To study Biology.

1. BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 5
The Working Cell
Modules 5.1 – 5.4
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

2. Cool “Fires” Attract Mates and Meals
• Fireflies use light,
instead of chemical
signals, to send signals
to potential mates
• Females can also use
light flashes to attract
males of other firefly
species — as meals, not
mates
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

3. • The light comes from
a set of chemical
reactions, the
luciferin-luciferase
system
• Fireflies make light
energy from chemical
energy
• Life is dependent on
energy conversions
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

4. ENERGY AND THE CELL
• Living cells are compartmentalized by
membranes
• Membranes are sites where chemical reactions
can occur in an orderly manner
• Living cells process energy by means of
enzyme-controlled chemical reactions
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

5. 5.1 Energy is the capacity to perform work
• Energy is defined as the capacity to do work
• All organisms require energy to stay alive
• Energy makes change possible
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

6. • Kinetic energy is
energy that is actually
doing work
Figure 5.1A
• Potential energy is
stored energy
Figure 5.1B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

7. 5.2 Two laws govern energy conversion
• First law of thermodynamics
• Energy can be changed from one form to
another
– However, energy cannot be created or destroyed
Figure 5.2A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

8. • Second law of thermodynamics
• Energy changes are not 100% efficient
– Energy conversions increase disorder, or
entropy
– Some energy is always lost as heat
Figure 5.2B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

9. 5.3 Chemical reactions either store or release
energy
• Cells carry out thousands of chemical reactions
– The sum of these reactions constitutes cellular
metabolism
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

10. • There are two types of chemical reactions:
– Endergonic reactions absorb energy and yield
products rich in potential energy
Potential energy of molecules
Products
Amount of
energy
INPUT
Reactants
Figure 5.3A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

11. – Exergonic reactions release energy and yield
products that contain less potential energy than
their reactants
Reactants
Potential energy of molecules
Amount of
energy
OUTPUT
Products
Figure 5.3B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

12. 5.4 ATP shuttles chemical energy within the cell
• In cellular respiration, some energy is stored in
ATP molecules
• ATP powers nearly all forms of cellular work
• ATP molecules are the key to energy coupling
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

13. • When the bond joining a phosphate group to
the rest of an ATP molecule is broken by
hydrolysis, the reaction supplies energy for
cellular work
Adenine
Phosphate
groups
Hydrolysis
Energy
Ribose
Adenosine triphosphate
Adenosine diphosphate
(ADP)
Figure 5.4A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

14. • How ATP powers cellular work
Potential energy of molecules
Reactants Products
Protein Work
Figure 5.4B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

15. • The ATP cycle
Dehydration synthesis
Hydrolysis
Energy from Energy for
exergonic endergonic
reactions reactions
Figure 5.4C
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings