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RESPIRATION
 Respiration is the process by which the
chemical bond energy stored in nutrients
is released for use in cells
RESPIRATION
 Why do cells need energy?
 To make new molecules
 Synthesis and hydrolysis
 For building membranes and
organelles
 Active transport
 Muscle contraction\movement
 Cell division
 Etc etc
Some facts about respiration:
 Respiration:
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
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Occurs continuously in all living things
Is a series of enzyme controlled reactions
May or may not use oxygen
Involves the exchange of gases between the
organism and the environment
 The energy in glucose is released when
bonds are broken
 The energy is stored in molecules of ATP
What is ATP???
 Just kidding! Don’t
use this answer on
the regents!!!
What is ATP ?
 ATP (adenosine triphosphate) is an
energy storage compound that stores the
energy from glucose and transfers it to
other biochemical reactions
 When energy is needed by the cell:
 ATP + H2O ------- ADP + P + energy
The enzyme ATP-ase controls the reaction
This is a hydrolysis reaction
Two types of Respiration
 Aerobic Respiration
 Uses oxygen
 Occurs in the mitochondria of cells
 The more energy a cell needs the
more mitochondria it will have (for
example muscle cells)
Aerobic Respiration
 Produces 36 molecules of ATP for each
molecule of glucose
 Reactants are oxygen and glucose
 Products are water, carbon dioxide and
ATP
General Equation
 C6H12O6 + 6O2- 6H2O + 6CO2 + 36 ATP
Two Types of Respiration
 Anaerobic Respiration
 Does not require oxygen
 Occurs in the cytoplasm
 Used by yeasts and some bacteria
 Net result of ATP produced is 2
molecules for each molecule of glucose
 Also called fermentation
Anaerobic respiration
 Reactant is glucose
 Products are carbon dioxide
 and ethyl alcohol
 or lactic acid
General Equations
Glucose-- 2 lactic acid + 2 ATP
(occurs in bacteria and muscle cells lacking
oxygen)
Glucose ----- 2 alcohol + 2 carbon dioxide + 2
ATP
( occurs in yeast cells)
Making bread and alcohol use the process
of fermentation
Respiration
Muscle Fatigue
 If muscle cells don’t have enough oxygen,
they will carry out anaerobic respiration
 This will produce lactic acid and cause
sore muscles and muscle fatigue
That was too easy!!
 C6H12O6 + 6O2- 6H2O + 6CO2 + 36 ATP
 Even thought the chemical reaction for respiration makes
it look simple, it is really a series of complex chemical
reactions!
That Was Too Easy!
 So Put On Your Thinking Caps!
 If it were one simple
step, all the energy
would be released at
once and most
would be released
as heat or light.
 This would not
provide the cell with
the continuous
supply of energy the
it needs.
The Steps of Cellular
Respiration:
 1. GLYCOLYSIS
 2. KREBS CYCLE
 3. ELECTRON TRANSPORT CHAIN
 Helpful information:
 NAD and FAD are co-enzymes that act as
Hydrogen/electron carriers
Glycolysis
 In this first step, glucose is broken down
into to smaller molecules called pyruvic
acid ( a 3 carbon sugar)
Glycolysis
 Glycolysis occurs in the cytoplasm and
does not require oxygen
 This step requires that 2 molecules of ATP
be used for activation energy, however 4
molecules are produced, for a net total of
2 from this stage
 C6H12O6 = glucose
 2 C3H4O3 = 2 pyruvic acids
 What’s missing?
 Missing 4 H’s
When glucose is broken down into pyruvic
acid, 4 extra H’s are picked up by NAD
and transferred to other biological
pathways
The Krebs Cycle
(citric acid cycle)
 Pyruvic acid is broken down into carbon
dioxide (this is what we exhale) in a series
of energy extracting reactions
 Some ATP is produced (2)
 Additional NADH and FADH2 are formed
which carry high energy electrons to the electron
transport chain
The Electron Transport Chain
 The electron transport chain uses the high
energy electrons from the Krebs cycle
(brought by the NADH and FADH2) to
convert ADP to ATP
 Oxygen acts as the final hydrogen
acceptor and combines with 2 hydrogens
to make water which is excreted or used
for cell metabolism
Heat
O2
H2O
CO2
Glucose
Pyruvate
ATP
Electron
Transport
System
NAD+
ATP
NADH
ATP
MITOCHONDRION
 1 molecule of glucose
The Totals
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produces:
Glycolysis= 2 ATP (4
– 2 for activation
energy)
Kreb Cycle= 2 ATP
Electron Transport
Chain = 32
For a grand total of 36
molecules of ATP
Is this efficient?
 Respiration is more
efficient than a car engine
that burns gasoline!
 The 36 molecules of ATP
that are made from 1
molecule of glucose
represent about 38% of
the total energy in
glucose.
 What do you think
happens to the other 62%
 It is released as heat