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CELLULAR RESPIRATION
Energy in Food
To do work, cells require energy
One gram of glucose contains 3811
calories
A calorie is defined as the amount of
energy needed to raise the temperature of
1 gram of water 1 degree Celsius
Food labels use the kilocalorie or Calorie
which is actually 1000 calories
Cellular Respiration
 Process by which glucose is broken down to
produce energy (ATP)
 The cellular respiration reaction is:
energy
C6H12O6 + 6O2
6H2O + 6CO2
 There are two types of cellular respiration:
Aerobic
Anaerobic
Aerobic Respiration
There are 3 steps in aerobic respiration:
Glycolysis
Krebs cycle
Electron transport
Glycolysis
Glucose is broken down to produce 2
molecules of pyruvic acid (a.k.a.
pyruvate) and the energy carriers ATP
and NADH
These reactions occur in the cytoplasm
2ATP
glucose
2ADP
4ADP
2PGAL
2NAD+
4ATP
2 pyruvic acid
2NADH + 2H+
Krebs Cycle (a.k.a. Citric Acid Cycle)
The pyruvic acid made during glycolysis is
converted into citric acid
The citric acid enters the Krebs cycle and
is converted into carbon dioxide (a waste
product), ATP, NADH, and FADH2
The NADH and FADH2 can now enter the
electron transport chain
These reactions take place in the
mitochondria
Electron Transport
NADH and FADH2 are put through the
chain so that their energy can be used to
convert ADP into ATP
These reactions require oxygen, which
accepts the H+ ions to form water
Occurs in the mitochondria
The entire process of aerobic respiration
produces 36 ATP molecules
ATP is made
during all 3
parts of
aerobic
respiration
Anaerobic Respiration
The extraction of energy from pyruvic acid
in the absence of oxygen
This is also known as fermentation
The process begins with glycolysis to
produce pyruvic acid
There are 2 types:
Alcoholic fermentation
Lactic acid fermentation
Alcoholic Fermentation
 pyruvic acid + NADH CO2 + ethanol + NAD+
This reaction occurs mainly in yeast cells
Used to make bread as well as alcoholic
beverages
Lactic Acid Fermentation
 pyruvic acid + NADH lactic acid + NAD+
This reaction occurs in muscle cells and it
is the build up of lactic acid that causes
muscle soreness
Excess Glucose
Excess glucose can be stored
Animal cells store it as glycogen or fat