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ATP (Adenosine tri-phosphate): ATP is a nucleotide with 3 phosphate groups instead of 1 phosphate group. The point of cellular respiration is to harvest chemical energy from food and store it in the chemical bonds of ATP. In this diagram Nitrogen= blue , Phosphate= yellow , Carbon= grey , Oxygen= red . Hydrogen atoms are not shown
Types of Cellular Respiration
There are two basic types of cellular respiration aerobic cellular respiration and anaerobic cellular respiration. Aerobic respiration requires the use of oxygen and anaerobic respiration which does not use oxygen. There are several types of anaerobic respiration, most familiar is a process called fermentation .
Equation of Aerobic Respiration
1.Aerobic Respiration – is the process by which ATP is produced by cells by the complete oxidation of organic compounds using oxygen.
Oxygen serves as the final electron acceptor, accepting electrons that ultimately come from the energy rich organic compounds we consume.
In the fig. the energy rich molecules (& heat) are in red , energy poor are in black .
Stages in Aerobic Respiration
Glycolysis – glucose is partially oxideized and broken down into 3 Carbon molecules called pyruvate . In the process, glycolysis produced 4 ATP for a net gain of 2 ATP & 2 molecules of NADH . Each NADH is carrying 2 energy rich electrons away from the glucose and these electrons can be used by the cell to do work. After glycolysis the pyruvate is processed to harvest 2 more NADH mol. & remove one carbon per pyruvate. The carbon and 2 oxygen are removed since it no longer has any useful energy. So it is waste. This little step is the source of some of the carbon dioxide we produce.
Kreb’s cycle – the remaining 2 carbon per pyruvate feed into a complicated set of reactions called Kreb’s cycle . It produces 8 more NADH molecules and 2 molecules of FADH2. Again both of these are carrying energy rich electrons.
Electron Transport Phosphorylation – most of the NADH and FADH2 travel to special membranes in the cell which have a series of molecules called electron transport system that harvest the energy rich electrons from the NADH & FADH2 and use that energy to make lots of ATP by a process called electron transport phosphorylation.
2. Fermentation & Anaerobic respiration – if oxygen is absent, many cells are still able to use glycolysis to produce ATP. 2 ways this can be done are through fermentation and anaerobic respiration. Fermentation is the process by which electrons and hydrogen ions from the NADH produced by glycolysis are donated to another organic molecule.
Stages in Anaerobic Respiration
The Point of Fermentation
The reason this is done is to produce NAD+ which in tern is needed to keep glycolysis going. Remember that unless the cell has some sort of electron transport system, the NADH is not usable. At the same time NAD+ is needed for glycolysis and its much less expensive in terms of energy for the cell to simply to take the NADH that would normally go to the mitochondria and use it to generate the NAD+.
Notice that the NADH produced by glycolysis donates its hydrogen ions and electrons that in aerobic respiration would have ended up powering electron transport phosphorylation.
Composition of Air
Carbon Dioxide: 0.033%
The air that leaves a person's lungs during exhalation contains 14% oxygen and 4.4% carbon dioxide.
Atmospheres with oxygen concentrations below 19.5 percent can have adverse physiological effects, and atmospheres with less than 16 percent oxygen can become life threatening.
Gas molecules inside a volume (e.g. a balloon) are constantly moving around freely. During this molecular motion they frequently collide with each other and with the surface of any enclosure there may be (in a small balloon that would be many thousands of billions of collisions each second)
The internal gas pressure in a balloon, PB, is given by the impacts of moving gas molecules, as they collide with the skin of the balloon from the inside
The force of impact of a single one such collision is too small to be sensed. However, taken all together, this large number of impacts of gas molecules exerts a considerable force onto the surface of the enclosure: the gas pressure
The larger the number of collisions per area of enclosure, the larger the pressure:
The SI-unit of pressure is Pascal [Pa], but in Meteorology it is accepted to use millibars [mb], where 100 kPa = 1000 mb.
The direction of this gas pressure force is always perpendicular to the surface of the enclosure at every point.