Biology: cell theory

Tutoring biology, or any subject, essential concepts can continue to deliver surprises. The tutor looks at cell theory.

Cell theory is perhaps the first brick in the structure of modern biological understanding. It states the following:

  1. Every living organism is made of cells.
  2. There is no smaller unit of life than the cell.
  3. Cells can only arise from other living cells.

A modern inclusion to the cell theory is the following:

  • In the context of a living organism, its energy consumption happens within cells.

The last idea is perhaps a little more surprising than the others. For instance, it suggests that the heat constantly radiating from a large mammal like a human being is evolved from the individual metabolic activities within its cells. No energy is consumed in the fluid of the blood or the tissue fluid, but only by the surrounding cells.

Ultimately, of course, the energy consumed by a cell is transformed to ATP in its mitochondria. Since mitochondria only exist within cells (as far as I’m aware, anyhow), the idea makes perfect sense.


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

Lifestyle, biology: A twin-spotted sphinx moth?

I find that being outside in the summertime leads to constant self-tutoring. The tutor shares a find from the siding this morning: a twin-spotted sphinx moth (Smerinthus jamaicensis)

I don’t remember seeing one of these. A quick internet search yielded what I believe is a match. Indeed, Smerinthus jamaicensis is meant to live in southern BC: I think that’s what this handsome moth is. (I didn’t disturb it; it seems to be fine with the paparazzi:)


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

Biology, Lifestyle: food preservation by irradiation

Tutoring biology, you might be asked about food irradiation. The tutor briefly talks about it.

Food irradiation is a preservation method that exposes food to radiation to kill organisms that might cause spoilage.

A question I had was, “Why doesn’t irradiation damage the nutrients in food?” From reading, I’ve surmised that the radiation separates the organisms’ DNA into building blocks, rendering it useless (so that they mostly die or just can’t reproduce). However, those building blocks are still useful as raw materials to whoever consumes the food – that’s as I understand, anyway.

Food irradiation has been an accepted technique for decades; the US space program has used irradiated food since the 1970s.


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

Biology: cells that don’t require insulin to import glucose

Tutoring biology, insulin is bound to come up. The tutor shares a discovery he made today.

Apparently, not all body cells require insulin to import glucose from the blood. I first read that brain and liver cells don’t. Next, I discovered a resource on facebook that suggests not only those, but also red blood cells, skeletal muscles engaged in exercise, and kidney cells can use glucose from the blood without insulin.

Interesting, eh?


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

Lifestyle: carbohydrates, part 2: simple, complex, and the glycemic index

More nutritional self-tutoring: the tutor continues about comparisons between carbohydrates.

In my last two articles, here and here, I discuss simple vs complex carbohydrates, then the glycemic index, respectively.

The original talking-point of this series of articles is that we typically seem to hear that complex carbohydrates should be chosen over simple ones. The obvious question:

  • Are complex carbohydrates always more beneficial than simple ones, and why?

The simple answer is no, not necessarily.

First, recall from my article here that simple carbohydrates can be thought of as sugars, whereas complex carbohydrates can be thought of as starch.

From a dietary point of view, the general rule about carbohydrates is that the lower the glycemic index (GI) (see yesterday’s article), the better. Some starches have a high glycemic index – white bread can have GI very close to that of glucose itself. Yet, since white bread is mainly starch, rather than sugar, it’s still complex carbohydrate.

Vegetables with high soluble fibre content tend to have a low GI (kidney beans, for instance).

Fructose, a sugar, has a surprisingly low GI of 19.

Therefore, a complex carbohydrate can have a high GI, while a simple one can have a low GI. From a dietary point of view, the general rule for carbohydrates seems to be that low GI is better than high, rather than that complex is better than simple.

Which foods are low vs high can be confusing at first, but there are a couple of sources below that have very useful tables to help.


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

Lifestyle: carbohydrates, part 1: what is the glycemic index?

Tutoring school subjects, the glycemic index might rarely be mentioned. In other contexts it’s important. The tutor briefly explains the glycemic index.

In yesterday’s post I began about carbohydrates from a dietary point of view, discussing the difference between simple and complex ones.

To go further with the discussion, a definition is needed: the glycemic index.

When carbohydrates are digested, they are separated into individual molecules called simple sugars. Glucose is a simple sugar, for example. The simple sugars are then absorbed into the blood, which elevates blood sugar.

A food’s glycemic index measures the rise in blood sugar caused by eating that food, relative to eating glucose itself. On the scale, glucose is given a glycemic index (GI) of 100.

≤55 low
56 to 69 medium
≥70 high

Next post I’ll discuss the connection between carbohydrates and the glycemic index.


Lifestyle: carbohydrates, part 0: simple vs complex, from an eater’s point of view

Nutrition involves constant self-tutoring. The tutor brings up carbohydrates.

We typically hear the notion that we should steer away from simple carbohydrates, towards complex ones. That very direction implies a question:

  • What is the difference between simple and complex carbohydrates?

I did some research today and found that, from a common point of view, a simple carbohydrate – aka a sugar – has two or less rings, while a complex carbohydrate has three or more. Sucrose, for example, has two rings, while glucose has one (or is one, depending on how you word it).

Thinking of a complex carbohydrate as many glucose molecules strung together is a useful way to understand it, but the specific molecules may not all be glucose necessarily. Fructose is also a single-ring sugar.

Starch is a complex carbohydrate. It’s a chain, possibly branched, that can contain hundreds of rings, or more. Starch is the carbohydrate found in vegetables such as beans, as well as grains.

When people talk about complex carbohydrates from a dietary point of view, they usually mean starch. However, that’s not the end of the discussion. I’ll be talking more about carbohydrates from a nutritional point of view:)


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

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

Lifestyle, botany: yard find: knapweed

Plant identification means constant self-tutoring. The tutor shares a recent lesson.

I’ve noticed this perennial in the yard since I can remember:

Apparently, it’s a knapweed.



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

Biology: what is non-competitive inhibition?

Tutoring biology, non-competitive inhibition may be mentioned. The tutor explains it.

In yesterday’s post I explain competitive inhibition.

Non-competitive inhibition is similiar to competitive inhibition in that it hinders enzyme function. The difference is that, with non-competitive inhibition, the inhibitor doesn’t bind to the enzyme’s active site; with competitive inhibition, it does.

A non-competitive inhibitor may be a bulky atom such as a heavy metal, or a bulky molecule. This bulky species will attach itself to the enzyme somewhere other than the active site. However, the enzyme’s function is still impeded by one of two possible ways:

  1. The bulk of the inhibitor, though not occupying the active site, may still make it hard to reach, just as a long vehicle in a parking stall can prevent the use of the stall past it.
  2. The inhibitor may change the chemistry of the enzyme, making it less attractive to its intended substrate.



Biology 12, module 1. Open School BC, 2007.

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

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

Biology: what is competitive inhibition?

Tutoring biology, you might be asked about competitive inhibition. The tutor explains it.

In my November 25, 2013 post, I explain what an enzyme is. Simply put, an enzyme is a biological catalyst that the body uses to speed up a chemical process. An enzyme is not consumed by the reaction, but works alongside it, so can be reused.

Competitive inhibition reduces the effectiveness of an enzyme, possibly with fatality. Along with some preliminary ideas, here’s how it happens:

  1. The molecule an enzyme works on is called the substrate. The enzyme speeds the transformation of the substrate into what the body needs.
  2. The substrate, normally, binds to the enzyme at what’s called the enzyme’s active site in order for the enzyme to work on it.
  3. Therefore, let’s imagine that enzyme E works on substrate S to make necessary molecule M.
  4. Once S transforms to M, enzyme E is released; E is not attracted to M.
  5. Competitive inhibition starts with the arrival of a different substrate, ¬S, that is
    • attractive to enzyme E at the active site
    • not transformable to the necessary molecule M
    • will not become M, so will not release E (or not very quickly, anyway)
  6. The result is that E becomes busy with ¬S, so its active site is inaccessible to S.
  7. Without access to the active site of E, S can’t transform into M.
  8. The body needs M; without it, health consequences, possibly even death, will manifest.

Such is the mechanism of competitive inhibition. Some poisons are competitive inhibitors.


Biology 12 Module 1. Open School BC, 2007.

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

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