Enzymology Essential

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Topic 2 Enzymology Essential
Chapter 5 The Working Cell

Learning outcome
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

PowerPoint Lectures for

Campbell Biology: Concepts & Connections, Seventh Edition
Reece, Taylor, Simon, and Dickey

Lecture edited Edward J. Zalisko
Lecture by by Harttini N.

© 2012 Pearson Education, Inc.

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

5.11 Chemical reactions either release or store
energy

ENERGY AND THE CELL

Exergonic reactions is a chemical reaction that
release energy.
– These reactions release the energy in covalent bonds of
the reactants.
– Burning wood releases the 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.

© 2012 Pearson Education, Inc.

Potential energy of molecules

5.11 Chemical reactions either release or store
energy
An endergonic reaction requires an input of energy and
yields products rich in potential energy.

Reactants

Endergonic reactions
Amount of
energy
released
Energy
Products

– 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.

Exergonic reaction, energy released
© 2012 Pearson Education, Inc.

1

Potential energy of molecules

5.11 Chemical reactions either release or store
energy
A living organism carries out thousands of
endergonic and exergonic chemical reactions.

Products

Energy

Amount of
energy
required

Reactants

The total of an organism’s chemical reactions =
metabolism.
A metabolic pathway is a series of chemical
reactions that either
– builds a complex molecule or
– breaks down a complex molecule into simpler
compounds.

Endergonic reaction, energy required
© 2012 Pearson Education, Inc.

5.11 Chemical reactions either release or store
energy
Energy coupling uses energy released from
exergonic reactions to drive endergonic reactions
– usually using the energy stored in ATP molecules.

5.12 ATP drives cellular work by coupling
exergonic and endergonic reactions
ATP, adenosine triphosphate consists of
– the nitrogenous base adenine,
– the five-carbon sugar ribose, and
– three phosphate groups.

© 2012 Pearson Education, Inc.

© 2012 Pearson Education, Inc.

5.12 ATP drives cellular work by coupling
exergonic and endergonic reactions

ATP:

Adenosine Triphosphate
Phosphate
group

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

P

P

P

Adenine
Ribose

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

Hydrolysis

P
ADP:

P

H2 O

P

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

Energy

Adenosine DiphosphateThe structure and hydrolysis of ATP

© 2012 Pearson Education, Inc.

2

5.12 ATP drives cellular work by coupling
exergonic and endergonic reactions

Chemical work

Mechanical work

Transport work

ATP

ATP

ATP

3 main types of cellular work driven by ATP:
1. chemical

Solute
P

2. mechanical

Motor
protein

P
P

Reactants

Membrane protein

3. transport
P
P
P

Product
Molecule formed

ADP
© 2012 Pearson Education, Inc.

5.12 ATP drives cellular work by coupling
exergonic and endergonic reactions

P

Protein filament moved

ADP
P
How ATP powers cellular work...
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