8.2 Photosynthesis

This was taught concurrently with Core content. To review the basics, click here to go back to the Core content.

Let’s start with some higher-level, Lyrical Science silliness:

Notice how he starts the song with the light-independent reactions before moving on to the light-dependent reactions? It is a good reminder that all of these processes are happening all of the time. You could think of the LD reactions as a method for replacing the electrons, H+ and ATP used up in the LI reactions.

Here is the AHL/ Option C stuff:

This Essential Biology document covers the Core content as well as Option C/ AHL.

Step-through – Garrett and Grisham Biochemistry

John Kyrk again – very detailed

Simple, not entirely relevant – University of Aberdeen

Old-school animations, useful explanations – Teachnet

How close are we to making artifical leaves? Check out this article.


Light dependent reactions:

Nice and simple – St Olaf college

Another simple animation – on the webpage of National Louis University


Light Independent Reactions:

Calvin cycle step-through – National Louis University

Nice interactive Calvin cycle – Smith College


Limiting Factors: Phytoplankton Blooms

When a nutrient is in limited supply, the rate of metabolic reactions is limited. This is the concept to limiting factors. For some spectacular evidence of what happens when that nutrient is no longer limited, enlarge this amazing photo of a phytoplankton bloom from space, taken from the ESA Enviro Sat:

Phytoplankton Bloom from the ESA Enviro Sat. Click to enlarge.

Phytoplankton Bloom from the ESA Enviro Sat. Click to enlarge.

So what’s happening? Well, in marine phytoplankton, iron is often a limiting micronutrient, along with other mineral elements. These tend to sink to the bottom of the ocean, but upwelling currents can push them up to the near-surface, making them available for use and resulting in a population explosion. Cool.


Finally, see if  you can spot the errors in this cartoon:

Photosynthesis FakeScience

FakeScience funnies, fakescience.tumblr.net

Key terms: photosynthesis, chloroplast, membrane, stroma, chlorophyll, thylakoid, granum, light-dependent, light-independent, photophosphorylation, chemiosmosis, protons, photoactivation, electron transport, photosystem, photolysis, cyclic, non-cyclic, reduction, NADP+, NADPH, RuBP, carboxylase, ribulose, glycerate-3-phosphate, triose phosphate, regeneration, carbohydrates, action, absorption, spectrum, pigment, limiting factor.

  1. Elizabeth Copeland

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  2. This website is awesome 😀

  3. I really love your website! I very upset that we will change the biology curriculum next year because a lot will change. I hope you keep adding to your website more of the new curriculum as it comes out. Thanks a lot!

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  5. Stephen
    Can I echo the grateful thanks of so many teachers new to teaching IB Biology, for your contribution to saving our sanity, our marriages, our students…and inspiring us to thank you through commitment to good causes and contributing to a global resource network. Let me know how I can help share from my own wee field of knowledge, animal physiology….

  1. Pingback: AHL Photosynthesis | DP1 Biology Blog

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