potential energy.
Diving converts potential
energy to kinetic energy.
associated with motion
• Potential energy
– Is stored in the location of
matter
– Includes chemical energy
stored in molecular
structure
• Energy can be converted
from one form to another
Climbing up converts kinetic In the water, a diver has
energy of muscle movement less potential energy.
to potential energy.

8. Laws of Energy Transformation
• Thermodynamics is the study of energy
changes.
• Two fundamental laws govern all energy
changes in the universe. These 2 laws are
simply called the first and second laws of
thermodynamics:

9. The First Law of Thermodynamics
• According to the first law of thermodynamics
– Energy cannot be created or destroyed
– Energy can be transferred and transformed
Chemical
energy
For example, the chemical (potential) energy
in food will be converted to the kinetic
energy of the cheetah’s movement

10. Second Law of Thermodynamics
• The disorder (entropy) in the universe is continuously increasing.
– Energy transformations proceed spontaneously to convert matter from a more
ordered, less stable form, to a less ordered, more stable form
– Spontaneous changes that do not require outside energy increase the entropy, or
disorder, of the universe
– For a process to occur without energy input, it must increase the entropy of the
universe

11. Second Law some of the energy dissipates into the
– During each conversion,
of Thermodynamics
environment as heat.
– During every energy transfer or transformation, some energy is unusable,
often lost as heat
– Heat is defined as the measure of the random motion of molecules
– Living cells unavoidably convert organized forms of energy to heat
– According to the second law of thermodynamics, every energy transfer or
transformation increases the entropy (disorder) of the universe
Heat co2
+
H2O
For example, disorder is added to the cheetah’ssurroundings in the form of heat and
the small molecules that are the by-products of metabolism.

12. Biological Order and Disorder
• Cells create ordered structures from less ordered
materials
• Organisms also replace ordered forms of matter
and energy with less ordered forms
• The evolution of more complex organisms does not
violate the second law of thermodynamics
• Entropy (disorder) may decrease in an organism,
but the universe’s total entropy increases

13. Biological Order and Disorder
• Living systems
– Increase the entropy of the universe
– Use energy to maintain order
– A living system’s free energy is energy that can do
work under cellular conditions
– Organisms live at the expense of free energy
50µm

14. Free Energy
• Free energy is the portion of a system’s energy that is able to
perform work when temperature and pressure is uniform
throughout the system, as in a living cell
• Free energy also refers to the amount of energy actually
available to break and subsequently form other chemical
bonds
• Gibbs’ free energy (G) – in a cell, the amount of energy
contained in a molecule’s chemical bonds (T&P constant)
• Change in free energy - ΔG
– Endergonic - any reaction that requires an input of
energy
– Exergonic - any reaction that releases free energy

15. Exergonic reactions
• Reactants have more free energy than the products
• Involve a net release of energy and/or an increase in entropy
• Occur spontaneously (without a net input of energy)
Reactants
Amount of
energy
released
Free energy
(∆G <0)
Energy
Products
Progress of the reaction
(a) Exergonic reaction: energy released

16. Endergonic Reactions
• Reactants have less free energy than the products
• Involve a net input of energy and/or a decrease in
entropy
• Do not occur spontaneously
Products
Amount of
energy
Free energy
released
(∆G>0)
Energy
Reactants
Progress of the reaction
(b) Endergonic reaction: energy required

17. Energy released Energy supplied
Product
Energy
must be
supplied.
Reactant Reactant Energy is
released.
Product
Endergonic Exergonic
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

18. Understanding Heat Transfer,
Conduction, Convection and
Radiation

19. Heat Transfer
• Heat always moves from a warmer place to a
cooler place.
• Hot objects in a cooler room will cool to room
temperature.
• Cold objects in a warmer room will heat up to
room temperature.

20. Question
• If a cup of coffee and a red popsickle were left
on the table in this room what would happen
to them? Why?
• The cup of coffee will cool until it reaches
room temperature. The popsickle will melt
and then the liquid will warm to room
temperature.

21. Heat Transfer Methods
• Heat transfers in three ways:
–Conduction
–Convection
–Radiation

22. Conduction
When you heat a metal strip at one end, the heat
travels to the other end.
As you heat the metal, the particles vibrate, these
vibrations make the adjacent particles vibrate, and so on
and so on, the vibrations are passed along the metal and
so is the heat. We call this? Conduction

23. Metals are different
The outer e______ of metal atoms
lectrons
drift, and are free to move.
When the metal is heated, this
‘sea of electrons’ gain k_____
energy and transfer it
inetic
throughout the metal.
Insulators, such as w___ and p____, do not have this ‘sea of
ood lastic
electrons’ which is why they do not conduct heat as well as
metals.

24. Why does metal feel colder than wood, if they
are both at the same temperature?
Metal is a conductor, wood is an insulator. Metal
conducts the heat away from your hands. Wood
does not conduct the heat away from your hands as
well as the metal, so the wood feels warmer than
the metal.

25. Convection
What happens to the particles in a liquid or a
gas when you heat them?
The particles spread out and
become less dense.
This effects afluid movement.
What is or gas.
A liquid fluid?

26. Fluid movement
Cooler, more d____, fluids
ense
sink through w_____, less
armer
dense fluids.
In effect, warmer liquids and gases r___
up. ise
Cooler liquids and gases s___. ink

27. Water movement
Cools at the Convection
surface
current
Cooler Hot water
water sinks rises

28. Why is it windy at the seaside?

29. Cold air sinks
Where is the Freezer
freezer compartment
compartment
put in a fridge?
It is warmer at
the bottom, so
this warmer air
It is put at the top,
rises and a
because cool air
convection
sinks, so it cools the
current is set up.
food on the way
down.

30. The third method of heat transfer
How does heat energy get
from the Sun to the Earth? There are no particles between
the Sun and the Earth so it
CANNOT travel by conduction or
by convection.
RADIATION
?

31. Radiation
Radiation travels in straight lines
True/False
Radiation can travel through a vacuum
True/False
Radiation requires particles to travel
True/False
Radiation travels at the speed of light
True/False

32. Emission experiment
Four containers were filled with warm water. Which
container would have the warmest water after ten minutes?
Dull metal Shiny black
Shiny metal Dull black
shiny metal
The __________ container would be the warmest after ten
minutes because its shiny surface reflects heat radiation back
_______
dull black
into the container so less is lost. The ________ container
emitting
would be the coolest because it is the best at _______ heat
radiation.

33. Absorption experiment
Four containers were placed equidistant from a heater. Which
container would have the warmest water after ten minutes?
Dull metal Shiny black
Shiny metal Dull black
dull black
The __________ container would be the warmest after ten
radiation
minutes because its surface absorbs heat _______ the best.
shiny metal
The _________ container would be the coolest because it is
absorbing
the poorest at __________ heat radiation.

34. Convection questions
Why does hot air rise and cold air sink?
Cool air is more dense than warm air, so the cool air ‘falls
through’ the warm air.
Why are boilers placed beneath hot water
tanks in people’s homes?
Hot water rises.
So when the boiler heats the water, and the hot water rises, the water tank
is filled with hot water.

35. Radiation questions
Why are houses painted white in hot countries?
White reflects heat radiation and keeps the house cooler.
Why are shiny foil blankets wrapped around marathon runners at the end of a
race?
The shiny metal reflects the heat radiation from the runner back in, this stops
the runner getting cold.

36. 1. Which of the following is not a
method of heat transfer?
A. Radiation
B. Insulation
C. Conduction
D. Convection

37. 2. In which of the following are
the particles closest together?
A. Solid
B. Liquid
C. Gas
D. Fluid

38. 3. How does heat energy reach
the Earth from the Sun?
A. Radiation
B. Conduction
C. Convection
D. Insulation

39. 4. Which is the best surface for
reflecting heat radiation?
A. Shiny white
B. Dull white
C. Shiny black
D. Dull black

40. 5. Which is the best surface for
absorbing heat radiation?
A. Shiny white
B. Dull white
C. Shiny black
D. Dull black