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[compost_tea] Re: What is a protein vs an enzyme was (malt vs molasses)
On Sunday, February 2, 2003, at 02:00 PM, Jeff Lowenfels wrote:
This involves maltase, an enzyme which must be a protein(?). There are also the cell wall proteins in the original stock.
A little biology; All enzymes are proteins. They are the machinery of the cell. A cell is what it is and does what it does, largely because of the kinds of enzymes it contains, just as the activities and products of a factory are determined by the kinds of machines it contains. Enzymes are globular proteins that act as biological catalysts. Catalysts (inorganic or organic) speed up (expedite) chemical reactions without being changed or used up in the reaction. Maltase to alters the structure of maltose, the sugar. In this case a covalent bond holding two glucose molecules together is broken. The enzyme maltase is shaped in such a way that it can break the bond and free the two glucose pieces. The only thing maltase can do is break maltose molecules, but it can do that very rapidly and efficiently. This requires energy. Enzymes act as a catalysts for the change. They lower the energy required by altering the immediate environment around the reaction. If a reaction can be sped up with altered pH or increased temperature then enzymes speed up this reaction to a biologically useful rate without having to resort to heat and/or acid.
In an enzymatic reaction, the enzyme combines with its substrate to form an enzyme-substrate complex in which the enzyme and its substrate combine very temporarily in a tight fit. The reaction occurs and the complex dissociates releasing the products of the reaction and the enzyme (which has not been affected by the reaction). The enzyme-substrate complex forms at a particular spot on the enzyme molecule called the active site. The active site of the enzyme has a shape and an array of charges and/or hydrophobic zones that are exactly complementary to the shape, charges and hydrophobic zones of the substrate so that the enzyme and substrate fit together like a lock and key.
Membrane Structure and Function. Membranes control the movement of substances across themselves. The cell membrane controls what enters and leaves the cell. The molecular components of a membrane operate much like a fence (that prevents anything from crossing) with gates in it (that allow certain things to cross, e.g., people with the right kind of tickets). The membrane "fence" is a bilayer of phospholipid molecules. The phospholipid bilayer acts like a stabilized layer of grease. Charged or polar molecules or ions will not cross the greasy layer because their hydrophilic nature is not compatible with the uncharged, nonpolar hydrophobic greasy layer in the center of the membrane.
Having established a molecular fence, the membrane also includes gates which allow certain specific molecules to cross. The gates are transport proteins, embedded in the membrane, that act somewhat like enzymes in that they are very specific with respect to the molecules with which they interact. They usually do not change these molecules, however, as an enzyme does. When the properly shaped dissolved molecule happens to bump into one of its particular transport protein molecules, recognition and interaction take place and the dissolved molecule is transported from one side of the membrane to the other. All membranes are similar in having a phospholipid bilayer and associated proteins, but different membranes control the movement of different substances so they must contain different transport proteins.
Bacteria are simple creatures with only 'one fence', their membrane. Higher order single celled creatures have organelles that also have membranes. Organelles act like our internal organs do, by carrying out specific activities. The nucleus contains DNA and various proteins. DNA replication and RNA transcription occur inside the nucleus but protein production occurs outside the nuclear membrane. This allows separation of functions which in turn allows more control over the process with the increased time it takes. On the other hand it makes for a slower response to environmental changes.