Download Cellular Respiration: Supplying Energy to Metabolic Reactions

Cellular Respiration: Supplying Energy to Metabolic Reactions
ATP powers most of the processes in a cell including:
* Muscle movement
* Active Transport
ATP also provides the necessary activation energy to
* Synthesise organic compounds (endergonic, anabolic reactions)
* Speed up many exergonic, catabolic reactions.
You use HEAPS of ATP. Here are some estimates
* 10 million molecules per muscle cell per second!
* The average vertebrate consumes its own body weight in ATP every day!
It is important, therefore, that ATP/ADP is recyclable- like a
rechargeable battery. Respiration is the metabolic
reaction that recharges ADP to ATP.
Cellular Respiration
Thursday, April 29, 2010
Coenzymes
Coenzymes are relatively small organic non-protein molecules that catalyse reactions by acting as carriers of
electrons and protons. They may also carry specific atoms or groups of atoms, such as phosphate, that are
required for, or produced by, chemical reactions.
The coenzymes we study in VCE Biology cycle between “loaded” and “unloaded” states. The process of
respiration draws on 3 of these listed molecules.
Coenzyme
Abbreviation
Function
Unloaded
Loaded
Adenosine Triphosphate
ADP
ATP
Energy Transfer in many processes
Nicotinamide adenine dinucleotide
phosphate
NADP
NADPH
Transfer of electrons and protons
in photosynthesis
Nicotinamide adenine dinucleotide
NAD+
NADH
Transfer of electrons and protons
in respiration
Flavin adenine dinucleotide
FAD
FADH2
Transfer of electrons and protons
in respiration
Cellular Respiration: Coenzymes
Thursday, April 29, 2010
The ATP Cycle
Remember this?
ATP is the most important molecule for the transport of usable chemical energy in cells.
Anabolic reactions
build molecules
Catabolic reactions break
down molecules
Endergonic reactions
absorb energy
Exergonic reactions
release energy
The ATP Cycle
After it “unloads” energy its terminal phosphate group an ADP molecule can undergo a
second reaction that adds a new phosphate group and “reloads” it as ATP.
Cellular Respiration: The ATP Cycle
Thursday, April 29, 2010
Cellular Respiration Pathways
Respiration is the metabolic process by which glucose is broken down to release energy and make ATP
There are three different pathways for cellular respiration to occur. Each pathway has multiple stages.
A. Aerobic Cellular Respiration (oxygen present)
1. Glycolysis
2. Krebs Cycle
3. Electron Transport Chain
B. Anaerobic Respiration (oxygen absent)
1. Glycolysis
2. Alcohol Fermentation
C. Anaerobic Respiration (oxygen absent)
1. Glycolysis
2. Lactic Acid Fermentation
As you can see, glycolysis is common to all respiration pathways.
Cellular Respiration: Pathways
Thursday, April 29, 2010
Cellular Respiration Pathways
Respiration is the metabolic process by which glucose is broken down to release energy and make ATP
There are three different pathways for cellular respiration to occur. Each pathway has multiple stages.
A. Aerobic Cellular Respiration (oxygen present)
1. Glycolysis
2. Krebs Cycle
3. Electron Transport Chain
B. Anaerobic Respiration (oxygen absent)
1. Glycolysis
2. Alcohol Fermentation
C. Anaerobic Respiration (oxygen absent)
1. Glycolysis
2. Lactic Acid Fermentation
As you can see, glycolysis is common to all respiration pathways.
Cellular Respiration: Pathways
Thursday, April 29, 2010
Cellular Respiration Pathways
Respiration is the metabolic process by which glucose is broken down to release energy and make ATP
There are three different pathways for cellular respiration to occur. Each pathway has multiple stages.
A. Aerobic Cellular Respiration (oxygen present)
1. Glycolysis
2. Krebs Cycle
3. Electron Transport Chain
Bork Bork Bork!
B. Anaerobic Respiration (oxygen absent)
1. Glycolysis
2. Alcohol Fermentation
C. Anaerobic Respiration (oxygen absent)
1. Glycolysis
2. Lactic Acid Fermentation
As you can see, glycolysis is common to all respiration pathways.
Cellular Respiration: Pathways
Thursday, April 29, 2010
Location
The mitochondrion is the primary location for respiration. It consists of;
* A smooth outer membrane
* An inner membrane whose many folds make up the cristae
* A fluid rich intermembrane space
* The matrix
Do not rely too much
on shape.
Mitochondria can look
like a ball, jellybean or
cigar!
Cellular Respiration: Location
Thursday, April 29, 2010
1. Glycolysis Reaction
All respiration begins in the cytoplasm with glycolysis. This is a very complex 10 step reaction and
you needn’t learn it all- an appreciation of the reactions is enough.
Watch and note:
* Inputs and Outputs;
especially involving ATP
* The location where
glycolysis occurs
* The formation of G3P
and its conversion to
pyruvate.
Video Link
Cellular Respiration: Glycolysis
Thursday, April 29, 2010
1. Glycolysis: Inputs and Outputs
Know your net inputs and outputs
IN
OUT
2x
Glucose
2 x Pyruvate
2x
2x
Cellular Respiration: Glycolysis
Thursday, April 29, 2010
The next step.....
oxygen present
Glycolysis
oxygen absent
oxygen absent
Krebs Cycle
Lactic Acid
Fermentation
Alcohol
Fermentation
Electron
Transport Chain
Aerobic Respiration
Most plants, animals,
protists, fungi, bacteria
Anaerobic Respiration
Animals
Anaerobic Respiration
Many microorganisms
(eg. yeast, some bacteria)
Cellular Respiration: Pathways
Thursday, April 29, 2010
Aerobic Cellular Respiration
You will be familiar with this equation from Yr 11
6O2 + C6H12O6
Oxygen
+ Glucose
6H2O + 6CO2 + 38
Water + Carbon Dioxide + 38 ATP
This basic equation applies to aerobic respiration and you need to have memorised this.
The energy captured as ATP and sent to where it is needed elsewhere in the cell.
What does this suggest to you about cells possessing high numbers of mitochondria?
Cellular Respiration: Aerobic
Thursday, April 29, 2010
2. Aerobic Respiration- Krebs Cycle (Complex)
If oxygen is available, glycolysis will be followed by the Krebs Cycle (also called citric acid cycle) in the
matrix.
Watch and note:
* Inputs and Outputs
* Conversion of pyruvate
to Acetyl CoA prior
to entering the Krebs
Cycle
* The location in which
the Krebs Cycle occurs
Video Link
Cellular Respiration: Aerobic
Thursday, April 29, 2010
2. Aerobic Respiration- Krebs Cycle
Know the significant inputs and outputs: At this stage I have only included numbers where significant.
INPUT
NET OUTPUT
Carbon Dioxide
2 x Acetyl CoA (from pyruvate)
6x
2x
(from glycolysis)
2x
2x
FAD+
2x
FADH2
Cellular Respiration: Aerobic
Thursday, April 29, 2010
3. Aerobic Respiration- Electron Transport Chain
The NADPH and FADH2 produced in both glycolysis and the Krebs cycle is fed into the Electron
Transport Chain. The Electron Transport produces far more ATP than the previous two stages and happens
on the inner membrane.
Watch and note
* The purpose of the
electron carriers in
driving the proton gradient
* The purpose of oxygen
and its conversion to water
* The use of the chemical
gradient to drive ATP
synthesis.
Cellular Respiration: Aerobic
Thursday, April 29, 2010
3. Aerobic Respiration- Electron Transport Chain
Know the significant inputs and outputs: I have only included numbers where significant.
IN
or
OUT
FADH2
or
FAD+
Water
Oxygen
+
34 x
Cellular Respiration: Aerobic
Thursday, April 29, 2010
Aerobic Respiration- Overview
DO NOT PANIC- in all likelihood knowing this diagram will be enough!
2
2
34
Cellular Respiration: Aerobic
Thursday, April 29, 2010
Video here
Aerobic Respiration- Overview
Cellular Respiration: Aerobic
Thursday, April 29, 2010
Anaerobic Pathways: Fermentation
oxygen present
Glycolysis
oxygen absent
oxygen absent
Krebs Cycle
Lactic Acid
Fermentation
Alcohol
Fermentation
Electron
Transport Chain
Aerobic Respiration
Most plants, animals,
protists, fungi, bacteria
Anaerobic Respiration
Animals
Anaerobic Respiration
Many microorganisms
(eg. yeast, some bacteria)
Cellular Respiration: Pathways
Thursday, April 29, 2010
Anaerobic Respiration: Lactic Acid & Alcohol Fermentation
In anaerobic respiration oxygen is not available to drive the Krebs Cycle and Electron Transport Chain.
* Instead the cell enters either a lactic acid or alcohol fermentation stage.
* Essentially this pathway provides a way to metabolise the pyruvate and recycle the NADH/NAD+ that
was produced by glycolysis.
* Lactic acid or ethanol are the final products of glucose catabolism. Overall the only ATP produced in
this reaction was from the glycolysis stage making fermentation highly inefficient.
Lactic Acid Fermentation- Animals
Remember
the word
equations
C6H12O6
Glucose
2CH3CH(OH)COOH + 2
Lactic Acid
+ 2 ATP
Alcohol Fermentation- Yeast and other Microorganisms
C6H12O6
Glucose
2CH3CH2OH + 2CO2 + 2
Ethanol + Carbon Dioxide + 2 ATP
Cellular Respiration: Anaerobic
Thursday, April 29, 2010
Video here
Anaerobic Respiration: Lactic Acid & Alcohol Fermentation
Cellular Respiration: Anaerobic
Thursday, April 29, 2010
Cellular Respiration: Overview of all Pathways
Cellular Respiration: Overview
Thursday, April 29, 2010
Respiration and Evolution: Interesting Facts
Aerobic Respiration recovers about 40% of the energy in glucose- more efficient than a modern car engine.
Glycolysis recovers only about 3% of the energy stored in glucose; nevertheless for a long period much of the
history of life was written by organisms that could perform only glycolysis.
Many of the most successful organisms in existence are anaerobic and thus only achieve 3% efficiency.
Nonetheless it was only after the evolution of the Krebs Cycle and
Electron Transport Chain that respiration could achieve a level
of efficiency capable of sustaining larger, and more
complex, multicellular organisms.
Facultative bacteria are able
to meet energy demands
by either aerobic or
anaerobic respiration.
Respiration and Evolution
Thursday, April 29, 2010