Cellular Respiration: Harvesting Chemical Energy Figures 6.1 – 6.5 CHAPTER 6 Cellular Respiration: Harvesting Chemical Energy Figures 6.1 – 6.5

Bacteria are used to produce yogurt, sour cream, pepperoni, and cheese Both carbon monoxide and cyanide kill by disrupting cellular respiration

All the energy in all the food you eat can be traced back to sunlight If you exercise too hard, your muscles shut down from a lack of oxygen

BIOLOGY AND SOCIETY: FEELING THE “BURN” When you exercise Muscles need energy in order to perform work Your cells use oxygen to release energy from the sugar glucose

Aerobic metabolism Anaerobic metabolism When enough oxygen reaches cells to support energy needs Anaerobic metabolism When the demand for oxygen outstrips the body’s ability to deliver it

Anaerobic metabolism Without enough oxygen, muscle cells break down glucose to produce lactic acid Lactic acid is associated with the “burn” associated with heavy exercise If too much lactic acid builds up, your muscles give out

Physical conditioning allows your body to adapt to increased activity The body can increase its ability to deliver oxygen to muscles Long-distance runners wait until the final sprint to exceed their aerobic capacity Figure 6.1

ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE Fuel molecules in food represent solar energy Energy stored in food can be traced back to the sun Animals depend on plants to convert solar energy to chemical energy This chemical energy is in the form of sugars and other organic molecules

Producers and Consumers Photosynthesis Light energy from the sun powers a chemical process that makes organic molecules This process occurs in the leaves of terrestrial plants

Autotrophs Heterotrophs “Self-feeders” Plants and other organisms that make all their own organic matter from inorganic nutrients Heterotrophs “Other-feeders” Humans and other animals that cannot make organic molecules from inorganic ones

Producers Biologists refer to plants and other autotrophs as the producers in an ecosystem Consumers Heterotrophs are consumers, because they eat plants or other animals Figure 6.2

Chemical Cycling Between Photosynthesis and Cellular Respiration The ingredients for photosynthesis are carbon dioxide and water CO2 is obtained from the air by a plant’s leaves H2O is obtained from the damp soil by a plant’s roots Chloroplasts rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules Oxygen gas is a by-product of photosynthesis

Both plants and animals perform cellular respiration Cellular respiration is a chemical process that harvests energy from organic molecules Cellular respiration occurs in mitochondria The waste products of cellular respiration, CO2 and H2O, are used in photosynthesis

Sunlight energy Ecosystem Photosynthesis (in chloroplasts) Glucose Carbon dioxide Oxygen Water Cellular respiration (in mitochondria) for cellular work Heat energy Figure 6.3

CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY The main way that chemical energy is harvested from food and converted to ATP This is an aerobic process—it requires oxygen

The Relationship Between Cellular Respiration and Breathing Cellular respiration and breathing are closely related Cellular respiration requires a cell to exchange gases with its surroundings Breathing exchanges these gases between the blood and outside air

Breathing Lungs Muscle cells Cellular respiration Figure 6.4

The Overall Equation for Cellular Respiration A common fuel molecule for cellular respiration is glucose This is the overall equation for what happens to glucose during cellular respiration Glucose Oxygen Carbon dioxide Water Energy Unnumbered Figure 6.1

The Role of Oxygen in Cellular Respiration During cellular respiration, hydrogen and its bonding electrons change partners Hydrogen and its electrons go from sugar to oxygen, forming water

Redox Reactions Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions Redox reactions for short

The loss of electrons during a redox reaction is called oxidation The acceptance of electrons during a redox reaction is called reduction

[Glucose loses electrons (and hydrogens)] Oxidation [Glucose loses electrons (and hydrogens)] Glucose Oxygen Carbon dioxide Water Reduction [Oxygen gains electrons (and hydrogens)] Unnumbered Figure 6.2

Why does electron transfer to oxygen release energy? When electrons move from glucose to oxygen, it is as though they were falling This “fall” of electrons releases energy during cellular respiration Release of heat energy Figure 6.5