PowerPoint PresentationCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
From PowerPoint® Lectures for Biology: Concepts & Connections
CHAPTER 5
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
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
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
ENERGY AND THE CELL
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
Potential energy is stored energy
Figure 5.1A
Figure 5.1B
5.2 Two laws govern energy conversion
First law of thermodynamics
However, energy cannot be created or destroyed
Figure 5.2A
Second law of thermodynamics
Some energy is always lost as heat
Figure 5.2B
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
There are two types of chemical reactions:
Endergonic reactions absorb energy and yield products rich in potential energy
Figure 5.3A
Exergonic reactions release energy and yield products that contain less potential energy than their reactants
Figure 5.3B
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
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
Figure 5.4A
How ATP powers cellular work
Figure 5.4B
The ATP cycle