Download Ch. 9 Cellular Respiration

9-1 Chemical Pathways
Ch. 9 Cellular Respiration
Biology
Ms. Haut
Copyright Pearson Prentice Hall
9-1 Chemical Pathways
Food serves as a source of raw materials for the
cells in the body and as a source of energy.
Copyright Pearson Prentice Hall
Both plant and animal cells carry out the final
stages of cellular respiration in the mitochondria.
Outer membrane
Intermembrane
Mitochondrion
space
Animal Cells
Plant Cells
Inner
membrane
Matrix
Copyright Pearson Prentice Hall
Chemical Energy and Food
Chemical Energy and Food
One gram of the sugar glucose (C6H12O6), when
burned in the presence of oxygen, releases 3811
calories of heat energy.
A calorie is the amount of energy needed to raise
the temperature of 1 gram of water 1 degree
Celsius.
Copyright Pearson Prentice Hall
Chemical Energy and Food
Cells don't “burn” glucose. Instead, they gradually
release the energy from glucose and other food
compounds.
This process begins with a pathway called
glycolysis.
Glycolysis releases a small amount of energy.
Copyright Pearson Prentice Hall
Overview of Cellular Respiration
Overview of Cellular Respiration
If oxygen is present, glycolysis is followed by the
Krebs cycle and the electron transport chain.
Glycolysis, the Krebs cycle, and the electron
transport chain make up a process called cellular
respiration.
Copyright Pearson Prentice Hall
Overview of Cellular Respiration
Copyright Pearson Prentice Hall
Overview of Cellular Respiration
• Cellular respiration is the process that releases
energy by breaking down glucose and other food
molecules in the presence of oxygen.
• The equation for cellular respiration is:
6O2 + C6H12O6 → 6CO2 + 6H2O + Energy
oxygen + glucose → carbon dioxide + water + Energy
Copyright Pearson Prentice Hall
Overview of Cellular Respiration
Each of the three stages of cellular respiration
captures some of the chemical energy available in
food molecules and uses it to produce ATP.
Copyright Pearson Prentice Hall
Overview of Cellular Respiration
Glycolysis takes place in the cytoplasm. The Krebs
cycle and electron transport take place in the
mitochondria.
Glycolysis
Glycolysis
• Glycolysis is the
process in which one
molecule of glucose is
broken in half,
producing two
molecules of pyruvic
acid, a 3-carbon
compound.
Copyright Pearson Prentice Hall
Glycolysis
ATP Production
At the beginning of glycolysis, the cell uses up 2
molecules of ATP to start the reaction.
Copyright Pearson Prentice Hall
Glycolysis
When glycolysis is complete, 4 ATP molecules
have been produced.
Copyright Pearson Prentice Hall
Glycolysis
This gives the cell a net gain of 2 ATP molecules.
Copyright Pearson Prentice Hall
Glycolysis
NADH Production
One reaction of glycolysis removes 4 high-energy
electrons, passing them to an electron carrier
called NAD+.
Copyright Pearson Prentice Hall
Glycolysis
Each NAD+ accepts a pair of high-energy electrons
and becomes an NADH molecule.
Copyright Pearson Prentice Hall
Glycolysis
The NADH molecule holds the electrons until they
can be transferred to other molecules.
Copyright Pearson Prentice Hall
Glycolysis
The Advantages of Glycolysis
1. The process of glycolysis is so fast that cells
can produce thousands of ATP molecules in a
few milliseconds.
2. Glycolysis does not require oxygen.
Copyright Pearson Prentice Hall
Fermentation
Fermentation
When oxygen is not present, glycolysis is followed
by a different pathway. The combined process of
this pathway and glycolysis is called fermentation.
Fermentation releases energy from food
molecules by producing ATP in the absence of
oxygen.
Copyright Pearson Prentice Hall
Fermentation
During fermentation, cells convert NADH to NAD+
by passing high-energy electrons back to pyruvic
acid.
This action converts NADH back into NAD+, and
allows glycolysis to continue producing a steady
supply of ATP.
Fermentation does not require oxygen—it is an
anaerobic process.
Copyright Pearson Prentice Hall
Alcoholic Fermentation
• Yeasts and a few other
microorganisms use
alcoholic fermentation,
forming ethyl alcohol and
carbon dioxide as wastes.
Lactic Acid Fermentation
•Commercially important products: cheese & yogurt
•Human muscle cells switch to lactic acid fermentation
when O2 is scarce. Lactate accumulates, slowly carried to
liver and converted back to pyruvate when O2 is available
9-1
The raw materials required for cellular
respiration are
a. carbon dioxide and oxygen.
b. glucose and water.
c. glucose and oxygen.
d. carbon dioxide and water.
Copyright Pearson Prentice Hall
9-1
Glycolysis occurs in the
a. mitochondria.
b. cytoplasm.
c. nucleus.
d. chloroplasts.
Copyright Pearson Prentice Hall
9-1
The net gain of ATP molecules after glycolysis is
a. 3 ATP molecules.
b. 2 ATP molecules.
c. 3 pyruvic acid molecules.
d. 4 pyruvic acid molecules
Copyright Pearson Prentice Hall
9-1
Fermentation releases energy from food
molecules in the absence of
a. oxygen.
b. glucose.
c. NADH.
d. alcohol.
Copyright Pearson Prentice Hall
9-1
The first step in fermentation is always
a. lactic acid production.
b. the Krebs cycle.
c. glycolysis.
d. alcohol production.
Copyright Pearson Prentice Hall
END OF SECTION
9-2 The Krebs Cycle and Electron
Transport
Ch 9
Biology
Ms. Haut
Copyright Pearson Prentice Hall
9-2 The Krebs Cycle and
Electron Transport
• Oxygen is required for the final steps of
cellular respiration.
• Because the pathways of cellular respiration
require oxygen, they are aerobic.
Copyright Pearson Prentice Hall
The Krebs Cycle
• In the presence of oxygen, pyruvic acid
produced in glycolysis passes to the second
stage of cellular respiration, the Krebs cycle.
Copyright Pearson Prentice Hall
The Krebs Cycle
• During the Krebs cycle, pyruvic acid is broken
down into carbon dioxide in a series of energyextracting reactions.
Copyright Pearson Prentice Hall
The Krebs Cycle
• The Krebs cycle begins when pyruvic acid produced
by glycolysis enters the mitochondrion.
• One carbon molecule is removed, forming CO2, and
electrons are removed, changing NAD+ to NADH.
Copyright Pearson Prentice Hall
The Krebs Cycle
• Coenzyme A joins the 2-carbon molecule,
forming acetyl-CoA.
Copyright Pearson Prentice Hall
The Krebs Cycle
• Acetyl-CoA then adds the 2-carbon acetyl
group to a 4-carbon compound, forming citric
acid.
Copyright Pearson Prentice Hall
The Krebs Cycle
• Citric acid is broken down into a 5-carbon
compound, then into a 4-carbon compound.
The Krebs Cycle
• Two more molecules of CO2 are released and
electrons join NAD+ and FAD, forming NADH
and FADH2
Copyright Pearson Prentice Hall
The Krebs Cycle
• In addition, one molecule of ATP is generated.
The Krebs Cycle
• The energy tally from 1 molecule of pyruvic
acid is
– 4 NADH
– 1 FADH2
– 1 ATP
Copyright Pearson Prentice Hall
The Krebs Cycle
• What does the cell do with all those highenergy electrons in carriers like NADH?
• In the presence of oxygen, those high-energy
electrons can be used to generate huge
amounts of ATP.
Copyright Pearson Prentice Hall
Electron Transport
• The electron transport chain uses the highenergy electrons from the Krebs cycle to
convert ADP into ATP.
Copyright Pearson Prentice Hall
Electron Transport
• High-energy electrons from NADH and FADH2 are passed
along the electron transport chain from one carrier protein to
the next.
Copyright Pearson Prentice Hall
Electron Transport
• At the end of the chain, an enzyme combines these electrons
with hydrogen ions and oxygen to form water.
Copyright Pearson Prentice Hall
Electron Transport
• As the final electron acceptor of the electron transport chain,
oxygen gets rid of the low-energy electrons and hydrogen ions.
Copyright Pearson Prentice Hall
Electron Transport
• When 2 high-energy electrons move down the electron
transport chain, their energy is used to move hydrogen ions
(H+) across the membrane.
Electron Transport
• During electron transport, H+ ions build up in the
intermembrane space, so it is positively charged.
Copyright Pearson Prentice Hall
Electron Transport
• The other side of the membrane, from which those H+ ions are
taken, is now negatively charged.
Copyright Pearson Prentice Hall
Electron Transport
• The inner membranes of the mitochondria contain protein
spheres called ATP synthases.
ATP
synthase
Copyright Pearson Prentice Hall
Electron Transport
• As H+ ions escape through channels into these proteins, the ATP
synthase spins.
Channel
ATP
synthase
Copyright Pearson Prentice Hall
Electron Transport
• As it rotates, the enzyme grabs a low-energy ADP, attaching a
phosphate, forming high-energy ATP.
Channel
ATP
synthase
ATP
Copyright Pearson Prentice Hall
Electron Transport
• On average, each pair of high-energy electrons
that moves down the electron transport chain
provides enough energy to produce molecules
of ATP from ADP.
1 NADH = 3 ATP
1 FADH2 = 2 ATP
10 NADH = 30 ATP
2 FADH2 = 4 ATP
34 ATP
Copyright Pearson Prentice Hall
The Totals
• Glycolysis produces just 2 ATP molecules per
molecule of glucose.
• The complete breakdown of glucose through
cellular respiration, including glycolysis, results
in the production of 38 molecules of ATP.
Copyright Pearson Prentice Hall
The Totals
Copyright Pearson Prentice Hall
Comparing Photosynthesis and
Cellular Respiration
• The energy flows in photosynthesis and
cellular respiration take place in opposite
directions.
Copyright Pearson Prentice Hall
Comparing Photosynthesis and
Cellular Respiration
• On a global level, photosynthesis and cellular
respiration are also opposites.
– Photosynthesis removes carbon dioxide from the
atmosphere and cellular respiration puts it back.
– Photosynthesis releases oxygen into the
atmosphere and cellular respiration uses that
oxygen to release energy from food.
Copyright Pearson Prentice Hall
9-2
– The Krebs cycle breaks pyruvic acid down into
•
•
•
•
oxygen.
NADH.
carbon dioxide.
alcohol.
Copyright Pearson Prentice Hall
9-2
– What role does the Krebs cycle play in the cell?
• It breaks down glucose and releases its stored energy.
• It releases energy from molecules formed during
glycolysis.
• It combines carbon dioxide and water into high-energy
molecules.
• It breaks down ATP and NADH, releasing stored energy.
Copyright Pearson Prentice Hall
9-2
– In eukaryotes, the electron transport chain is
located in the
•
•
•
•
cell membrane.
inner mitochondrial membrane.
cytoplasm.
outer mitochondrial membrane.
Copyright Pearson Prentice Hall
9-2
– To generate energy over long periods, the body
must use
•
•
•
•
stored ATP.
lactic acid fermentation.
cellular respiration.
glycolysis.
Copyright Pearson Prentice Hall
9-2
– Which statement correctly describes
photosynthesis and cellular respiration?
• Photosynthesis releases energy, while cellular
respiration stores energy.
• Photosynthesis and cellular respiration use the same
raw materials.
• Cellular respiration releases energy, while
photosynthesis stores energy.
• Cellular respiration and photosynthesis produce the
same products.
Copyright Pearson Prentice Hall
END OF SECTION