topic 2 enzymology essential

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© 2012 Pearson Education, Inc. PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 5 The Working Cell Topic 2 Enzymology Essential Lecture edited by Harttini N.

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Page 1: Topic 2 Enzymology Essential

© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko

PowerPoint Lectures forCampbell Biology: Concepts & Connections, Seventh EditionReece, Taylor, Simon, and Dickey

Chapter 5 The Working Cell

Topic 2 Enzymology Essential

Lecture edited by Harttini N.

Page 2: Topic 2 Enzymology Essential

1. Explain how energy is transformed during life processes

2. Explain how a chemical reaction can either release energy or store energy

3. Describe ATP and explain why it is considered to be the energy currency of a cell

4. Define enzyme and explain how enzymes cause a chemical reaction to speed up

5. Discuss the specificity of enzymesCopyright © 2009 Pearson Education, Inc.

Learning outcome

Page 3: Topic 2 Enzymology Essential

ENERGY AND THE CELL

© 2012 Pearson Education, Inc.

Page 4: Topic 2 Enzymology Essential

5.11 Chemical reactions either release or store energy

___________________is a chemical reaction that release energy.

– These reactions release energy in covalent bonds of the reactants.

– Burning wood releases energy in glucose as heat and light.

– Cellular respiration releases energy slowly and uses some of the released energy to produce ATP.

© 2012 Pearson Education, Inc.

Page 5: Topic 2 Enzymology Essential

Reactants

EnergyProducts

Amount ofenergy

released

Pote

ntia

l ene

rgy

of m

olec

ules

Exergonic reaction, energy released

Page 6: Topic 2 Enzymology Essential

5.11 Chemical reactions either release or store energy

An ______________________ requires an input of energy and yields products rich in potential energy.

Endergonic reactions

– begin with reactant molecules that contain relatively little potential energy

– end with products that contain more chemical energy.

– Eg. photosynthesis that produced energy-rich sugar molecules from energy in sunlight.

© 2012 Pearson Education, Inc.

Page 7: Topic 2 Enzymology Essential

ReactantsEnergy

Products

Amount ofenergy

required

Pote

ntia

l ene

rgy

of m

olec

ules

Endergonic reaction, energy required

Page 8: Topic 2 Enzymology Essential

5.11 Chemical reactions either release or store energy

A living organism carries out thousands of endergonic and exergonic chemical reactions.

The total of an organism’s chemical reactions = ___________________.

A _________________a series of chemical reactions that either

– builds a complex molecule

– breaks down a complex molecule into simpler compounds.

© 2012 Pearson Education, Inc.

Page 9: Topic 2 Enzymology Essential

5.11 Chemical reactions either release or store energy

_______________ uses energy released from exergonic reactions to drive endergonic reactions

– usually using the energy stored in ATP molecules.

© 2012 Pearson Education, Inc.

Page 10: Topic 2 Enzymology Essential

______, adenosine triphosphate consists of

– nitrogenous base adenine

– five-carbon sugar ribose

– three phosphate groups

5.12 ATP drives cellular work by coupling exergonic and endergonic reactions

© 2012 Pearson Education, Inc.

Page 11: Topic 2 Enzymology Essential

5.12 ATP drives cellular work by coupling exergonic and endergonic reactions

Hydrolysis of ATP releases energy by transferring its third phosphate from ATP to some other molecule in a process called _________________.

Most cellular work depends on ATP energizing molecules by phosphorylating them.

© 2012 Pearson Education, Inc.

Page 12: Topic 2 Enzymology Essential

ADP: Adenosine Diphosphate

P P P Energy

H2OHydrolysis

RiboseAdenine

P P P

Phosphategroup

ATP: Adenosine Triphosphate

Hydrolysis of ATP releases energy by transferring its third phosphate from ATP to other molecule in phosphorylation

The structure and hydrolysis of ATP

Page 13: Topic 2 Enzymology Essential

5.12 ATP drives cellular work by coupling exergonic and endergonic reactions

3 main types of cellular work driven by ATP:

1. chemical

2. mechanical

3. transport

© 2012 Pearson Education, Inc.

Page 14: Topic 2 Enzymology Essential

ATP ATP ATP

ADP ADP ADPP P P

P

P

P

P PP

Chemical work Mechanical work Transport work

Reactants

Motorprotein

Solute

Membrane protein

Product

Molecule formed Protein filament moved Solute transported

How ATP powers cellular work

Page 15: Topic 2 Enzymology Essential

ATP is a renewable source of energy for the cell.

In the ATP cycle, energy released in an exergonic reaction, such as the breakdown of glucose,is used in an endergonic reaction to generate ATP.

Energy fromexergonicreactions

Energy forendergonicreactions

ATP

ADP P

5.12 ATP drives cellular work by coupling exergonic and endergonic reactions

© 2012 Pearson Education, Inc.

The ATP cycle

Page 16: Topic 2 Enzymology Essential

Gp. Disc.: ATP

ATP can be broken down or synthesized

Does AMP → ADP require or release energy? *Why?

Is ADP → ATP an exergonic or endergonic reaction? *Why?

Page 17: Topic 2 Enzymology Essential

Which can be represented by the graph:

• ADP → ATP?• OR

• ADP → AMP?

Page 18: Topic 2 Enzymology Essential

Which can be represented by the graph:• ADP → ATP?

OR• ADP → AMP?

Page 19: Topic 2 Enzymology Essential

E.g., Glycolysis

Is energy is used up or released when a phosphate group is removed from a molecule?

ADP → ATP: energy is used up or released?

Page 20: Topic 2 Enzymology Essential

Glycolysis (Later)

•Is energy is used up orreleased when ATP is broken down to ADP?

•Is energy is used up or released to transferphosphate to glucose?

Page 21: Topic 2 Enzymology Essential

HOW ENZYMES FUNCTION

© 2012 Pearson Education, Inc.

Page 22: Topic 2 Enzymology Essential

5.13 Enzymes speed up the cell’s chemical reactions by lowering energy barriers

Although biological molecules possess much potential energy, it is not released spontaneously.

– An energy barrier must be overcome before a chemical reaction can begin.

– This energy is called ________________________.

© 2012 Pearson Education, Inc.

Activationenergy barrier

Reactant

Products

Without enzyme With enzyme

Reactant

Products

EnzymeActivationenergy barrierreduced byenzyme

Ener

gy

Ener

gy

The effect of an enzyme in lowering EA

Page 23: Topic 2 Enzymology Essential

5.13 Enzymes speed up the cell’s chemical reactions by lowering energy barriers

Enzymes

– function as biological catalysts by lowering the EAneeded for a reaction to begin

– increase the rate of a reaction without being consumed by the reaction

– are usually proteins, although some RNA molecules can function as enzymes

© 2012 Pearson Education, Inc.

Page 24: Topic 2 Enzymology Essential

© 2012 Pearson Education, Inc.

Animation: How Enzymes WorkRight click on animation / Click play

Page 25: Topic 2 Enzymology Essential

Reactants

Products

Ener

gy

Progress of the reaction

a

b

c

The graph illustrate the course of a reaction with and without an enzyme. 1. Which curve represents the enzyme-catalyzed reaction? 2. What energy changes are represented by the lines a, b and c?

Page 26: Topic 2 Enzymology Essential

5.14 A specific enzyme catalyzes each cellular reaction

An enzyme

– is very selective in the reaction it catalyzes

– has a shape that determines the enzyme’s specificity.

The specific reactant that an enzyme acts on is called the enzyme’s ____________.

A substrate fits into a region of the enzyme called the ______________.

Enzymes are specific because their active site fits only specific substrate molecules.

© 2012 Pearson Education, Inc.

Page 27: Topic 2 Enzymology Essential

1

Enzyme(sucrase)

Active site

Enzyme availablewith empty activesite

The catalytic cycle of an enzyme

1. Sucrase starts with an empty active site

Page 28: Topic 2 Enzymology Essential

2

1

Enzyme(sucrase)

Active site

Enzyme availablewith empty activesite

Substrate(sucrose)

Substrate bindsto enzyme withinduced fit

The catalytic cycle of an enzyme

2. Sucrose enters the active site. The active site changes shape slightly to embrace substrate more snugly (induced fit)

Page 29: Topic 2 Enzymology Essential

3

2

1

Enzyme(sucrase)

Active site

Enzyme availablewith empty activesite

Substrate(sucrose)

Substrate bindsto enzyme withinduced fit

Substrate isconverted toproducts

H2O

The catalytic cycle of an enzyme

3. The strained bonds react with water, and the substrate is converted to products

Page 30: Topic 2 Enzymology Essential

4

3

2

1

Products arereleased

Fructose

GlucoseEnzyme(sucrase)

Active site

Enzyme availablewith empty activesite

Substrate(sucrose)

Substrate bindsto enzyme withinduced fit

Substrate isconverted toproducts

H2O

4. The enzyme releases the products and emerges unchanged

Page 31: Topic 2 Enzymology Essential

5.14 A specific enzyme catalyzes each cellular reaction

For every enzyme, there are optimal conditions under which it is most effective.

Temperature affects molecular motion.

– An enzyme’s optimal temperature produces the highest rate of contact between reactants and enzyme’s active site.

– Most human enzymes work best at 35–40ºC.

Optimal pH for most enzymes is near neutrality.

© 2012 Pearson Education, Inc.

Page 32: Topic 2 Enzymology Essential

Increasing temperature causes molecules to ___________________ Weak bonds break first: H-bonds, hydrophobic interactions Stronger bond break later: ionic bonds

Structure and surface configurations (including active site) are altered

Enzyme losses its catalytic functions

Enzyme is said to be denatured

When the structure of the enzyme is fully destroyed, no catalysis takes place

Temperature

Page 33: Topic 2 Enzymology Essential

1. Every enzyme has an optimum temperature that usually reflects the environment where the enzyme is naturally found

2. Reaction rate is highest at the optimal temperature

Page 34: Topic 2 Enzymology Essential

Changes in pH changes the concentration of _______in the medium

As [H+] changes, charges on the R groups change

This causes the ____________between charged R groups to break as the charges are _____________________

The 3-dimensional structure is then destroyed

The enzyme loses all catalytic activities and is completely denatured.

pH

Page 35: Topic 2 Enzymology Essential

Rat

e of

reac

tion

pH109876543210

Every enzyme has an optimum pH that usually reflects the environment where the enzyme is naturally found

Optimum pH (trypsin)

Optimum pH (pepsin)

Maximum rate of reaction trypsin

pepsin

trypsin

Maximum rate of reaction pepsin

Page 36: Topic 2 Enzymology Essential

a.

b. c.

d.

e.

f.

Page 37: Topic 2 Enzymology Essential

You should now be able to

© 2012 Pearson Education, Inc.

1. Explain how energy is transformed during life processes

2. Explain how a chemical reaction can either release energy or store energy

3. Describe ATP and explain why it is considered to be the energy currency of a cell

4. Define enzyme and explain how enzymes cause a chemical reaction to speed up

5. Discuss the specificity of enzymes