Biology of Belief

The activity of one specific channel type, sodium-potassium APTase, merits special attention. Every cell has thousands of these channels built into the membrane. Collectively, their activity uses almost half of your body’s energy every day. This channel opens and closes so frequently that it resembles a revolving door in a department store on the day of a big sale. Every time this channel revolves, it shuttles three positively charged sodium atoms out of the cytoplasm and simultaneously admits two positive-charged potassium atoms into the cytoplasm from the environment.

Sodium-potasium ATPase not only uses up a lot of energy, it also creates energy as surely as store-bought batteries provide energy … the energy-producing activity of sodium-potassium ATPase … turns the cell into a constantly recharging biological battery. (p. 85)

Chapter 6, Growth and Protection

Evolution has provided us with lots of survival mechanisms. They can be roughly divided into two functional categories: growth and protection. These growth and protection mechanisms are the fundamental behaviors required for an organism to survive. I’m sure you know how important it is to protect yourself. You may not realize though that growth is vitally important for your survival as well. (p. 145)

Comments: The key in this book is about the tradeoff between growth and protection. This can be understood as the tradeoff between fixed cost and variable cost. Growth is the increase of fixed cost.

Stress, which is a defense mechanism against external threat, inhibits growth. Stress also inhibits immune system, which is the defense system against bacteria and virus. In other words, the allocation of resources to external defense reduces the resources for growth and internal defense. That is why stressed people are easy to get sick.

Comments: Copy more from the book for materials for a paper on economy of life.

At the University of Melbourne, E. Marilyn Wintour’s research on pregnant sheep, who are physiologically quite similar to humans, has found that prenatal exposure to cortisol eventually leads to high blood pressure [Dodic, et al, 2002]. Fetal cortisol levels play a very important regulatory role in the development of the kidney’s filtering units, the nephrons. A nephron’s cells are intimately involved with regulating the body’s salt balance and consequently are important in controlling blood pressure. Excess cortisol absorbed from a stressed mother modifies fetal nephron formation. An additional effect of excess cortisol is that it simultaneously switches the mother’s and the fetus’ system from a growth state to a protection posture. As a result, the growth-inhibiting effect of excess cortisol in the womb causes the babies to be born smaller. (p. 175)

Comments: I’ve read Dodic, et al, 2002. I shall study these problems systematically. Understanding the function of sodium systematically could be the key to understand life. Learn how the structure of nephron affect the level of sodium in the blood. How the level of sodium affect blood pressure. How the level of sodium affect sodium potassium pump. Why plants need more potassium while animals need more sodium? There are many questions I need to learn.