Ch 11Photosynthesis in Higher Plants — Class 11 Biology, concept-first.

Every gram of food a human eats, every breath of oxygen taken, and almost every joule of energy that flows through the living world can be traced back to one process: photosynthesis.

The modern picture of photosynthesis was assembled gradually, experiment by experiment, over nearly two hundred years, and the sequence of discoveries is itself instructive: each experiment resolved e…

Photosynthesis in higher plants occurs almost entirely within a specialised, double-membrane-bound organelle called the chloroplast, one of a family of related plastids found in plant and algal cells.…

The molecules directly responsible for capturing light energy in photosynthesis are called pigments, and they can be separated from a crushed leaf extract and identified individually using chromatogra…

Alongside the chlorophylls, every green leaf also contains a second broad class of pigments called carotenoids, which are yellow to orange in colour and are usually masked in an intact leaf by the muc…

The photochemical (light) phase of photosynthesis begins when light energy is absorbed by pigment molecules embedded in the thylakoid membrane.

The photoactivation event at Photosystem II described in the previous section leaves the reaction-centre chlorophyll, now written P680+, in an oxidised state, having lost one of its own electrons.

The synthesis of ATP that is coupled to the light-driven electron transport chain described in the previous sections is given a specific name: photophosphorylation, meaning, quite literally, light-dri…

Having established, in the preceding sections, that the light reaction pumps and generates protons on one specific side of the thylakoid membrane -- from the splitting of water directly, and from elec…

The biosynthetic (dark) phase of photosynthesis, unlike the light reaction, takes place in the fluid stroma of the chloroplast rather than on its membranes, and does not itself require light directly…

While most plants rely exclusively on the Calvin cycle described in the previous section, a significant number of plant species -- including many economically important tropical and sub-tropical speci…

A second, quite distinct strategy for improving photosynthetic efficiency under difficult environmental conditions is found in a group of plants adapted specifically to hot, arid habitats -- succulent…

The enzyme RuBisCO, introduced in the section on the Calvin cycle as the key CO2-fixing enzyme of the C3 pathway, has one important biochemical limitation: its full name, ribulose bisphosphate carboxy…

The rate at which a leaf actually photosynthesises at any given moment, in any real field or greenhouse, is not set by any single variable in isolation but is jointly governed by several external envi…

Bringing together the material of the preceding sections, C3, C4 and CAM photosynthesis can usefully be understood as three related but distinct evolutionary solutions to a single underlying biochemic…

Photosynthesis is the process by which chlorophyll-bearing autotrophs convert light energy into the chemical energy of carbohydrate, fixing atmospheric CO2 using water as the ultimate source of electr…