Cellular Respiration
Chapters 8-10
Warm Up Exercise
• Explain the difference between
competitive and noncompetitive
inhibitors
• Describe the negative feedback
demonstrated by ATP/ADP.
Cellular Respiration
Cellular Respiration
• Cell respiration is a catabolic
pathway.
• Aerobic Cellular Respiration
• Anaerobic Cellular Respiration (aka:
Fermentation)
Cellular Respiration
• Organic compounds possess
potential energy as a result of their
arrangement of atoms
• Fermentation – partial degradation
of sugars that occur without Oxygen
• Aerobic Respiration – most
prevalent and efficient catabolic
pathway (Oxygen is consumed)
Cellular Respiration
• Most eukaryotic and many prokaryotic
can carry out aerobic respiration
• Some prokaryotes can use substances
other than oxygen as reactants –
anaerobic respiration
Cellular Respiration
• Cellular Respiration uses both aerobic
and anaerobic processes
• However, usually refers to aerobic
processes
Cellular Respiration
C6H12O6 +6O2 -> 6 CO2 + 6 H2O+ Energy (ATP +Heat)
Cellular Respiration
• Catabolic processes do not directly do
the work; instead, catabolism is linked to
work by chemical drive shaft – ATP
• Require the regeneration of ATP… This
is where Cellular Respiration comes into
play
Redox Reactions
• How do the catabolic pathways that
decompose glucose yield energy???
Redox Reactions
• How do the catabolic pathways that
decompose glucose yield energy???
• Due to the transfer of electrons during the
chemical reaction.
• Relocation of electrons releases energy
stored in organic molecules and this energy
is used to synthesize ATP
Redox Reactions
• Reduction vs. Oxidation
• Why are carbs and fats the best molecules for
energy?
• Why must glucose be broken down in a
series of steps rather than one quick
reaction?
Redox Reactions
• Generally, there exists a transfer of one or
more electrons from one reactant to another
• This transfer leads to what is called an
oxidation – reduction reaction (Redox)
Redox Reactions
• Oxidation – loss of electrons from one
substance
• Reduction – addition of electrons to another
substance
• Adding electrons
• Negatively charged electrons added to atom
reduce amount of positive charge of that atom
Redox Reactions
• Reducing Agent – Electron donor
• Oxidizing agent – Electron acceptor
• Transfer is ONLY between the Reactants in a chemical
equation
• Is this an ionic or covalent bond?
REDOX Reaction
Electron Transport
• Dehydrogenase- removes electrons from glucose (or
other substrate) transferring them to its coenzyme
(NAD+) which is reduced to NADH. (NADH =
potential energy)
• NAD+ (nicotinamide adenine dinucleotide)- an
electron carrier.
• Cycles between NAD+ and NADH
NAD to NADH
NAD to NADH
• NAD + is one of the most versatile electron acceptors
in cellular respiration and functions in several redox
steps during the breakdown of glucose
• This is due to the fact that electrons lose very little of
their potential energy when they are transferred from
glucose to NAD+
• NADH represents stored energy that can be used to
make ATP
Electron Transport
• As glucose is broken down (in many small reactions)
electrons are shuttled (by NADH) down the Electron
Transport Chain (ETC).
• ETC is used to break the fall of electrons to Oxygen
into several energy-releasing steps
• ETC has many molecules (mostly proteins) built into
the inner membrane of mitochondria of eukaryotic
cells and the plasma membrane of aerobically
respiring prokaryotes
• Ultimately, oxygen is the final electron acceptor.
Electron Transport
• Electrons removed from glucose are
shuttled by NADH to the “top”, higherenergy end of the chain.
• At the “bottom”, lower-energy end of the
chain O awaits
• Ultimately, oxygen is the final electron
acceptor.
Electron Transport
• Electron transfer from NADH to O is
exergonic with free-energy change of -53 kcal /
mol.
• Instead of one with one big step and a greater
loss of energy, electrons cascade down the
chain from one carrier molecules to the next in
series of redox reactions
• Lose a small amount of energy with each step
Electron Transport
• Each downhill carrier is more electronegative
• Is it oxidizing or reducing it’s “uphill”
neighbor?
Electron Transport
• Each downhill carrier is more
electronegative
• Is it oxidizing or reducing it’s “uphill”
neighbor?
• Oxidizing it’s uphill neighbor
• Overall process:
• Glucose-> NADH -> ETC -> Oxygen
Warm Up Exercise
• What is the function of NAD+?
• Explain the terms oxidation and reduction.
• What is the difference between aerobic and anaerobic
respiration?
What the Stages of
Respiration?
• On a piece of paper, list the stages of
cellular respiration and list where each
stage occurs. When you are finished
turn it into the tray.
Stages of Respiration
• Glycolysis (in cytoplasm)- can occur with or without
oxygen.
• Pyruvate Oxidation (in mitochondria)
• Citric Acid Cycle (in mitochondria)
• Oxidative Phosphorylation: Electron Transport
Chain and Chemiosmosis (in the outer membrane of
the mitochondria)
Stages of Respiration
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Stages of Respiration
• Glycolysis (in cytoplasm)- catabolic
• Citric Acid Cycle (catabolic)
• Oxidative Phosphorylation: Electron Transport
Chain and Chemiosmosis (in the outer membrane of
the mitochondria)
Stages of Respiration
• Glycolysis (in cytoplasm)- begins process by breaking
down glucose into two molecules of pyruvate
• Citric Acid Cycle in mitochondrial matrix – completes
breakdown of glucose by oxidizing a derivative of
pyruvate to carbon dioxide
• Oxidative Phosphorylation: Electron Transport
Chain and Chemiosmosis powered by the redox
reactions of the ETC
ADP to ATP
• Oxidative Phosphorylation- inorganic phosphate is
added to ADP to produce ATP.
• Occurs in ETC and chemiosmosis.
• Accounts for 90% of the ATP generated by respiration
• Substrate-Level Phosphorylation- an enzyme transfers
a phosphate group from a substrate molecule to ADP
to form ATP.
• Occurs in glycolysis and citric acid cycle.
• Substrate = an organic molecule generated as an
intermediate in glycolysis.
Glycolysis
• Sugar –splitting
• 6C sugar is split into two 3C sugars
• Can be divided into 2 phases: energy investment and energy
payoff
• Energy investment – cell actually spends payoff
• Payoff – substrate- level phosphorylation produces ATP and
reduction of NAD
• Net Yield:
• 2 ATP
• 2 NADH
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Warm Up Exercise
• Without using your notes, name the four major
processes of cellular respiration and where in the cell
they occur.
• Explain the difference between oxidative and substratelevel phosphorylation.
Oxidative
Phosphorylation
• Pyruvate enters mitochondria (via active transport) and
is converted to Acetyl CoA
Citric Acid/
Kreb’s Cycle
Citric Acid/Kreb’s
Cycle
• Acetyl CoA (from oxidative phosphorylation) enters
the Citric Acid cycle and combines with oxaloacetate
to form citrate, the ionized form of citric acid.
Warm Up Exercise
• Walk through the Kreb’s cycle, stating the reactants
and the products and where they came from, or go to
ETC
• Cytochromeselectron carriers in
ETC. They are
proteins with a Heme
group attached.
• Represent a series of
redox reactions.
Chemiosmosis
• Chemiosmosis- energy
coupling mechanism that
uses H+ gradient to drive
cellular work.
• ATP Synthase- enzyme that
makes ATP from ADP in the
inner membrane of
mitochondria.
Chemiosmosis
• Proton Motive Force- the H+ gradient that results
from the pumping of H+ ions from the matrix of the
mitochondria to the intermembrane space.
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Energy Totals
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Warm Up
-Cell Resp Challenge• Why does NADH have more energy than FADH2?
• Explain the idea of energy coupling that occurs in
chemiosmosis.
• What element (atom) helps to pull electrons down the
ETC?
• How many total ATPs are produced per molecule of
glucose in aerobic respiration?
Alternatives to
Aerobic Respiration
• Anaerobic Respiration- uses ETC with a different final
electron receptor (besides oxygen)
• Fermentation- no ETC. Glycolysis followed by a
fermentation process.
• Two main types: Alcoholic and Lactic Acid
Fermentation
• Alcoholic Fermentation- pyruvate is converted to
acetaldehyde then to ethanol (ethyl alcohol). CO2
byproduct.
Fermentation
• Lactic Acid Fermentation- pyruvate is reduced by
NADH to form lactate, with no release of CO2.
Aerobic vs. Anaerobic
• Obligate Anaerobesorganisms that cannot
survive in the presence of
oxygen.
• Carry out only fermentation
or anaerobic respiration.
• Facultative Anaerobesorganisms that can survive
using fermentation or
respiration.