What Does The Gall Bladder Do?

The Gall Bladder is a storage vessel for liver bile. It acts as a reservoir for holding bile on its way from the liver to the intestines

liver:

The liver is a large, meaty organ that sits on the right side of the belly. Weighing about 3 pounds, the liver is reddish-brown in color and feels rubbery to the touch. Normally you can't feel the liver, because it's protected by the rib cage.

1.       Temperature

Enzymes have an optimum temperature at which they work fastest. For mammalian enzymes this is about 40°C, but there are enzymes that work best at very different temperatures, e.g. enzymes from the arctic snow flea work at -10°C, and enzymes from thermophilic bacteria work at 90°C.

Up to the optimum temperature the rate increases geometrically with temperature (i.e. it's a curve, not a straight line). The rate increases because the enzyme and substrate molecules both have more kinetic energy so collide more often, and also because more molecules have sufficient energy to overcome the (greatly reduced) activation energy. The increase in rate with temperature can be quantified as a Q₁₀, which is the relative increase for a 10°C rise in temperature. Q₁₀ is usually 2-3 for enzyme-catalysed reactions (i.e. the rate doubles every 10°C) and usually less than 2 for non-enzyme reactions.

The rate is not zero at 0°C, so enzymes still work in the fridge (and food still goes off), but they work slowly. Enzymes can even work in ice, though the rate is extremely slow due to the very slow diffusion of enzyme and substrate molecules through the ice lattice.

Above the optimum temperature the rate decreases as more and more of the enzyme molecules denature. The thermal energy breaks the hydrogen bonds holding the secondary and tertiary structure of the enzyme together, so the enzyme (and especially the active site) loses its shape to become a random coil. The substrate can no longer bind, and the reaction is no longer catalysed. At very high temperatures this is irreversible. Remember that only the weak hydrogen bonds are broken at these mild temperatures; to break strong covalent bonds you need to boil in concentrated acid for many hours.

How do enzymes work? 

There are three ways of thinking about enzyme catalysis. They all describe the same process, though in different ways, and you should know about each of them.

Enzymes are biological catalysts. There are about 40,000 different enzymes in human cells, each controlling a different chemical reaction. They increase the rate of reactions by a factor of between 10⁶ to 10¹² times, allowing the chemical reactions that make life possible to take place at normal temperatures. They were discovered in fermenting yeast in 1900 by Buchner, and the name enzyme means "in yeast". As well as catalysing all the metabolic reactions of cells (such as respiration, photosynthesis and digestion), they also act as motors, membrane pumps and receptors.

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