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Cellular Respiration: Supplying Energy to Metabolic Reactions

Cellular Respiration

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.

Thursday, April 29, 2010

Coenzymes

Cellular Respiration: 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.

CoenzymeAbbreviationAbbreviation

FunctionCoenzymeUnloaded Loaded

Function

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+ NADHTransfer of electrons and protons

in respiration

Flavin adenine dinucleotide FAD FADH2Transfer of electrons and protons

in respiration


The ATP Cycle

Cellular Respiration: The ATP Cycle

Remember this? ATP is the most important molecule for the transport of usable chemical energy in cells.

Endergonic reactions absorb energy

Anabolic reactions build molecules

Exergonic reactions release energy

Catabolic reactions break down molecules

The ATP CycleAfter 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 Pathways

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 Cycle3. Electron Transport Chain

B. Anaerobic Respiration (oxygen absent)1. Glycolysis2. Alcohol Fermentation

C. Anaerobic Respiration (oxygen absent)1. Glycolysis2. Lactic Acid Fermentation

As you can see, glycolysis is common to all respiration pathways.


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 Cycle3. Electron Transport Chain

B. Anaerobic Respiration (oxygen absent)1. Glycolysis2. Alcohol Fermentation

C. Anaerobic Respiration (oxygen absent)1. Glycolysis2. Lactic Acid Fermentation

As you can see, glycolysis is common to all respiration pathways.

Bork Bork Bork!


Location

Cellular Respiration: 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!


1. Glycolysis Reaction

Cellular Respiration: Glycolysis

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


http://www.youtube.com/watch?v=x-stLxqPt6E&feature=related

http://www.youtube.com/watch?v=x-stLxqPt6E&feature=related

1. Glycolysis: Inputs and Outputs

Cellular Respiration: Glycolysis

IN OUT

Glucose

2 x

2 x 2 x

2 x Pyruvate

Know your net inputs and outputs


The next step.....


Glycolysis

Krebs Cycle

Electron Transport Chain

Lactic Acid Fermentation

Alcohol Fermentation

oxygen present

oxygen absent

oxygen absent

Aerobic RespirationMost plants, animals,

protists, fungi, bacteria

Anaerobic RespirationAnimals

Anaerobic RespirationMany microorganisms

(eg. yeast, some bacteria)


Aerobic Cellular Respiration

Cellular Respiration: Aerobic

You will be familiar with this equation from Yr 11

6H2O + 6CO2 + 386O2 + C6H12O6

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?

+ Glucose Water + 38 ATP+ Carbon DioxideOxygen


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


http://www.youtube.com/watch?v=aCypoN3X7KQ&feature=related

http://www.youtube.com/watch?v=aCypoN3X7KQ&feature=related

2. Aerobic Respiration- Krebs Cycle


INPUT NET OUTPUT

6 x

2 x

Carbon Dioxide

2 x Acetyl CoA (from pyruvate)

Know the significant inputs and outputs: At this stage I have only included numbers where significant.

2 x (from glycolysis)

FAD+2 x 2 x FADH2


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.


3. Aerobic Respiration- Electron Transport Chain


IN OUT

FADH2or

Oxygen Water

34 x

FAD+or

+

Know the significant inputs and outputs: I have only included numbers where significant.


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Aerobic Respiration- Overview


DO NOT PANIC- in all likelihood knowing this diagram will be enough!

2 2 34


Aerobic Respiration- Overview


Vid

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http://www.youtube.com/watch?v=iXmw3fR8fh0























Anaerobic Pathways: Fermentation


Glycolysis

Krebs Cycle

Electron Transport Chain

Lactic Acid Fermentation

Alcohol Fermentation

oxygen present

oxygen absent

oxygen absent

Aerobic RespirationMost plants, animals,

protists, fungi, bacteria

Anaerobic RespirationAnimals

Anaerobic RespirationMany microorganisms

(eg. yeast, some bacteria)


Anaerobic Respiration: Lactic Acid & Alcohol Fermentation

Cellular Respiration: Anaerobic

C6H12O6 2CH3CH(OH)COOH + 2

C6H12O6 2CH3CH2OH + 2CO2 + 2

Glucose Lactic Acid + 2 ATP

Glucose Ethanol + 2 ATP+ Carbon Dioxide

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

Alcohol Fermentation- Yeast and other Microorganisms

Remember the word equations


Anaerobic Respiration: Lactic Acid & Alcohol Fermentation

Cellular Respiration: Anaerobic

Vid

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http://www.youtube.com/watch?v=y_k8xLrBUfg























Cellular Respiration: Overview of all Pathways

Cellular Respiration: Overview


Respiration and Evolution: Interesting Facts

Respiration and Evolution

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.


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