Review What is photosynthesis? Where does this occur? What is the difference between ATP and ADP? What is the difference between NADPH and NADP+? Light dependent vs. Light independent reactions
Chemical Energy & Food Organisms get the energy they need from FOOD. Energy stored in food is expressed in units of CALORIES. 1 calorie = the amt. of energy needed to raise the temp. of 1 g of H2O by 1°C.
Chemical Energy & Food Different foods are capable of storing different amounts of energy: 1 g glucose: 3811 calories (3.811 kcal) 1 g beef fat: 8893 calories (8.893 kcal)
How is the energy in sugar (glucose) molecules released so it can be used by the cells of an organism? cellular respiration! Cellular Respiration occurs in both plant & animal cells
WHERE????
CYTOPLASM & MITOCHONDRIA!!!
The POWERHOUSE of the Cell!!
Cellular Respiration… A Controlled Process
Food (glucose), like fuel, is "burned" by our cells for energy
however, 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 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
AMP
ADP
P P
ATP
Cellular Respiration:
A process 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:
Glycolysis Krebs cycle Electron transport chain
“RESPIRATION” (uses oxygen)
GLYCOLYSIS (glyco= sugar, lysis = breaks down) Process occurs in the cytoplasm Breaks glucose down from 6-carbon compound into two 3-carbon compounds (called PYRUVATE or PYRUVIC ACID) ACID Equation for glycolysis:
C6H12O6
enzymes in cytoplasm
2 pyruvates + 2 ATP
Glycolysis can occur if oxygen is present (aerobic) or absent (anaerobic) Glycolysis is ALWAYS the first step in breaking down glucose If oxygen IS present, then cells proceed with Krebs cycle & electron transport chain If oxygen is NOT present, then cells will carry out fermentation
Cellular Respiration can be broken down into 3 processes: 1) Glycolysis: glucose is broken into 2 pyruvate; 2 ATPs produced; electrons from glucose passed to NAD + NADH 2) Krebs Cycle: pyruvate broken down into CO2 (waste) & electrons are passed to NAD+ NADH; 2 ATPs produced 3) Electron Transport Chain: high energy elec. from glycolysis & Krebs (NADH) are used to convert ADP ATP; oxygen must be present
GLUCOSE
CO2
H2O & heat energy
O2
Glucose + Oxygen
C6H12O6
+ 6O2
Carbon Dioxide + Water
6CO2
Look familiar???
+
6H2O
Krebs Cycle & E.T.C.
Occur in the MITOCHONDRIA of a cell Only if oxygen is PRESENT (aerobic) Use the pyruvic acid from glycolysis to produce carbon dioxide, water, and ATP
Products: 34 ATP per molecule of glucose carbon dioxide water
So how does this happen? The KREBS CYCLE breaks the bonds of pyruvate; high-energy electrons are passed to NAD + NADH; waste product CO2 produced; 2 ATPs produced. ELECTRON TRANSPORT CHAIN: uses high-energy electrons from NADH (&FADH2) from gly. & Krebs to convert ADP ATP
The NADH and FADH2 (from glycolysis & Krebs cycle) carry energy to the electron transport chain to make more ATP (this requires oxygen; oxygen acts as the final electron acceptor in the chain)
Equation for Respiration: C6H12O6 + 6O2
6CO2 + 6 H2O + 36 ATP
Summary of Cellular Respiration GLYCOLYSIS “break sugar” Location in the cell: It starts with: It ends with: Is Oxygen required? # of ATP’s Produced:
Krebs Cycle & E.T.C.
Cytoplasm
Mitochondria
C6H12O6 (glucose)
2 pyruvic acid O2 H2O, CO2, ATP
2 (C3H6O3) pyruvic acid NO (ANAEROBIC) 2 (tiny)
YES! (AEROBIC) 34 (lots!)
GRAND TOTAL = 36 ATP!!
2 are produced in Glycolysis, 2 in Krebs Cycle, and 32 in Elec. Trans. Chain 18
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 36% 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 64%??? It is released as heat.
