Cellular Respiration: Obtaining Energy from Food

1. Cellular Respiration: Obtaining Energy from Food Chapter 6 Part I

3. Muscles need energy to perform work • Energy is obtained from glucose through reactions that require O2 • To keep moving muscles need a steady supply of O2

4. Aerobic and Anaerobic Energy • Aerobic – O2 used by your cells to support their energy - as muscles work harder, you breathe faster and deeper to inhale more O2 - demand for O2 outstrips body’s ability to deliver it • Aerobic capacity – max rate at which O2 can be taken in and used by your cells • Anaerobic – ‘emergency mode’ breaks down glucose and produces lactic acid - lactic acid causes ‘the burn’, too much your muscles give out

5. Feeling the Burn • Physical conditioning allows your body to adapt to increased activity - the body can increase its ability to deliver O2 to muscles • Long-distance runners wait until the final sprint to exceed their aerobic capacity Figure 6.1

6. Energy Flow and Chemical Cycling in the Biosphere • Fuel molecules in food represent solar energy - energy stored in all food can be traced back to the sun • Photosynthesis: plants convert solar energy to chemical energy in the form of sugars and other organic molecules - animals depend on plants for this chemical energy - occurs mainly in green cells within the leaves of plants - chlorophyll is the green pigment molecule contained in chloroplasts (organelles that trap light energy)

7. Autotrophs and Heterotrophs • Autotrophs – ‘self-feeders’ - include plants and other organisms that make all their own organic matter from inorganic nutrients (CO2, water, and minerals from the soil) • Heterotrophs – ‘other-feeders’ - organisms including humans and other animals that cannot make organic molecules from inorganic ones - depend on autotrophs for their organic fuel and material for growth and repair

8. Producers and Consumers • Producers – biologists refer to plants and other autotrophs as the producers in an ecosystem • Consumers – heterotrophs are consumers - obtain their food by eating plants or other animals that have eaten plants - depend on food for fuel and the raw organic materials we need to build our cells and tissues

9. Producer and Consumer • Photosynthetic organisms use light energy to drive the production of their own organic material • Animals depend on this photosynthetic product for their energy and building material Figure 6.2

10. Chemical Cycling between Photosynthesis and Cellular Respiration • The ingredients for photosynthesis are carbon dioxide (CO2) and water (H2O) - CO2 is obtained from the air by a plant’s leaves through tiny pores - 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 (O2) is a by-product of photosynthesis

11. Cellular Respiration • Plants have chloroplasts and are capable of producing fuel from sunlight - animals and plants use these organic fuel compounds to obtain energy • Both plants and animals perform cellular respiration - a chemical process that harvests energy stored in sugars and other organic molecules - uses O2 to convert energy extracted from these organic fuels to the chemical energy, ATP - ATP is produced mainly in mitochondria • The waste products of cellular respiration CO2 and H20 are used in photosynthesis

12. Energy flow and chemical cycling in ecosystems • Energy enters as sunlight - exits in the form of heat • Organisms temporarily trap the energy for their work • Photosynthesis in chloroplasts of plants convert light energy to chemical energy • Cellular respiration in the mitochondria harvest the food energy to generate ATP • ATP drives most cellular work • Chemical elements essential for life recycle between cellular respiration and photosynthesis Figure 6.3

13. Checkpoint • Although they are ‘self-feeders’ photosynthetic autotrophs are not totally self-sufficient. What chemical ingredients do they require from the environment in order to synthesize sugar? 2. Why are plants called producers? Why are animals called consumers? 3. What is misleading about the following statement? “Plants perform photosynthesis, whereas animals perform cellular respiration.

14. Answers • Carbon dioxide and water; also soil minerals • Plants produce organic molecules by photosynthesis. Consumers must acquire organic material by consuming it rather than making it. • It implies that cellular respiration does not occur in plants but it does.