The Role of Enzymes in the Human Digestive System

In eigth/ninth grade Biology you’ve learned about compononts of a healthy diet and how a healthy diet contributes to our well-being. You also learned that our diet consists of nutrients that contain energy (carbohydrates, lipids and proteins) and other components that contain no energy (water, minerals, vitamins).

In this sequence you’re researching on the organs of human digestion and cellular processes taking place in the human digestive system (with special regard to the role of enzymes).

Use your workbook, the IB Biology 2nd Edition Website and other internet resources to …

… explain the properties of enzymes and the role of enzymes in metabolic processes.

… outline the stages of digestion in the human body and the function of the human liver.

… illustrate the biochemical properties of carbohydrates in general and the specific structure of glucose, starch and glycogen

… illustrate the structure of proteins and how amino acids form a three dimensional protein.

… describe and distinguish condensation and hydrolosis reactions.

These animations are useful to begin exploring the different topics:

Organs of digestion

Digestion metabolism overview

Enzyme action and the hydrolysis of sucrose

This independent learning sequence is designed for three hours and two homework sessions. You can individually choose to complete tasks in writing full texts or making notes, visualizing ideas in a mindmap/ concept map/ figures.

We are going to discuss and present results next Tuesday.

Active Membrane Transport: Resources for Independent Learning

While passive transport processes don’t require energy as substances move along their concentration gradient, active transport processes require energy because they move substances up a concentration gradient or involve the intake of larger particles.

These interactive tutorials or animations are brilliant resources for further independent learning (including a quiz to test your knowledge) and illustrate some of the principles of active membrane transport:

Primary Active Transport

Secondary Active Transport


Endocytosis and Exocytosis 

Active Transport by Group Location

Nutrient and Mineral Cycles

All organisms require various nutrients besides energy. As you know, energy flows through an ecosystem and matter cycles in an ecosystem. For each element, the cycle can involve a reservoir, in which the nutrient is present, an exchange pool, which is the primary source of nutrients, and the biotic community, which consists of the organisms through which nutrients pass (click for an example).

Watch these animations and make an own labeled Carbon Cycle diagram

The Carbon Cycle animation I and The Carbon Cycle animation II.

Please note that the German terminology distinguishes nutrients (= Nährstoffe) and minerals (= Mineralstoffe).

The Nitrogen Cycle – Animation I

The Nitrogen Cycle – Animation II

The Phoshorus Cycle – Animation I

The Phosphorus Cycle – Animation II


Coevolution- An Evolutionary Arms Race

One passage in Lewis Carrol’s „Through the Looking Glass, and what Alice Found There“ (1871, sequel to Alice’s Adventures in Wonderland“) has been picked up and used as an analogy for evolutionary processes:

Well, in our country,‘ said Alice, still panting a little, ‚you’d generally get to somewhere else—if you ran very fast for a long time, as we’ve been doing.‘

‚A slow sort of country!‘ said the Queen. ‚Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!‘

The Red Queen Hypothesis suggests a constant evolutionary arms race: there are constant interactive selection pressures on  involved organisms leading to evolutionary change: coevolution.

Here are the links to the materials we used in class:

Evolutionary arms race (film)

Evolutionary arms race (materials and exercises)


Q1 Biology- Independent Learning: Liebig’s Law of the minimum and the intermediate disturbance hypothesis

Research about …

– … the intermediate disturbance hypothesis

– … Liebig’s law of the minimum

What are the consequences of Liebig’s law for populations in their habitat?

Why does -according to the intermediate disturbance hypothesis – a lower number of populations provide more stability for an ecosystem than the climax in the number of species in ecological successions? (here you need to look at figure 2 in your „Ecological successions“ handout)

Try to avoid Wikipedia as there are many different good resources on the internet. It’s also a good idea to begin your research with an image search (here for Liebig’s Law and here for the intermediate disturbance hypothesis). The advantage here is a simple idea: if a website provides high-quality images, it most likely contains (high-)quality content.

You need to be able to present/read out your ideas on Friday.

Modern Evolutionary Synthesis – Evolution Before our Eyes

As we have combined the ideas of many biological disciplines to a theory of modern evolutionary synthesis, we can apply this theory to evolutionary events that occur right before our eyes:  for example, the evolution of antibiotic resistance.

Watch this animation: Mutation- Selection: The Bacteria Resist

Furthermore, read „The Evolution of Antibiotic resistance“ on page 115 in your workbook.

Then evaluate in detail to what extend parts of the modern synthetic theory of evolution can be applied. Also explain why this example displays „evolution before our eyes“.


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