Cellular RespirationVocabulary:-Glycolysis-Krebs Cycle-Pyruvic acid-Fermentation-Aerobic Reaction-Anaerobic Reaction
ReviewWhat is photosynthesis?Where does this occur?What is the difference between ATP and ADP?What is the difference between NADPH and NADP+?Light vs. Dark reactions
After glucose is made in photosynthesis, how is the energy in the sugar molecules released so it can be used by the organism? cellular respiration!Cellular Respiration occurs in both plant & animal cells WHERE????CYTOPLASM & MITOCHONDRIA!!! The Power House of the Cell!!
Cellular RespirationA Controlled ProcessFood (glucose), like fuel, is "burned" by our cells for energyif it's burned all at once, too much energy is releasedtherefore, the reaction is broken down into many small steps controlled by ENZYMESCells gradually release the energy from glucose and other compounds
the energy is transferred to the bonds of ATP which stores and releases the energy in usable amounts to be used by the cell
energy is stored in bonds between phosphate groups
Cellular RespirationProcess that releases ENERGY by breaking down food molecules in the presence of oxygen
Occurs in both plants and animals
Cell respiration occurs in 3 stages:
GlycolysisCitric (Krebs) cycleElectron transport chain
Glycolysis(glyco= sugar, lysis = breaks down)Process occurs in the cytoplasmBreaks glucose down from 6-carbon compound into two 3-carbon compounds (called pyruvate)Equation: enzymes in C6H12O6 2 pyruvates + 2 ATP cytoplasm
Glycolysis can occur if oxygen is present (aerobic) or absent (anaerobic)Glycolysis is ALWAYS the first step in breaking down glucoseIf oxygen IS present, then cells proceed with Respiration/KrebsIf oxygen is NOT present, then cells ferment
Cellular Respiration can be broken down into 2 processes:
Glycolysis: breaking down glucose
Respiration (Krebs Cycle & Electron Transport Chain): uses oxygen to finish breaking down products from Glycolysis & release energy
GLUCOSEO2CO2H2O & heat energyGlucose + Oxygen Carbon Dioxide + WaterC6H12O6 + 6O2 6CO2 + 6H2O Look familiar???
Respiration/Krebs Occurs in the Mitochondria of cellOnly if oxygen is PRESENT (aerobic)Uses the pyruvic acid from glycolysis to produce carbon dioxide, water, and ATPProducts: 34 ATP per molecule of glucose carbon dioxidewater
So how does this happen?The Citric (Krebs) cycle and the electron transport chain turn the pyruvate into CO2, H2O, and ATP
To do this, pyurvate loses a carbon atom to make Acetyl CoA
Acetyl CoA enters the Krebs Cycle to produce CO2, NADH, and FADH2The NADH and FADH2 carry energy to the electron transport chain to make more ATP (this requires oxygen)
C6H12O6 + 6O2 6 CO2 + 6 H2O + 36 ATP
Summary of Cellular Respiration
GLYCOLYSISbreak sweetnessRESPIRATION/ Krebs CycleLocation in the cell:CytoplasmMitochondriaIt starts with:C6H12O6 (glucose)2 pyruvic acidIt ends with:2 (C3H6O3) pyruvic acidH2O, CO2, ATPIs Oxygen required?NOYES! AEROBIC# of ATPs Produced:2 (tiny)34 (lots!)
GRAND TOTAL= 36 ATP!!2 are produced in Glycolysis and 34 in Respiration/ Krebs Cycle18 times more ATP are produced in the presence of Oxygen!!
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 doesnt seem like much, this is more efficient than your cars gas burning engine
What happens to the remaining 62%??? It is released as heat.
What happens if your cells arent getting enough oxygen?Respiration/Krebs CANNOT proceedFermentation occursPyruvic Acid builds up in animal muscle cells as LACTIC ACID feel the burn!
In other organisms, the pyruvic acid builds up, ferments, and becomes alcohol
Fermentation: release of energy from food molecules in absence of oxygen (anaerobic)
Enables cells to carry out energy production in the absence of Oxygenresult of glycolysis + fermentation yields 2 ATP molecules per 1 molecule of glucose (not nearly as much energy!!!!)
2 Fermentation Pathways:1.Lactic Acid Fermentation:pyruvic acid from glycolysis is converted to lactic acidlactic 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
Energy & Exercise: Quick EnergyMuscle cells only contain enough ATP for a few seconds of burst energy emergency, starting gun of raceWhen this is gone, cells resort to lactic acid fermentation which can provide enough ATP for about 90 seconds
Long Term EnergyIf a race or energy need is longer, your body must go through cellular respiration to get enough ATP to continueEven well-conditioned athletes have to pace themselvesYour body stores energy in muscleglycogen these stores are enough to last for 15-20 minutes of activity when broken down through cellular respirationAfter this, your body begins to break down fats and other stored molecules
Alcoholic Fermentation: Occurs in yeast cells & some other microorganismsPyruvic acid is broken down into a 2-Carbon alcohol plus carbon dioxide
Alcoholic FermentationImportant to brewers & bakers! When yeast in dough runs out of oxygen it ferments, giving off bubbles of carbon dioxide gaswhich forms air space in breadAlcohol produced in the dough evaporates when bread is baked*(when the level of alcohol reaches 12%, yeast cells die)