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What is more abundant is smooth endoplasmic reticulum?
A. Cisternae & vesicles
B. Tubules
C. Tubules and vesicle
D. Cisternae

Answer
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Hint: Endoplasmic reticulum is present in two forms namely a type with ribosome-studded surface and another with a smooth surface and These are called the smooth endoplasmic reticulum, and the former is known as the rough endoplasmic reticulum. Vesicles are usually round or spherical structures, and are rich in pancreatic cells. Tubules are unusually branched tube-like structures that form a network along with other elements.

Complete answer: These membranes make continuous folds, eventually joining the outermost layer of the nuclear membrane. Except for sperm cells and red blood cells, the endoplasmic reticulum is observed in every other type of eukaryotic cell.
-Cisternae are smooth unbranched sac-like structures. They lie parallel to each other and they are inter-connected and enveloped with ribosomes.
-Vesicles which are usually round or spherical structures, are rich in pancreatic cells. When cells are disrupted at the time of cell fractionation, the ER comes to an end into small vesicles.
-Tubules are unusually branched tube-like structures that form a network along with other elements. They do not possess ribosomes on their surface.
-The endoplasmic reticulum in absence of ribosomes appears smooth and is called the smooth endoplasmic reticulum. It is composed mainly of tubules and vesicles.
So, the correct option is 'Tubules and vesicles', i.e., C.

Note: Some important points of smooth endoplasmic reticulum: does not have ribosomes, the smooth endoplasmic reticulum has a tubular form, responsible for the synthesis of essential lipids such as phospholipids, cholesterol, and the production and secretion of steroid hormones, it is also responsible for the metabolism of carbohydrates, it stores and releases calcium ions, these are quite important for the nervous system and muscular system.