Energy and the Cell

What do you know…

• About energy?

• Is it matter?

• What kinds are there?

• Can it be transformed to other forms?

What is energy?

• “Capacity to do work”

• Do living organisms need energy?

• YES!!!!!!!!!

Contrast

Explain potential and kinetic energy of the roller coaster

Two Types of Energy

• Kinetic

• Actually doing work (moving)

• Potential

• Stored energy

• Due to location or arrange-

• ment (of atoms)

0-C-0

Examples

• Kinetic• Pedaling a bike

• Heat = moves molecules

• electron jumps

• (go to Bohr’s quantum behavior of an atom)

ICE

STEAM

Potential Energy

• Potential• Water behind a dam

• Electron’s position in an atom

Name the type:

What’s the most important type to living organisms?

•Chemical• The energy in food molecules can

be stored in the bonds

Explain the energy transfers:

When you break bonds…

• You release the energy that held the bonds together

• This energy can do work in the body.

Thermodynamics

• laws governing energy transfer

First Law of thermodynamics

• in closed system, energy can neither be created nor destroyed, only changed in form.

First Law of Thermodynamics Examples

• Light energy to chemical energy (from sun to sugar in a plant)

• Water behind a dam (potential) is released (kinetic)

How does this explain energy transfers?

What energy transfers are occurring?

Second Law of Thermodynamics

• energy transformations inevitably involve increased disorder or entropy.

• NOTE: it is the environment that is increasing disorder, not the cell

Entropy…what is that?

• Living things use this energy to create order (reduce entropy) locally, but the overall entropy of the solar system invariably increases.

In other words…

• If a particular system becomes more ordered, its surrounding become more disordered

• A cell makes organelles to increase order, but its surroundings become less orderly

Second Law

• energy of all kinds in our material

world disperses or

dissipates if it is not hindered from doing so

Must be spontaneous

• All spontaneous happenings in the material world are examples of the second law because they involve energy dispersing.

Could you explain that in other words?

• heat flows from hot (more energy) to cold (less energy)

• diffusion leads to substances becoming uniformly dispersed

• You could think of cells as

• “Islands of Low Entropy”

Is the transformation perfect?

• A cell cannot transfer or transform energy with 100% efficiency.

• Where does the lost energy go?

• Mostly lost as heat.

NOT Just organizing your desk

Do Worksheet

• Hot pans of water

• Water on Niagara

• Air in tires that got a puncture

• Speeding car hits a brick wall

• Spark in contact with gasoline

• Sun’s energy hits the ocean

• Huge earthquake under the ocean

Exergonic Reaction

• Releases Energy

• Begins with reactants whose covalent bonds contain more energy than its products

Exergonic: Releasing Energy

• Burning

• One big step

• Breaking bonds

• Many smaller steps

Exergonic Example

• Glucose (reactant) breaks down into carbon dioxide and water (products)

• C6H12O6 CO2 + H2O

“Cellular Respiration”

• Breaking glucose molecules to release energy and store it in a form the cell can use (ATP molecules)

• “slow burn”

Endergonic Reaction

• The products have more energy than the reactants

• Requires an input of energy

• Usually in the form of ATP

Endergonic Reaction

• Carbon dioxide and water combine to form glucose

CO2 + H2O C6H12O6

“Cellular Metabolism”

• Sum of exergonic and endergonic reactions of cells

• CO2 + H2O C6H12O6

• Less energy more energy molecules molecules

ATP

• No…not the new rock band from Japan

• Well, what is it?

ATP

• Adenosine Triphosphate

• “cell’s batteries”

• “energy currency”

ATP

How are they different?

• Adenosine triphosphate

• Adenosine diphosphate

Third Phosphate

• Acts as an energy shuttle

Making ADP + Pi

• ATP is energy rich and breaks down into ADP and Pi (inorganic phosphate) + energy

• is exergonic

Making ATP

• energy + ADP + Pi -> ATP is endergonic

• requiring the input of energy.

Which has more energy?

• ATP or ADP?

• Answer: ATP

Phosphorylation

• Adding of a phosphate group to a molecule

Energy Coupling

• Energy released from exergonic reactions drive endergonic reactions

ADP + Pi <=> ATP+

REACTIONS

• The end products of a reaction may have more (endergonic) or less (exergonic) energy than the substrate molecules.

REACTIONS

• Most reactions are reversible, occur in both directions -

• reactants -> end products

• AND end products -> reactants.

REACTIONS

• Reversible reactions move

toward an equilibrium, a state in which the reaction

occurs at about the same rate in both directions.

So...

•ATP is like money in a checking account

P P P

Adenosine triphosphate (ATP)Adenosine triphosphate (ATP)

P P P++

Adenosine diphosphate (ADP)Adenosine diphosphate (ADP)

Hydrolysis of ATP•ATP + H2O ADP + P (exergonic)

HydrolysisHydrolysis(add water)(add water)

P P P

Adenosine triphosphate (ATP)Adenosine triphosphate (ATP)

P P P++

Adenosine diphosphate (ADP)Adenosine diphosphate (ADP)

Dehydration of ATP•ADP + P ATP + H2O (endergonic)

Dehydration synthesisDehydration synthesis (remove water)(remove water)

ATP

• Breaks down readily

• Would break down spontaneously except for the energy barrier

If entropy is spontaneous…• Why aren’t we all just

spontaneously combusting?

Energy of Activation EA

• The amount of energy that reactants must absorb to start a chemical reaction

But what if…

• The barrier is too great and the reaction cannot go…

• Use ENZYMES

Enzymes

• “Biological Catalysts”• (speed up a reaction without being changed themselves)

Enzymes

• Usually end in –ase

• Usually named for what they work on

• EXAMPLE: Lipase works on Lipids

How do enzymes work?

•Each enzyme has a specific shape, which will determine which reactants it will work on

• Active Site- small area where enzyme and substrate work

•Substrate=A substance that the enzyme acts on

Induced Fit

• Slight change in the shape of the active site of an enzyme as it embraces its substrate (like grasping hands)

• Enzyme animation

Is an enzyme…

• Able to be used over and over?

• YES!!!!!!!!!

Most enzymes…

• Work best at what temperature?

• 35-40oC

• What happens at high temperatures?

• Denatures them (unravels)

• Why is salty bad?

• Salt ions interfere with chemical bonds

Most enzymes…

• What is the optimal pH?

• 6-8

• What does too low (too acidic) of pH do to enzymes?

• Extra H+ ions interfere with chemical bonds

Cofactores

• Nonprotein helpers

• EXAMPLES:

• Zn, Fe, Cu (inorganic ones)

• Vitamins like B6 (organic ones)=also called coenzymes

Enzyme Inhibition

• Competetive inhibitor• Resembles the enzyme and competes for

the active site

• Noncompetetive inhibitor• Does not enter the activ site• Binds somewhere outside the active site• Inhibitor animations

Negative Feedback

• When a cell’s supply exceeds the demand

• Negative Feedback animation