Energy:
• All living things must obtain
and use energy E
• Energy cannot be created
nor destroyed
• Energy can be transformed
Energy (cont).
• The only constant source of
energy for the earth is the sun
• Almost all living cells depend
on the sun for energy either
directly or indirectly.
Glucose and the cell:
• C6H12O6
• Glucose is the final product of
photosynthesis
• Glucose is used by most living
cells as the primary food
molecule.
Photosynthesis
Chemical Reaction
of Photosynthesis:
6CO2 + 6H2O + LIGHT 
C6H12O6 + 6O2
Photosynthetic
Organisms:
• Autotrophs or Producers
convert the E in sunlight to
chemical E in food (sugar)
Autotrophs:
• Examples of autotrophs
include: Plants, algae, and
some bacteria.
b/g
Plant algae
algae
Autotroph
• Auto ---- “self”
• Troph ---- “feeder”
• Autotrophs produce their
own food, and are the
basis for the food chain.
Photosynthesis:
•Stores light E in the
chem bonds of sugar:
6CO2 + 6H2O + LIGHT 
C6H12O6 + 6O2
Photosynthesis
• The  in the reaction represents
many intermediate steps.
• Two main categories:
–light reactions- trapping E
from sunlight
–dark reactions- storing E in
sugars
Chlorophyll
• Chlorophyll- the material that
allows plants to trap the E from
sunlight.
• Chlorophyll absorbs blue and
UV light, and red light.
• Chlorophyll reflects green, and
most yellow light
Photosynthesis
• Takes place in the
chloroplasts
• Light Reactions occur in the
thylakoids
• Dark Reactions occur in the
stroma
Light
H 2O
CO2
Light
Reactions
Dark
Reactions
O2
Glucose
Light Reactions
• Process by which the energy
from sunlight is captured by
chlorophyll. (in the thylakoid
membrane)
• O2 is given off as a byproduct
Dark Reactions
(aka Calvin Cycle)
• Process by which energy from
the light reactions and CO2
are used to build glucose
molecules.
• C6H12O6
Cellular
Respiration
THE GOAL:
TO PRODUCE
ATP FOR USE
WITHIN THE
CELL!
Energy Storing
Compounds
• Starches, sugars, even
gasoline are E-storing
compounds
• Principle E-storing
compound for the cell is
ATP
ATP
• “Adenosine Triphosphate“
• Made up of
–Adenine (nitrogenous
base)
–Ribose (5-C sugar)
–Three phosphates
ATP
• Energy is stored when
phosphates are added
– ADP + P (+ energy)  ATP
• Energy is released when
phosphates are removed
– ATP  ADP + P (+ energy)
Cellular Respiration
• Catabolism is breaking down
chemicals into their parts
• Cellular Respiration is
catabolism that releases
energy for use in the cell (ATP)
• Can be Aerobic (with O2), or
Anaerobic (without O2)
Aerobic Respiration
C6H12O6+O2CO2+H20 + (E)
Energy is released from the
sugar in the form of ATP
for use within the cell.
Aerobic Respiration
• Requires the
presence of O2
• Extremely efficient
– produces approx. 36 ATP
per glucose molecule
Steps of Aerobic
Respiration:
1. Glycolysis
2. Krebs Cycle
3. Electron Transport Chain
(ETC)
Glycolysis
• Takes place in the cytoplasm
• “Glyco” meaning “sugar”
• “lysis” meaning “to break”
• Glucose molecules are broken
down into pyruvic acid which
will then enter the Krebs cycle
Cytoplasm
Krebs Cycle
• Takes place in the matrix of the
mitochondria
• Pyruvic acid from glycolysis is
broken down to produce high
energy molecules (NADH and
FADH2 - which go to the ETC)
• CO2 is given off as a byproduct
Mitochondria
Mitochondrion
Matrix
Electron Transport
Chain (ETC)
• Like the Krebs Cycle, ETC
takes place in the mitochondria
• Specifically, the ETC occurs in
the Inner Membrane and the
Intermembrane Space of the
mitochondria.
Mitochondrion
Inner Membrane
Mitochondrion
Outer Membrane
Mitochondrion
Intermembrane Space
ETC cont.
• Folds and projections
called crista (cristae) in the
inner membrane of the
mitochondria increase the
surface area available for
the reactions.
Mitochondrion
Crista
ETC cont.
• Most of the ATP from Aerobic
Respiration is generated by the
Electron Transport Chain
• This series of reactions
converts the high energy
molecules from the Krebs Cycle
into ATP for use in the cell
• Oxygen is required
Anaerobic
Respiration
• Takes place when O2 is not
present.
• Far less efficient than
aerobic respiration
–produces approx. 2 ATP
per glucose molecule