How do living organisms fuel
their actions?
Cellular respiration
Cellular Respiration
Harvesting Chemical
Energy
ATP
Cellular Respiration
(1) fuel and (2) oxygen.
 Potential energy stored in chemical
bonds of sugar, protein, and fat
molecules.
 Breaks bonds to release the high-energy
electrons captured in ATP.
 Oxygen is electron magnet.
 Requires
Cellular Respiration
Photosynthesis
Cellular Respiration
Function
Energy Storage
Energy Release
Location
Chloroplasts
Mitochondria
Reactants
CO2 and H2O
C6H12O6 and O2
Products
C6H12O6 and O2
CO2 and H2O
Equation
6CO2 + 6H2O  C6H12O6 + 6O2
C6H12O6 + 6O2
6CO2 + 6H2O
Clarification - Two Types of
Respiration
• External – exchange of gases through
breathing (O2 in, CO2 out)
• Internal/Cellular – breakdown of food with
or without O2 to produce ATP for the cell
Conversion of Energy
• Energy is the ability to
do work
• 1st Law of
Thermodynamics:
Energy cannot be
created or
destroyed, but can
be inter-converted
What is energy in biology?
ATP
HOT
stuff!!!
• All organisms are energy consumers
– What do we need energy for?
•
•
•
•
•
synthesis (building for growth)
reproduction
active transport
movement
temperature control (making heat)
Where do we get energy?
• Energy is stored in organic molecules
– carbohydrates, fats, proteins
• Animals eat these organic molecules  food
– digest food to get
• fuels for energy (ATP)
• raw materials for building more molecules
– carbohydrates, fats, proteins, nucleic acids
• Plants break
down the food
they produced in
photosynthesis
ATP
What is Cellular Respiration?
• The process in which organisms take molecules
broken down from food and release the
chemical energy stored in the chemical bonds
of those molecules.
• It’s important to remember that food is not the
direct source of energy.
• The energy that is released from chemical
bonds during cellular respiration is stored in
molecules of ATP.
Food Is Used to Power the
Operations of Life
1. ATP is the energy unit of the cell.
2. Food is “burned” in the cell to produce
ATP.
3. 3 mechanisms exist to produce ATP.
4. Different foods can be inter-converted
and used for energy or stored.
Energy Is Created During Internal
Respiration
• True
• False
When water moves through a
hydroelectric power plant some of
the energy of the water
A.
B.
C.
D.
is lost
is converted into electrical energy
Is converted into ATP
disappears
What do we need to make energy?
• The “Furnace” for making energy
– mitochondria
• Fuel
– food: carbohydrates, fats, proteins
• Helpers
– oxygen
– enzymes
food
• Product
enzymes
– ATP
• Waste products
– carbon dioxide
• then used by plants
– water
O2
ATP
CO2
H2O
Mitochondria are everywhere!!
animal cells
plant cells
Using ATP to do work?
Can’t store ATP
 too unstable
 only used in cell
that produces it
 only short term
energy storage
 carbohydrates & fats
are long term
energy storage
ATP
Adenosine TriPhosphate
work
Adenosine DiPhosphate
ADP
A working muscle recycles over
10 million ATPs per second
ATP-ADP Interconversion
Energy for Cell
Adenine
O
P
P
P P
Energy from
Glucose
Adenine
O
P
P
A Body’s Energy Budget
1
eat
food
make energy
ATP
2
3
synthesis
(building)
storage
{
{
{
• energy needed
even at rest
• activity
• temperature
control
• growth
• reproduction
• repair
• glycogen
(animal starch)
• fat
Which of the following is a form of
energy used directly by organisms
for its processes?
A.
B.
C.
D.
NADH
ATP
Carbohydrates
Fats
It is necessary for a cell to convert
sugars into ATP and NADH
because:
A.
B.
C.
D.
Sugar is unstable in the cell
ATP and NADH are easier to use by the cell
The cell gains energy in this process
The cell needs water and CO2 that this
process releases.
Food Can be “Burned” to Produce
ATP
Burning of Food to produce ATP is called
The Cellular Respiration Equation
C6H12O6 + 6O2
6CO2 + 6H2O + energy (ATP)
Glucose
carbon dioxide water
oxygen
Notice that the cellular respiration equation is the
breakdown of those molecules made through
photosynthesis and that it also uses the waste products
of photosynthesis. Notice that photosynthesis uses
those products made by cellular respiration.
Cellular Respiration and Photosynthesis
This is representative of a cycle.
• Overall, cellular respiration is a process
that is aerobic. Aerobic means that it
requires the presence of oxygen.
• Some steps within the process of cellular
respiration do not require the presence of
oxygen and are therefore anaerobic.
Where does cellular respiration
occur?
• Cellular respiration takes place in the
mitochondria of the eukaryotic cell.
• Recall that the mitochondria is considered
to be the “powerhouse” of the cell because
it produces the majority of a cell’s ATP.
Energy Carriers Found in Cellular
Respiration
• ATP
• NADH (similar to NADPH in photosynthesis)
• FADH2
In eukaryotic cells, respiration has
three stages:
•
Glycolysis
Glucose
 2 Pyruvate
 2 NADH
 2 ATP
•
Kreb’s Cycle
Pyruvate
•
Electron Transport Chain
 34 ATP
NADH/FADH2
 4 NADH
 1 FADH2
 2 ATP
Oxygen
not
required
Oxygen
required
Cellular Respiration
Cellular respiration breaks down into these
major steps.
1. Glycolysis (anaerobic)
2. Krebs Cycle (aerobic)
3. Electron Transport Chain (aerobic)
The first step of cellular respiration:
glycolysis is the universal energy-releasing
pathway.
Glycolysis: the universal energy-releasing
pathway
1. Glycolysis
Glyco - glucose/sugar
Lysis – to break
•
•
•
•
•
Makes ATP in all cells that use glucose for food
Glycolysis takes place in the cytoplasm of the cell
Energy in glucose bonds is captured in several steps
Each step is catalyzed by an enzyme
Energy is stored in chemical bonds of ATP, NADH
and pyruvate
• Oxygen is not required.
A glucose molecule has bonds that
that contain a lot of energy
The energy of glucose bonds is
stored in different chemicals in the
cell
Pyruvate
NADH
ATP
Glycolysis – step by step breaking of glucose
bonds
In eukaryotic cells, respiration has
three stages:
•
1. Glycolysis
Glucose
 2 Pyruvate
 2 NADH
 2 ATP
•
2. Kreb’s Cycle
Pyruvate
•
3. Electron Transport Chain
NADH/FADH2
 4 NADH
 1 FADH2
 2 ATP
 34 ATP
Oxygen
not
required
Oxygen
required
The second step of cellular
respiration: the Krebs cycle
extracts energy from sugar.
What moves on to the next Stage?
Pyruvic acid is the main goal of glycolysis
and these molecules will move on to the
Krebs Cycle.
Pyruvic Acid
NADH
ATP
Krebs Cycle
ETC (Electron Transport Chain)
Usable Energy
Though the Krebs cycle does not directly
require oxygen, it can only take place
when oxygen is present because it
relies on by-products from the electron
transport chain, which requires oxygen.
The Krebs cycle is therefore an aerobic
process.
In eukaryotic cells, respiration has
three stages:
•
Glycolysis
Glucose
 2 Pyruvate
 2 NADH
 2 ATP
•
Kreb’s Cycle
Pyruvate
•
Electron Transport Chain
 34 ATP
NADH/FADH2
 4 NADH
 1 FADH2
 2 ATP
Oxygen
not
required
Oxygen
required
The third step
in cellular respiration: ATP is built
in the electron transport chain.
FIGURE 4.36
What is the starting point of
glycolysis?
A.
B.
C.
D.
E.
Glucose
Oxygen
ATP
Pyruvate
C and D
What is the ending point of
glycolysis?
A.
B.
C.
D.
E.
Glucose
Oxygen
ATP
Pyruvate
C and D
When glucose is broken down,
where does its energy go?
A.
B.
C.
D.
It is lost
Into the cell
Into other energy containing compounds
Into the mitochondria
What types of cells use glycolysis?
A.
B.
C.
D.
All types
Eukaryotic cells only
Only those that use glucose for food
Prokaryotic cells only
Practice Questions 1
1.
2.
3.
4.
5.
6.
7.
8.
9.
What are the four main points in how energy is obtained from food?
Describe an example of the 1st Law of Thermodynamics.
What are the functions in an organism that require ATP?
How do external and internal respiration differ? How are they
similar?
What are the three stages of cellular respiration?
What is the purpose of glycolysis and where does it occur?
What are the beginning and ending substances in glycolysis?
If a starch molecule containing 100 glucose units is fully broken
down by glycolysis, how many ATP molecules will be produced?
What is the relationship between glucose, ADP and ATP, and
glycolysis?
After Glycolysis What Happens?
Glycolysis
If O2 is not
present
Fermentation
If O2 is
present
Krebs Cycle
Aerobic
Respiration
Anaerobic Respiration and
Fermentation
• Glycolysis does not require oxygen and so
is known as ANAEROBIC respiration.
• It is only able to capture some of the
energy of glucose.
• Many organisms continue to break down
the glucose even more using oxygen
• But some organisms cannot do this and so
further processes to extract more energy
from glucose after glycolysis. This is
called FERMENTATION
Chemical Formula of Fermentation
C6H12O6 + 6O2  6CO2 + ATP +
Lactic Acid or Ethanol
Lactic Acid
When you are exercising and your muscles
begin to burn, it is because your cells are
not getting enough oxygen and they are
producing ATP by fermentation. The burn
you feel is lactic acid buildup.
Good things can be made by
fermenting micro-organisms
Bread rises
because of CO2
produced by
yeast
Yeast
produces
ethanol
(alcohol)
in wine
and beer
4.16 Beer,
wine, and
spirits are
by-products
of cellular
metabolism
in the
absence of
oxygen.
Take-home message 4.16
 Oxygen
deficiency limits the breakdown of
fuel because the electron transport chain
requires oxygen as the final acceptor of
the electrons generated during glycolysis
and the Krebs cycle.
Take-home message 4.16
 When
oxygen is unavailable, yeast resort
to fermentation, in which they use a
different electron acceptor, pyruvate,
generating ethanol in the process, the
alcohol in beer, wine, and spirits.
4.17 Eating a
complete diet:
cells can run
on protein and
fat as well as
on glucose.
Take-home message 4.17
 Humans
and other organisms have
metabolic machinery that allows them to
extract energy and other valuable
chemicals from proteins, fats, and
carbohydrates in addition to the simple
sugar, glucose.
Anaerobic respiration is a type of
process that:
A.
B.
C.
D.
Requires oxygen
Produces a great deal of ATP
Occurs only in complex organisms
Requires no oxygen
The purpose of fermentation is to:
A. Capture more energy from glucose
B. Make alcohol and lactic acid
C. Completely break down glucose into
carbon dioxide.
D. Allow people to make bread and beer
Which of the following is NOT a
part of the fermentation process?
A.
B.
C.
D.
Oxygen
Carbon Dioxide
Lactic acid
ATP
After Glycolysis What Happens?
Glycolysis
If O2 is not
present
Fermentation
If O2 is
present
Krebs Cycle
Aerobic
Respiration
The Aerobic Pathway
Glycolysis and fermentation cannot
produce enough ATP to sustain
complex organisms
To get all the energy out of the bonds of
glucose, organisms have evolved a
process which uses oxygen to fully oxidize
glucose – AEROBIC respiration.
Aerobic Respiration
• Occurs in the mitochondria of all
eukaryotic cells
• Requires oxygen
• Produces 36 ATP for each molecule of
glucose used
• Consists of Kreb’s Cycle and the Electron
Transport Chain (ETC)
Mitochondrion – where aerobic
respiration occurs
Kreb’s Cycle
• Starts with pyruvate from glycolysis
• Completes the breakdown of glucose into
carbon dioxide
• Captures energy of glucose molecule in
NADH, FADH2 and ATP
Kreb’s (Citric Acid) Cycle
NADH
Sugar + O2
NADH
FADH2
NADH
CO2+ H2O
Results: 1 cycle = 3NADH2 + 1FADH2
In what organelle does aerobic
respiration take place?
A.
B.
C.
D.
Nucleus
Lysosome
Ribosome
Mitochondrion
Which of the following is not a part
of aerobic respiration?
A. Glycolysis
B. Kreb’s Cycle
C. Electron Transport Chain
Which of the following is NOT an
end product of Kreb’s Cycle?
A.
B.
C.
D.
Pyruvate
FADH2
NADH
CO2
What is the function of Kreb’s
Cycle?
A.
B.
C.
D.
To produce CO2
To efficiently extract energy from pyruvate
To quickly burn glucose
To prevent fermentation from happening
Electron Transport Chain
What is the purpose of the electron
transport chain?
A.
B.
C.
D.
To produce ATP
To produce water
To produce CO2
To produce glucose
Which of the following chemicals
are not required for ATP production
in the electron transport chain?
A.
B.
C.
D.
Pyruvate
NADH
FADH2
Hydrogen ions
Practice Questions 2
1.
2.
3.
4.
5.
6.
7.
8.
9.
What is the relationship between Kreb’s Cycle and Glycolysis?
Where does Kreb’s Cycle occur?
What is the overall purpose of Kreb’s cycle?
What is the relationship between Kreb’s Cycle the Electron
Transport Chain?
Compare the amount of energy captured by each of the three
stages of respiration.
Why is it essential for complex organisms like humans to use
aerobic respiration?
Compared to a skin cell, a muscle cell has a huge density of
mitochondria. Propose a logical reason to explain this.
In what ways is a hydroelectric dam a good analogy for a
mitochondrion?
Explain how respiration is a much more useful way for living
things to release energy from carbohydrates compared to fire.
Cellular Respiration ATP Tally
1. Glycolysis – 2 ATP
2. Krebs Cycle – 2 ATP
3. ETC – up to 34 ATP
Grand Total = 36-38 ATP
1.
2.
3.
4.
5.
6.
Questions
What is the real benefit of fermentation?
What is the cellular respiration equation?
What factor determines the pathway that
pyruvic acid takes after leaving glycolysis?
What is the importance of cellular respiration to
us?
Explain how cellular respiration complements
photosynthesis.
What is the ultimate end product of cellular
respiration?