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Anaerobic Respiration. All organisms need energy to survive. Animals obtain their energy from the food they eat, but plants can make their own food by photosynthesis. - PowerPoint PPT Presentation

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Anaerobic Respiration

Anaerobic RespirationAll organisms need energy to survive.

Animals obtain their energy from the food they eat, but plants can make their own food by photosynthesis.In both cases, however, energy must first be converted into a form that can easily be used by cells. This process is called respiration.

22Photo credit: 2007 Jupiterimages CorporationBoardworks GCSE Additional Science: BiologyAnaerobic Respiration

Anaerobic respiration takes place without oxygen. Less energy is released per glucose molecule than in aerobic respiration because glucose is only partially broken down.

Aerobic respiration uses oxygen to break down glucose. It releases a lot of energy from each glucose molecule by breaking it down completely into carbon dioxide and water.

33Teacher notesIn aerobic respiration, 38 ATP molecules are formed from each glucose molecule. In aerobic respiration, only two ATP molecules are formed from a molecule of glucose, although more can be produced later when lactic acid breaks down.

The information on this slide regarding the efficiency of anaerobic respiration is higher tier for AQA GCSE Additional Science.

Photo credit: 2007 Jupiterimages Corporation

Boardworks GCSE Additional Science: BiologyAnaerobic Respiration

Respiration in animalsWhen an animal cell is getting enough oxygen and glucose, it carries out aerobic respiration. When the animal cell does not have the necessary oxygen to break down glucose molecules, it has to carry out anaerobic respiration. This can occur in muscle cells during strenuous exercise.

lactic acidglucose ( energy)+

oxygencarbon dioxideglucose++water( energy)+

44Teacher notesStudents should understand that anaerobic respiration does not replace aerobic respiration. Only cells that require more energy, such as muscle cells, will carry out anaerobic respiration if there is not enough oxygen present.

The information on this slide regarding the causes of anaerobic respiration is higher tier for OCR Gateway GCSE Additional Science.

Boardworks GCSE Additional Science: BiologyAnaerobic Respiration

Plants and some micro-organisms, such as yeast, will also carry out anaerobic respiration if necessary.

glucose carbon dioxide + ethanol (+ energy)The products of anaerobic respiration are different in plants than in animals. Anaerobic respiration might take place in waterlogged root cells, or in bacteria infecting deep puncture wounds.

55Teacher notesAlthough some bacteria make lactic acid during anaerobic respiration, most micro-organisms produce ethanol.Boardworks GCSE Additional Science: BiologyAnaerobic Respiration

When does anaerobic respiration occur?

6Teacher notesAnaerobic bacteria can either be aerotolerant, or able to grow in the presence of oxygen, or obligate anaerobes, meaning they cannot survive in an environment with oxygen. Clostridium tetani is an obligate anaerobe, although its spores can survive in oxygen. Puncture wounds often take bacteria, such as Clostridium tetani which causes tetanus, deep into the tissue where oxygen is not available. This allows them to respire and reproduce, producing toxins.6Boardworks GCSE Additional Science: BiologyAnaerobic Respiration

Lactic acidThe incomplete breakdown of glucose during anaerobic respiration produces lactic acid.

After vigorous exercise, the body needs to remove lactic acid before it damages cells. Some lactic acid is broken down in the muscles. Some passes into the bloodstream and is taken to the liver to be broken down there. Lactic acid builds up in muscle cells and prevents the muscles from contracting efficiently. The build-up of lactic acid can cause fatigue, pain and cramping.

77Teacher notesStudents could investigate lactic acid build-up by holding objects at arms length and timing how long it takes before their muscles begin to feel fatigued.

The information on this slide is higher tier for OCR Gateway GCSE Additional Science.

Photo credit: Jupiterimages Corporation

Boardworks GCSE Additional Science: BiologyAnaerobic Respiration

Oxygen debt

The amount of oxygen needed to break down lactic acid remaining after exercise is called excess post-exercise oxygen consumption (EPOC), or an oxygen debt.Following strenuous exercise, an individual breathes heavily and maintains an elevated heart rate. This moves lactic acid to the liver and supplies liver and muscle cells with the necessary oxygen to break down lactic acid. Oxygen is needed to break lactic acid into water and carbon dioxide.

88The information on this slide regarding the oxygen debt is higher tier for AQA GCSE Additional Science and OCR Gateway GCSE Additional Science.

Photo credit: Jupiterimages CorporationBoardworks GCSE Additional Science: BiologyAnaerobic Respiration

How does running affect your pulse?

99Teacher notesStudents could design and carry out their own experiments to investigate the effects of exercise and recovery on pulse. Pulse and breathing rate can me measured manually or with appropriate sensors and data loggers. Students should observe appropriate safety measures and you should make sure you are aware of any students with illnesses such as asthma. Boardworks GCSE Additional Science: BiologyAnaerobic Respiration

Complete the sentences

10Boardworks GCSE Additional Science: BiologyAnaerobic Respiration

biofuels.Respiring micro-organisms are used in the commercial production of many different products, including:breadalcoholThese micro-organisms break substances down using aerobic or anaerobic respiration. The effect of anaerobic respiration is often called fermentation.

1111Photo credit: (David H. Seymour), Shutterstock 2009Boardworks GCSE Additional Science: BiologyAnaerobic Respiration

Yeast is a type of fungus used in bread production. Yeast digests the carbohydrates in flour, producing carbon dioxide. This carbon dioxide causes bread to rise. It also creates gas pockets in the dough, giving baked bread a spongy texture.At first the yeast respires aerobically, but once it uses up the available oxygen it begins to respire anaerobically.

1212Teacher notesEthanol is also made during the fermentation process, but this evaporates when the bread is baked.

Photo credit: 2006 Jupiterimages Corporation

Boardworks GCSE Additional Science: BiologyAnaerobic Respiration

Yeast is used to make alcoholic beverages such as beer, wine, rum, whiskey and vodka.

The amount of ethanol produced is limited as alcohol becomes toxic to microbes at certain concentrations.Glucose comes from different sources in the production of different alcohols. For example, in winemaking, natural sugars in the grapes form the energy source for yeast.

During fermentation, anaerobic respiration in yeast cells converts glucose into ethanol.

1313Boardworks GCSE Additional Science: BiologyAnaerobic Respiration

Anaerobic respiration in biogas

1414Teacher notesBacteria that produce methane as a product of respiration are known as methanogenic bacteria. These inhabit anaerobic environments. They can be found in the guts of cattle.Boardworks GCSE Additional Science: BiologyAnaerobic Respiration