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 highenergy bonds between
the last two phosphates
in ATP
WHEN IS ATP MADE IN THE
BODY?
During a Process called Cellular
Respiration that takes place in both
Plants & Animals
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
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
GLYCOLYSIS SUMMARY
• Produces 2 NAD and 4 ATP molecules
• (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.
Electrons carried by NADH are transferred to the first
molecule in the electron transport chain.
2.
The electrons continue along the chain that includes
several cytochrome proteins and one lipid carrier.
3.
The electrons carried by FADH2 added to a later point
in the chain.
4.
Electrons from NADH or FADH2 ultimately pass to
oxygen.
5.
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
Copyright Cmassengale
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 Anaerobic Respiration
Anaerobic respiration is respiration
without oxygen; the process uses a
respiratory electron transport
Definition Aerobic respiration uses oxygen
chain but does not use oxygen as
the electron acceptors
Production
of lactic
acid:
Amount of
energy
released:
Does not produce lactic acid
High (36-38 ATP molecules)
Produces lactic acid (in lactic acid
fermentation but not in alcoholic
fermentation)
Low (2 ATP molecules)
Products:
Carbon dioxide, water, ATP
Lactic Acid Fermentation - lactic
acid, ATP Alcoholic Fermentation ethyl alcohol, ATP, carbon dioxide
Reactants
glucose, oxygen
glucose
Aerobic
Anaerobic
Site of
reactions:
Cytoplasm and mitochondria
Cytoplasm
Stages:
Glycolysis, Krebs cycle, Electron
Transport Chain
Glycolysis, fermentation
• 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.
• The lactic acid system need 8 to 10
seconds to produce energy
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??