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Hello. Welcome to this Principles of Biochemistry lecture series.
This is lecture 14.
I am Jerry Feigenson,
a professor in the Department of Molecular Biology and Genetics
at Cornell University in the USA.
In the 13th lecture,
you learned some things about carbohydrates.
They have roles in energy use,
in structures needed by cells and in being recognized and bound.
They have a huge range of possible structures,
but determining their three-dimensional structures is often very difficult.
In this 14th lecture,
you will start to learn about reactions being connected and kept in balance.
And you will see this very interesting behavior of Delta G_0 of hydrolysis
measuring the molecule-by-molecule comparison that describes high-energy molecules.
We will see the role of concentration in the Gibbs function.
We will see the role of transmembrane electrical potential for ion transport.
And we will get some idea of what is special about redox reactions in biochemistry.
So this new topic that we're starting on now is metabolism,
the chemical reactions of life.
So we'll start on this slide with some general principles.
So one principle is that,
all of the chemical reactions in biology are in balance.
One example is that the synthesis and
the breakdown of a given molecule are essentially equal,
otherwise that molecule would build up or be depleted.
In general, the molecules do not change their concentration much.
We will see that reactions of all the reactions,
amino acids and proteins,
nucleic acids, lipids, carbohydrates,
all these reactions communicate with each other.
We say they are interconnected. And not obvious,
but this is a fact,
all of the reactions tend to occur.
That means either a favorable Delta G_0 for
each reaction or product concentration being kept low drives the reaction.
Which reactions occur is determined by enzymes.