Transcript Anaerobic Respiration

CHAPTER 6 - RESPIRATION
O2
HEAT + ENERGY
Glucose
CO2
+
H2O
The only reason humans need to
breathe oxygen is to accept electrons in
the final stage of ATP synthesis in the
mitochondria.
CHAPTER OUTLINE
I. OVERVIEW
II. GLYCOLYSIS
Getting to glucose
Mechanisms by which ATP is synthesized
Glycolysis – steps in the process
Glycolysis - summary
III. THE AEROBIC PATHWAY
Mitochondrion structure
A preliminary step
The Krebs cycle
Oxidative phosphorylation
IV. ANAEROBIC PATHWAYS
V. OTHER TYPES OF RESPIRATION
OVERVIEW
All organisms harvest energy from
stored chemicals (starch, sugars,
lipids) in the same way
The metabolic pathways by which
organisms liberate stored energy are
referred to as cellular respiration
THE OVERALL EQUATION
FOR
RESPIRATION OF GLUCOSE
C6H12O6 + O2
CO2 + H2O + ENERGY
Carbon Dioxide
Cellular Respiration
Cellular Respiration
Glucose → CO2 + H2O + energy (ATP)
This is the same equation for starting
a fire using glucose as a fuel.
The difference is that the reaction in
living systems is tightly controlled and
energy normally lost as heat is
captured for other uses.
Glucose is used as a source of energy for two kinds of
respiration:
Aerobic
Anaerobic
Aerobic Respiration - requires oxygen as the terminal
electron acceptor
1) Stages involved
a) Krebs cycle
b) Oxidative phosphorylation (synthesis of ATP)
2) Disposition of Energy
a) Some energy is stored in ATP and in other
compounds
b) Other energy dissipates as heat
Anaerobic Respiration: (without oxygen)
Fermentation: Metabolic pathways by
which energy is liberated from pyruvic
acid, the end product of glycolysis, in the
absence of oxygen.
GLYCOLYSIS
Getting to Glycolysis
Glycolysis is the breakdown of
glucose to pyruvic acid (pyruvate).
•
•
GLUCOSE IS NOT ABUNDANT IN
CELLS
CELLS OBTAIN GLUCOSE BY
BREAKING DOWN GLUCOSECONTAINING STORAGE MOLECULES,
OFTEN SUCROSE OR STARCH
Sucrose, Starch, Fructose, etc
Fig 6-2
COMMON GLUCOSE STORAGE COMPOUNDS
•SUCROSE (TABLE SUGAR), FRUCTOSE (FRUIT SUGAR)
AND OTHER SUGARS
•STARCH
•POLYMERS OF FRUCTOSE
GLUCOSE IS RETREIVED FROM
SUCROSE BY BY HYDROLYSIS
Requires the enzyme “sucrase”
STARCH IS A BRANCHED POLYMER
MADE UP OF GLUCOSE MOLECULES
SEVERAL DIFFERENT
KINDS OF ENZYMES
ARE REQUIRED TO
BREAKDOWN
STARCH
•Amylases
•Starch phosphorylase
•Debranching enzymes
Amylases hydrolyze alpha 1-4
glucose linkages
Starch phosphorylase
cleaves glucose at the end of a
chain end by adding a
phosphate to it
starch + H2PO4 → glucose 1-phosphate
Debranching enzymes
hydrolize starch at branch points
GLYCOLYSIS
Mechanisms by which ATP is synthesized
ATP is synthesized during respiration by 1. Substrate-level phosphorylation
2. ATP synthase complexes in
mitochondrial and chloroplast membranes
(Oxidative Phosphorylation)
PHOSPHOENOLPYRUVIC
ACID
=Transfer of a
phosphate directly
from an organic
molecule to ADP to
make ATP
ATP synthase complex
Oxidative
Phosphorylation =
Coupling energy from
an electron donor
with an
electrochemical
gradient that spans a
membrane to
phosphorylate ADP
Fig 6-15
GLYCOLYSIS
Steps in the process
This is glycolysis
Fig 6-2
Glycolysis occurs in the cytoplasm!!!!
Uses 1 ATP
Fig 6-4
Uses 2nd ATP
We will follow what
happens to glyceraldehyde
3-phosphate only. Note-all
products are from this
point on are doubled
2 molecules
Generates 2 NADH
Generates 2 ATP
2 molecules
2 molecules
Generates 2 ATP
Total yield of energy-transport molecules from glycolysis
Fig 6-17
AEROBIC
RESPIRATION
Mitochondrion structure
Pyruvic acid is imported into mitochondria
The Krebs cycle occurs in the matrix of
the mitochondria
AEROBIC
RESPIRATION
Oxidative decarboxylation of
pyruvate
Pyruvate is transported into the mitochondria
Fig 6-7
Fig 6-17
AEROBIC
RESPIRATION
Krebs Cycle
Fig 6-2
The Krebs cycle is also called the
TCA cycle (tricarbocylic acid cycle)
because citric acid has three carboxyl
groups)
or
The citric acid cycle
The chemical reaction repeatedly recycles,
taking in two carbons and producing two
CO2 molecules
Two carbons enter
Fig 6-8
Two CO2
molecules are
produced
(4/molecule of
glucose)
Fig 6-8
Three molecules of
NADH are
produced
(6/molecule of
glucose)
Fig 6-8
One molecule of
ATP is produced
(2/molecule of
glucose)
Fig 6-8
One molecules of
FADH2 is produced
(2/molecule of
glucose)
Fig 6-8
Fig 6-17
AEROBIC
RESPIRATION
Oxidative phosphorylation
Fig 6-2
NADH and ubiquinol from the Krebs cycle start
a series of oxidation reduction reactions that
move electrons through a series of carriers.
The electron carriers together are called an
“electron transport chain”
See next slide
for
oxidationreduction of
CoQ
Fig 6-10
Fig 6-13
See next slide
for
cytochrome
structure
Fig 6-10
Fig 6-11
ELECTRON TRANSPORT
Energy from the flow of electrons maintains a
proton gradient across the inner mitochondrial
membrane
This proton gradient drives the synthesis of ATP.
This process is called
“oxidative phosphorylation”
H+
H+
H+
H+
Fig 6-17
ANAROBIC
RESPIRATION
Glycolysis works in an oxygen free environment
and can occur in either anaerobic or aerobic
respiration
The Krebs cycle and electron transport are
inhibited by a lack of oxygen
Inhibited
Not Inhibited
Fig 6-2
If NADH from glycolysis
builds up (because it’s not
being used in oxidative
phosphorylation), NAD+
will become depleted
NAD+ is required to
oxidize glyceraldehyde-3 phosphate
Therefore, glycolysis will
stop
Excess NADH can be removed by
conversion of pyruvic acid to
acetaldehyde
Fig 6-18
In some animals (you), in some fungi and
bacteria, pyruvic acid is reduced to lactic acid
instead of alcohol
Aerobic respiration
Anaerobic respiration
Glycolysis
Pyruvic acid
Krebs cycle
Electron transport
Alcohol or lactic acid
36ATP
2ATP
OTHER TYPES
OF
RESPIRATION
Lipids, proteins, etc
Fig 6-19
Lipids are important storage compounds.
They can be metabolized to yield acetyl Co-A
for aerobic respiration
OTHER TYPES
OF
RESPIRATION
Cyanide resistant respiration
Cyanide-resistant
electron transport
Cyanide
Fig 6-10
CYANIDE RESISTANT
RESPIRATION
Aerobic respiration is inhibited when the
terminal electron carrier combines with
cyanide, azide or certain other negatively
charged ions
This poisons the enzyme and stops electron
transport
Some plants, fungi and bacteria
This pathway produces heat rather than ATPs
but is aerobic (i.e., oxygen is the terminal
electron acceptor)
Energy is captured from light by
Philodendron leaves and used
for life processes and growth
When it flowers, the
Philodendron flower heats to
as high as 46 C (115 F). The
heat protects the flowers from
freezing at night and disperses
compound that attract
polinators
Light energy —> Heat
END