Biology
Class Notes
4-3
Topic: Cellular Respiration
Aim: How do cells produce energy?
(A) CHEMICAL ENERGY & FOOD
 food provides living things with the chemicals they need to
survive—to perform all life processes
 Food serves as a source of energy
 Cells gradually release the energy from glucose and other
food compounds
 Glycolysis: when a molecule of glucose is broken down—first
step in cellular respiration
 no oxygen present--fermentation
(B) CELLULAR RESPIRATION



In the presence of oxygen, glycolysis is followed by the Krebs
cycle and the electron transport chain.
**cellular respiration: the process that releases energy by
breaking down glucose and other food molecules in the
presence of oxygen
Three stages of cellular respiration—each one captures some
of the energy available to make ATP
o Glycolysis
o Kreb’s cycle
o Electron transport chain
Glycolysis
*the process in which
one molecule of
glucose is broken in
half
*produces pyruvic
acid
**2 ATP/GLUCOSE
Kreb’s cycle
*carbon dioxide is
produced
Electron transport
chain
*uses the electrons
from the Kreb’s cycle
to convert ADP to ATP
**the end result is 36
ATP per one
GLUCOSE molecule
(C) Comparing
 If you were to think of these processes as being in an energy
bank
o photosynthesis—deposits energy
o respiration—withdraws energy
Photosynthesis
Cellular Respiration
Function
Energy capture
Energy release
Occurs in
Chloroplast
mitochondria
Reactants
Water + Carbon Dioxide
Oxygen + glucose
Products
Oxygen + glucose
Water + carbon dioxide +
ATP
Equation
Water + carbon dioxide → Oxygen + glucose → water +
oxygen + glucose
carbon dioxide + ATP
(energy)