CONCEPTS IN BIOLOGY
PART II. CORNERSTONES: CHEMISTRY, CELLS, AND METABOLISM
2. The Basics of Life
CFLs, A Bright Idea With Potential Health Problems
Lightbulbs cause for concern?
Fluorescent lightbulbs were invented in the 1890s. However, it wasn’t until the 1970s that compact fluorescent lights (CFLs), were developed as a spinoff of a world-wide oil shortage. The shortage stimulated research into ways of getting people to use the more energy-efficient bulbs. CFLs use only about 25% of the energy needed to produce the same amount of light as an incandescent bulb and last about 10 times longer. Replacing incandescent bulbs with CFLs will reduce the amount of fossil fuels burned to generate electricity, thus reducing greenhouse gases such as carbon dioxide. Ultimately, this will help to control global warming.
All fluorescent bulbs contain the element mercury, essential for their operation. Electricity vaporizes the mercury, causing it to emit UV light, which, in turn, causes other chemicals to light up; that is, they fluoresce. At first glance CFLs might seem to be a win-win situation (i.e., longer-lasting, lower-energy bulbs and less greenhouse gases). However, there is another problem.
Once released, certain bacteria can change mercury into the molecule methylmercury, which is highly toxic to the brain, heart, kidneys, lungs, and immune system, and is especially harmful to fetuses and children. In fact, about one in six children in the United States is at risk for learning disabilities from exposure to methylmercury. According to the EPA, the amount of mercury released from CFL bulbs can exceed U.S. federal guidelines for chronic exposure. As more CFLs are used, it may become essential to regulate their use and disposal.
• What are elements and molecules?
• What should you do if one of these CFL bulbs breaks or wears out?
• Will you stop using such potentially dangerous products in favor of safer ones?
ü Background Check
Concepts you should already know to get the most out of this chapter:
• The scientific method (chapter 1)
• Features that make something alive (chapter 1)
• The levels of biological organization (chapter 1)
2.1. Matter, Energy, and Life
All living things have the ability to use matter and energy to their advantage. Bees, bacteria, broccoli—in fact, all organisms—use energy to move about, respond to change, reproduce, make repairs and grow; in other words, to stay alive. Energy is the ability to do work or cause things to move. There are two general types of energy: kinetic and potential. A flying bird displays kinetic energy, or energy of motion. Potential energy is described as stored energy. When we talk about the energy in chemicals, substances used or produced in processes that involve changes in matter, we are talking about the potential energy in matter. Matter is anything that has mass1 and takes up space. This energy has the potential to be converted to kinetic energy used to do life’s work. Since energy has predictable properties, all organisms have similar ways of handling it.
There are five forms of energy, and each can be either kinetic or potential: (1) mechanical, (2) nuclear, (3) electrical, (4) radiant, and (5) chemical. All organisms interact in some way with these forms of energy. A race horse or a track athlete displays potential mechanical energy at the start line; the energy becomes kinetic mechanical energy when the athlete is running (figure 2.1). Nuclear energy is the form of energy from reactions involving the innermost part of matter, the atomic nucleus. In a nuclear power plant, nuclear energy is used to generate electrical energy. Electrical energy is associated with the movement of charged particles. All organisms use charged particles as a part of their metabolism. Radiant energy is most familiar as heat and visible light, but there are other forms as well, such as X-radiation and microwaves. Chemical energy is a kind of internal potential energy. It is stored in matter and can be released as kinetic energy when chemicals are changed from one form to another. For example, the burning of natural gas involves converting the chemical energy of gas into heat and light. A more controlled process releases the potential chemical energy from food in living systems, allowing them to carry out life’s activities.
FIGURE 2.1. Potential and Mechanical Energy
This horse has converted the potential energy in its food to the kinetic energy of motion. This is why, for centuries, horses have been called “hay burners.”
One of the predictable properties of energy is known as the law of conservation of energy, or the first law of thermodynamics. This law says that energy is not created or destroyed; but, energy can be converted from one form to another. For example, potential energy can become kinetic energy, and electrical energy can become heat energy as in a glowing CFL. However, the total energy in a system remains the same. Because living systems use energy, these systems are also subject to this law. As a result, when biologists study energy use in living organisms and ecosystems, they must account for all the energy.
Scientists define all living things as being composed of matter. There is no scientific evidence of a living thing composed of pure energy (despite what you might see on television), or being spiritual. To understand how organisms use these elements, you need to understand some basic principles about matter. Chemistry is the science concerned with the study of the composition, structure, and properties of matter and the changes it undergoes (figure 2.2).
FIGURE 2.2. Biology and Chemistry Working Together
In order to understand living things, researchers must investigate both their structure and their function. At the core of modern biology is an understanding of molecular structure, including such molecules as DNA, the molecule of which genes are composed.
2.1. CONCEPT REVIEW
1. What is potential energy?
2. Why is the first law of thermodynamics important to biology?
1 Don’t confuse the concepts of mass and weight. Mass refers to an amount of matter, whereas weight refers to the amount of force with which an object is attracted by gravity. Because gravity determines weight, your weight would be different on the Moon than it is on Earth, but your mass would be the same.