Some more Important Facts of Physiology and Biochemistry

Compensation point:

The light intensity at which rate of photosynthesis is equal to the rate of respiration i.e., in morning, in evening.

Photosynthesis:

Anabolic, endergonic, oxidation – reduction process.

NADP:

Acts as hydrogen acceptor during photosynthesis in plant cells.

Rubisco:

RuBP carboxylase enzyme, is a large protein molecule and constitute about 16% of the chloroplast protein and is the most abundant protein on the earth.

Grass Alloteropsis semi-alata possesses both C₃ and C₄ ecotypes.

Fret membranes:

Membranes of thylakoids.

Plastidome:

Plastid complex of a cell.

Keilin (1925):

Coined the term cytochrome.

Electrons accepted from reaction centres by the acceptors are passed down hill through the electron transport chain.

The reaction centre of PS II is P₆₈₀ (or chlorophyll a₆₈₀) and that of PS I is P₇₀₀ (or chlorophyll a₇₀₀).

Assimilatory power:

NADPH + H⁺ produced in light reaction constitute assimilatory power i.e., reducing power.

Redox potential:

The tendency of an atom/ molecule to give or take up electrons. Electrons move from substances having low redox potentials to those having high redox potentials.

In C₃ plants, more CO₂ is released in light than in dark (due to photorespiration).

Solarisation:

Destruction of chlorophyll due to high light intensity.

Carbon dioxide:

Most common limiting factor for photosynthesis.

Only 0.2% of the light energy falling on the earth is utilised by photosynthetic organisms.

The reaction centre in bacteria is B-890.

The size of quantosome is about 180 x 155 x 100 A.

DCMU (Dichlorophenyl dimethyl Urea) – a herbicide which inhibits PS II and oxygen release in light phase.

Calvin cycle is exhibited by A triplex rose us whereas Hatch-Slack cycle is exhibited by A. hastata.

In bacteria only one ATP molecule is generated during cyclic or non-cyclic electron transport.

K⁺ ions:

Helps in the translocation of solutes.

Annually, about 75 x 1012 kg of carbon (in the form of CO) is fixed through

Photosynthesis, producing about 1700 million tonnes of dry matter. About 90% of it is carried out in the oceans (mostly by the phytoplanktons and algae).

Photosynthetic material:

264 g of CO₂ and 216 g of water give rise to 108 g of water, 192 g of O₂ and 180 g of glucose.

PEP or Phosphoenol pyruvate:

Primary CO₂ acceptor in C₄ and CAM plants. Combination of CO₂ and PEP is called initial fixation. It takes place in me

ophyll cells and the enzyme is pepco.

RuBP or ribulose biphosphate:

Secondary/ final, CO₂ acceptor in C₄ and CAM plants. The phenomenon is called final fixation. It takes place in bundle sheath chloroplasts of C₄ plants and mesophyll cells in CAM plants and the enzyme is rubisco.

C.G. Strokes (1864):

First to separate pure fractions of Chlorophyll a and Chlorophyll b.

Protochlorophyllide a is reduced to chlorophyllide an in presence of light and then esterified with phytol group to form chlorophyll.

Orange wavelength (586-647 nm) is least absorbed and also least effective.

T.W. Englemann (1880) determined the approximate action spectrum of photosynthesis.