The Biosphere Blog

Last week’s post on the stroma was a prelude to posts-to-come on the light-independent reactions of photosynthesis. These reactions are the Calvin Cycle, in which the inorganic carbon in carbon dioxide (CO2) is ‘fixed’ into organic… 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 »

I noticed random jujube trees looking a bit ‘not right’ one day in November 2022. And then almost overnight they looked even more ‘not right’ - as in looked like they were outright dying! Pathetic drooping brown leaves covering… more »

The Angiospermae Angiospermae, also called angiosperms, are the flowering plants. Flowers, when fertilised, produce fruit containing seeds. The only other seed-producing group, the Gymnospermae or gymnosperms, produce seeds in cones. Both angiosperms… more »

Introduction Jujube tree trunks and branches are, botanically-speaking, stems. A stem is one of several plant organs, and, like all organs plant or animal, is specialised for specific roles. A stem is the plant organ which provides structure and… more »

Introduction Single-celled organisms are biochemical multitaskers — they need to be if they are to survive, as every process required for their existence must be doable by that single cell. Multicellular life probably began as colonies of independent… more »

I always keep back a few trees every year. As soon as the last bare-rooted tree leaves for a customer, these trees too are packed exactly as if going in the mail. They do not see the light of day, and are completely untouched and undisturbed the whole… 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 »