Structure 9f cyanobacteria
Answers
Explanation:
Cyanobacterial cells are larger and more elaborate than bacteria. Cell structure is typically prokaryotic— one envelope organisation with peptidogly can wall, naked DNA, 70S ribosomes and absence of membrane bound structures like endoplasmic reticulum, mitochondria, Golgi bodies, plastids, lysosomes, sap vacuoles.
The cell wall is four layered with peptidoglycan present in the second layer. The outer part of the protoplast contains a number of photosynthetic thylakoids. It is called chromoplasm. The thylakoids lie freely in the cytoplasm. Their membranes contain chlorophyll a, carotenes and xanthophyll’s. Chlorophyll b is absent.
Attached to the thylakoid membranes are small granules known as phycobilisomes. The latter possess accessory photosynthetic pigments known as phycobilins. The phycobilins are of three types— phycocyanin (blue), allophycocyanin (blue) and phycoerythrin (red).
Differential formation of phycobilins produces specific colouration which is adapted to absorbing maximum amount of solar radiation. Therefore, cyanobacteria are not always blue green. They may appear purplish, violet, brownish, etc.
Instead of typical vacuoles or sap vacuoles, gas vacuoles or pseudo-vacuoles are found. Each gas vacuole consists of a number of submicroscopic units called gas vesicles. Gas vacuoles function as light screen; provide buoyancy regulating mechanism and pneumatic strength.
A naked, circular, double stranded DNA lies coiled generally in the central part of the cytoplasm known as centroplasm. The coiled up DNA is equivalent to a single chromosome of higher organisms. It is often called nucleoid. Like bacteria, small circular DNA segments may also occur in addition to nucleoid.
They are known as plasmids or transposons. 70S ribosomes occur here and there. Semicircular group of coiled membranes often attaches the plasma membrane with the nucleoid. It is known as lamella some. Four types of inclusions occur in the cells. They are α-granules (cyanophycean starch), β-granules (lipid droplets), volutin granules and polyhedral bodies (ribulose biphosphate carboxylase)
Explanation:
Explanation:
Cyanobacterial cells are larger and more elaborate than bacteria. Cell structure is typically prokaryotic— one envelope organisation with peptidogly can wall, naked DNA, 70S ribosomes and absence of membrane bound structures like endoplasmic reticulum, mitochondria, Golgi bodies, plastids, lysosomes, sap vacuoles.
The cell wall is four layered with peptidoglycan present in the second layer. The outer part of the protoplast contains a number of photosynthetic thylakoids. It is called chromoplasm. The thylakoids lie freely in the cytoplasm. Their membranes contain chlorophyll a, carotenes and xanthophyll’s. Chlorophyll b is absent.
Attached to the thylakoid membranes are small granules known as phycobilisomes. The latter possess accessory photosynthetic pigments known as phycobilins. The phycobilins are of three types— phycocyanin (blue), allophycocyanin (blue) and phycoerythrin (red).
Differential formation of phycobilins produces specific colouration which is adapted to absorbing maximum amount of solar radiation. Therefore, cyanobacteria are not always blue green. They may appear purplish, violet, brownish, etc.
Instead of typical vacuoles or sap vacuoles, gas vacuoles or pseudo-vacuoles are found. Each gas vacuole consists of a number of submicroscopic units called gas vesicles. Gas vacuoles function as light screen; provide buoyancy regulating mechanism and pneumatic strength.
A naked, circular, double stranded DNA lies coiled generally in the central part of the cytoplasm known as centroplasm. The coiled up DNA is equivalent to a single chromosome of higher organisms. It is often called nucleoid. Like bacteria, small circular DNA segments may also occur in addition to nucleoid.
They are known as plasmids or transposons. 70S ribosomes occur here and there. Semicircular group of coiled membranes often attaches the plasma membrane with the nucleoid. It is known as lamella some. Four types of inclusions occur in the cells. They are α-granules (cyanophycean starch), β-granules (lipid droplets), volutin granules and polyhedral bodies (ribulose biphosphate carboxylase)