The reason is that they have a mechanism that increases the concentration of CO₂ at the enzyme site. It occurs when C₄ acid from mesophyll cell is broken down in bundle sheath cells and releases CO₂, hence increasing CO₂ concentration intra cellular. It also ensures that RUBISCO acts as carboxylase to minimize oxygenase activity of it.

The pigments are chromoplasts; these are fat soluble carotinoid pigments like carotenes and xanthophylls. These are called accessory pigments; they absorb light and transfer energy to Chlorophyll a.

The Calvin cycle takes place in the bundle sheath cells.

Bundle sheath are arranged around vascular bundle in the shape of floral wreath. 'Kranz' means wreath, hence the name Kranz anatomy.

Carbon fixation occurs in the dark reaction or light-independent reaction of the photosynthesis process. The process of carbon fixation slightly differs in C₃, C₄, and CAM plants but the Calvin Cycle or C₃ pathway is the main biosynthetic pathway of carbon fixation.

The light reaction includes trapping of light energy, splitting of water, oxygen release and formation of ATP and NADPH.

12H₂O + 6CO₂ ⟶ C₆H₁₂O₆ + 6H₂O + 6O₂

Dark reactions are dependent on the products of light reaction that are ATP and NADPH to carryout reduction of CO₂ to form glucose. This does not need so, they are called dark reactions.

The acidic nature of lumen of thylakoids is due to the accumulation of protons by the photolysis of water. The same reaction does not occur in stroma so, it is basic in nature.

RuBP is known as Ribulose 1,5-Bisphosphate. It is the primary acceptor of carbon dioxide in Calvin cycle of C₃-plants. It forms the first stable compound of photosynthesis known as PGA.

The plants which are adapted to dry tropical regions have the C₄ pathway. However, the C₄-plants do not show any characteristic in external morphology. Therefore, it is difficult to say whether a plant is C₃ or C₄ by looking it only externally.

Cyanobacteria and some other photosynthetic bacteria have photosynthetic lamellae (membranes) suspended freely in the cytoplasm.These carry bacteriochlorophyll to conduct photosynthesis.

Two reasons are as follows
(i) It is the process by which food is manufactured for all living organisms.
(ii) It is the only natural process by which oxygen is liberated into the atmosphere. This O₂ is used by all living organisms respiring aerobically.

C₃ pathway or Calvin cycle represents phase-II, i.e. dark reaction of photosynthesis.In Calvin cycle, a 5C pentose sugar, Ribulose Bisphosphate (RuBP) acts as the first acceptor of CO₂ whereas, the C₄ pathway is also called Hatch-Slack pathway in which, the first CO₂ acceptor is 3C phosphoenolpyruvate (PEP).

ATPase enzyme consists of two parts, i.e., a stalk (F₀) and a headpiece (F₁)These two parts are located completely across the membrane of thylakoid membrane. The conformational changes occur in the headpiece (F₁ ) of this enzyme.