Cell Respiration

Sources of Energy Sunlight and Food –Both strive to provide cells with a source of Glucose! Glucose holds 90 times the energy of an ATP molecule. –Glucose can release 3811 Calories –Define calorie:

Cellular Respiration Instead of releasing all of the energy at once (would be disastrous for the cell) in a step-wise fashion. Glycolysis is the first step in this release of energy. Glycolysis is the splitting of glucose to create energy!! 6O 2 + C 6 H 12 O 6  6CO 2 + 6H 2 O + Energy

Glycolysis Takes place in the cytoplasm. –This should make sense! Why? Plant cell’s glucose is made where? Animal cell’s glucose comes from where? One molecule of Glucose is spit. 2 Pyruvic Acid molecules are created. 1*(C6) = 6 Carbons 2*(C3) = 6 Carbons

Glycolysis – The Energy Carriers Creates ATP Also creates NADH FADH 2 Each time NADH or FADH2 is created, electrons are transferred to create the compound.

Glycolysis 1 Glucose becomes 2 Pyruvic Acids. In order to create energy, Glycolysis needs a jumpstart. –2 ATP are put in to fuel the reactions –4 ATP are made –2 NADH are made –Net of 2 ATP

After Glycolysis Aerobic vs Anaerobic If Oxygen is present  Krebs Cycle + ETC –Takes place in the mitochondria No Oxygen  Anaerobic Respiration –Remains in the cytoplasm

Krebs Cycle In aerobic environments the second stage of cell respiration takes place in the mitochondria.

Krebs Cycle A. Before Pyruvate enters the Krebs Cycle it has to be prepared. –Pyruvate is brought into the Mitochondria –Pyruvate reacts with Conzyme A and NAD+ to make Acetly CoA, NADH and releases CO 2

Krebs Cycle B. The prepared Pyruvate, now Acetyl CoA, reacts with a 4C compound to make Citric Acid(6C). NADH+ is also converted to NADH. –Acetyl CoA 2C = 2C –4C compound = 4C –Citric Acid Total = 6C C. Citric Acid is broken down to a 5C compound, releasing CO2 and generating more NADH –Citric Acid = 6C –5C compound = 5C –1 CO 2 = 1C –Total = 6C

Krebs Cycle

D. The 5C compound is broken down to a 4C compound, making more CO 2, NADH AND ATP. –5C compound = 5C –1CO 2 = 1C –4C Compound = 4C –Total = 5C The 4C compound is transformed back into the starting 4C compound, and produces FADH 2.

Electron Transport Chain The molecules of ATP are used by the cell for activities. The NADH and FADH 2 made by the Krebs Cycle are brought to the inner membrane of the mitochondria where they are passed down the electron transport chain. Ultimately, the end of the ETC ends with Oxygen accepting the electrons and forms water.

Electron Transport Chain

As each complex passes the electrons brought in by HADH and FADH 2, H+ ions are pumped into the intermembrane space of the mitochondria. Just like with photosynthesis, these H+ ions are used to power ATP Synthase to create ATP from ADP and phosphate in the matrix.

Review H+ ions build up between the membranes. ATP is synthesized in the matrix! CO 2 is released

Totals – 36 ATP FORMED! Glycolysis: –2 ATP formed –2NADH formed  6 ATP Each NADH makes 3 ATP 6 more ATP Krebs Cycle: –2 ATP are formed in the cycle –8 molecules of NADH are formed  24 ATP Each NADH generates 3 ATP 24 additional ATP formed –2 molecules of FADH2 are formed  4 ATP Each FADH2 generates 2 ATP 4 additional ATP formed

Fermentation When Oxygen is not present Glycolysis is followed by another process. Fermentation Occurs! During this process, the lack of Oxygen prevents the Pyruvic Acid from entering the mitochondria. Instead, the NADH produced is recycled back to NAD+

Fermentation Alcohol Fermentation: formation of ethyl alcohol –Carried out by yeast. –Used to make bread –Pyruvic acid + NADH  alcohol + CO 2 + NAD+ Lactic Acid Fermentation: formation of lactic acid –Overworked muscle cells do this! –Used to make pickles and other foods –Unicellular organisms use this process to make ATP –Pyruvic acid + NADH  lactic acid + NAD+

Energy and Exercise Cells contain only a small amount of available ATP. This can only sustain them for a few seconds. After a few seconds, the only source of new ATP is from lactic acid fermentation (not enough Oxygen getting to your cells). Cell Respiration is a slower process, and can be used to sustain energy over longer periods.

Photosynthesis vs Cell Resp. PhotosynthesisCellular Respiration Function Location Reactants Products Equation