Download Chapter 9: Cellular Respiration

Chapter 9: Cellular Respiration
Breaking down glucose a little at a
time ….. It’s like turning a five
pound bag of sugar into several
tiny sugar packets worth of
energy in the form of ATP ….
Remember the
carbon cycle:
the
relationship
between
photosynthesis
and cellular
respiration
Section 9-1: Chemical Pathways

What does food provide?
 Chemical building blocks for
growth and reproduction
 Source of raw materials to make
new molecules
 A source of energy
Chemical Energy & Food


Food energy is measured in calories
A calorie = the amount of energy needed
to raise the temperature of 1 gram of
water 1 degree Celsius
Chemical Energy & Food, cont’d



Calories (with a capital C) are used on
food labels
1 Calorie = 1 kilocalorie = 1000 calories
One gram of sugar releases 3811 calories
of heat energy when burned in the
presence of O2
Overview of Cellular Respiration


Cellular Respiration = a complex process that
releases energy by breaking down glucose and
other food molecules in the presence of oxygen
The Overall Equation:
C6H12O6 + 6O2 → 6CO2 + 6 H20 + Energy
glucose +
oxygen → carbon dioxide + water + energy
Overview of Cellular Respiration,


cont’d
Q: What is the goal of cellular
respiration?
A: To release the energy stored in
glucose in a series of small steps
and store that released energy in
ATP
An Overview of Cellular Respiration
• Three stages
– Glycolysis
– Krebs cycle
– Electron
transport
chain
and oxidative
phosphorylation.
Glycolysis


The process in which one molecule of
glucose, a 6-carbon compound, is
broken in half to produce two
molecules of pyruvic acid, a 3carbon compound
Note: pyruvate = pyruvic acid
Glycolysis, cont’d



Takes place in the cytoplasm
Does not require oxygen
Splitting one glucose leads to the
formation of:
 2 pyruvic acid
 2 ATP (net gain)
 2 NADH, an electron carrier
Glycolysis, cont’d



Occurs very quickly
Can produce thousands of ATP
molecules within a few seconds
Needs a constant supply of NAD+ or
glycolysis stops
Fermentation




Purpose is to regenerate NAD+ so
glycolysis can continue
Occurs in the cytoplasm
Occurs in the absence of oxygen
(anaerobic)
Two types:


Alcoholic Fermentation
Lactic Acid Fermentation
Alcoholic Fermentation




pyruvic acid + NADH → alcohol + CO2 + NAD+
Occurs in yeasts and a few other
microorganisms
Process that causes bread dough to rise
Generates ethanol and carbon dioxide as
products
Lactic Acid Fermentation




pyruvic acid + NADH → lactic acid + NAD+
Occurs in muscles during rapid exercise
Buildup of lactic acid causes a painful
burning sensation
Prokaryotes using lactic acid fermentation
aid in the production of cheese, yogurt,
and, sour cream

Let’s review mitochondrion structure
before we begin to talk about cellular
respiration in detail…..
The mitochondrion, site of cellular respiration
Mitochondrion Structure



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Outer Membrane
Inner Membrane (cristae) = site of
electron transport chain
Intermembrane Space = where H+
accumulates in between the inner and
outer membrane
Matrix = the center of the
mitochondria, Krebs cycle occurs here
Section 9-2
The Krebs Cycle & Electron Transport



Glycolysis releases only 10% of the
energy stored in glucose
What happens to the other 90%?
That energy is released via the Krebs
cycle and the electron transport chain
Glycolysis



Reviewed
Remember that:
Glycolysis takes place in the cytoplasm
Splitting one glucose leads to the
formation of:
 2 pyruvic acid
 2 ATP (net gain)
 2 NADH, an electron carrier
The Krebs Cycle


Before the Krebs cycle can begin pyruvic
acid must move from the cytoplasm to
the mitochondria
During the crossing the following occurs
per glucose:
2 pyruvic acid
2 CO2
2 coenzyme A → 2 acetyl CoA
2 NAD+
2 NADH
The intermediate
reaction leads to
the production of
2 Acetyl CoA
& 2NADH & 2 CO2
per glucose
The Krebs Cycle
leads to the
production of
CO2, NADH,
FADH2 & ATP
The Krebs Cycle, cont’d


First step:
2 Acetyl CoA + 2 oxaloacetate → 2 citric acid
(2 carbon)
+
(4 carbon)
→
(6 carbon)
+ 2 Coenzyme A
Complicated series of steps continue on in the cycle…
The Krebs Cycle, cont’d


At the end of 2 cycles needed per glucose:
2 citric acid
→
2 oxaloacetates
4 CO2
6 NAD+
6 NADH
2 FAD
2 FADH2
2 ADP
2 ATP
The Krebs Cycle, cont’d


What do you need to know?
During the Krebs cycle:

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Pyruvic acid is completely broken down to
CO2
Most of the energy released during the
cycle is stored in the electron carriers
NADH and FADH2
2 ATP are produced during the Krebs cycle
The Krebs Cycle, cont’d

Other things to note:


Citric acid is produced in the first step so
the Krebs cycle is also called the citric acid
cycle
Other substances such as fatty acids and
amino acids can also enter the Krebs cycle
and be broken down to release energy
Electron Transport Chain


The electron transport chain uses the
high energy electrons from NADH &
FADH2 to convert ADP to ATP
In eukaryotes electron transport occurs
at the inner membrane of a
mitochondrion
Electron Transport
Hydrogen Ion Movement
ATP
synthase
Intermembrane
Space
Inner
Membrane
Matrix
ATP Production
Electron Transport



As high energy electrons move down the
electron transport chain, the released energy
is used to drive the movement of H+ into
the intermembrane space
H+ then moves down its concentration
gradient through ATP synthase
ADP is converted to ATP by ATP synthase
Electron Transport,



cont’d
O2 is the final electron acceptor
Oxygen picks up electrons and H+ and
is converted into water
Without O2, there would be a “traffic
jam” of backed up electrons and cellular
respiration would cease
ATP Structure, a review


Adenosine triphosphate = ATP
ATP consists of:



adenine
ribose (a 5
carbon sugar)
& three
phosphates
The ADP ↔ ATP Cycle
P
ATP
Cellular Respiration
or the Light Reactions
Photosynthesis
ADP
Cellular Work
or the Calvin Cycle of
Photosynthesis
P
Electron Carriers & ATP Production



Each NADH leads to the production of
3 ATP
Each FADH2 leads to the production of
2 ATP
The only exception seems to be the
NADH from glycolysis which leads to
formation of 2 ATP per NADH
Summary of ATP Production per
Glucose Molecule



Glycolysis
2 ATP
Intermediate
Reaction to make
acetyl CoA
Krebs Cycle 2 ATP
2 NADH → 4 ATP
2 NADH → 6 ATP
6NADH → 18ATP
2 FADH2 → 4 ATP
36 Total ATP
Energy & Exercise



Where does your body get the energy needed
for exercise?
First your body uses the small stores of
ATP normally found in a cell / there is
enough stored ATP to allow a few seconds
of intense activity
Second your body turns to lactic acid
fermentation which produces enough ATP
to last about 90 seconds
Energy & Exercise

If exercise lasts longer than 90 seconds,
cellular respiration must be used to
generate sufficient ATP


Glycogen stores in the liver and muscle are
broken down to glucose / can provide enough
energy for 15-20 minutes of intense activity
After glycogen stores are depleted after 20
minutes, body turns to fat as the fuel / fatty
acids enter the Krebs cycle in the form of
acetyl CoA
Comparing Photosynthesis &
Cellular Respiration


See handouts/graphic organizers…
Photosynthesis

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
“deposits” or stores energy
occurs in plants
Cellular Respiration

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“withdraws” or releases energy
occurs in both plant and animal cells
The Carbon Cycle



A strong cyclic relationship exists
between photosynthesis and cellular
respiration…
Photosynthesis
6CO2 + 6 H20 → C6H12O6 + 6O2
Cellular Respiration
C6H12O6 + 6O2 → 6CO2 + 6 H20
The carbon cycle
Fig. 54.17
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Analyzing Experimental Set-Ups

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Do you understand the set-up?
Can you identify the proper controls?
Can you identify what is being asked
for?
Can you make predictions as to what
the expected results might be based on
prior knowledge?
Electron Carriers, cont’d

NAD+ + H + + 2e - ↔ NADH

FAD+ + 2H + + 2e - ↔ FADH2