Photosynthesis
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Plants use photosynthesis to make food (glucose).
Photosynthesis requires inputs of sunlight, CO2, and H2O.
Photosynthesis outputs are glucose and O2.
Glucose (C6H12O6) is a simple sugar.
Glucose is a short-term source of chemical energy for nearly all
living things.
Chemical energy is stored in the chemical bonds of glucose.
When chemical bonds are broken, energy is released.
Without sunlight, CO2, or H2O, plants would die.
The balanced equation for photosynthesis is:
6CO2 + 6H2O + Light energy → C6H12O6 + 6O2
Cellular Respiration
 All living things “burn” glucose (C6H12O6) in a process called cellular
respiration.
 Cellular respiration requires inputs of C6H12O6 and O2.
 Cellular respiration outputs are H2O and CO2 and ATP
 Animals breathe in O2 and breathe out CO2.
 ATP is a quick source of chemical energy for nearly all living things.
 Chemical energy is stored in the chemical bonds of ATP.
 When chemical bonds are broken, energy is released.
 Without glucose (C6H12O6) or O2, living things would die.
 The balanced equation for cellular respiration is:
C6H12O6+ + 6O2 → 6CO2 + 6H2O + ATP
Energy-rich Molecules
 Glucose (C6H12O6) is a simple sugar.
 When hundreds to thousands of glucose molecules join together
in plants if forms starch.
 When hundreds to thousands of glucose molecules join together
in animals if forms glycogen.
 Glucose, Starch, and glycogen are carbohydrates.
 Glucose is a short-term source of chemical energy for all cells.
 Glycogen is an intermediate-term source of energy for animals.
 Lipids (fats) are a long-term source of chemical energy for
animals.
 Starch is a long-term source of energy for plants.
 ATP is a very quick source of chemical energy for all cells.
Relationships
What would happen if a snail and an elodea plant are placed in
a sealed test tube with some air, water, and sunlight?
Answer: The snail and elodea plant would keep each other alive.
The snail breathes out CO2 that elodea needs for photosynthesis.
With sunlight, CO2, and water, elodea makes glucose and O2.
Elodea uses some of its glucose to grow and reproduce. The snail
gets its glucose from eating some of the plant. The O2 released by
elodea is breathed in by the snail. The snail uses O2 to “burn”
glucose in a process called cellular respiration.
Carbon Cycle I
 CO2 is a gas in our atmosphere that contains the element carbon.
 Plants take the carbon from six CO2 molecules and place them in a
glucose (C6H12O6) molecule in a process called photosynthesis.
 Plants also use carbon to make organic molecules needed for
growth and reproduction.
 Organic molecules include proteins, lipids, nucleic acids, and
carbohydrates (like glucose). These all contain carbon.
 Plants are the source of carbon for all animals.
 Plants and animals “burn” glucose through cellular respiration.
 During cellular respiration, the carbon from glucose (C6H12O6) is
used to form six CO2.
 Animals return CO2 to the atmosphere when they breathe out.
Carbon Cycle II
 When animals and plants die, their organic matter is decomposed.
 Decomposers include mushrooms, worms, beetles, and bacteria.
 Decomposers break down organic matter, placing carbon into the
soil.
 Over millions of years, soil carbon is transformed into fossil fuels.
 Fossil fuels include oil, coal, and natural gas.
 The burning of fossil fuels releases CO2, returning carbon back to
the atmosphere.