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Cellular Respiration
We all need energy to function and we get this energy from the foods we eat. The most efficient way for cells to get energy stored in food is through cellular respiration.

Cellular respiration is a catabolic pathway for the production of ATP. ATP, a high energy molecule, is expended by working cells.

Cellular respiration occurs in both eukaryotic and prokaryotic cells. This type of respiration has three main stages:
- Glycolysis
- The citric acid cycle
- Electron transport.

Carbohydrates, fats and proteins can be used up and used as fuels in cellular respiration and produce ATP energy.
You Tube Video - Introduction to Cellular Respiration:

Glycolysis

Glycolysis means “splitting sugars” and is considered to be the first stage of both aerobic and anaerobic respiration. It takes place in the cytoplasm of the cell. In glycolysis, ATP is used to split glucose molecules into a three-carbon compound called pyruvate. This splitting creates energy that is kept in ATP and a molecule called NADH. The chemical formula for glycolysis is:

|| C6H12O6 + 2ATP + 2NAD+ ---> 2pyruvate + 4ATP + 2NADH
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In glycolysis, the 6-carbon sugar, glucose, is broken down into two molecules of a 3-carbon molecule called pyruvate. This change is accompanied by a net gain of 2 ATP molecules and 2 NADH molecules (Phschool - Science)


The Krebs Cycle

The Krebs cycle occurs in the mitochondrial matrix and generates a pool of chemical energy (ATP, NADH, and FADH2) from the oxidation of pyruvate, the end product of glycolysis.

Pyruvate is delivered into the mitochondria and loses carbon dioxide to form acetyl-CoA (a 2-carbon molecule). When acetyl-CoA is oxidized to carbon dioxide in the Krebs cycle, chemical energy is released and captured in the form of NADH, FADH2, and ATP.

The Electron Transport Chain
Electron Transport requires oxygen. The electron transport chain is a series of electron carriers in the membrane of the mitochondria in eukaryotic cells. Through a series of reactions, the "high energy" electrons are passed to oxygen. In the process, a gradient is formed, and ultimately ATP is produced.

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Image from: http://mwsu-bio101.ning.com/forum/topics/photosynthesiscellular-1

Respiration is conducted from the cell membranes through the prokaryotes, which is found inside the mitochondria.

There are two types of respiration; they are aerobic respiration and anaerobic respiration. Aerobic respiration is a process that requires oxygen; whereas, in anaerobic respiration, oxygen is not required. Therefore aerobic and anaerobic respiration differs in terms of the amount of energy that is produced.







Aerobic respiration

This type of respiration is more efficient and more complicated than anaerobic respiration. Aerobic respiration uses oxygen and glucose in order to produce carbon dioxide, water, and ATP. This process involves six oxygen molecules for every sugar molecule:

|| 6O2 + C6H12O6 -> 6CO2 + 6H2O + ATP energy
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Anaerobic respiration

Sometimes animal and plant cells cannot get enough oxygen to carry out aerobic respiration. However, they still need to obtain energy to stay alive. So they use an emergency system of reactions that is anaerobic respiration.

Animals
When you sprint for a bus, your muscles use so much oxygen that you cannot supply it in time. Therefore, this means that they cannot use aerobic respiration. Instead they use anaerobic respiration in the following way:

|| Glucose Lactic Acid + Energy
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This way of getting energy is not as efficient as aerobic respiration and it also leaves a poisonous chemical, lactic acid. This stops your muscles working and they get sore. When stopping the lactic acid is slowly destroyed but that needs oxygen. The amount of oxygen you need for this is called the 'oxygen debt'.

Plants
If the roots of a plant get waterlogged they start to run out of oxygen. Therefore, they need to use a different form of anaerobic respiration. The one they use is this:

|| Glucose Ethanol + Energy
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Advantages and Disadvantages of aerobic respiration and anaerobic respiration are:

Advantages:
- Aerobic produces lots of energy
- Anaerobic does not need oxygen, it could get energy in oxygen deprived situation

Disadvantages
- Aerobic happens only when oxygen is present.
- Anaerobic only produces small amount of energy and as a result, organisms grow much slower. This type of respiration also produce lactic acid that is toxic to the cell

Measuring and Recording Respiration
Steps to measure and record respiration:
  1. The first thing to do is to examine the injured person stomach or chest, keep watching until it rises and falls.
  2. Secondly, record the respiratory rate per minute by counting the number of times the stomach or chest rises for fifteen seconds and multiply it by four.
  3. Next, note the rhythm of the breathing and take into consideration if it is regular or irregular. Also, note how much effort it takes the person to breath and if the breathing is deep or shallow.
  4. Next, will be smell if there is any unusual odour, noting a fruity odour or a faecal odour.
  5. Lastly, record the findings in the following way: rate, rhythm, effort, depth, noise and odours (ehow – health)