How do Organisms Obtain Energy?
Cellular Respiration
¡ A cellular process that CATABOLIZES organic molecules and produces ATP (32-34)
¡ Consumes oxygen (O
2
)
¡ Cellular respiration is an AEROBIC PROCESS
¡ Glucose is broken down into
¡ Carbon dioxide (CO
2
)
¡ Hydrogen atoms
¡ Energy transfer occurs by Redox reaction
¡ Involves the coenzymes NAD+ and FAD
¡ Oxygen is the final electron acceptor
The Mitochondria
Inner and Outer Membrane
Matrix – Place where the Prep RXN and Citric Acid Cycle
Cristae – Location of the Electron Transport Chain
1

Phases of Cellular Respiration
① Glycolysis :
¡ Cytoplasm
¡ glucose è pyruvate
¡ Does not use O
2
¡ Nets 2 ATP
② Preparatory Reaction* :
¡ Mitochondrial matrix
¡ Pyruvate is oxidized
¡ Produces NADH
¡ CO
2 is released
③ Citric Acid Cycle :
¡ Mitochondrial matrix
¡ Produces NADH & FADH
2
¡ CO
2 is released
¡ Nets 2 ATP
④ Electron Transport Chain :
¡ Cristae
¡ Extracts energy from
NADH & FADH
2
¡ Produces 32 or 34 ATP
*steps 2-4 happen when O
2 is available
Overview of the 4 phases
1 – Glycolysis
2 – Prep Reaction
3 – Citric Acid Cycle
4 – Electron Transport Chain
Glucose Breakdown:
Summary of Cellular Respiration
¡ Glucose is oxidized and O
2 is reduced
¡ Glucose loses hydrogen to become CO
2
¡ Electrons and H+ combine with oxygen to become water
2

Oxidative
Phosphorylation
Uses enzymes and energy released by the oxidation of glucose to produce ATP
Substrate–Level Phosphorylation
Oxidative Phosphorylation
Breaking Sugar
3

Drawing Glycolysis
C" C" C"
Glucose(
C" C" C"
2(ATP(
Details of Glycolysis
¡ Occurs in the cytoplasm outside the mitochondria
¡ Energy Investment Step:
¡ 2 – ATP used form 2 G3P molecules
¡ Products of Glycolysis
¡ 2 pyruvate
¡ Energy Harvesting Step:
¡ 2 ATP
¡ 2 NADH
N A D + "
2 " A D P "
NADH(
C"
C"
C"
C"
G3P(
C"
C"
H+"and"2"e/"
C" C"
C" C"
Pyruvate(
C"
C"
4 " A D P "
4(ATP(
Anaerobic Respiration
4

• 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.
• There are two primary fermentation processes:
•
•
Lactic Acid Fermentation
Alcohol Fermentation
• Advantages
• Provides a quick burst of ATP energy for muscular activity.
• Disadvantages
•
•
Lactate and alcohol are toxic to cells.
Lactate changes pH and causes muscles to fatigue.
•
Yeast die from the alcohol they produce by fermentation
• Efficiency of Fermentation
• Only 2 ATP per glucose are produced, compared to 32 ATP molecules per glucose produced by cellular respiration.
J
5

• Occurs in the cytoplasm of muscle cells of animals
• Glucose is partially broken down into lactic acid
• If oxygen becomes available
•
Lactic acid (C
3
H
6
O
3
) can be oxidized
Exercise and Lactic Acid Fermentation
• Provides quick bursts of energy
• During strenuous exercise
• Lactic acid can accumulate in the muscles
• Accumulation of lactic acid causes…
•
Pain and cramping in the area
•
Increases and intensifies if exercise continues
• Lactic acid fermentation replaces the process of aerobic respiration
•
Provides the cell with a continual source of energy even if oxygen is absence
• The shift is only temporary
• Cells need oxygen for sustained activity
6

• Yeast and some bacteria
• Occurs in the cytoplasm
• Produces…
•
•
2 molecules of ATP
Carbon dioxide (CO
2
)
• Alcohol (C
2
H
5
OH).
Products of
Alcohol
Fermentation
7

Pyruvic oxidation &
Cyclical metabolic pathway
Drawing the Prep/Citric
Acid Cycle
8

Prep RXN (pyruvate oxidation)
¡ Prep reaction is called this because it prepares pyruvate for the Citric Acid Cycle
¡ Takes place in the matrix
¡ Pyruvate is oxidized by NAD+
¡ 1 CO
2 molecule is given off
The Citric Cycle
¡ Also Called the Krebs Cycle
¡ A cyclical pathway that takes place in the matrix
¡ For 1 C
2
ACETYL GROUP (There are two turns of the cycle)
¡ C
2
Acetyl group + C
4 oxaloacetate è C
6
Citric Acid
¡ C
6
Citric Acid is oxidized è C
4 succinate
¡ 2 NAD+ is reduced
¡ 2 CO
2 is produced
¡ 1 ATP
¡ C
4 succinate is oxidized è C
4 oxaloacetate
¡ FADH
2 and NADH
The Grand Totals So far…
¡ 6 CO
2
¡ 10 NADH
¡ 2 FADH
2
¡ 4 ATP
9

Drawing the ETC
The ETC
¡ Takes place in the cristae
¡ A series of proteins that accepts and pass electrons
¡ Energy is used to create a proton gradient
¡ Oxygen is the final electron acceptor
¡
NADH passes electron to Complex 1
¡
Pumps H+ into intermembrane space
¡ FADH 2 passes electron to Complex 2
¡ Pumps H+ into intermembrane space
¡ Complex 3
¡ Pumps H+ into intermembrane space
¡ ½ O
2
+ 2e- + 2H+
¡ ATP Synthase
è H
2
O
¡ Produces ATP via chemiosmosis
¡ Oxidative phosphorylation
10

Summary: ATP Production
¡ Current research shows
¡ 2.5 ATP per NADH
¡
1.5 ATP per FADH
2
¡ Glycolysis: ???
¡ 2 ATP + 2 NADH ☛ Nets 7 ATP
¡ Prep RXN: ???
¡ 2 NADH ☛ Nets 5 ATP
¡ Citric Acid Cycle: ???
¡ 2 ATP + 6 NADH (15 ATP) + 2 FADH 2 (3 ATP) ☛ Nets 20 ATP
¡ TOTAL = 32 ATP
Efficiency of Cellular
Respiration
¡ Gram Calorie (cal)
¡ The amount of energy needed to raise 1 gram of water by 1 0 c
¡ Kilogram Calorie (kcal)
¡ The amount of energy needed to raise 1 kilogram of water by 1 0 c
¡ 1 kcal = 1000 cal
¡ Calculate the how efficient the body is..
¡ The hydrolysis of ATP to ADP is about 7.0 kcal
¡ Glucose burned in air releases 686 kcal (lab setting)
¡ Cellular Respiration Efficiency ------- 33%
¡ Cars (www.fueleconomy.gov)
¡ Gasoline Efficiency ------- 14-30%
¡ Hybrid Efficiency ------- 25-40%
¡ Electric Efficiency ------- 74-94%
11