• Cells need energy because the organism
needs energy. Remember, cells do all of
an organism’s functions.
• Organisms get their energy by eating
foods containing Carbohydrates, Proteins,
• Here’s how it works…..
5. The energy inside of the food
molecules is released inside the
Today we will
learn how the
released so the
cell can use it.
Energy is like a Bank Account
• You DEPOSIT energy into your account
when you eat food.
• You WITHDRAW energy from your
account when your cells perform
respiration to break down the food.
• The Digestive System converts food into
GLUCOSE – a type of sugar.
• RESPIRATION – is the process cells use
to break down Glucose into useful cell
energy. IT REQUIRES OXYGEN.
• Cells in all living things use respiration
• Animal, Plant, and Bacteria cells all
Don’t get confused
• We often use the words respiration and
breathing in everyday life as the same
• WE ARE NOT TALKING ABOUT
• Our definition of respiration is the process
cells use to break down glucose into
useful cell energy.
Stages of Respiration
There are 2 stages of respiration. Together
they make up what we call respiration.
• Occurs in the Cytoplasm.
• Molecules of glucose are broken down into
smaller molecules. Oxygen is NOT involved
and only a small amount of energy is
Stages of Respiration
• Takes place in the Mitochondria.
• The small molecules from Stage 1 are
broken down even smaller. These chemical
reactions require oxygen and they release a
great deal of energy.
A TRANSPORT PROTEIN BRINGS THE
GLUCOSE INTO THE CELL
RESPIRATION: STAGE 1
The glucose is broken down into smaller
molecules in the cytoplasm. This gives off a
little bit of energy.
RESPIRATION: STAGE 2
• Chemical Equations are quick ways of
understanding the chemical reaction that
you are studying.
• They always look a certain way.
REACTANTS are all the chemicals that go into the
reaction. It’s what the process STARTS with.
There can be a lot of reactants or only a few. You
put a + sign in between them.
(LIKE INGREDIENTS FOR A CAKE)
PRODUCTS are all the chemicals that are
produced by the reaction. It’s what the process
ENDS with. There can be a lot of products or only
a few. You put a + sign in between them.
(LIKE THE FINISHED CAKE)
THE RESPIRATION CHEMICAL
C6H12O6 + 6O2 6CO2 + 6H2O + ENERGY
SUGAR + OXYGEN CARBON DIOXIDE + WATER +
PHOTOSYNTHESIS is the process PLANT CELLS
use to convert sunlight into sugar.
RESPIRATION is the process ALL CELLS use to
convert sugar into useful cell energy.
• These 2 processes are opposite of each other.
• For plants, these 2 processes work together.
• For animals, we eat food then do respiration.
Cycle (P-R Cycle)
• Plants use photosynthesis to store sugar
inside of them as starch.
• Animals eat plants for their starch
(Carbohydrates) and break the sugar
inside the plant down using respiration.
• Humans eat those animals for their
Carbohydrates and break them down
The P-R Cycle
Sugar & Oxygen
Carbon Dioxide &
FERMENTATION occurs when energy is
obtained from food WITHOUT THE USE
• This process is useful for single-celled
organisms that do not live with oxygen.
• Fermentation gives off MUCH LESS
energy than respiration.
2 Types of Fermentation
1. ALCOHOLIC FERMENTATION some
organisms use this type of Fermentation.
The products are Alcohol, Carbon Dioxide,
and Energy. YEAST (a fungus) uses this
2. LACTIC ACID FERMENTATION occurs
when the cell has used up the Oxygen
already. This type HAPPENS IN YOUR
MUSCLE CELLS when you’ve exercised
very hard. The products are Lactic Acid
• You’ve felt Lactic Acid when your muscles
are sore the day after you worked out.