Unit 3
• Living things use energy for
•Growth
•Repair
•Reproduction
•Metabolism
• The collection of reactions that occur in a cell
• Involves either:
• Using energy to build molecules
(condensation reactions)
or
• Breaking down molecules to
release the stored energy
(hydrolysis)
• Photosynthesis is the process by which
light energy is converted to chemical
energy
• Organisms that use energy from sunlight
(or from chemical bonds in inorganic
substances) to make organic compounds
are called autotrophs
• Organisms that must get energy from food
instead of directly from sunlight (or
inorganic substances) are called
heterotrophs
• Heterotrophs get energy from food
through the chemical process of cellular
respiration, remember that autotrophs
perform cellular respiration also!
• Photosynthesis changes the energy of
sunlight into the chemical energy stored in
glucose bonds
• Photosynthesis is the connection between
the sun and the energy needs of living
systems
• 6CO2 + 6H2O  C6H12O6 + 6O2
carbon dioxide +
water

glucose
+ oxygen
• In addition to water and carbon dioxide,
photosynthesis requires light and
chlorophyll
• The chlorophyll inside the chloroplast of
leaves absorb light
• Chlorophyll does not absorb all the
wavelengths of visible light equally
• Chloroplast – organelle
in plants where
photosynthesis takes
place
• Thylakoids – Saclike
photosynthetic
membranes
• Grana- Stacks of
thylakoids
• Stroma- aqueous region
outside the grana
• Breaks apart H2O to
produce oxygen gas
• Convert ADP and
NADH+ into ATP and
NADPH
• Takes place within the
thylakoid membranes in
the chloroplast
• Uses ATP and NADPH
from the light dependent
reactions
• Produces high-energy
sugars
• Takes place in the stroma
of the chloroplasts
• Does not require light
• Water
• Temperature
• Depends on enzymes that
function best between 0oC and
35oC
• Intensity of light
• Increasing light intensity increases
the rate of photosynthesis to a
point
• Carbon Dioxide Concentration
• Nutrients
• Glycolysis does not require oxygen.
• Aerobic respiration: oxygen is present, glycolysis is followed by
the Krebs cycle and then the electron transport chain.
• Anaerobic respiration: no oxygen, glycolysis is followed by
fermentation
• 3 Stages of Aerobic Cellular Respiration:
1. Glycolysis
2. the Krebs cycle
3. the electron transport chain
• Each of the 3 stages of cellular respiration uses energy from food to produce
ATP
• Respiration begins with a pathway called
Glycolysis.
•Glycolysis releases a small amount of energy.
•Uses 2 ATP to make 4 ATP and 2 pyruvic
acids
• The “power house” of the cell, because most of the ATP
is produced here.
• Oxygen is required
• During the Krebs cycle, pyruvic acid is broken down
into:
• CO2
• NADH
• FADH2
• ATP: The Krebs Cycle
makes 2 ATP
• Each pair of high-energy
electrons moves down the
electron transport chain
(ETC) and provides the
energy to produce more
ATP.
The break down of glucose
by aerobic cellular
respiration results in the
production of 36 molecules
of ATP.
• When oxygen is not present, glycolysis is
followed by a different pathway.
2 types of fermentation: anaerobic (no oxygen)
Lactic Acid Fermentation
Alcoholic Fermentation
• No ATP are produced
• Lactic Acid Fermentation
• Pyruvic acid  lactic acid
(lactate)
• Alcoholic Fermentation
• Pyruvic acid  ethanol & CO2
• DURING ANAEROBIC
RESPIRATION ONLY 2 ATP
ARE MADE
• A high energy molecule that stores energy
needed by cells
• Made in the mitochondria
• Composed of:
• Ribose (5 carbon Sugar)
• Adenine (nitrogenous base)
• 3 phosphate groups
(group of molecules made up of phosphorous and
oxygen)
• The removal of 1 phosphate group from ATP produces
ADP (Adenosine DiPhosphate)
• This reaction releases energy in a way that enables
cells to use the energy
• Plants also contain the organelle,
mitochondria, which converts the
high energy carbohydrates made
by the plant through photosynthesis
in the chloroplast into ATP for the
plant to use to perform cellular
functions.