Download Cellular Respiration

Cellular
Respiration
Biology 112
Chemical Energy and Food
 Food
can be broken down into fats,
sugars, and proteins
 All food is composed of calories – a unit of
energy that is needed to raise the
temperature of 1g of water 1oC
 Cells use this energy to carry out life
activities
 This beginning of this process is called
glycolysis
The Beginning of the Breakdown
of Food - Glycolysis
 Releases
only a small amount of energy
 When oxygen is present, glycolysis leads
to two other pathways that release a
great deal of energy
 If oxygen is not present, it leads to another
pathway
Cellular Respiration
 The
process of breaking down glucose
and other food molecules in the presence
of oxygen
6O2(g) + C6H12O6(g) → 6CO2(g) + 6H2O(g) + energy
 Energy
must be released gradually by
cells
 The release of ATP allows this to happen
The 3 Stages of Respiration
 All
three stages release ATP from the
breakdown of food molecules
 Glycolysis
 Krebs
takes place in the cytoplasm
cycle and the electron transport
chain takes place in the mitochondria
Glycolysis

One molecule of glucose is broken in half,
producing two molecules of pyruvic acid, a 3carbon compound
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this requires two molecules of ATP
Although this is an investment with ATP
energy, the cell will release 4 molecules of ATP
A net gain of 2 ATP results – available energy
NADH is also used to release energy for the
electron transport chain
It does not require oxygen
What Happens When There is
no Oxygen
 Glycolysis
follows a different pathway
 Fermentation releases energy from food
molecules by producing ATP in the
absence of oxygen
 Pyruvic acid is formed, then NADH
releases e- to the molecules
 ATP can continue being produced
 This is an anaerobic process
Alcoholic Fermentation
 Yeast
undergoes anaerobic fermentation,
releasing alcohol, CO2 and NAD+ as
products
 CO2 causes bread dough to rise
 The alcohol burns off when the bread is
baked
Lactic Acid Fermentation
(Mammals)
 Pyruvic
acid may be converted to lactic
acid with the release of the NAD+
 This can be built up in human muscle
when there is not enough oxygen being
provided to the tissues
 ATP is being produced by the NAD+
 This causes a burning sensation and
muscles get sore
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