4  •  Energy 135

From the sun to you in just two steps

Energy flows from the sun and through all life on earth. 136

4.1

Cars that run on french fry oil? Organisms and machines need energy to work. 136

4.2

Energy has two forms: kinetic and potential. 137

4.3

As energy is captured and converted, the amount of energy available to do work decreases. 139

4.4

ATP molecules are like free-floating rechargeable batteries in all living cells. 141

Photosynthesis uses energy from sunlight to make food. 143

4.5

Where does plant matter come from? Photosynthesis: the big picture. 143

4.6

Photosynthesis takes place in the chloroplasts. 145

4.7

Light energy travels in waves: plant pigments absorb specific wavelengths. 146

4.8

Photons cause electrons in chlorophyll to enter an excited state. 148

4.9

Photosynthesis in detail: the energy of sunlight is captured as chemical energy. 149

4.10

Photosynthesis in detail: the captured energy of sunlight is used to make food. 152

4.11

The battle against world hunger can use plants adapted to water scarcity. 153

Living organisms extract energy through cellular respiration. 157

4.12

How do living organisms fuel their actions? Cellular respiration: the big picture. 157

4.13

The first step of cellular respiration: glycolysis is the universal energy-releasing pathway. 158

4.14

The second step of cellular respiration: the Krebs cycle extracts energy from sugar. 160

4.15

The third step of cellular respiration: ATP is built in the electron transport chain. 162

4.16

This is how we do it: Can we combat the fatigue and reduced cognitive functioning of jet lag with NADH pills? 165

There are alternative pathways to energy acquisition. 167

4.17

Beer, wine, and spirits are by-products of cellular metabolism in the absence of oxygen. 167

4.18

Eating a complete diet: cells can run on protein and fat as well as on glucose. 169

StreetBIO: KNOWLEDGE YOU CAN USE

If you feed and protect your flowers in a vase, they’ll last longer. 170