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Chapter 6
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6-1
Energy and Organisms
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Organisms are classified based on the kind of energy
they use.
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Autotrophs
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Heterotrophs
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To use the energy from light to make organic molecules
All organisms use cellular respiration.
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Obtain organic molecules by eating the autotrophs
Use the energy in the organic molecules to make ATP
Autotrophs use photosynthesis.
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Use the energy from sunlight to make organic molecules (sugar)
Use the energy in the organic molecules to make ATP
To harvest the energy from organic molecules and use it to
makeCopyright
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Energy Transformation
6-3
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Review Oxidation and Reduction
6-4
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Aerobic Respiration: An Overview

A series of enzyme controlled reactions
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Oxygen is used to oxidize glucose.
Glucose is oxidized to form carbon dioxide.
Oxygen is reduced to form water.
During the oxidation of glucose
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The C-H and O-H bonds will be broken.
The electrons will be transferred to electron carriers, NAD
and FAD.
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The electrons will be passed through an electron transport
chain.
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6-5
Glycolysis and Kreb’s cycle
The energy from the electrons will be used to pump protons.
The energy from the diffusion of protons will be used to make
ATP.
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Aerobic Respiration and
Oxidation-Reduction Reactions
6-6
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Aerobic Cellular Respiration:
Overview
6-7
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**Glycolysis
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6-8
The breakdown of glucose
into pyruvic acid
Two ATP molecules are
used to energize glucose.
As glucose is metabolized,
enough energy is released
to
– Make 4 ATP molecules
 4 ATP made -2 ATP
used = net
production of 2 ATP
– Reduce 2 NAD+ to make
2 NADH
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Occurs in the
cytoplasm
Anaerobic
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The Details of Glycolysis
6-9
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Animation Glycolysis
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6-10
http://www.youtube.com/watch?v=ub1zTkZL
5sE&feature=related
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Kreb’s Cycle

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Also known as the citric acid
cycle or the tricarboxylic
acid (TCA) cycle
The breakdown of pyruvic
acid
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Enough energy is released
as one pyruvic acid
molecule is metabolized to
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6-11
Released as carbon dioxide
Make 1 ATP
Reduce 4 NAD+ to form 4
NADH
Reduce 1 FAD to form 1
FADH2.
Occurs in the mitochondrial
matrix
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The Details of the Kreb’s Cycle
6-12
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*Krebs Cycle video
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6-13
http://www.youtube.com/watch?v=juM2ROSL
Wfw
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Electron-Transport System
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6-14
NADH and FADH2 release the electrons they
received during glycolysis and the Kreb’s
cycle to the electron transport chain (ETC).
The proteins of the ETC transfer the
electrons and use the energy released to
pump protons.
– Protons are pumped from the matrix to the
intermembrane space.
– Creates a concentration gradient
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Review
Glycolysis
6-15
Conversion Step and
Kreb’s Cycle
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Electron-Transport System
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6-16
Oxygen is the final electron
acceptor at the end of the
ETC.
– Oxygen accepts the
electrons, combines with
protons and becomes
water.
The accumulated protons
diffuse back into the matrix
through ATP synthase.
 The energy released
from the diffusion
fuels the formation of
ATP.
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The Details of the Electron
Transport System
6-17
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*Animation
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Electron Transport
http://www.youtube.com/watch?v=xbJ0nbzt5
Kw&feature=related
ATPase
http://www.youtube.com/watch?v=3y1dO4nN
aKY&feature=related
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Cell Respiration / I Got a Feeling
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6-19
http://www.youtube.com/watch?annotation_i
d=annotation_381903&v=3aZrkdzrd04&featu
re=iv
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Total Yields for Aerobic Cellular
Respiration per Glucose Molecule
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Glycolysis
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Kreb’s cycle plus conversion step (pyruvate to acetyl)
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2 ATP
2 NADH (gets converted to 2 FADH2)
2 ATP
8 NADH
2 FADH2
Electron transport chain
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Each NADH made in mitochondria fuels the formation of 3 ATP.
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Each FADH2 fuels the formation of 2 ATP.
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8 NADH x 3 ATP = 24 ATP
4 FADH2 x 2 ATP = 8 ATP
Total ATP=2+2+24+8=36 ATP made from the metabolism of
one glucose molecule.
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Aerobic Respiration
in Prokaryotes
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6-21
Very similar to aerobic respiration in eukaryotes
Since prokaryotes have no mitochondria, it all occurs in the
cytoplasm.
Makes 2 more ATP because the NADH from glycolysis isn’t
converted to FADH2
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Anaerobic Cellular Respiration
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Some organisms do not have the enzymes for
Kreb’s cycle or the electron transport system.
Some organisms can metabolize glucose in the
absence of oxygen.
Metabolizing glucose in the absence of oxygen is
called anaerobic respiration.
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6-22
Involves the incomplete oxidation of glucose
Fermentation is an anaerobic pathway that uses an organic
molecule as the final electron acceptor.
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Anaerobic Cellular Respiration
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Anaerobic respiration usually starts with
glycolysis.
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The fermentation reactions oxidize NADH to
regenerate the NAD+ that is needed in
glycolysis.
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Glucose is metabolized into pyruvic acid.
2 ATP are made.
In the process, pyruvic acid is reduced to either
lactic acid or ethanol or another organic molecule.
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Types of Fermentation
6-24
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Alcoholic Fermentation
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Starts with glycolysis
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During alcoholic fermentation
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Pyruvic acid is reduced to form
ethanol.
Carbon dioxide is released.
Yeasts do this
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Glucose is metabolized to pyruvic
acid.
A net of 2 ATP is made.
Leavened bread
Sparkling wine
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Lactic Acid Fermentation
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Starts with glycolysis
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During lactic acid fermentation
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Pyruvic acid is reduced to form lactic acid.
No carbon dioxide is released.
Muscle cells have the enzymes to do this, but brain
cells do not.
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Glucose is metabolized to pyruvic acid.
A net of 2 ATP is made.
Muscle cells can survive brief periods of oxygen deprivation,
but brain cells cannot.
Lactic acid “burns” in muscles.
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Metabolizing Other Molecules
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Cells will use the energy in carbohydrates first.
– Complex carbohydrates are metabolized into
simple sugars.
Cells can use the energy in fats and proteins as well.
– Fats are digested into fatty acids and glycerol.
– Proteins are digested into amino acids.
Cells must convert fats and proteins into molecules
that can enter and be metabolized by the enzymes
of glycolysis or the Kreb’s cycle.
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Fat Respiration
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Fats are broken down into
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Glycerol
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Converted to acetylCoA
Enter the Kreb’s cycle
Each molecule of fat fuels the formation of many
more ATP than glucose.
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Converted to glyceraldehyde-3-phosphate
Enters glycolysis
Fatty acids
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Glycerol
Fatty acids
This makes it a good energy storage molecule.
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Protein Respiration
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Proteins are digested into amino acids.
Then amino acids have the amino group
removed.
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Generates a keto acid (acetic acid, pyruvic acid,
etc.)
Enter the Kreb’s cycle at the appropriate place
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The Interconversion of Fats,
Carbohydrates and Proteins
6-30
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The Bottom Line
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Carbohydrates, fats and proteins can all be
used for energy.
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Glycolysis and the Kreb’s cycle allow these types
of molecules to be interchanged.
If more calories are consumed than used
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The excess food will be stored.
Once the organism has all of the proteins it needs
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And its carbohydrate stores are full
The remainder will be converted to and stored as fat.
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Chapter 6 homework 2011
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6-32
Basic Review 1-8
Concept Review: 1,4,5,6,7,8,9
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