Photosynthesis and
Respiration
What is photosynthesis?
• A chemical reaction that occurs in plants
that changes light energy to chemical
energy
• Energy is stored as sugar
• Occurs in plants and some algae
• Takes place in chloroplasts in
chlorophyll
What happens during photosynthesis?
• Plants capture light energy and use it to make
glucose
• Sunlight provides the energy to change
molecules of carbon dioxide and water into
glucose
• Oxygen is a byproduct and is released during
this process
The photosynthesis recipe
LIGHT ENERGY
Carbon Dioxide + water
REACTANTS
Glucose + oxygen
PRODUCTS
The equation of the chemical reaction
photosynthesis
LIGHT ENERGY
6 CO2 + 6 H2O
REACTANTS
C6H12O6 + 6O2
PRODUCTS
Why is this important to us?
• We cannot make our own food, and depend on
producers such as plants to provide glucose and
energy
• Plants are the first part of food chains, and an
integral (important) part of food webs
• Without producers, consumers would not be able
to get energy, and would most likely die
What about the oxygen released?
• This becomes part
of the air that we
breathe, and is
necessary for all
living things
From the producer to the consumer…
• Once the energy from the sunlight is
converted into chemical energy by
photosynthesis, an organism has to transfer
that energy into a usable form, called ATP
• Transferring the energy into a usable form is
called cellular respiration
Cellular Respiration
• Takes place in the cells and mitochondria of
all living things
• That means Animals AND Plants
• Is a step by step process that breaks down
glucose molecules to release energy
The recipe for cellular respiration
Glucose + oxygen
REACTANTS
Carbon Dioxide + water
+ ENERGY
PRODUCTS
The chemical equation for cellular
respiration is
C6H12O6 + 6O2
6 CO2 + 6 H2O
+ ENERGY
REACTANTS
PRODUCTS
Aerobic Respiration
• Organisms that use Oxygen to free the energy
from their food are said to use Aerobic
Respiration
• Aerobic means “using oxygen”
Anaerobic Respiration
• Organisms that do not use oxygen but have
developed another way to release the energy
from their food are said to use Anaerobic
Respiration.
• Remember that the prefix A- or An- means
NOT so Anaerobic means “not aerobic” or
without oxygen.