Mills 2012 Chapter 6 Metabolism: Energy and Enzymes Read chapter 6 of textbook Read Enzyme Activity Lab in AP Lab Manual (#13) Read pages 22 (chemical

Mills 2012

Chapter 6Metabolism: Energy and

Enzymes

Read chapter 6 of textbookRead Enzyme Activity Lab in AP Lab Manual (#13)

Read pages 22 (chemical reactions and metabolic processes)

in CliffsAP (3rd)

Do MC questions on pg 25-28 of Cliffs – Due Sept 17Be sure you could answer the free response questions

pg 29

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Chapter 6Metabolism: Energy and

Enzymes• Topics

– 6.1 Cells and the Flow of Energy– 6.2 Metabolic Reactions and Energy

Transformations– 6.3 Metabolic Pathways and Enzymes– 6.4 Metabolic Pathways and Oxidation Reduction

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Metabolism: Energy and Enzymes6.1 Energy

• Energy = capacity to do work or bring about a change

• All living things need energy• Many kinds of energy

– Kinetic energy

• Energy of motion

• Mechanical

– Potential energy

• Stored energy

• Chemical energy

Flow of Energy

4

solarenergy

heat

heat

heat

heat

Mechanical energy

Chemicalenergy

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

sunCO2

H2O

solar energy producercarbohydrate

heat

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• Two laws of thermodynamics– Law of conservation of

energy• Energy cannot be created

or destroyed, only converted from one form to another

– Second law (Entropy)• Energy cannot be

converted from one form to another without a loss of usable energy

Energy = Mass x The Velocity of Light squared

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• Entropy– A measure of randomness or disorder– Things tend toward more entropy – takes

energy to keep organized

Cells and Entropy

H+

H2O

C6H12O6

• more organized• more potential energy• less stable (entropy)

a.

Carbon dioxideand water

• less organized• less potential energy• more stable (entropy)

CO2

kineticenergy

channel protein

H+

H+

H+

H+

H+

H+

H+

H+H+

H+

H+

Unequal distributionof hydrogen ions

Equal distributionof hydrogen ions

• more organized• more potential energy

b.• less stable (entropy)

• less organized• less potential energy• more stable (entropy)

Glucose

H+

H+

H+H+

H+

H+

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• Whole ecosystem also follows these rules– Ultimately all energy

ends up as heat, which is very random energy (high entropy)

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Metabolism: Energy and Enzymes6.2 Metabolic Reactions and Energy

Transformations• Metabolism = sum of all reactions that go on in body

– Free energy • = amount of energy (G) that is still available (free) to do work after a

chemical reaction has occurred. (change in energy is designated delta G)• If delta G is negative it means the products have less energy than the

reactants did. And the reaction will occur spontaneously– Exergonic – give off energy

• Delta G is negative• ATP ADP +P + free Energy

– Endergonic – need energy• Delta G is positive – products have more free energy than reactants.• Free Energy + Reactants Products

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Metabolism: Energy and Enzymes6.2 Metabolic Reactions and Energy

Transformations

• Coupled reactions– Many reactions in body are coupled

• One gives off energy and the other uses it

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Metabolism: Energy and Enzymes

6.2 Metabolic Reactions and Energy Transformations

• ATP; energy for Cells– Adenosine triphosphate is

a common source of stored energy for cells

– Provides energy for:• Chemical work –

synthesizing macromolecules

• Transport work – pumps substances across membranes

• Mechanical work – muscle contractions, cilia, flagella, cytoskeleton

– Energy stored in third phosphate bond

ATP is a nucleotide

Coupled Reactions

12

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

1 2 3

P

Myosin assumes itsresting shape whenIt combines with ATP.

ATP splits into ADPand p , causingmyosin to change itsshape and allowing itto attach to actin.

Release of ADP andp cause myosin toagain change shapeand pull against actin,generating force andmotion.

ADPmyosin

actin

ATP

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Metabolism: Energy and Enzymes6.3 Metabolic Pathways and Enzymes

• Metabolic pathways– Series of consecutive reactions– Each step catalyzed by an enzyme

• Enzymes (organic catalysts) are made of proteins• Lower the activation energy

– Substance enzyme reacts with is called a substrate

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• Importance of Enzymes– Enzymes are needed for most chemical reactions to

occur in living cells, lower activation energy• Such as getting “energy” from sugars

– We would die without enzymes– Enzyme acts on a substrate– Enzyme names often end in “ase”– Enzymes are organic (usually globular proteins)

catalysts• Speed up a reaction without being used up themselves

– Can speed up a reaction by as much as a million times

Starch degradation by enzyme amylase animation ..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\starch degrade animation.dir

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• How Enzymes Work– Enzymes have active sites

• Enzyme-substrate complex

– Bind to specific spot on substrate

– Can put substrates together or break them apart

– Two theories to explain how• Lock and key• Induced fit

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• Fit together like a lock and key

Hydrogen proxide

catalase

Water and oxygen

catalase

Degradation

Synthesis

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• Induced fit– Once enzyme substrate complex has formed,

enzyme changes shape slightly for a better fit

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• Factors affecting ezymatic speed– Many factors can affect

enzyme action• Substrate concentration• Temperature• pH• Enzyme concentration• Enzyme inhibition• Enzyme co-factors

– Affect only the rate of the reaction, not the amount of end products

– Only very small amounts of enzyme are needed to catalyze reactions

The enzyme catalase (present in our liver) can break up 5 Million molecules of hydrogen peroxide in one minute (at Oo C = 32o F).

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• Read Lab 2 – Enzyme Catalysis– Oct 14th lab – in your AP Lab Manual pg

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• Temperature• Generally higher temp

increases rate of reaction

• In living tissues, don’t want high temp

• Enzymes work best at optimal temp

– Usually the normal temp of the cell they are in

• If temp too high enzymes are denatured

– Boiled egg

What is optimal temp for this enzyme in Fahrenheit degrees?

Formula: oF = (9/5) oC + 32

oF = (9/5) o42 + 32 = 107.6oF

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• Enzyme and substrate concentrations– Increasing the amount of substrate or enzyme will

increase the reaction rate, but only up to a maximum point

Start

Fixed amount of substrate-add more and more enzyme.

Maximum point – adding more enzyme will not increase rate any more.

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Start

Fixed amount of enzyme- add more and more substrate.

Maximum point – adding more substrate will not increase rate any more.

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• pH– Enzymes also have an

optimal pH at which they work best

• Optimal pH for pepsin?• Where might you find

it?• Optimal pH of trypsin?

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• Enzyme inhibition– Competitive

inhibition• Molecule binds and

blocks active site

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• Enzyme inhibition– Non-competitive

inhibition• Molecule does not

bind to active site, binds to allosteric site

• Feedback inhibition (see next slide) works this way

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• Feedback Inhibition– Many biological systems (metabolic

pathways)work this way

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• Enzyme cofactors– Some enzymes are not made

entirely of protein, contain other substances that help them function

• These are substances are called cofactors

– Can be inorganic (such as minerals Cu, Zn, Fe) or ,

– Can be organic- called coenzymes organic –non protein (such as vitamins)

– Some vitamins are coenzymes• Humans cannot synthesize most

vitamins, so need to take in diet

– Help enzyme perform it’s function

http://store2.yimg.com/I/sagarbollywood_1698_23164966

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Metabolism: Energy and Enzymes6.4 Organelles and the Flow of Energy

• Oxidation and Reduction– Occur together = redox– Oxidation = loss of electrons

• In living systems H often accompanies the electron (usually as e- + H+)

• So usually means loss of hydrogen atom

– Reduction = gain of electrons• In living systems H often accompanies the electron (usually as e-

+ H+)• So usually means gain of hydrogen atom

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Metabolism: Energy and Enzymes 6.4 Organelles and the Flow of Energy

• Two energy capturing pathways that use redox reactions (we will look at in the next two chapters)

– Photosynthesis – Ch 7– Cell respiration – Ch 8

• Both systems make use of an electron transport system and produce ATP

• We will look closer at these systems in chapters 7 and 8.

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• Photosynthesis overview– Takes energy from the sun and converts it

into chemical energy– Equation Summarizing Photosynthesis

• 6CO2 + 12H2O C6H12O6 + 6H2O + 6O2

Light

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Metabolism: Energy and Enzymes6.4 Metabolic Pathways and Oxidation

Reduction

• Photosynthesis overview– Many reactions involved– At one point, a coenzyme called NADP+, is

used to carry electrons from one place to another – usually to the ETS

NADP+ + 2e- + H+ NADPH

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• Cell Respiration Overview– Takes energy from glucose and makes ATP– Equation summarizing cell respiration

• C6H12O6 + 6H2O + 6O2 6CO2 + 12H2O + 36 ATP + heat

– Uses coenzyme NAD to carry electrons to ETS• NAD+ (is reduced) + 2e- + 2H+ NADH + H+

Oxidation

Reduction

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• Electron Transport System Overview– Series of carrier

molecules that pass electrons along

– Electrons lose a little bit of energy each time passed

– Carriers are oxidized and reduced

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Will discuss in more detail later

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Metabolism: Energy and Enzymes6.4 6.4 Organelles and the Flow of Energy

• ATP Production Overview– Uses energy from ETS– ETS located within membranes of

mitochondria and chloroplasts– Process called chemiosmosis

• ETS deposits H on one side of the membrane• H flow down electrochemical gradient through

ATP synthase complex• Flowing through the complex provides the

energy to add a P to ADP ATP

Animations from http://www.cat.cc.md.us/courses/bio141/lecguide/unit4/metabolism/cellresp/etsch.html

http://www.cat.cc.md.us/courses/bio141/lecguide/unit4/metabolism/cellresp/etsch.html

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Peter Mitchell

1978 Nobel Prize

Chemiosmosis Theory

Chemiosmosis blah, blah blah, blah blah, blah blah,

blah blah, blah…..

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ATP synthesis and the electron transport chain animation

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• Chemiosmosis website animation– From: http://www.tvdsb.on.ca/westmin/science/sbioac/plan

ts/chemios.htm

http://www.tvdsb.on.ca/westmin/science/sbioac/plants/chemios.htm

http://www.tvdsb.on.ca/westmin/science/sbioac/plants/chemios.htm

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The End

Read Connecting the Concepts with the Big Ideas pg 115

Documents

Mills 2012 Chapter 6 Metabolism: Energy and Enzymes Read chapter 6 of textbook Read Enzyme Activity Lab in AP Lab Manual (#13) Read pages 22 (chemical