[compost_tea] Re: What is a protein vs an enzyme was (malt vs molasses)

From: Nicole Nelson (nnelson8587@qwest.net)
Date: Mon Feb 03 2003 - 15:30:51 EST



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.


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