Cell Metabolism - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 474

We study cells because we want cells to help us to produce a desired product or accom-
plish a desired process. How a certain substrate is transported into the cell and converted
to the desired product? How cells maintain viable? How cell works?
You have now learned something about how cells are constructed (Chapter 2) and how
enzymes function (Chapter 8). We are now ready to move into more complex systems.
A cell is like a bag filled with lipids, amino acids, sugars, enzymes, and nucleic acids, which
you have been exposed to in Chapter 2. The cell must control how these components are
made and modulate how these components interact with each other. The processes involved
all have the fundamental bases from Chapters 3, 4, 5, 6, and 9. In this chapter, we explore
some examples of metabolic regulations and how the metabolic regulations are reflected
through the bioprocess kinetics. It is this ability to coordinate a wide variety of chemical reac-
tions that makes a cell a living cell.
The key to metabolic regulation is the flow and control of information. Humanity is
a perfect example to illustrate the importance of the flow and control/manipulation of
information. Our full grasp of computers has led the “Information Age.” Prior to the inven-
tion of paper, scientific discoveries were extremely slow to appear and spread. Our ability
to gather and communicate message or information was more or less limited to verbal
dialog. The limitation in the scope of learning and assembling of information by individ-
uals hindered the “evolution” of new knowledge, and thus inventions. Our comfortable
level of living standards was rising very slowly. Paper had become a convenient means
of storing and disseminating information and knowledge since about 200 AD. When topics
become readily available, literature spreads were faster starting in the 1700s and 1800s.
A booming increase in scientific discoveries and our understanding of the universe began
to unravel rapidly. A revolutionary change occurred again when computers entered into
our daily life. For example, literature is no longer limited to physical contacts and topics.
Our way of living is no longer limited to individuals. Communication among individuals
becomes mechanized and the human society becomes an integrated entity. There are many
analogies between human society's need to use and exchange information and a cell's need
to use and exchange information between subcellular components. Today, human society
depends primarily on electronic signals for information storage, processing, and transmis-
sion; cells use chemical signals for the same purposes. Molecular biology is primarily the
study of information flow and control. How chemicals or sensors are released and received
forms the basis of cell-to-cell and cell to environment interactions. In this chapter, we will
learn the biological process of cell growth and fermentation or information and nutrient
flow and control in cells.
10.1. THE CENTRAL DOGMA
Almost all living organisms have the same core approach to the storage, expression, and
utilization of information. On a grand scale, we can perceive is the human society as depicted
in the above section. The modern human society is a good analogy to all the living systems.
Information is stored in the DNA molecule in cells as depicted in Fig. 10.1 . Like information
on a computer disc or drive, the information stored in the DNA can be replicated. It can also
be played back or transcribed to produce a message. The message must translate into some
action, such as production of RNA, and protein, for the message to carry a profound impact.