Cellular Respiration Harvesting Chemical Energy ATP

“Burn fuels” to make energy combustion making heat energy by burning fuels in one step CO2 + H2O + heat fuel (carbohydrates) O2 aerobic respiration making ATP energy (& some heat) by burning fuels in many small steps Movement of hydrogen atoms from glucose to water ATP food (carbohydrates) O2 ATP + CO2 + H2O (+ heat)

Energy needs of life Animals are energy consumers What do we need energy for? synthesis (building for growth) reproduction active transport movement temperature control (making heat) Which is to say… if you don’t eat, you die… because you run out of energy. The 2nd Law of Thermodynamics takes over!

Where do we get energy? ATP Energy is stored in organic molecules carbohydrates, fats, proteins Animals eat these organic molecules  food digest food to get fuels for energy (ATP) raw materials for building more molecules carbohydrates, fats, proteins, nucleic acids ATP We eat to take in the fuels to make ATP which will then be used to help us build biomolecules and grow and move and… live! heterotrophs = “fed by others” vs. autotrophs = “self-feeders”

Adenosine TriPhosphate What is energy in biology? ATP Adenosine TriPhosphate

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 ATP food O2 Movement of hydrogen atoms from glucose to water glucose + oxygen  energy + carbon + water dioxide C6H12O6 6O2 ATP 6CO2 6H2O  +

Turn to your partner and… Discuss sources of energy Discuss organelle where ATP is produced Why is cellular respiration considered “aerobic”?

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 Make ATP! Make ATP! All I do all day… And no one even notices! food ATP enzymes CO2 H2O O2

Mitochondria are everywhere!! animal cells plant cells

Using ATP to do work? Can’t store ATP ATP too unstable only used in cell that produces it only short term energy storage carbohydrates & fats are long term energy storage Adenosine TriPhosphate work Adenosine DiPhosphate ADP A working muscle recycles over 10 million ATPs per second

In your science notebook…. Reflect on: Why must cells continuously make ATP?

{ { { ATP A Body’s Energy Budget make energy eat food synthesis 1 make energy • energy needed even at rest • activity • temperature control { ATP eat food • growth • reproduction • repair { 2 synthesis (building) • glycogen (animal starch) • fat { 3 storage

Label the diagram Glycolysis involves the breaking down of glucose molecules from carbohydrates into molecules of pyruvate, which will continue on to the Krebs Cycle. This process occurs in the cytosol of the cell and can proceed regardless of the presence of oxygen The reactions of glycolysis produces a net gain of 2 ATP molecules, as well as a release of 2 water molecules and 2 NADH molecules (these are another type of energy-rich molecule) As pyruvate is being shuttled from the cytosol to the interior of the mitochondrion, a microenzyme removes one carbon and two oxygens from each molecule, producing Aceytl CoA. This two-carbon sugar that actually enters the Krebs Cycle. The Krebs Cycle is a series of steps, catalyzed by enzymes, which completely oxidize the Aceytl CoA molecule. The Krebs Cycle is an aerobic process, meaning it needs oxygen to function. Two complete turns of the Krebs Cycle must occur to produce: 4 carbon dioxide molecules, 6 NADH molecules, 2 ATP molecules and 2 FADH2 molecules (yet another energy-yielding molecule). Most of the energy locked in the original glucose molecule will be released by the electron transport chain and oxidative phosphorylation. The electron transport chain is a network of electron-carrying proteins located in the inner membrane of the mitochondrion. These proteins transfer electrons from one to another, down the chain, much in the way a bucket brigade passes buckets of water. These electrons will eventually be added, along with protons, to oxygen, which is the final electron acceptor. This produces water, but does not produce any ATP. The ATP is actually produced by a proton motive force. This force is a store of potential energy created by the gradient formed when hydrogens (protons) are moved across a biological membrane. Therefore, the electron transport chain merely produces a gradient through which ATP can be made (this is known as chemiosmosis). The electron transport chain produces the remaining 32-34 ATP.

Where does cellular respiration take place? Glycolysis occurs in the cytoplasm, while the Krebs cycle and the ETC occurs in the mitochondria

Steps of Cellular Respiration

One more way to look at it….

What if oxygen is missing? No oxygen available = can’t complete aerobic respiration Anaerobic respiration also known as fermentation alcohol fermentation lactic acid fermentation no oxygen or no mitochondria (bacteria) can only make very little ATP large animals cannot survive yeast bacteria

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

Why is it an adaptive advantage to a cell to be able to perform either fermentation or the krebs cycle? The Krebs cycle provides a pathway for obtaining energy when oxygen is present-Aerobic respiration Fermentation provides a pathway for obtaining energy when oxygen is not present-Anaerobic respiration Krebs provides a pathway for obtaining energy when oxygen is present, Fermentation provides a pathway for obtaining energy when oxygen is not present

Prior to entering the krebs cycle, two molecules of ____are broken down to form _____ C6H12O6, pyruvate C6H12O6, acetyl-CoA pyruvate, acetyl-CoA acetyl-CoA, C6H12O6 Two molecules of pyruvate are broken down to form acetyl-CoA

In what type of cell’s would you expect to find the most mitochondria? Muscle cells

What role does oxygen play in cellular respiration and photosynthesis? O2 serves as a reactant in cellular respiration and as a product in photosynthesis