CELLULAR RESPIRATION How Cells Obtain Energy To Sustain Life
ORIGIN OF ENERGY• Nearly all energy for life on earth comes from
sunlight
• Energy in sunlight is captured by photosynthesis
CELLULAR RESPIRATION• The physical act of breathing
and the process of cellular respiration share reactants and products
C
C
C
C
C
C
H
H O
H
H
H
H
HHO
OH
OH
OH
OH
1
2
3
4
5
6
CH2OH
C
C
C
C
COH
OH
HO
H
H
H
OH
HO
H
6
5
4
3 2
1
STARTING MATERIAL FOR CELLULAR RESPIRATION
STARTING MATERIALGlucose:
• All cells must break C-bonds in glucose to release energy
• Energy stored in bonds
ATPEnergyADPWater
P P P P P Pi
Inorganicphosphate
+
H2O+ +
7.3 kcal/molATP
HYDROLYSIS OF ATP RELEASES ENERGY
Bonds in ATP hold significant amount of energy!
MANY REACTIONS REQUIRE AN INPUT OF ENERGY
CATYLSTS INCREASE RATES OF REACTION
• Even with enough energy, there is no guarantee rxns will proceed at a suitable speed
CATYLSTS INCREASE RATES OF REACTIONLock & Key
Model:• Substrate fits into
enzyme like a key
fits into a lock
• Enzyme then catalyzes the chemical reaction and releases the products
Substrate
Enzyme
Substrate (Key)
Enzyme (Lock)
A B —CA B C
A— B C
Shape change
LOCK & KEY MODEL OF ENZYME AND SUBSTRATE
CATYLSTS INCREASE RATES OF REACTION
MOLECULAR HELPERS Two Molecules Help Cell Respiration Proceed:
• Carry (and store) high energy electrons
• Later transfer energy to other molecules