Download Notes 4-2

Notes 4-2
Respiration
Food = Energy?
 Not exactly!
 It’s a complicated process…
 Eat food  food broken down into small molecules
by digestive system  molecules move through
bloodstream to body cells  energy from molecules
released
Respiration
 Cells break down food (sugars) and
release their energy
 The cells of ALL living things respire
(yes, plants do too!)
 As food is converted into energy, your
cells store the energy until your body
needs it
 Think of this like a bank account; a
bank stores your money until you
need it, then you take it out.
Respiration has
2 stages:
Stage 1:
 Takes place in the
cytoplasm of cells
 Glucose (sugars from the
food you eat) is broken
down into smaller
molecules
 A small amount of energy
is release
 No oxygen is involved in
step 1
Stage 2:
 Takes place in the
mitochondria
 Smaller molecules combine
with oxygen
 A chemical reaction occur
that releases a lot of energy,
along with water and carbon
dioxide (this is why the
mitochondria is the
“powerhouse”)
Two Stages of
Respiration
 During respiration, cells break down simple food
molecules such as sugar and release the energy they
contain.
Respiration Equation
 The equation states that sugar (glucose) combined
with oxygen yields water, carbon dioxide, and energy
Where does it come from?
 Where does the sugar
 The food we eat!
come from?
 Where does the oxygen
come from?
 Plants release it as a
waste product during
photosynthesis and we
breathe it in!
What do we do with it?
 What happens to the
carbon dioxide we
make?
 What happens to the
water we make?
 We release it as a waste
product when we
exhale, and plants then
take it in to
photosynthesize.
 Some of it is used for
normal cellular
functions and some of it
is release when we
exhale.
Photosynthesis and
Respiration
 You can think of photosynthesis and respiration as
opposite processes.
Fermentation
 Some cells can obtain energy without the oxygen
through fermentation
 Yields much less energy than respiration!
 Examples: some single celled organisms that live deep
in the ocean where there is no oxygen
Alcoholic fermentation
 Yields alcohol, carbon dioxide and a small amount of
energy
 Example: carbon dioxide made by yeast during baking
makes air bubbles in bread causing it to rise
 Example: bubbles in beer and sparkling wine caused
by carbon dioxide
Lactic Acid fermentation
 Yields a product known as lactic acid
 When you exercise, your cells eventually
run out of oxygen, yet they still need to
provide your body with energy…. They
do this by fermentation.
 The lactic acid your cells make leave
your muscles feeling weak or sore.
 How many of you have experienced
this?