Cellular
Respiration
Cellular Respiration
All living things
need energy
 Energy in the form
of…

Food=chemical
energy

Cell energy=
ATP
How Do We Get Energy From
ATP?
By breaking the
high- energy bonds
between the last
two phosphates in
ATP
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When is ATP Made in the
Body?
During
a
Process
called
Cellular Respiration that takes
place in both Plants & Animals
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What is cellular respiration ?
Cellular respiration is the set of the
metabolic reactions and processes that take
place in the cells of organisms to convert
biochemical energy from nutrients into
(ATP),
 The reactions involved in respiration are
catabolic reactions, which break large
molecules into smaller ones, releasing energy

Cellular Respiration

Includes pathways that require
oxygen

Breakdown of one glucose molecule
produces 38 ATP molecules
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Overall Equation for
Cellular Respiration
C6H12O6
+ 6O2
YIELDS
6CO2 + 6H20 + 38ATP’s
Important Molecules in
Cellular Respiration

CO2 – Carbon Dioxide

ATP – Adenine triphosphate

NAD – Nicotinamide adenine
dinucleotide

FAD – Flavin adenine dinucleotide
What are the Stages of
Cellular Respiration?
 STEP
1 - Glycolysis
 STEP 2 - The Krebs Cycle
 STEP 3 - The Electron Transport
Chain (ETC)
Where Does Cellular
Respiration Take Place?
 It
actually
takes place in
two parts of
the cell:
Glycolysis occurs
in the Cytoplasm
Krebs Cycle &
ETC Take place in
the Mitochondria
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STEP 1 Glycolysis
Glycolysis is takes place in the cytosol
of cells in all living organisms.
 This pathway can function with or
without the presence of oxygen.
 process converts one molecule of
glucose into two molecules of pyruvate
(pyruvic acid),


generating two net molecules of ATP.
 Four molecules of ATP per glucose are
actually produced,
 however, two are consumed as part of
the preparatory phase.
 The overall reaction can be expressed
this way:


Glucose + 2 NAD+ + 2 Pi + 2 ADP → 2 pyruvate + 2 NADH + 2
ATP + 2 H+ + 2 H2O + heat
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Glycolysis Summary
 Produces
molecules
2
NAD
and
4
ATP
•
(2 ATP Used & 4 Produced so
overall 2 ATP molecules from
glycolysis)
•
2 molecule of Pyruvate
Steps 2: The Fate of PYRUVATE
1. As pyruvate enters the mitochondrion,
a modifies pyruvate to acetyl CoA which
enters the Krebs cycle in the matrix.
2. A carboxyl group is removed as CO2.
3. A pair of electrons is transferred from
the to NAD+ to form NADH

2 molecule of pyruvate produce 2 NADH
When oxygen is present, the
mitochondria will undergo aerobic
respiration which leads to the Krebs
cycle.
 However, if oxygen is not present,
fermentation
of
the
pyruvate
molecule will occur.
 In the presence of oxygen, when
acetyl-CoA is produced, the molecule
then enters the citric acid cycle
(Krebs cycle)

inside the mitochondrial matrix, and
gets oxidized to CO2
 while at the same time reducing NAD
to NADH.
 NADH can be used by the electron
transport chain to create further
ATP
as
part
of
oxidative
phosphorylation.
 The citric acid cycle is an 8-step
process involving different enzymes
and co-enzymes.

Steps3: KREBS CYCLE or TCA
This is also called the citric acid or the
tricarboxylic acid cycle
 Takes place in matrix of mitochondria
 Requires Oxygen (Aerobic)
 Each cycle produces 1 ATP, 3 NADH,
and 1 FADH

The TCA or KREBS CYCLE
4
CO2
6NADH
2FADH
2
more ATP
NETS: 3NADH, 1ATP, 1FADH2, & 2CO2
The conversion of pyruvate and the Krebs cycle
produces large quantities of electron carriers.
•
So what do you think the major purpose of the
Krebs cycle is??
Electron Transport
The mitochondria
has two
membranes
the outer one and the inner membrane
 The H+ which are brought to mitochondria
accumulate between these two membranes.


the electrons move from molecule to
molecule until they combine with oxygen
and hydrogen ions to form water.

As they are passed along the chain, the
energy carried by these electrons is stored
in the mitochondrion in a form that can be
used to synthesize ATP
1.
2.
3.
4.
5.
Electrons carried by NADH are transferred to
the first molecule in the electron transport
chain
The electrons continue along the chain
that includes several cytochrome proteins and
one lipid carrier.
The electrons carried by FADH2 added to
a later point in the chain.
Electrons from NADH or FADH2 ultimately
pass to oxygen.
The electron transport chain generates no ATP
directly.
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ONE GLUCOSE MOLECULE PRODUCES 38 ATP
Each NADH
3 ATP
Each FADH
2 ATP
•Glycolysis (2 NADH)
•Prep for Citric Acid
•Citric Acid (6 NADH)
•
(2 FADH2)
•
•direct
•total
6 ATP
6 ATP
18 ATP
4 ATP
34 ATP
4 ATP
38 ATP
What happens when there is no oxygen
to accept the electrons?
•
If no oxygen is available, cells can obtain energy
through the process of anaerobic respiration.
• A common anaerobic process is fermentation.
•
Fermentation is not an efficient process and results in
the formation of far fewer ATP molecules than aerobic
respiration.
There are two primary fermentation processes:
1. Lactic Acid Fermentation
2. Alcohol Fermentation
Fermentation allows the production of a small
amount of ATP without oxygen.
Lactic acid fermentation occurs when oxygen is not
available.
For example,
in muscle tissues during rapid and hard exercise, muscle
cells may be depleted of oxygen. They then switch from
respiration to fermentation.
The pyruvic acid formed during glycolysis is broken down
to lactic acid and energy is released (which is used to form
ATP).
Glucose → Pyruvic acid → Lactic acid + energy
•Lactic acid that builds up in the tissue causes a burning,
painful sensation. results in muscle soreness
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Alcohol fermentation
 occurs in yeasts and some bacteria.
Alcohol Fermentation

Pyruvate
is
converted
to
ethanol
(ethyl alcohol) in 2 steps.
1. carbon dioxide is released from
pyruvate,
which
is
converted
to
acetaldehyde.
2. acetaldehyde is reduced by NADH to
ethanol.
• Regenerating a supply of NAD+
Aerobic Respiration
respiration
Anaerobic Respiration
Definition
Aerobic
oxygen
uses Anaerobic
respiration
is
respiration without oxygen; the
process uses a respiratory
electron transport chain but
does not use oxygen as the
electron acceptors
Production of
lactic acid:
Does not produce lactic acid
Produces lactic acid (in lactic
acid fermentation but not in
alcoholic fermentation)
Amount of
energy
released:
High (36-38 ATP molecules)
Products:
Carbon dioxide, water, ATP
Lactic Acid Fermentation lactic acid, ATP Alcoholic
Fermentation - ethyl alcohol,
ATP, carbon dioxide
Reactants:
glucose, oxygen
glucose
Low (2 ATP molecules)
Aerobic
Anaerobic
Site of
reactions:
Cytoplasm and mitochondria
Stages:
Glycolysis, Krebs cycle, Electron Glycolysis, fermentation
Transport Chain
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Cytoplasm
The aerobic system requires 60 to 80
seconds
to
produce
energy
for
resynthesizing ATP from ADP + P.
 The heart rate and respiratory rate must
increase sufficiently to transport the
required amount of O2 to the muscle cells,
allowing glycogen to break down in the
presence of oxygen.

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
the lactic acid system need 8 to 10
seconds to produce energy
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Summary Quiz
What are the reactants of aerobic
respiration?? Products? Equation?
 List the three respiratory stages:

– Where in the cell do each occur?
– What are the products of each?

How much ATP is produced by
– Anaerobic gylcolysis?
– Aerobic glycolysis?

List the 2 types of fermentation??