Download Cellular Respiration

Cellular
Respiration
Cellular Respiration: Harvesting Chemical Energy
Ppt from: aurumscience.com
Life Requires Energy
• Living cells require energy from outside
sources
• Some animals, such as the giant panda,
obtain energy by eating plants; others feed
on organisms that eat plants
• Energy flows into an ecosystem as sunlight
and leaves as heat
• Photosynthesis uses sunlight to generate
oxygen and glucose sugar.
• Cell respiration uses chemical energy in the
form of carbohydrates, lipids, or proteins, to
produce ATP.
ATP
• ATP stands for Adenosine Tri-Phosphate
• ATP is a molecule that serves as the most
basic unit of energy
• ATP is used by cells to perform their daily tasks
ATP
• ATP can be broken down into a molecule of
ADP by removing one of the phosphate
groups.
o This releases energy.
• ADP can be remade into ATP later when the
cell has food that can be broken down (i.e.
glucose)
NADH
• NADH is a molecule that can “carry” H+ ions
and electrons from one part of the cell to
another.
o NADH is the “energized” version of this molecule that is
carrying the H+ ion and two high-energy electrons.
o NAD+ is the “non-energized” version of this molecule that
does not have the ion or the extra two electrons.
LE 8-9
P
P
P
Adenosine triphosphate (ATP)
H2O
Pi
+
Inorganic phosphate
P
P
Adenosine diphosphate (ADP)
+
Energy
LE 9-2
Light
energy
ECOSYSTEM
Photosynthesis
in chloroplasts
CO2 + H2O
Simple sugars + O
2
(Glucose)
Cellular respiration
in mitochondria
ATP
powers most cellular work
Heat
energy
Cell Respiration and
Production of ATP
• The breakdown of organic molecules
(carbohydrates, lipids, proteins) releases
energy.
• Cellular respiration consumes oxygen and
organic molecules and yields ATP
• Although carbohydrates, fats, and proteins
are all consumed as fuel, it is helpful to trace
cellular respiration with the sugar glucose:
C6H12O6 + 6O2  6CO2 + 6H2O + Energy
Glycolysis
• Glycolysis is the first stage
of cellular respiration.
• Occurs in cytoplasm.
• During glycolysis, glucose
is broken down into 2
molecules of the 3-carbon
molecule pyruvic acid.
o ATP and NADH are
produced as part of the
process.
ATP Production
• 2 ATP molecules are
needed to get
glycolysis started.
ATP Production
• Glycolysis then
produces 4 ATP
molecules, giving the
cell a net gain of +2
ATP molecules for
each molecule of
glucose that enters
glycolysis.
NADH Production
• During glycolysis, the
electron carrier 2
NAD+ become 2
NADH.
• 2 NADH molecules
are produced for
every molecule of
glucose that enters
glycolysis.
Glycolysis
• Glycolysis uses up:
o 1 molecule of glucose (6-carbon sugar)
o 2 molecules of ATP
o 2 molecules of NAD+
• Glycolysis produces
o 2 molecules of pyruvic acid (3-carbon acids)
o 4 molecules of ATP
o 2 molecules of NADH
Advantages of Glycolysis
• Glycolysis produces ATP very fast, which is an
advantage when the energy demands of the cell
suddenly increase.
• Glycolysis does not require oxygen, so it can quickly
supply energy to cells when oxygen is unavailable.
Movement to the Citric
Acid Cycle
• Before the next stage can begin, pyruvic acid
must first be transported inside the
mitochondria.
• Pyruvic acid is combined with an enzyme
called Coenzyme A. This enzyme helps with
the transportation.
o Pyruvic acid + Coenzyme A make Acetyl CoA
o One more molecule of NADH is produced.
o This also releases one molecule of CO2 as a waste product.
LE 9-10
MITOCHONDRION
CYTOSOL
NAD+
NADH
+ H+
Acetyl Co A
Pyruvate
Transport protein
CO2
Coenzyme A
Krebs Cycle
• During the citric acid
cycle, pyruvic acid
produced in glycolysis is
broken down into carbon
dioxide and more energy
is extracted.
Citric Acid Cycle
• Acetyl-CoA from
glycolysis enters
the matrix, the
innermost
compartment of
the
mitochondrion.
• Once inside, the
Coenzyme A is
released.
Citric Acid Cycle
• The molecule of
acetate that
entered from
glycolysis joins up
with another 4carbon molecule
already present.
• This forms citric acid.
Citric Acid Cycle
• Citric acid (6-carbon
molecule) is broken
down one step at a
time until it is a 4carbon molecule.
• The two extra
carbons are
released as carbon
dioxide.
Citric Acid Cycle
• Energy released by
the breaking and
rearranging of
carbon bonds is
captured in the forms
of ATP, NADH, and
FADH2.
• FADH2 has the same
purpose as NADH –
to transport highenergy electrons and
H+ ions.
Citric Acid Cycle
• For each turn of the
cycle, the following
are generated:
o 1 ATP molecule
o 3 NADH molecules
o 1 FADH2 molecule
Citric Acid Cycle
• Remember! Each
molecule of glucose
results in 2 molecules of
pyruvic acid, which enter
the Krebs cycle.
• So each molecule of
glucose results in two
complete “turns” of the
Krebs cycle.
• Therefore, for each
glucose molecule:
o
o
o
o
6 CO2 molecules,
2 ATP molecules,
8 NADH molecules,
2 FADH2 molecules are
produced.
LE 9-11
Pyruvic acid
(from glycolysis,
2 molecules per glucose)
CO2
NAD+
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
Citric
acid
cycle
FADH2
2 CO2
3 NAD+
3 NADH
+ 3 H+
FAD
ADP + P i
ATP
ATP
Electron Transport Chain
• The electron transport chain occurs in the
inner membrane of the mitochondria.
• Electrons are passed along the chain, from
one protein to another.
• Each time the electron is passed, a little bit of
energy is extracted from it.
• Electrons drop in energy as they go down the
chain and until they end with O2, forming
water
Electron Transport Chain
• NADH and FADH2 pass their high-energy
electrons to electron carrier proteins in the
electron transport chain.
Electron Transport Chain
• At the end of the electron transport chain, the
electrons combine with H+ ions and oxygen to
form water.
Electron Transport Chain
• Energy generated by the electron transport
chain is used to move H+ ions (from NADH
and FADH2) against a concentration gradient.
• This creates a “dam” of H+ ions in the outer
fluid of the mitochondria.
• The electron transport chain generates no ATP
• The chain’s function is to break the large freeenergy drop from food to O2 into smaller steps
that release energy in manageable amounts.
• The end result is a “reservoir” of H+ ions that
can be tapped for energy, much like a
reservoir in a hydroelectric dam.
Chemiosmosis
• The electron transport chain has created a
high concentration of H+ ions in the outer fluid
of the mitochondria.
• H+ then moves back across the membrane,
into the inner fluid.
o H+ ions pass through a channel protein called
ATP Synthase
• ATP synthase uses this flow of H+ to convert
ADP molecules (low energy) into ATP (high
energy)
LE 9-14
INTERMEMBRANE SPACE
H+
H+
H+
H+
H+
H+
A rotor within the
membrane spins
as shown when
H+ flows past
it down the H+
gradient.
H+
A stator anchored
in the membrane
holds the knob
stationary.
A rod (or “stalk”)
extending into
the knob also
spins, activating
catalytic sites in
the knob.
H+
ADP
+
P
ATP
i
MITOCHONDRAL MATRIX
Three catalytic
sites in the
stationary knob
join inorganic
phosphate to
ADP to make
ATP.
Total ATP Production
• During cellular respiration, most
energy flows in this sequence:
glucose  NADH
 electron transport chain
chemiosmosis ATP
• About 40% of the energy in a
glucose molecule is transferred
to ATP during cellular
respiration, making about 38
total ATP
o Remainder is lost as waste
heat
Fermentation
• Cellular respiration requires O2 to produce ATP
• Glycolysis can produce ATP with or without O2
(in aerobic or anaerobic conditions)
• In the absence of O2, glycolysis can couples
with a process called fermentation to
produce ATP.
Types of Fermentation
• Fermentation consists of glycolysis + reactions
that regenerate NAD+, which can be reused
by glycolysis
• Two common types are alcohol fermentation
and lactic acid fermentation
Alcohol Fermentation
• Yeast and a few other microorganisms use
alcoholic fermentation that produces ethyl
alcohol and carbon dioxide.
• This process is used to produce alcoholic
beverages and causes bread dough to rise.
Pyruvic acid + NADH → Alcohol + CO2 + NAD+
Lactic Acid Fermentation
• Most organisms, including humans, carry out
fermentation using a chemical reaction that
converts pyruvic acid to lactic acid.
• Pyruvic acid + NADH  Lactic acid + NAD+
• In lactic acid fermentation, pyruvate is
reduced to NADH, the only end product is
lactic acid. No carbon dioxide is released.
• Lactic acid fermentation by some fungi and
bacteria is used to make cheese and yogurt
• Human muscle cells use lactic acid
fermentation to generate ATP when O2 is
scarce (out of breath)
o Result: Soreness!
• Yeast and many bacteria are facultative
anaerobes, meaning that they can survive
using either fermentation or cellular respiration
• Most other organisms cannot survive in the
long-run using glycolysis and fermentation,
they require oxygen.
o These are obligate aerobic organisms.
LE 9-18
Glucose
CYTOSOL
Pyruvate
No O2 present
Fermentation
O2 present
Cellular respiration
MITOCHONDRION
Ethanol
or
lactate
Acetyl CoA
Citric
acid
cycle
The Evolutionary
Significance of Glycolysis
• Glycolysis occurs in nearly all organisms
• Glycolysis probably evolved in ancient
prokaryotes before there was oxygen in the
atmosphere
Other Energy Sources
• Catabolic pathways funnel electrons from many
kinds of organic molecules into cellular respiration
• Glycolysis accepts a wide range of
carbohydrates
• Proteins must be digested to amino acids; amino
groups can feed glycolysis or the citric acid cycle
• Fats are digested to glycerol (used in glycolysis)
and fatty acids (used in generating acetyl CoA)
• An oxidized gram of fat produces more than
twice as much ATP as an oxidized gram of
carbohydrate
LE 9-19
Proteins
Carbohydrates
Amino
acids
Sugars
Glycerol Fatty
acids
Glycolysis
Glucose
Glyceraldehyde-3- P
NH3
Fats
Pyruvate
Acetyl CoA
Citric
acid
cycle
Oxidative
phosphorylation
Video Review on ATP &
Respiration
• https://www.youtube.com/watch?v=00jbG_cfGuQ
&list=PL3EED4C1D684D3ADF&index=7&feature=plpp
_video