Cellular Respiration

Harvesting energy stored in food• Cellular respiration

– breaking down food to produce ATP• in mitochondria

• using oxygen– “aerobic” respiration

– usually digesting glucose• but could be other sugars,

fats, or proteins

C6H12O6 6O26CO2 6H2O→+ + +

glucose + oxygen → + carbon dioxide + water

O2

food ATP

MitochondriaLocated in plant and animal cells

What do we need to make energy?• The “Furnace” for making energy

– mitochondria • Fuel

– food: carbohydrates, fats, proteins• Helpers

– oxygen– enzymes

• Product– ATP

• Waste products– carbon dioxide

• then used by plants

– water

O2

food

ATP

enzymes

CO2 H2O

Chemical Structure of ATP

Cellular Respiration

C6H12O6 + 6O2 6 CO2 + 6 H2O + 36-38 ATP

• Uses O2 (aerobic)

• Starts in the cytoplasm but ends in mitochondria• Eukaryotic organisms• 3 steps:

– Glycolosis– Kreb’s cycle (citric acid cycle) – Electron transport chain

• 36-38 ATP are produced

Metabolism of Glucose

• A multistep pathway• Catalyzed by an enzyme at every step• Energy is transferred to ATP• 3 major processes that are important for the

“harvest” of energy from glucose– Glycolysis – splitting into pyruvic acid

– Fermentation - anaerobic

– Cellular Respiration - aerobic

cellular

Anaerobic Respiration• Fermentation

– alcohol fermentation• yeast

– glucose → ATP + CO2+ alcohol

– make beer, wine, bread

– lactic acid fermentation• bacteria, animals

– glucose → ATP + lactic acid– bacteria make yogurt– animals feel muscle fatigue

Fermentation C6H12O6 2CO2 + C2H5OH + 2 ATP

• Occurs in the cytoplasm of the cell• NO O2 is present (anaerobic)

• Prokaryotic organisms (don’t have membrane-bound

organelles) and sometimes in eukaryotic*• Two short fermentation pathways are the best

understood– Lactic acid:

• End byproduct is lactic acid

– Alcohol:• End byproduct is ethyl alcohol

• 2 ATP are produced

Lactic Acid Fermentation

• Occurs in many microorganisms & in some muscle tissues*

• *Energy is needed for muscle contraction– Blood cannot supply muscles with O2 fast

enough so muscle cells revert to lactic acid fermentation

– Lactic acid build is what causes muscle cramping

Alcohol Fermentation• Occurs in some yeasts & plants cells under

anaerobic conditions

• Result is ethyl alcohol

• Alcohol beverages and bread are made using this type of fermentation

Summary of Cellular Energy Processes

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