Energy and Metabolism

Muhammad Fahad Ansari 12IEEM14

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

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

Startingmolecule

Product

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.

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

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.

Forms of Energy• Kinetic energy is the 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

On the platform, a diverhas more potential energy.

Diving converts potentialenergy to kinetic energy.

Climbing up converts kinetic

energy of muscle movement

to potential energy.

In the water, a diver has less potential energy.

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:

The First Law of Thermodynamics• According to the first law of thermodynamics

– Energy cannot be created or destroyed– Energy can be transferred and transformed

For example, the chemical (potential) energy in food will be converted to the kinetic energy of the cheetah’s movement

Chemicalenergy

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

– During each conversion, some of the energy dissipates into the 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

Second Law of Thermodynamics

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.

Heat co2

H2O+

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

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

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

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

Products

Energy

Progress of the reaction

Amount ofenergyreleased (∆G <0)

Fre

e e

ne

rgy

(a) Exergonic reaction: energy released

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

Energy

Products

Amount ofenergyreleased (∆G>0)

Reactants

Progress of the reaction

Fre

e e

ne

rgy

(b) Endergonic reaction: energy required

Reactant Reactant

Product

Product

ExergonicEndergonic

Energy isreleased.

Energymust besupplied.

En

erg

y s

up

plie

dE

ner

gy

re

lea

sed

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Understanding Heat Transfer, Conduction, Convection and Radiation

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.

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.

Heat Transfer Methods

• Heat transfers in three ways:–Conduction–Convection–Radiation

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

Metals are different

The outer e______ of metal atoms drift, and are free to move.

When the metal is heated, this ‘sea of electrons’ gain k_____ energy and transfer it throughout the metal.

Insulators, such as w___ and p____, do not have this ‘sea of electrons’ which is why they do not conduct heat as well as metals.

lectrons

inetic

ood lastic

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.

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 fluid movement.What is a fluid?A liquid or gas.

Fluid movement

Cooler, more d____, fluids sink through w_____, less dense fluids.

In effect, warmer liquids and gases r___ up.

Cooler liquids and gases s___.

ensearmer

ise

ink

Water movement

Hot water rises

Cooler water sinks

Convection current

Cools at the surface

Why is it windy at the seaside?

Cold air sinks

Where is the freezer

compartment put in a fridge?

Freezer compartment

It is put at the top, because cool air sinks, so it cools the food on the

way down.

It is warmer at the bottom, so this warmer air

rises and a convection

current is set up.

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

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

Emission experiment

Four containers were filled with warm water. Which container would have the warmest water after ten minutes?

Shiny metal

Dull metal

Dull black

Shiny black

The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost. The ________ container would be the coolest because it is the best at _______ heat radiation.

shiny metal

radiation

dull black

emitting

Absorption experiment

Four containers were placed equidistant from a heater. Which container would have the warmest water after ten minutes?

The __________ container would be the warmest after ten minutes because its surface absorbs heat _______ the best. The _________ container would be the coolest because it is the poorest at __________ heat radiation.

dull black

radiation

shiny metal

absorbing

Shiny metal

Dull metal

Dull black

Shiny black

Convection questions

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.

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.

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.

1. Which of the following is not a method of heat transfer?

A. Radiation

B. Insulation

C. Conduction

D. Convection

2. In which of the following are the particles closest together?

A. Solid

B. Liquid

C. Gas

D. Fluid

3. How does heat energy reach the Earth from the Sun?

A. Radiation

B. Conduction

C. Convection

D. Insulation

4. Which is the best surface for reflecting heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black

5. Which is the best surface for absorbing heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black