Chapter 3 Section 3
Energy for Life
• Chemical energy stored in food molecules is
changed inside cells into forms needed to
perform all the activities necessary for life
• All of the activities of an organism invole
chemical reactions in some way
• Metabolism= the total of all chemical
reactions in an organism
Enzymes
• Chemical reactions of
metabolism need
enzymes
• Enzymes assist
reactions and causes a
change, but the enzyme
stays the same
• Enzymes can be used
again and again
Living Things
• Divided into two groups: producers and
consumers
• Producers- organisms that make their own
food. Also called autotrophs
• consumers- organisms that cannot make their
own food. Also called heterotrophs
Plants
• Are autotrophs
• Use the energy from sunlight to make their
own food through photosynthesis
• Photosynthesis- when producers convert light
energy into chemical energy, or sugars that
can be used as food.
Where the Magic Happens….
• Chlorophyll- a green
pigment that is used in
photosynthesis to
capture light. They are
found in chloroplasts
What Happens…
• Captured light energy
powers a chemical
reaction that turns
carbon dioxide and
water into oxygen and
sugar
• Excess sugar is stored as
starches or used to
make other
carbohydrates
Respiration
• The process in which chemical reactions break
down food molecules into simpler substances
and release stored energy
Respiration
• Begins in the cytoplasm
• Carbohydrates are
broken down into
glucose molecules
Next
• Moves into the
mitochondria
• Two simpler molecules
are broken down again,
releasing more energy
• This process uses
oxygen and produces
carbon dioxide and
water as waste
Fermentation
• Cells that do not have enough oxygen for
respiration use fermentation to release some
of the stored energy in glucose molecules
– Occurs in the cytoplasm
– Produces lactic acid, alcohol, and carbon dioxide
as waste
– Also called anaerobic respiration
Lactic Acid
• Why your muscles hurt
during tough workouts
Alcohol
Did You Know..?
• Bread is made using the
process of fermentation
• Yeast, a fungi, is an
ingredient in the bread
dough that uses anaerobic
respiration
• As the yeast eats up the
sugar in the dough, it begins
to release gas bubbles of
carbon dioxide, and small
amounts of ethanol alcohol,
causing the bread to rise