Chapter 06 Lecture and Animation Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. See separate PowerPoint.

Chapter 06

Lecture and Animation Outline

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes and

animations.

To run the animations you must be in Slideshow View. Use the buttons on the animation to play, pause, and turn

audio/text on or off.

Please Note: Once you have used any of the animation functions (such as Play or Pause), you must first click on the slide’s background before you can advance to the next slide.

2

Energy and Metabolism

Chapter 6

3

Flow of Energy

• Thermodynamics– Branch of chemistry concerned with energy

changes

• Cells are governed by the laws of physics and chemistry

• Energy – capacity to do work– 2 states

1. Kinetic – energy of motion

2. Potential – stored energy

– Many forms – mechanical, heat, sound, electric current, light, or radioactivity

– Heat the most convenient way of measuring energy

• 1 calorie = heat required to raise 1 gram of water 1ºC

• calorie or Calorie?

4

5

a. Potential energy b. Kinetic energy


• Energy flows into the biological world from the sun

• Photosynthetic organisms capture this energy

• Stored as potential energy in chemical bonds

6

7

Redox reactions

• Oxidation– Atom or molecule loses an electron

• Reduction– Atom or molecule gains an electron– Higher level of energy than oxidized form

• Oxidation-reduction reactions (redox)– Reactions always paired

8


e–

A BA + B +A+ B–

Loss of electron (oxidation)

Gain of electron (reduction)

Lower energy Higher energy

Laws of thermodynamics

• First law of thermodynamics– Energy cannot be created or destroyed– Energy can only change from one form to

another– Total amount of energy in the universe

remains constant– During each conversion, some energy is lost

as heat

9

10

• Second law of thermodynamics– Entropy (disorder) is continuously increasing– Energy transformations proceed

spontaneously to convert matter from a more ordered/less stable form to a less ordered/ more stable form


Disorder happensspontaneously

Organizationrequires energy

© Jill Braaten

12

Free energy

• G = Energy available to do work

• G = H – TS H = enthalpy, energy in a molecule’s chemical

bonds T = absolute temperature S = entropy, unavailable energy

ΔG = ΔH – TS• ΔG = change in free energy• Positive ΔG

– Products have more free energy than reactants– H is higher or S is lower– Not spontaneous, requires input of energy– Endergonic

• Negative ΔG – Products have less free energy than reactants– H is lower or S is higher or both– Spontaneous (may not be instantaneous)– Exergonic

13

14


a.

b.

0

0

Course of Reaction

Products

G > 0

G < 0

Reactants

Reactants

Course of Reaction

Products

Fre

e E

ne

rgy

(G

)E

ne

rgy

Re

lea

se

d E

ne

rgy

Su

pp

lie

dF

ree

En

erg

y (

G)

En

erg

y R

ele

as

ed

En

erg

y S

up

pli

ed

Energy isreleased

Energy mustbe supplied

Exergonic

Endergonic

Activation energy

• Extra energy required to destabilize existing bonds and initiate a chemical reaction

• Exergonic reaction’s rate depends on the activation energy required– Larger activation energy proceeds more slowly

• Rate can be increased 2 ways1. Increasing energy of reacting molecules (heating)

2.Lowering activation energy

15

16


ΔG

En

erg

y R

ele

as

ed E

ner

gy

Su

pp

lied

Fre

e E

ne

rgy

(G

) Activationenergy

Activationenergy0

uncatalyzed

catalyzed

Course of Reaction

Product

Reactant

Catalysts

• Substances that influence chemical bonds in a way that lowers activation energy

• Cannot violate laws of thermodynamics– Cannot make an endergonic reaction

spontaneous

• Do not alter the proportion of reactant turned into product

17

18


ΔG

En

erg

y R

ele

as

ed E

ner

gy

Su

pp

lied

Fre

e E

ne

rgy

(G

) Activationenergy

Activationenergy0

uncatalyzed

catalyzed

Course of Reaction

Product

Reactant

19

ATP

• Adenosine triphosphate• Chief “currency” all cells use• Composed of

– Ribose – 5 carbon sugar– Adenine– Chain of 3 phosphates

• Key to energy storage• Bonds are unstable• ADP – 2 phosphates• AMP – 1 phosphate – lowest energy form

20


AM

P C

OR

E

O

O–

O

O

O

HH H

H

O

CC

NN

N

C

N

C

CHH

P O–

O P

O P O

AD

PA

TP

Triphosphategroup

O–

CH2

High-energybonds

a.

Adenine NH2

Ribose

OHOH

b.

21

ATP cycle

• ATP hydrolysis drives endergonic reactions– Coupled reaction results in net –ΔG

(exergonic and spontaneous)

• ATP not suitable for long-term energy storage– Fats and carbohydrates better– Cells store only a few seconds worth of ATP

22


+

+

Pi

Energy fromexergoniccellularreactions

ATP H2O

ADP

Energy forendergoniccellularprocesses

23

Enzymes: Biological Catalysts• Most enzymes are protein

– Some are RNA

• Shape of enzyme stabilizes a temporary association between substrates

• Enzyme not changed or consumed in reaction

• Carbonic anhydrase– 200 molecules of carbonic acid per hour made without

enzyme– 600,000 molecules formed per second with enzyme

24


Active site

a. b.

Enzyme Enzyme–substrate complex

Substrate

Active site

• Pockets or clefts for substrate binding

• Forms enzyme–substrate complex

• Precise fit of substrate into active site

• Applies stress to distort particular bond to lower activation energy– Induced fit

25

26


1. The substrate, sucrose, consists of glucose and fructose bonded together.

2. The substrate binds to the active site of the enzyme, forming an enzyme– substrate complex.

3. The binding of the substrate and enzyme places stress on the glucose– fructose bond, and the bond breaks.

4. Products arereleased, andthe enzyme isfree to bind othersubstrates.

BondGlucose

Fructose

Active site

Enzymesucrase

H2O

27

Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

28

• Enzymes may be suspended in the cytoplasm or attached to cell membranes and organelles

• Multienzyme complexes – subunits work together to form molecular machine– Product can be delivered easily to next

enzyme– Unwanted side reactions prevented– All reactions can be controlled as a unit

29

Nonprotein enzymes

• Ribozymes• 1981 discovery that certain reactions

catalyzed in cells by RNA molecule itself1. 2 kinds

1. Intramolecular catalysis – catalyze reaction on RNA molecule itself

2. Intermolecular catalysis – RNA acts on another molecule

Enzyme function

• Rate of enzyme-catalyzed reaction depends on concentrations of substrate and enzyme

• Any chemical or physical condition that affects the enzyme’s three-dimensional shape can change rate– Optimum temperature– Optimum pH

30

31


a.

b.

Rat

e o

f R

eact

ion

Optimum pH for pepsin

Rat

e o

f R

eact

ion

pH of Reaction

Optimum pH for trypsin

1 2 3 4 5 6 7 8 9

30 40 50 60 70 80

Temperature of Reaction (˚C)

Optimum temperaturefor human enzyme

Optimum temperature for enzymefrom hotsprings prokaryote

32

Inhibitors

• Inhibitor – substance that binds to enzyme and decreases its activity

• Competitive inhibitor– Competes with substrate for active site

• Noncompetitive inhibitor– Binds to enzyme at a site other than active

site– Causes shape change that makes enzyme

unable to bind substrate

33

a. Competitive inhibition b. Noncompetitive inhibition

Enzyme Enzyme

Allosteric site

Activesite

Competitive inhibitor interfereswith active site of enzyme sosubstrate cannot bind

Allosteric inhibitor changesshape of enzyme so it cannotbind to substrate

Activesite


Substrate Substrate

Inhibitor Inhibitor

34

Allosteric Enzymes

• Allosteric enzymes – enzymes exist in active and inactive forms

• Most noncompetitive inhibitors bind to allosteric site – chemical on/off switch

• Allosteric inhibitor – binds to allosteric site and reduces enzyme activity

• Allosteric activator – binds to allosteric site and increases enzyme activity

35

Metabolism

• Total of all chemical reactions carried out by an organism

• Anabolic reactions/anabolism– Expend energy to build up molecules

• Catabolic reactions/catabolism– Harvest energy by breaking down molecules

36

Biochemical pathways

• Reactions occur in a sequence

• Product of one reaction is the substrate for the next

• Many steps take place in organelles

37


Initial substrate

Intermediatesubstrate A

Intermediatesubstrate B

Intermediatesubstrate C

End product

Enzyme1

Enzyme2

Enzyme3

Enzyme4

Feedback inhibition

• End-product of pathway binds to an allosteric site on enzyme that catalyzes first reaction in pathway

• Shuts down pathway so raw materials and energy are not wasted

38

39


a. b.

Enzyme 1

Enzyme 2

Enzyme 3

Enzyme 1

Enzyme 2

Enzyme 3End product End product

Initialsubstrate

Intermediatesubstrate A

Intermediatesubstrate B

Initialsubstrate

40

Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

Chapter 06 Lecture and Animation Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. See separate PowerPoint.

Documents

energy available

energy flows

energy changescells

energy jill braaten

electronhigher level

mcgrawhill companies

free energyg

free energypositive