Transcript Chapter 6 Cellular Respiration

Chapter 6 Cellular Respiration
6.1-6.6
Student 2014-2015
Introduction
 In eukaryotes, cellular respiration
• harvests energy from food,
• yields large amounts of ATP,
– Used for?
 What is the original source of energy?
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6.1 The relationship between C.R. and
Photosynthesis
• How are these processes related?
• What is misleading about the following
statement? “Plant cells perform
photosynthesis , and animal cells perform
cellular respiration”
6.2 Breathing supplies O2 for use in cellular
respiration and removes CO2
How is your breathing (respiration) related to
cellular respiration?
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6.3 Cellular respiration banks energy in ATP molecules
• Cellular respiration is an exergonic process that
transfers energy from the bonds in glucose to
form ATP
– Energy is gradually released
• Not like the marshmallow!
 Other foods (organic molecules) can also be
used as a source of energy.
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Figure 6.3
C6H12O6
6
Glucose
Oxygen
O2
6 CO2
Carbon
dioxide
6
H2O
ATP
Water
 Heat
Why are sweating and other body-cooling
Mechanisms necessary during vigorous exercise?
Why do you experience heavy breathing during vigorous
exercise?
Where do you see evidence of entropy?
6.4 CONNECTION: The human body uses energy from ATP
for all its activities
• The average adult human needs about 2,200 kcal of
energy per day.
– About 75% of these calories are used to maintain a
healthy body.
• Your brain utilizes 120 g or ¼ lb of glucose/day
and approx. 15% of total O2
– Other activities?
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6.4 CONNECTION: The human body uses energy from ATP
for all its activities
• A kilocalorie (kcal) is
– the quantity of heat required to raise the
temperature of 1 kilogram (kg) of water by 1oC,
– the same as a food Calorie
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Figure 6.4
Activity
kcal consumed per hour
by a 67.5-kg (150-lb) person*
Running (8–9 mph)
979
Dancing (fast)
510
Bicycling (10 mph)
490
Swimming (2 mph)
408
Walking (4 mph)
341
Walking (3 mph)
245
Dancing (slow)
Driving a car
Sitting (writing)
204
61
28
*Not including kcal needed for
body maintenance
6.5 Cells tap energy from electrons “falling” from
organic fuels to oxygen
• The energy necessary for life is contained in the
arrangement of electrons in chemical bonds in
organic molecules.
• An important question is how do cells extract
this energy?
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6.5 Cells tap energy from electrons “falling” from
organic fuels to oxygen
• When the carbon-hydrogen bonds of glucose are
broken, electrons are transferred to oxygen.
– Oxygen has a strong tendency to attract electrons.
• An “electron acceptor”
– An electron loses potential energy when it “falls” to
oxygen.
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6.5 Cells tap energy from electrons “falling” from
organic fuels to oxygen
• The movement of electrons from one molecule to
another is an oxidation-reduction reaction, or redox
reaction. In a redox reaction,
– the loss of electrons from one substance is called
oxidation,
– the addition of electrons to another substance is called
reduction,
– a molecule is oxidized when it loses one or more
electrons, and
– reduced when it gains one or more electrons.
• Oxidation and reduction always happen together.
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6.5 Cells tap energy from electrons “falling” from
organic fuels to oxygen
• A cellular respiration equation is helpful to show
the changes in hydrogen atom distribution.
• Glucose
– loses its hydrogen atoms and (consists of 1 proton
and 1 electron)
– becomes oxidized to CO2.
• Oxygen
– gains hydrogen atoms and
– becomes reduced to H2O.
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Figure 6.5A
Loss of hydrogen atoms
(becomes oxidized)
C6H12O6
6 O2
6 CO2
6 H2O
Glucose
Gain of hydrogen atoms
(becomes reduced)
ATP
 Heat
6.5 Cells tap energy from electrons “falling” from
organic fuels to oxygen
• Enzymes are necessary to oxidize glucose and
other foods.
• NAD+ (Nicotinamide adenine dinucleotide)
– is an important enzyme in oxidizing glucose,
– accepts electrons, and
– becomes reduced to NADH.
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Figure 6.5B
Becomes oxidized
2H
Becomes reduced
NAD
2H
2 H
NADH
2
(carries
2 electrons)
H
6.5 Cells tap energy from electrons “falling” from
organic fuels to oxygen
• There are other electron “carrier” molecules
that function like NAD+.
– They form a staircase where the electrons pass from
one to the next down the staircase.
– These electron carriers collectively are called the
electron transport chain.
– As electrons are transported down the chain, ATP is
generated.
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Figure 6.5C
NADH
NAD
ATP
2
Controlled
release of
energy for
synthesis
of ATP
H
2
1 O
2 2
2 H
H 2O
STAGES OF CELLULAR RESPIRATION
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6.6 Overview: Cellular respiration occurs in three main
stages
• Cellular respiration consists of a sequence of
steps that can be divided into three stages.
– Stage 1 – Glycolysis
– Stage 2 – Pyruvate oxidation and citric acid cycle
– Stage 3 – Oxidative phosphorylation
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6.6 Overview: Cellular respiration occurs in three main
stages
• Stage 1: Glycolysis
– occurs in the cytoplasm,
– begins cellular respiration, and
– breaks down glucose into two molecules of a threecarbon compound called pyruvate.
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6.6 Overview: Cellular respiration occurs in three main
stages
• Stage 2: The citric acid cycle
– takes place in mitochondria,
– oxidizes pyruvate to a two-carbon compound, and
– supplies the third stage with electrons.
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6.6 Overview: Cellular respiration occurs in three main
stages
• Stage 3: Oxidative phosphorylation
– involves electrons carried by NADH and FADH2,
– shuttles these electrons to the electron transport
chain embedded in the inner mitochondrial
membrane,
– involves chemiosmosis, and
– generates ATP through oxidative phosphorylation
associated with chemiosmosis.
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Figure 6.6
CYTOPLASM
NADH
Electrons
carried by NADH
NADH
Glycolysis
Glucose
Pyruvate
Pyruvate
Oxidation
Citric Acid
Cycle
FADH2
Oxidative
Phosphorylation
(electron transport
and chemiosmosis)
Mitochondrion
ATP
Substrate-level
phosphorylation
ATP
Substrate-level
phosphorylation
ATP
Oxidative
phosphorylation