The Biosphere Blog

Photosynthesis can be broken down into the light-dependent reactions (covered earlier here), and the light-independent reactions which will be covered in this section. It is well worth getting up to speed on the light-dependent reactions first before… more »

Photosynthesis can be broken down into the light-dependent reactions (which this entire section will cover), and the light-independent reactions (covered in the next section). Both occur within the chloroplasts of cyanobacteria, plants, and algae. Fig.… more »

What is the Stroma? Fig. 1 below is a simple rendition of a chloroplast, the photosynthesising organelle of plants and algae. The stroma is the fluid-filled space surrounding the grana (thylakoid stacks) inside that chloroplast. The stroma of a… more »

A Summary of Oxygenic Photosynthesis to Date Oxygenic photosynthesis produces oxygen gas (O2), and is performed by plants, algae and cyanobacteria. (Many other bacteria can photosynthesise, but these are anoxygenic photosynthesisers, typically producing… more »

Electron Flow All life is driven by electron flows through incredibly involved pathways called ‘electron transport chains’. (That it happens at all is just awe-inspiring!) All such pathways begin with a primary electron donor and end with a… more »

Overview Photosystem I (PSI) is the second of two photosystems, and the third of four major protein complexes in the thylakoids of cyanobacteria and chloroplasts. (A protein complex is a unit of several protein subunits.) The thylakoids are where… more »

Drilling Down There are two types of photosynthesis: anoxygenic and oxygenic. Anoxygenic photosynthesis was the first to appear on Earth around 3.5 billion years ago, was and is performed solely by several groups of bacteria to this day, and… more »

Electron Flow Chemical reactions involve atoms and molecules, but chemistry at its heart is really the study of the electron flow between those atoms and molecules when these react. Similarly, biochemistry at its heart is the study of the electron flow… more »

Drilling Down In the cells of plants and algae are structures called chloroplasts (Fig. 1). (And there is much evidence that these chloroplasts were once independently-living cyanobacteria.) Chloroplasts have an inner and outer membrane (just like… more »

What Are Thylakoids? Thylakoids are unique to chloroplasts and their ancestral cyanobacteria, and are where photosynthesis begins for both. This chapter will focus on the thylakoids in chloroplasts, but with references to cyanobacteria where relevant.… more »

Backstory: Of Prokaryotes and Eukaryotes Prokaryotes Prokaryotes (pronounced ‘pro-carry-oats’) comprise the two Domains Bacteria and Archaea. Prokaryotes are defined as unicellular organisms without membrane-bound nuclei, and contain a… more »

Photons and the Electromagnetic Spectrum ‘Photons’ are commonly thought of as the particles of light, but they are actually the particles of radiation, of which light is just one form. Radio waves, microwaves, infrared waves, visible light… more »

What is Photosynthesis? Photosynthesis (from the Ancient Greek combining form φωτω-, phōtō-, from φῶς, phôs, ‘light’, and σύνθεσις, synthesis, ‘a putting together’:  ‘a putting together with light’) is the process by which plants, algae, cyanobacteria,… more »

Back Story These days it’s ‘just known’ that we/animals take in oxygen to survive (exhaling carbon dioxide as a waste product), while plants take in carbon dioxide to survive (releasing oxygen as a waste product). Yet right up into the… more »

Photosynthesis is the process by which plants, algae, cyanobacteria, and a few other bacterial species convert light energy into chemical energy, which is stored as a food source. Photosynthetic organisms thus produce their own food, and are called… more »