Cell Energy
Photosynthesis and
Respiration
Photosynthesis
• Photosynthesis- process by which plants
& certain other organisms use sunlight
to make sugar
• Energy conversionsolar energy food (sugar)
• Takes place in chloroplasts containing
chlorophyll (green pigment in cells)
Sources of Energy
• Nearly all living things obtain energy either
directly or indirectly from the energy of
sunlight captured during photosynthesis.
• Autotrophs-organism that make its own
food
• Heterotrophs-organism that cannot make its
own food; obtain food by eating other
organisms or absorbing their food.
Stages of Photosynthesis
• 1. Sunlight is captured by chlorophyll,
this happens during the day.
• Chlorophyll acts like the solar cell of a
calculator.
• 2. Energy is used to make food or
manufacture sugar; this can happen
during the day or at night.
Ingredients of Photosynthesis
• Raw Materials:
• H2O (water), absorbed through the roots
• CO2 (carbon dioxide) gas enters through
stomata (small hole) in leaves
• Products:
• C6H12O6 (sugar), uses the energy to carry out
important cell functions.
• O2 (oxygen), exits through the stomata
Formula
sunlight
6 CO2 + 6 H2O --- C6H12O6 + 6 O2
chlorophyll
Oxygen-Carbon Dioxide Cycle
• Gases are exchanged between
organisms
-------- CO2
O2 -----
What is Cellular Respiration?
• Respiration is the process by which
cells obtain energy from glucose.
• Cells break down simple food molecules, like
sugar and release the energy they contain.
• Energy stored in cells is like money in a savings
account; you can withdraw it as needed.
• Why would plants need to use stored energy
during the winter months?
Stages of Aerobic Respiration
1. First stage takes place in the cytoplasm of
cells. Molecules of glucose (sugar) are broken
down into smaller molecules. Oxygen is not
involved, little energy released.
2. Second stage takes place in mitochondria,
the “powerhouse.” Here the small molecules
are broken down even smaller.
Respiration
Formula for respiration:
• C6H12O6 + 6 O2  6 CO2 + 6 H2O + ATP
(energy)
Photosynthesis and respiration are opposites of
each other.
• 6 CO2 + 6 H2O --- C6H12O6 + 6 O2
Fermentation
• Provides cell with energy
without using oxygen
• Yeast and other single-celled organisms
break down sugar and in the process
energy is released.
• Products = CO2 + alcohol + ATP (energy)
• Beer, wine, bread are produced with yeast
Lactic Acid Fermentation
• Sometimes the need of
muscles for energy is
greater than the ability
to obtain oxygen.
• When this happens,
muscles use
fermentation to get
energy and you may
feel tired and sore.