Energy in food
 Carbohydrates (17 kJ g -1 )
Proteins (17 kJ g -1 )
Lipids (34 kJ g -1 )


These are sources of reduced carbon
This can supply hydrogen atoms
 protons (H + ) + electrons (e )
© 2010 Paul Billiet
ODWS

Energy transformations
Light

Chemical (mostly in chemical bonds)
Chemical

Heat
Chemical

Kinetic (movement)
Chemical

Chemical
COUPLED REACTIONS e.g. Food

ATP
© 2010 Paul Billiet
ODWS

The energy in Adenosine
Triphosphate (ATP)
ADP + Pi

ATP + H
2
O

E = + 30.5 kJ mol -1
Inorganic phosphate
ADENOSINE

P

P

P
High energy bond
© 2010 Paul Billiet
ODWS

A stepwise energy release is needed
Complete oxidation of glucose
C
6
H
12
O
6
+ 6O
2

6CO
2
+ 6H
2
O

E = 2880 kJ mol -1
Complete oxidation of a fat (lipid)
C
18
H
34
O
2
+ 25.5O
2

18CO
2
+ 17H
2
O

E = 9800 kJ mol -1
© 2010 Paul Billiet
ODWS

Respiration is efficient







This is too much to handle all at once
Energy is released step by step
Coupled to ATP synthesis
The energy in 1 molecule of glucose is used to synthesise 36 molecules of ATP
37.5 % efficient
This is a very efficient energy conversion
Because the release of the energy from the food molecules is done stepwise
© 2010 Paul Billiet
ODWS

Coupling the energy released from glucose to ATP
Two reaction pathways
 GLYCOLYSIS in the cytoplasm
 KREB'S CYCLE in mitochondria of eukaryotes (in the cytoplasm of prokaryotes)
© 2010 Paul Billiet
ODWS