Transcript Slide 1

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HOW CELLS HARVEST CHEMICAL ENERGY
(CELLULAR RESPIRATION)
Important points to review….
• Energy is one-way flow.
• Energy is not created or destroyed it can only
be converted from one form to another.
Solar energy
(sun)
Chemical energy
(stored in glucose molecule)
Overview Photosynthesis Reaction:
6CO2 + 12 H2O
C6H12O6 + 6O2 + 6 H2O
2nd Important Energy
Reaction
Overview Cellular Respiration Reaction:
C6H12O6 + 6O2
6CO2 + 6 H2O + (32 ATP)
Cellular respiration is an exergonic process that
transfers energy from the bonds in glucose to
form ATP.
Photosynthesis and cellular respiration provide
energy for life - 4 important points
1.
2.
3.
4.
© 2012 Pearson Education, Inc.
Sunlight energy
ECOSYSTEM
Photosynthesis
in chloroplasts
The
connection
between
photosynthesis
and cellular
respiration
CO2
Glucose
H2O
O2
Cellular respiration
in mitochondria
(for cellular
work)
ATP
Heat energy
Breathing supplies O2 for use in cellular respiration and removes CO2
O2
The
connection
between
breathing
and
cellular
respiration
Breathing
CO2
Lungs
CO2
Bloodstream
O2
Muscle cells carrying out
Cellular Respiration
Glucose  O2
CO2  H2O  ATP
CONNECTION: The human body uses energy
from ATP for all its activities
 The average adult human needs about 2,200 kcal
(the same as a food Calorie) of energy per day.
– About 75% of these calories are
used to maintain a healthy body.
– The remaining 25% is used to
power physical activities.
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?
– When the carbon-hydrogen bonds of glucose are
broken, electrons are transferred to oxygen.
– Oxygen has a strong tendency to attract electrons.
– An electron loses potential energy when it “falls” slowly
to oxygen. That energy can be picked up by ATP!
Cells tap energy from electrons “falling” from
organic fuels to oxygen
 Energy can be released from glucose by simply
burning it.
 The energy is dissipated as heat and light and is
not available to living organisms.
 On the other hand, cellular respiration is the
controlled breakdown of organic molecules.
 Summation: Energy is
– ___________________________________
– ___________________________________
– ___________________________________
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.
Cells tap energy from electrons “falling” from
organic fuels (glucose) to oxygen
 Enzymes are necessary to oxidize glucose and
other foods.
 NAD+
– is an important enzyme in oxidizing glucose,
– accepts electrons, and
– becomes reduced to NADH.
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.
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 – ______________________
– Stage 2 – ______________ and ___________________
– Stage 3 – ______________________
Mitochondria
Overview: Cellular respiration occurs in
three main stages
 Stage 1: Glycolysis



Glycolysis harvests chemical energy by
oxidizing glucose to pyruvate
 In glycolysis,
– a single molecule of ____________
is enzymatically cut in half
through a series of steps,
– two molecules of _____________
are produced,
– two molecules of NAD+
are reduced to two molecules
of ____________, and
– a net of two molecules of _________
is produced.
P
P
NAD
NAD
P
NADH
P
NADH
H
H
P
P
P
ADP
P
1,3-Bisphosphoglycerate
P
3-Phosphoglycerate
ADP
6
ATP
ATP
P
P
P
2-Phosphoglycerate
H2O
H2O
P
P
ADP
ATP
ADP
Phosphoenolpyruvate (PEP)
ATP
Pyruvate
Glycolysis harvests chemical energy by
oxidizing glucose to pyruvate
 The steps of glycolysis can be grouped into two
main phases.
– In steps 1–4, the energy investment phase,
– energy is consumed as two ATP molecules are used to
energize a glucose molecule,
– which is then split into two small sugars that are now primed
to release energy.
– In steps 5–9, the energy payoff,
– two NADH molecules are produced for each initial glucose
molecule and
– 4 ATP molecules are generated. (net gain of 2!)
Glycolysis harvests chemical energy by
oxidizing glucose to pyruvate
 ATP is formed in glycolysis by substrate-level
phosphorylation during which
– an enzyme transfers a ____________ group from a
substrate molecule to ADP and
– ATP is formed.
Overview: Cellular respiration occurs in
three main stages
 Stage 2: The citric acid cycle



Pyruvate is oxidized prior to the citric acid cycle
 Two molecules of pyruvate are produced for each molecule of glucose
that enters glycolysis.
 Pyruvate does not enter the citric acid cycle, but undergoes some
chemical grooming in which
– a carboxyl group is removed and given off as _______,
– the two-carbon compound remaining is oxidized while a molecule
of NAD+ is reduced to __________,
– coenzyme A joins with the two-carbon group to form acetyl
coenzyme A, abbreviated as acetyl CoA, and
– acetyl CoA enters the citric acid cycle.
The citric acid cycle completes the oxidation of
organic molecules, generating
many NADH and FADH2 molecules
 The citric acid cycle
– is also called the Krebs cycle (after the German-British
researcher Hans Krebs, who worked out much of this
pathway in the 1930s),
– completes the oxidation of organic molecules (glucose),
and
– generates many NADH and FADH2 molecules.
Acetyl CoA
During the citric acid cycle the
two-carbon group of acetyl CoA
is added to a four-carbon
compound, forming citrate,
citrate is degraded back to the
four-carbon compound,
two CO2 are released, and
___ ATP,
___ NADH, and
__-FADH2 are produced.
CoA
CoA
2 CO2
Citric Acid Cycle
3 NAD
FADH2
3 NADH
FAD
3 H
ATP
ADP
P
The citric acid cycle completes the oxidation of
organic molecules, generating many
NADH and FADH2 molecules
 Remember that the citric acid cycle processes two
molecules of acetyl CoA for each initial glucose.
 Thus, after two turns of the citric acid cycle, the
overall yield per glucose molecule is
– 2 ATP,
– 6 NADH, and
– 2 FADH2.
Acetyl CoA
CoA
CoA
2 carbons enter cycle
Oxaloacetate
1
Citrate
NADH
H
NAD
5
NAD
NADH
2
H
Citric Acid Cycle
CO2 leaves cycle
Malate
FADH2
Alpha-ketoglutarate
4
3
FAD
CO2 leaves cycle
NAD
Succinate
ADP
Step 1
Acetyl CoA stokes
the furnace.
P
Steps 2 – 3
ATP
NADH, ATP, and CO2
are generated during redox reactions.
NADH
H
Steps 4 – 5
Further redox reactions generate
FADH2 and more NADH.
Overview: Cellular respiration occurs in
three main stages
 Stage 3: Oxidative phosphorylation
 Use _____________ and __________ already formed
in previous stages
 Produce ___ ___ ___
Most ATP production occurs by
oxidative phosphorylation
 Electrons from NADH and FADH2 travel down the
electron transport chain to ______.
 Oxygen picks up H+ to form water.
 Energy released by these redox reactions is used
to pump H+ from the mitochondrial matrix into the
intermembrane space.
 In __________________, the H+ diffuses back
across the inner membrane through
________________complexes, driving the
synthesis of ATP.
H
Intermembrane
space
H
H
H
H Mobile
electron
carriers
Protein
complex
of electron
carriers
H ATP
synthase
IV
I
II
FADH2
Electron
flow
NADH
Mitochondrial
matrix
H
H
III
Inner mitochondrial
membrane
H
NAD
FAD
2 H
1
2 O2
H2O
H
ADP
P
ATP
H
Electron Transport Chain
Oxidative Phosphorylation
Chemiosmosis
Review: Each molecule of glucose yields many
molecules of ATP
 Recall that the energy payoff of cellular respiration involves
– glycolysis,
– alteration of pyruvate,
– the citric acid cycle, and
– oxidative phosphorylation.
 The total yield is about 32 ATP molecules per glucose
molecule.
 This is about 34% of the potential energy of a glucose
molecule.
 In addition to the ATP, _______and _______are produced.
https://Cellular Respiration Rap
CYTOPLASM
Electron shuttles
across membrane
2 NADH
Mitochondrion
2 NADH
or
2 FADH2
6 NADH
2 NADH
Glycolysis
2
Pyruvate
Glucose
Pyruvate
Oxidation
2 Acetyl
CoA
Citric Acid
Cycle
2 FADH2
Oxidative
Phosphorylation
(electron transport
and chemiosmosis)
Maximum
per glucose:
2
ATP
by substrate-level
phosphorylation
2
ATP
by substrate-level
phosphorylation
 about
28 ATP
by oxidative
phosphorylation
About
32 ATP
http://Cellular Respiration Animation
Watch it until it makes sense!
Glycolysis - Fermentation Animation
Fermentation enables cells to produce
ATP without oxygen
 Fermentation is a way of harvesting chemical energy
that does not require oxygen. Fermentation
– takes advantage of glycolysis….so..
– produces _____ ATP molecules per glucose, and
– reduces NAD+ to _________.
 The trick of fermentation is to provide an anaerobic
path for recycling NADH back to NAD+.
Your muscle cells and certain bacteria can oxidize NADH through lactic acid fermentation, in which
NADH is oxidized to NAD+ and
pyruvate is reduced to lactate.
The baking and winemaking industries have used alcohol
fermentation for thousands of years.
In this process yeasts (single-celled fungi)oxidize NADH back to
NAD+ and convert pyruvate to CO2 and ethanol.
Animation: Fermentation Overview
Right click on animation / Click play
EVOLUTION CONNECTION: Glycolysis
evolved early in the history of life on Earth
 Glycolysis is the universal energy-harvesting process of life.
 The role of glycolysis in fermentation and respiration dates back to
– life long before oxygen was present,
– when only prokaryotes inhabited the Earth,
– about 3.5 billion years ago.
 The ancient history of glycolysis is supported by its
– occurrence in all the domains of life and
– location within the cell, using pathways that do not involve any
membrane-bounded organelles.
Cells use many kinds of organic molecules as fuel
for cellular respiration
 Although glucose is considered to be the primary
source of sugar for respiration and fermentation,
ATP is generated using
– carbohydrates,
– fats, and
– proteins.
© 2012 Pearson Education, Inc.
Food, such as
peanuts
Carbohydrates
Sugars
Fats
Proteins
Glycerol Fatty acids
Amino acids
Amino
groups
Glucose
G3P
Pyruvate
Glycolysis
Pyruvate
Oxidation
Acetyl CoA
ATP
Citric
Acid
Cycle
Oxidative
Phosphorylation
Food molecules provide raw materials for
biosynthesis
 Cells use intermediates from cellular respiration for
the biosynthesis of other organic molecules.
You should now be able to
1. Compare the processes and locations of cellular
respiration and photosynthesis.
2. Explain how breathing and cellular respiration are
related.
3. Provide the overall chemical equation for cellular
respiration.
4. Explain how the human body uses its daily supply
of ATP.
You should now be able to
5. Explain how the energy in a glucose molecule is
released during cellular respiration.
6. Describe the general roles of dehydrogenase,
NADH, and the electron transport chain in cellular
respiration.
7. Compare the reactants, products, and energy
yield of the three stages of cellular respiration.
You should now be able to
9. Compare the reactants, products, and energy
yield of alcohol and lactic acid fermentation.
10. Briefly explain how carbohydrates, fats, and
proteins are used as fuel for cellular respiration.
Aerobic respiration……
an animation to help you visualize
http://www2.nl.edu/jste/aerobic_respiration.htm
Cellular
respiration
has three stages
generates
oxidizes
uses
produce
some
produces
many
energy for
glucose and
organic fuels
(a)
(b)
(d)
to pull
electrons down
(c)
cellular work
(f)
by a process called
chemiosmosis
uses
(g)
H diffuse
through
ATP synthase (e)
uses
pumps H to create
H gradient
to
Proton Pump/Chemiosmosis
AN OVERVIEW OF AEROBIC RESPIRATION