Page 29 - 84 human physiolofy part-1

Cell Physiology

form one ATP; three molecules of NAD are reduced; and one molecule of FAD is reduced.
Although one molecule of GTP leads to the production of one ATP, the production of the
reduced NAD and FAD are far more significant in the cell's energy-generating process. This is
because NADH and FADH donate their electrons to an electron transport system that generates
2
large amounts of energy by forming many molecules of ATP.

To see a visual summary of "Kreb Cycle" please click here.

Electron Transport System

The most complicated system of all. In the respiration chain, oxidation and reduction reactions
occur repeatedly as a way of transporting energy. The respiratory chain is also called the electron
transport chain. At the end of the chain, oxygen accepts the electron and water is produced.

Redox Reaction

This is a simultaneous oxidation-reduction process whereby cellular metabolism occurs, such as
the oxidation of sugar in the human body, through a series of very complex electron transfer processes.

The chemical way to look at redox processes is that the substance being oxidized transfers
electrons to the substance being reduced. Thus, in the reaction, the substance being oxidized (aka. the
reducing agent) loses electrons, while the substance being reduced (aka. the oxidizing agent) gains
electrons. Remember: LEO (Losing Electrons is Oxidation) the lion says GER (Gaining Electrons is
Reduction).

+
+
The term redox state is often used to describe the balance of NAD /NADH and NADP /NADPH
in a biological system such as a cell or organ. The redox state is reflected in the balance of several sets
of metabolites (e.g., lactate and pyruvate, beta-hydroxybutyrate and acetoacetate) whose
interconversion is dependent on these ratios. An abnormal redox state can develop in a variety of
deleterious situations, such as hypoxia, shock, and sepsis.

Carbohydrates

Carbohydrate molecules consist of carbon, hydrogen, and oxygen. They have a general formula
C (H O) . There are several sub-families based on molecular size.
n 2 n

Carbohydrates are chemical compounds that contain oxygen, hydrogen, and carbon atoms, and no
other elements. They consist of monosaccharide sugars of varying chain lengths.

Certain carbohydrates are an important storage and transport form of energy in most organisms,
including plants and animals. Carbohydrates are classified by their number of sugar units:
monosaccharides (such as glucose and fructose), disaccharides (such as sucrose and lactose),
oligosaccharides, and polysaccharides (such as starch, glycogen, and cellulose).

The simplest carbohydrates are monosaccharides, which are small straight-chain aldehydes and

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