Cellular Respiration Vocabulary Glycolysis Cellular respiration Fermentation Anaerobic Aerobic ATP Glucose

After glucose is made in photosynthesis, energy in the bonds of the glucose molecule are broken down to release energy. Remember: all food we eat is eventually broken down into glucose Occurs in two steps: Glycolysis: Breaks down glucose Cell respiration: Uses oxygen to finish breaking down the products from glycolysis Cellular Respiration occurs in both plant & animal cells in the cytoplasm and the mitochondria

Glucose + Oxygen Carbon Dioxide + Water C6H12O6 + 6O2 6CO2 + 6H2O Animal GLUCOSE CO2 O2 H2O & heat energy cell Glucose + Oxygen Carbon Dioxide + Water   C6H12O6 + 6O2 6CO2 + 6H2O Look Familiar?

Chemical Energy and Food Cells gradually release energy from food Food (glucose), like fuel, is "burned" by our cells for energy if it's burned all at once, too much energy is released Therefore, the reaction is broken down into many small steps controlled by ENZYMES Cells gradually release the energy from glucose and other compounds

The energy our body uses exists in the form of ATP. ATP provides a base chemical reaction that allows all body functions to occur regularly energy is stored in bonds between phosphate groups

Step 1: Glycolysis Process of releasing energy from carbohydrates starts with gylcolysis Glycolysis= breaking down glucose Glucose is broken in half Product= 2 3-carbon molecules called pyruvic acid Takes place in the cytoplasm of a cell NO oxygen required Needs two ATP to get started (an “investment”) Produces 4 ATP when done NAD+ accepts high energy electrons from food  NADH Electron carrier

After glycolysis, it all depends on oxygen If oxygen IS present, the cell next takes a pathway called Respiration (Krebs Cycle) If oxygen is NOT present, the cell next takes a pathway called fermentation

Respiration/Krebs Cycle takes place in the Mitochondria Only happens if oxygen is PRESENT (aerobic) Uses the pyruvic acid from glycolysis to produce carbon dioxide, water, and 34 ATP per molecule of glucose

The folds of the mitochondria provide more surface area for these chemical reactions

The Kreb Cycle or Citric Acid Cycle can be very confusing!! We only need to know that pyruvate goes in and C02 comes out.

Summary of Cellular Respiration GLYCOLYSIS “breaks down glucose” RESPIRATION/ Kreb’s Cycle Location in the cell: Cytoplasm Mitochondria It starts with: C6H12O6 (glucose) 2 pyruvic acid It ends with: 2 (C3H6O3) pyruvic acid H2O, CO2, ATP Is Oxygen required? NO YES!  AEROBIC # of ATP’s Produced: 2 (tiny) 34 (lots!)

GRAND TOTAL= 36 ATP!! 2 are produced in Glycolysis 34 in Respiration/ Kreb’s Cycle How efficient is this?? The 36 ATP molecules the cell makes per 1 glucose represents about 38% of the total energy in glucose Even though it doesn’t seem like much, this is more efficient than your car’s gas burning engine What happens to the remaining 62%??? It is released as heat.

Changes NADH back to NAD+ so glycolysis can continue Fermentation: release of energy from food molecules in absence of oxygen (anaerobic) Enables cells to carry out energy production in the absence of Oxygen Fermentation occurs in many organisms: In Humans and animals, lactic acid fermentation occurs In yeast and other microorganisms, alcoholic fermentation occurs Result of glycolysis + fermentation yields 2 ATP molecules per 1 molecule of glucose (not nearly as much energy!!!!) Changes NADH back to NAD+ so glycolysis can continue

2 Fermentation Pathways: 1. Lactic Acid Fermentation: pyruvic acid from glycolysis is converted to lactic acid lactic acid is produced in muscles during rapid exercise (body can't supply enough O2 to the tissues) the build-up of lactic acid causes a burning, painful sensation in your muscles Without enough oxygen, the body can’t produce all of the ATP that is required Lactic Acid Fermentation allows the body to “catch up” from an oxygen deficit so that glycolysis/Krebs cycles can continue (producing more ATP)

Lactic Acid Fermentation Without enough oxygen, the body can’t produce all of the ATP that is required Lactic Acid Fermentation allows the body to “catch up” from an oxygen deficit so that glycolysis/Krebs cycles can continue (producing more ATP)

Alcoholic Fermentation: Occurs in yeast cells & some other microorganisms Pyruvic acid is broken down into a 2-Carbon alcohol plus carbon dioxide

Remember… Glycolysis can occur if oxygen is present or absent Glycolysis is ALWAYS the first step in breaking down glucose If oxygen IS present, then cells proceed with Respiration/Krebs If oxygen is NOT present, then cells ferment