chapter # 3 energy and the...

Copyright © 2005 Pearson Prentice Hall, Inc.

Chapter # 3

Energy and the Ecosystem • Energy Types

• Laws of thermodynamics

• Energetics of chemical reactions

• Basic chemical reactions of life

- Aerobic respiration

- Photosynthesis

• ATP / ADP cycling

• Food chains and webs

• Enzymes and activation energy

• Digestion

http://www.svh.richland2.org/~bcheatha/bad_hair_day.jpg


Kinetic Energy


Potential energy


Chemical Potential Energy

Glucose

http://www.youtube.com/watch?v=gL1xUWgBlFw


CHO


The First Law of

Thermodynamics

E=MC2

Energy cannot be

created nor destroyed

gas

100 units

Chemical

Potential

Energy

(Low entropy)

75 units heat

energy 25 units kinetic energy

(motion)

+

The Second Law of

Thermodynamics

In


“Lost” Energy

• This “lost” energy is

• Heat is

• Increase in disorganization is called

E


How does life fight entropy?

Constant input of

energy


Exergonic Reactions

• Reactions which

Explosion

http://www.youtube.com/watch?v=gL1xUWgBlFw

E

reactants

products

Exergonic

Reaction

C O

O O

O O

H H oxygen

Burning

energy released

glucose

6

6 6

water carbon dioxide

A


Exergonic Reactions Examples

• Breaking

• Burning

• Forming

• Nuclear

Energy


Endergonic Reactions

• Chemical reactions which require

energy to complete

Endergonic Reactions

reactants

products

energy used

O H H

O

C O O

O 6

6 6

carbon dioxide

water

P

glucose oxygen

energy


www.teara.govt.nz/.../Standard/4/en

Chemosynthesis

Energy

http://www.teara.govt.nz/.../Standard/4/en


Endergonic Reactions Examples

• P

• C

• Building fructose

• H

Energy

O


How Does Energy Flow in

Chemical Reactions?

• Many chemical reactions work together

to perform cellular actions.

• Exergonic reactions.

• Endergonic (cellular work) reactions to

complete their function.

• Cells must have easily transformed

energy carrying molecules to complete

cellular work.


Exergonic Reaction

ATP ADP P Energy


Endergonic Reaction

Energy


Coupled Reactions

Exergonic and Endergonic

ATP ADP P Heat

Entropy

+ + 100 units

energy released

+

+

+ + 80 units energy

released as heat

20 units

energy

+

relaxed

muscle

relaxed

muscle

P ADP ATP

ADP P ATP

Exergonic reaction:

Endergonic reaction:

Coupled reaction:

contracted

muslce

contracted

muslce

Coupled Reactions Endergonic and Exergonic


Energy Carrier Molecules of The

Cell

• AMP / ADP / ATP

Hold

• NADH / FADH2 / NADPH

Hold

C

Energy

content

Shorthand

representations or

low

"high-energy”

bond

adenine

phosphate groups

ribose

Adenosine diphosphate (ADP)

CH2

H

N CH

N

C HC

N

NH2

OH OH

H

O

C N

H H

O P P O–

O–

O O

O–

O

A P P ADP

ATP synthesis: Energy is stored in ATP

energy

ADP

A P P

phosphate

P ATP

A P P P

O

ATP or

high

"high-energy”

bonds

Adenosine triphosphate (ATP)

CH2

H

N CH

N

C HC

N

NH2

OH OH

H

O

N

H H

O P

O

O

O–

P

C C

O– O–

O–

O O

P

P P P A

phosphate groups

phosphate

ATP breakdown: Energy of ATP is released

A

ADP

energy

A P P P

P P P

ATP


High Energy Molecules Can Be

Used To Couple Reactions

ATP ADP P Heat

Entropy

NAD+

e_

e_

H

NADH

Electron carrier molecules transport energy

net exergonic

"downhill" reaction

(energized

carrier)

(depleted

carrier) endergonic

reaction

exergonic

reaction

CO2 + H2O + heat

glucose

Coupled reaction: glucose breakdown and protein synthesis

ADP heat

protein

A

A

endergonic

(ATP synthesis)

endergonic

(protein synthesis)

exergonic

(glucose

breakdown)

exergonic

(ATP breakdown)

P P P

P P P

net exergonic

"downhill" reaction

amino

acids


Both Exergonic and Endergonic

Reactions Require

Burning glucose (sugar): an exergonic reaction

high

low

Photosynthesis: an endergonic reaction

high

low

energy

content

of

molecules

progress of reaction progress of reaction

energy

content

of

molecules

activation energy needed

to ignite glucose

energy released

by burning glucose

glucose + O2

CO2 + H2O

glucose activation

energy from

light captured

by photosynthesis

CO2 + H2O

net energy

captured by

synthesizing

glucose

Exergonic Reaction Endergonic Reaction

Burning glucose an Exergonic reaction

high

low

progress of reaction

energy

content

of

molecules

activation energy needed

to ignite glucose

energy released

by burning glucose

glucose + O2

CO2 + H2O

Photosynthesis an Endergonic reaction

high

low

energy

content

of

molecules


glucose activation

energy from

light captured

by photosynthesis

CO2 + H2O

net energy

captured by

synthesizing

glucose


Enzymes

• Enzymes are

• Enzymes

• Enzymes

• Enzymes

• Enzymes

• Enzymes

low

high

energy content

of molecules


reactants

products

activation energy

without

enzymes

activation energy

with enzyme

Enzymes speed reactions by lowering

activation energy

Lock and Key Hypothesis

1) Enzyme fits active site 2) Substrate is stressed 3) Chemical reaction occurs

Activation energy lowered as bond

is stressed speeding the reaction

•

• Sucrose H2O Glucose Fructose

•

•

• Sucrase

substrates

active site

of enzyme

enzyme

Induced Fit

Hypothesis

1) Substrate enters

active site

2) Active site changes

shape

3) Substrate goes

through chemical

reaction

4) Product is released from

enzyme and enzyme returns

to original shape

substrates

enzyme

active site of enzyme

Enzymes work

best in specific

environments

pH

pH

pH

Pepsin

Lipase


How Do Cells Control Their

Metabolic Reactions?

• Enzymes

• Enzymes

PATHWAY 1

Initial reactant Intermediates Final products

enzyme 1 enzyme 2 enzyme 3 enzyme 4

PATHWAY 2

enzyme 5 enzyme 6

A B D E

F

C

G

Multiple enzymes forming product

E or G

Regulating Enzyme

Action

active site

substrate

enzyme

allosteric

regulatory site


Allosteric

Inhibition

and

Activation


allosteric regulator molecule

Allosteric Enzyme

Regulation

A change in shape of the

active site due to inhibitor

shuts off or on enzyme

Competitive Inhibition

enzyme 1 enzyme 2 enzyme 3 enzyme 4 enzyme 5

isoleucine

(end-product amino acid) threonine

(substrate amino acid)

A B C D

Feedback inhibition:

Isoleucine inhibits enzyme 1

OH

C

CH3

H

COOH

NH3

C

H

CH3

H C

CH2

CH3

C

COOH

NH3 H

Inhibition can be used to slow

pathways


Enzymes Aid in Digestion

chapter # 3 energy and the...

Documents