Biochemistry-Anaerobic Respiration

Contents 1.0 Introduction | PAGE | 2.0 | PAGE | 3.0 Lactic Acid Fermentation 3.1 Types of Fermentation 3.2 Energy Produced from Lactic Acid Fermentation | PAGE | 4.0 Anaerobic Exercise 4.1 Benefits of Anaerobic Exercise 4.2 Anaerobic threshold (AT) 4.3 Male vs. female anaerobic exercise characteristics | | 5.0 Conclusion | PAGE | 6.0 References | PAGE |

1.0 Introduction Respiration usually occurs in two ways, aerobically and anaerobically. Aerobic respiration uses oxygen to function and anaerobic respiration functions without oxygen. Generally, anaerobic respiration starts by breaking down the molecules of glucose and produces pyruvic acid. The pyruvic acid then undergoes fermentation to produce ATP, the basic energy source in our human body. Although this kind of respiration is less efficient in producing energy, because it produces only two ATP molecules in comparison to the 38 molecules produced during aerobic respiration, however, this form of respiration is very primitive and had actually started from the time when oxygen was missing in our atmosphere. Many living organisms have successfully adapted to anaerobic form of respiration to survive due to insufficient of oxygen supply.

3.0 Lactic Acid Fermentation Lactic acid fermentation of human beings is the simplest type of fermentation for which is a typical redox reaction. In anaerobic conditions, the primary mechanism of ATP production of a cell is glycolysis. Glycolysis will transfer electron (reduction) to NAD+, forming NADH. However, during lactic acid fermentation, the supply of NAD+ is limited in a cell. For glycolysis to continue, NADH must be oxidized (gives away electron) to regenerate the NAD+. This is done through an electron transport chain in oxidative phosphorylation in a condition that there is the presence of oxygen. NADH will donate the extra electrons to the pyruvate molecules during glycolysis. Since the NADH has lost electrons, NAD+ is being regenerated to undergo glycolysis. Lactic acid, C3H6O3 is formed by the reduction of pyruvate molecules.

3.1 Types of Fermentation There are two types of fermentation processes which may take place in the absence of oxygen after the glycolysis process, either heterolactic acid fermentation or homolactic fermentation. In heterolactic acid fermentation, glucose molecule is converted into lactate, ethanol and carbon dioxide. The reaction proceeds as follows, with one molecule of glucose being converted to one molecule of lactic acid, CH3CHOHCOOH, one molecule of ethanol, C2H5OH, and one molecule of carbon dioxide, CO2 which is also known as alcohol fermentation as ethanol is being produced. The equation for this reaction is as follow:

C6H12O6 → CH3CHOHCOOH + C2H5OH + CO2

On the other hand, homolactic fermentation breaks down the pyruvate into lactate. It occurs in the muscles of animals when they need energy faster than the blood can supply oxygen. It also occurs in some kinds of bacteria and some fungi. The bacteria convert lactose into lactic acid, for example, in the production of yogurt, giving the sour taste of yogurt. These lactic acid bacteria can be classed as homofermentative, where the end-product is mostly lactate, or heterofermentative, where some lactate is further metabolized and results in carbon dioxide, acetate, or other metabolic products. Heterolactic acid fermentation is unique because it is a respiration process which does not produce a gas as a byproduct. There are two possible outcomes, either one molecule of glucose is converted to two molecules of lactic acid, CH3CHOHCOOH: C6H12O6 → 2 CH3CHOHCOOH Or, one molecule of lactose, C12H22O11 and one molecule of water reacted to form four molecules of lactate (as in yogurts and cheeses): C12H22O11 + H2O → 4 CH3CHOHCOOH

3.2 Energy Produced from Lactic Acid Fermentation
The overall equation of muscle glycolysis in the absence of oxygen (lactic acid fermentation) is:

C6H12O6 2 CH3CHOHCOOH (lactic acid) + 2ATP G = -150kJ mol-1 Lactic acid fermentation usually takes place in the fluid portion of the cytoplasm whereas aerobic respiration takes place in the mitochondria. This leaves a lot of energy in the form of lactate molecules that the cell cannot utilize and must be excreted.

Only about 10% of the energy is released in the complete oxidation of glucose molecules in anaerobic respiration ( G = -150kJ mol-1) as compared to aerobic respiration ( G = -2880kJ mol-1). When oxygen is limited, the oxidation of NADH to NAD+ by the electron transport chain is not enough to maintain glycolysis process. Under these conditions NAD+ is regenerated by the reduction of pyruvate to lactic acid. The production of NAD+ is crucial because glycolysis requires it and would halt when its supply was used up, resulting in necrosis (cell death).

4.0 Anaerobic Exercise in Human Beings
Anaerobic exercise is a short lasting, high intensity exercise where the body demand for oxygen exceed the oxygen supply available. Anaerobic exercise relies on energy sources that are stored in the muscles and is not dependent on oxygen from the air. Examples of anaerobic exercise are, heavy weight lifting, jumping rope, hill climbing, isometrics, and any rapid burst hard exercises.

4.1 Benefits of Anaerobic Exercise
Muscles are utilized at high intensity at short time, during this time, a person can develop:
1) Stronger muscles
2) Able to improve VO2 max (maximum amount of oxygen consumed during exercise), thus improving cardio-respiratory fitness
3) Increase capacity to withstand buildup of waste substances such as lactic acid and remove them from the body. (This will improve endurance and ability to fight fatigue.)

4.2 Anaerobic threshold (AT) The anaerobic threshold (AT) is the exercise intensity at which lactate (lactic acid) starts to accumulate in the blood stream. This happens when it is produced faster than it can be removed (metabolized). This point is sometimes referred to as the lactate threshold, or the onset of blood lactate accumulation (OBLA). When exercising below the AT intensity any lactate produced by the muscles is removed by the body without it building up. The anaerobic threshold is a useful measure for deciding exercise intensity for training and racing in endurance sports (e.g. distance running, cycling, rowing, swimming and cross country skiing), and can be increased greatly with training. Fartlek (speed-play) training and interval training take advantage of the body being able to temporarily exceed the anaerobic threshold, and then recover (reduce blood-lactate) while operating at below the threshold, but still doing physical activity. Fartlek and interval training are similar, the main difference being the relative intensities of the exercise, best illustrated in a real-world example: Fartlek training would involve constantly running, for a period time running just above the anaerobic threshold, and then running at just below it, while interval training would be running quite high above the anaerobic threshold, but then slowing to a walk during the rest periods. Fartlek would be used by people who are constantly moving, with occasional bouts of speed, such as basketballers, while interval training is more suited to sprinters, who exert maximum effort and then can stop exerting completely. With both styles of training, you can exert more effort before fatiguing and burn more calories than exercising at a constant pace (continuous training), but will emphasize training the anaerobic system rather than the aerobic system. Long duration training below the anaerobic threshold is recommended to primarily work the aerobic system.

4.3 Male vs. female anaerobic exercise characteristics
Anaerobic characteristics of female are generally less than male during young and middle aged adulthood. The major difference is due to the smaller overall muscle mass of average female compared to the average male.

* Accumulation of lactate
Resting level of lactate is the same for male and female. Lactate thresholds, when expressed as percentage of VO2 max, are also the same for both sexes, although the absolute workload at which the lactate threshold occur is higher for males than for females. * Mechanical power and capacity
Males produce higher absolute work output than females. But both sexes get tired at the same rate. * Mechanism
The key to these male to female anaerobic differences lies in muscle. The same factors implicated in mechanisms for differences between maturing boys and girls operate between adult males and females. The young male adds muscle during maturation under the influence of testosterone, whereas the young female is adding fat under the influence of estrogen. Therefore both absolutely and relatively, guys have greater muscle mass than female. In addition, males have larger muscle fiber size (especially FT) when compared to females.

5.0 Differences between Anaerobic Respiration and Aerobic Respiration | Aerobic Respiration | Anaerobic Respiration | Oxygen required | Yes | No | Places where reactions take place | Cytoplasm and mitochondria | Cytoplasm | Production of ATP | 38mol ATP per 1mol glucose | 2mol ATP per 1mol glucose | Duration and Intensity of workout | Indefinitely and moderate intensity | Short term and high intensity | Process undergo | Glycolysis, Citric Acid Cycle, Oxidative Phosphorylation, Kreb Cycle | | Equation | C6H12O6 + 6O2 6CO2 + 6 H2O + 36 or 38 ATP | C6H12O6 → 2C3H6O3 + 2 ATP | Goals of respiration | Strengthening muscles, improve circulation of blood and transportation of oxygen in body, reduces blood pressure and burns fat | Helps in building strength and muscle mass, stronger bones and increase speed, power, muscle strength and metabolic rate, concentrates on burning calories |

6.0 Conclusion When oxygen is absent, many cells are still able to use glycolysis to produce ATP. Two ways this can be done are through fermentation and anaerobic respiration. Lactic acid fermentation is the process by which the electrons and hydrogen ions from the NADH produced by glycolysis are donated to another organic molecule. For human beings, anaerobic exercise is better at building strength and muscle mass and still benefits the heart and lungs. In the long run, the increased muscle mass helps a person become leaner and manage the weight of the body as the body consumes large amount of calories.

7.0 References
Reference Guide to Anaerobic Exercise An In-Depth Look at High Intensity Exercise, Jen Mueller and Nicole Nichols, Fitness Experts

Anaerobic Respiration, Aharon Oren, The Hebrew University of Jerusalem, Jerusalem, Israel, September 2009, pp 123-136.

Anaerobic Respiration, Frederic P Miller, Agnes F Vandome, John McBrewster, VDM Publishing House Ltd., 2010, pp 67-78.

Biochemistry 2nd Edition, by Keshav Trehan, 1990, New Age International, pp 327-338.

http://www.anaerobicrespiration.net/general/glycolysis-and-anaerobic-respiration/
http://hyperphysics.phy-astr.gsu.edu/hbase/biology/celres.html

References: Reference Guide to Anaerobic Exercise An In-Depth Look at High Intensity Exercise, Jen Mueller and Nicole Nichols, Fitness Experts Anaerobic Respiration, Aharon Oren, The Hebrew University of Jerusalem, Jerusalem, Israel, September 2009, pp 123-136. Anaerobic Respiration, Frederic P Miller, Agnes F Vandome, John McBrewster, VDM Publishing House Ltd., 2010, pp 67-78. Biochemistry 2nd Edition, by Keshav Trehan, 1990, New Age International, pp 327-338. http://www.anaerobicrespiration.net/general/glycolysis-and-anaerobic-respiration/ http://hyperphysics.phy-astr.gsu.edu/hbase/biology/celres.html