Biology: pH range of blood

Tutoring biology, as well as hearing new ideas about nutrition, might lead to the topic of blood pH.

On the pH scale, 7 is neutral, below 7, acid, and above 7, alkaline (or base).

Human blood pH range, for health, is between 7.35 and 7.45. For survival, it’s between 6.8 and 7.8, according to conventional wisdom.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Biology, nursing: what is blood plasma?

Tutoring biology, you might be asked about blood plasma. The tutor mentions its defintion.

blood plasma:

the liquid that holds the red blood cells, white blood cells, and platelets. The plasma consists of water and substances suspended or dissolved therein: proteins, salts, etc.

Plasma does not include blood cells or platelets.


Mader, Sylvia S. Inquiry into Life, 9th ed. Toronto: McGraw-Hill, 2000.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Health: what is cortisol and what does it do, part 0

Researching the human body can mean continual self-tutoring. The tutor begins about the critical hormone cortisol.

Cortisol is a hormone produced by the adrenal glands. Its release is augmented when the person feels stress. It has many effects; what follows is one mechanism in which it participates. The first two points are necessary background, while the third explains a function of cortisol:

  1. The human body interprets stress as physical danger rather than a social condition.
  2. Neither brain cells nor exercising skeletal muscle cells need insulin for glucose uptake. However, as I understand, fat cells do need insulin to import glucose.
  3. Cortisol increases blood sugar but inhibits insulin secretion and possibly even insulin sensitivity. Doing so channels the glucose (blood sugar) towards use by the muscles and brain, rather than by the fat cells (which would change it to fat for storage). Therefore, under stress, the muscles and brain have access to lots of energy so they can respond.

I hope to talk more about cortisol:)


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Biology: what is a basement membrane?

Tutoring biology, terminology is so important. The tutor gives a definition of the term basement membrane.

basement membrane: a boundary layer that fastens overlying epithelial tissue to connective tissue beneath. The basement membrane comprises glycoprotein from the epithelial tissue, with collagen fibres from the connective tissue.
A basement membrane backs the lining of the intestine, for instance.


Mader, Sylvia S. Inquiry into Life, 11th ed. Toronto: McGraw-Hill, 2006.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Biology: digestive enzymes: pepsin and trypsin

Approaching another biology workshop, the tutor looks at the human body’s two main digestive enzymes aimed at proteins.

For each type of food molecule the body has its own specific digestive enzyme(s). For protein, there are two: pepsin and trypsin.

Why does the human body use two different enzymes to digest protein? The answer is that the enzymes have different optimal environments. Pepsin works at a low (acid) pH of 1 to 3. The body uses it to digest proteins in the stomach, which is an acidic environment.

Trypsin works best in an alkaline, or basic, environment. Specifically, its optimal pH centers around 8. The body uses trypsin to digest proteins in the small intestine, wherein the environment is basic because of the release of sodium bicarbonate from the pancreas.

I’ll be talking more about digestive enzymes in future posts:)


Mader, Sylvia S. Inquiry into Life, 11th ed. New York: McGraw-Hill, 2006.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Biology: insulin response and insulin resistance

The tutor defines insulin response and insulin resistance and explains their connection.

Recall: herein, ACV means apple cider vinegar.

In yesterday’s post I mentioned my discovery that apple cider vinegar potentially increases the effectiveness of insulin.

As carbohydrates are digested, glucose (a type of sugar) enters the blood from the digestive system. The body’s response to the rising blood sugar is to release insulin. It’s known as the insulin response. Insulin enables glucose to enter cells so they can use it for energy or fat storage.

Sometimes, body cells may become less sensitive to insulin, which is known as insulin resistance. Then, the insulin is less effective at conducting glucose from the blood into the cells; more insulin is needed to do the same as before.

Therefore, if insulin resistance increases, so must the insulin response. The fact that ACV seems to increase insulin’s effectiveness leads to the consequence that it apparently lowers the body’s insulin response.

I’ll be discussing related ideas in coming posts:)


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Biology: nervous system: action potential

The tutor offers a summary of how a nerve impulse propagates.

The cells that carry nerve impulses are called neurons. Neurons have long conduits through which the impulses travel. A nerve impulse, as it conducts along a neuron, can be called an action potential. At the point of progress, the potential difference (aka voltage) swings from -65mV (rest potential) to +40mV (action potential) back to -65mV (rest potential).

The voltage refers to the potential difference across the cell membrane. It is managed by deployment of ions. The swing from -65mV to +40mV is accomplished by sudden controlled migration of Na+ ions into the cell. The return swing from +40mV to -65mV results from controlled departure of K+ ions. (The neuron controls when those ions can cross its membrane.)

After the action potential, the ions need to be reset so they are ready to propagate the next one. The Na+ ions are put back outside, while the K+ ions are brought back inside. This period can be referred to as the refractory period. The neuron may not be able to “fire” again until its completion.



Mader, Sylvia S. Inquiry into Life, 9th Ed. Toronto: McGraw-Hill, 2000.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Fibre: soluble, insoluble?

The tutor has wondered about fibre ever since he heard about soluble fibre.

Back in the early 90s, when I was in university so cut off from day-to-day culture (no TV, no money, no time), a few snippets still did reach me.  One was the term “soluble fibre.” I was highly skeptical; how could fibre, undigestible by definition, yet be soluble?

At an early age I was taught that fibre passes through the intestines, keeping the bowels loose and the stool easy to pass.  It can do so because it’s not digestible.  At the same time, it holds water, keeping the stool soft.  Therefore, it speeds the movement of material through the gut.  To do so, wouldn’t you expect it to be insoluble?

Well, the insoluble fibre is the kind I’ve just described above.  However, soluble fibre also exists, but serves a different function.  In contrast with insoluble fibre, soluble fibre slows food’s exit from the stomach.  Apparently, as it dissolves in water, it forms a complex with the water molecules, giving them more inertia.  Possibly, cholesterol can get stuck in the complex as well, making it less likely to be absorbed.  Anyhow, the effect is that, with the soluble fibre binding together the water molecules in which it’s dissolved, the liquified food in the stomach is more sluggish.  Therefore, it stays in the stomach longer.  One result is feeling “full” for a longer duration after eating.  The other is a slower release of glucose into the bloodstream, which may help offset – or even prevent – symptoms of diabetes.

The sources of both soluble and insoluble fibre are numerous.  A variety of fresh fruits and vegetables, plus a variety of whole grains, will likely avail plenty of both. Here’s a fun fact, though:  oat bran provides soluble fibre, while wheat bran provides insoluble.  I seem to recall, from the 90s to the early 2000s, an increased focus on oat bran rather than just bran.

Soluble and insoluble fibre: now we know:)


Web MD

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Biology: oxygen and carbon dioxide transfer through the blood

Tutoring biology 12, you cover the circulatory system.  The tutor mentions a specific issue about it.

The number one reason for the circulatory system is transport of oxygen to the cells and carbon dioxide away from them.  This is done via the blood, which is water-based.  The immediate problem might be that gases don’t necessarily dissolve very well in water.

Red blood cells contain hemoglobin (which is why they are red).  Hemoglobin attracts and holds oxygen very effectively, enabling the red blood cells to carry the oxygen through the circulatory system to the capillaries.  There, the oxygen is dropped off to the cells.

Carbon dioxide can be carried by red blood cells (as carbaminohemoglobin), but not very effectively.  In the blood, most carbon dioxide combines with water to form carbonic acid (H2CO3), next breaking into hydrogen ion H+ and bicarbonate ion HCO3. Ions travel easily in water. At the lungs, the hydrogen ion and bicarbonate ion recombine into carbonic acid, which then separates into carbon dioxide and water. The carbon dioxide is exhaled.



Mader, Sylvia S. Inquiry into Life, 11th edition. New York: McGraw-Hill, 2006.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.