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Cellular
Respiration
Chapter 9: Cellular Respiration
Cellular Respiration
Living cells require
Organisms use
their main energy source
as
Cellular respiration is the
process of
Energy is released in the process of
respiration when the cells of plants
and animals
Respiration
 The breakdown of organic
molecules is
 Aerobic respiration
consumes
 Anaerobic respiration is
similar to aerobic respiration
but
 Fermentation is a
Cellular Respiration
 Cellular respiration includes both
but is often used
to refer to
 Although carbohydrates, fats, and proteins
are all consumed as fuel, it is helpful to trace
cellular respiration with the
:
Redox Reactions
 The
during chemical reactions
 This released energy is used to
 Chemical reactions that transfer electrons between
reactants are called
 In oxidation, a substance
, or is
 In reduction, a substance
, or is
 In cellular respiration, the
NAD+
 In cellular respiration, glucose and
other organic molecules are broken
down in a series of steps

• As an electron acceptor, NAD+
functions as an
• Each NADH (the reduced form
of NAD+)
• NADH passes the electrons to
the
Electron Transport Chain
 Unlike an uncontrolled
reaction, the electron
transport chain passes
electrons in a series of
steps instead of one
explosive reaction
• O2 pulls electrons
• The energy yielded is
Stages of Cellular
Respiration
1) Glycolysis - Anaerobic
2) Citric Acid Cycle - Aerobic
3) Oxidative phosphorylation - Aerobic
Mitochondria
1) Glycolysis
•
2) Citric Acid Cycle
•
3) Oxidative
Phosphorylation (ETC)
•
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Step 1: Glycolysis
 “Splitting of sugar”
 Breaks down glucose
(C6H12O6) into

 Occurs in the
 NAD picks up H+ and
electrons to form NADH2
Glycolysis Summary
Location:
Reactants
Products






• **
Simple Summary
Summary total
Bridge Reaction
 In the presence of O2,
 Before the citric acid cycle can begin,
 In the mitochondria matrix…
1) Pyruvic Acid loses a C to form
2) The lost carbon
3)Acetic acid binds with
Step 2: The Kreb’s Cycle
(Citric Acid Cycle)
 Takes place within the
 There are
, each
catalyzed by a specific enzyme
 The acetyl group of acetyl CoA joins
the cycle by combining with
oxaloacetate
 The next seven steps
Step 2: The Kreb’s Cycle
(Citric Acid Cycle)
 2 molecules of CO2 are
 NAD+ and FAD (flavin adenine dinucleotide - another
ion carrier)
 The NADH and FADH2 produced by the cycle relay
electrons extracted from food
 The cycle generates
 Recall that two molecules of pyruvate are formed
during glycolysis resulting in
Kreb’s Cycle Summary
Location:
Reactants
Products





Kreb’s Summary
Kreb's Summary 2
Step 3: Electron Transport
Chain (ETC)

•
 Takes place in the
 A series of molecules that
excited electrons pass along,
 Most of the chain’s
components are
which exist in
,
Step 3: Electron Transport
Chain (ETC)
 Following glycolysis and the citric acid cycle,
NADH and FADH2 account for most of the energy
extracted from food
 These two electron carriers donate electrons to the
electron transport chain, which powers ATP
synthesis via
 The carriers alternate
as they accept and donate electrons
 Electrons
 They are finally passed to O2
,forming
NADH and FADH2
 Dump the electrons and protons they’ve gathered
throughout glycolysis and the citric acid cycle
 Again,
• O2 + 2e- + 2H+  H2O
 Electrons are passed through a number of proteins
 The chain’s function is to break the large freeenergy drop from food to O2 into smaller steps that
release energy in manageable amounts

Chemiosmosis
 Electron transfer in the ETC causes
proteins to
 H+ then moves back across the
membrane, passing through
channels in
 ATP synthase uses the exergonic
flow of H+ to drive
 This is an example of
chemiosmosis,

ETC Summary
ETC
ETC Summary
Location:
Reactants


Product

•
•
Simpler ETC Summary
Best ETC Summary
Whole Respiration Process
Song I Found...
Total Energy
Total ATP from 1 molecule of glucose in
Stage
Glycolysis
ATP
+ 4 Total
(b/c 2 are used in the first step)
CA Cycle
ETC
_________________
TOTAL
During cellular respiration, most energy flows in this sequence:
Glucose -> NADH -> electron transport chain -> proton-motive
force -> ATP
Fermentation
 Most cellular respiration requires
 Glycolysis can produce ATP
, glycolysis couples with
to produce ATP
 Fermentation uses instead of an electron transport
chain to generate ATP
 2 Types:
•
•

Lactic Acid Fermentation
 In lactic acid
fermentation,
 Lactic acid fermentation
by some fungi and
bacteria is used
 Human muscle cells use
lactic acid fermentation
Lactic Acid Fermentation
 Example: Burning feeling
in muscles during a
workout
• From oxygen debt
•
• Lactate
Alcohol Fermentation
 In alcohol
fermentation,
pyruvate is
• Bacteria and fungi
(yeast)
 Alcohol fermentation
by yeast is used in
Fermentation
 Obligate anaerobes
carry out fermentation
or anaerobic respiration
and
 Yeast and many
bacteria are
facultative
anaerobes, meaning
that
Review
Role of Macromolecules
 Catabolic pathways funnel electrons from many
kinds of organic molecules into cellular respiration
 Glycolysis accepts a wide range of

• Amino groups can feed
 Fats are digested to
• Fatty acids are broken down by beta oxidation
and yield
 An oxidized gram of
produces more than
twice as much ATP as an oxidized gram of
Regulation of Cell Respiration

is the
most common mechanism
for control
• If ATP concentration begins
to
, respiration
• When there is
ATP, respiration
of
 Control of catabolism is
based mainly on
Review Questions
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Define cellular respiration and state its importance as a life process.
Differentiate between aerobic respiration, anaerobic respiration, and
fermentation.
State and explain the chemical equation for cellular respiration.
Define oxidation and reduction and explain the idea of redox reactions.
Explain the use of NAD+ as a coenzyme.
Explain the electron transport chain (ETC).
Name the 3 major stages of cell respiration, along with their locations.
Explain glycolysis, stating the reactants, products, and major activities.
Explain the bridge reaction, stating the reactants, products, and major activities.
Explain the Kreb’s cycle, stating the reactants, products, and major activities.
Explain glycolysis, stating the reactants, products, and major activities.
Explain the ETC, stating the reactants, products, and major activities.
Explain the role of oxygen in the ETC.
Define chemiosmosis and explain its role in cellular respiration.
Differentiate between lactic acid fermentation and alcohol fermentation.
Differentiate between oblicate anaerobes and facultative anaerobes.
Explain the role of macromolecules in cellular respiration.
Explain how cell respiration is regulated.