1. Cellular Respiration, Photosynthesis, & Plants
I. Cellular Respiration
Cellular Respiration – the process
that releases energy by breaking
down glucose & other food
molecules in the presence of oxygen.
Equation :
6O2 + C6H12O CO2 + 6H2O + Energy
Oxygen + glucose carbon dioxide + water + Energy
(Reactants) (Products)
*The most common source of food energy is found in the
carbohydrates that organisms eat.
*Most important product of respiration is energy for life
processes.

2. Cellular Respiration occurs in 3 steps :
1. Glycolysis – process in which 1
molecule of glucose is broken in half, producing 2 molecules of pyruvic acid, a 3-carbon compound.
-End result of glycolysis is 4 ATP
molecules.
ATP – (adenosine triphosphate)
main energy-storing molecule
used by organisms.
-In the absence of oxygen,
glycolysis is followed by
fermentation – production of
ATP without oxygen (anaerobic
respiration).

3. 2 Main types of fermentation :
A. Alcoholic fermentation – produces alcohol & CO2 (bread) as wastes.
B. Lactic acid fermentation – produces lactic acid that builds
up in muscle.
-Happens when the body can’t supply
enough oxygen to the tissues-
muscles fatigue, ache, or burn.
-The last 2 steps of cellular respiration
are aerobic (need oxygen to happen).
-Oxygen’s role in cellular respiration
is to act as the final hydrogen
(electron) acceptor in the reaction.

4. The Krebs Cycle
2. The Krebs cycle – process by which pyruvic acid is broken down into carbon dioxide.
-The Krebs cycle generates
high-energy electrons that are
passed to NADH & FADH2.
-The energy stored in NADH
& FADH2 hydrogen bonds
are transferred to ATP
phosphate bonds in the
electron transport chain.

5. Electron Transport Chain
series of proteins in which
high-energy electrons are
used to convert ADP into
ATP.
*Most ATP produced by
cellular respiration is
formed here.

6. II. Photosynthesis Photosynthesis – process by which
plants use the energy of sunlight to
convert water & carbon dioxide into
carbohydrates (sugar & starches) &
oxygen. Equation :
(Light energy)
6CO2 + 6H2O C6H12O6 + 6O2
(Reactants) (Products)
Carbon dioxide + water sugar + oxygen
-The most important product of the reaction, glucose (an
organic molecule), is used by plants to store energy for the
production of ATP. No glucose = no energy for cells.

7. Photosynthesis happens in 2 stages :
1. Light-dependent reactions that
produce oxygen, ATP, & NADPH.
2. The Calvin cycle that produces sugars (C6H12O6).
-The separation of carbon from
carbon dioxide (carbon fixation)
occurs in the Calvin cycle.
-The major photosynthetic pigment,
chlorophyll is needed by plants in
order to do photosynthesis.
-Chlorophyll doesn’t absorb green
light, it reflects it. Plants appear to be
green in color but do not use the green
wavelength of light for photosynthesis.