Question

All of the following have membrane boundaries EXCEPT

A. coated vesicles

B. lysosomes

C. tonoplasts

D. microtubules

The cytoskeleton is defined by all of the following EXCEPT

A. microtubules

B. endoplasmic reticulum

C. intermediate filaments

D. microfilaments

Answer 1

Ans.1

The correct answer is (D) microtubules

Explanation:

Organelles are specialized structures that allow individual cells to complete their functions.Other than organelles,a cell is filled with thick fluid called cytoplasm,where all the internal organs float.Some of these organelles are filled with a fluid.A membrane bound organelles is the one which is surrounded by a plasma membrane,which separates their inside from the rest of the cytoplasm.In other words,the plasma membrane or the membrane boundary helps in creating a boundary between the objects in the cytoplasm.For example:

• Coated Vesicle - It is a vesicle that has a membrane coated with the protein clathrin and involved in the transportation of proteins from one site of the membrane to another.
• Lysosomes -It is a membrane bound organelle containing digestive enzymes and involved in numerous cell processes like breakdown of excess or worn out cells.
• tonoplasts - It is a membrane that surround the large vacuole in plant cells.

Now, non-membrane bound organelles are those that are not fluid filled and do not need to be separated from the other region of the cell.For example: Ribosomes and cytoskeleton.

Microtubule is a type of cytoskeletal fiber that has no membrane boundary.Its function is to provide support to the plasma membrane and give the cells its overall shape.

Ans.2:

The correct answer is (B) Endoplasmic reticulum

Explanation:

A cytoskeleton is a complex network of protein filaments,comprising of microtubules,microfilaments and intermediate filaments,that gives the cell its shape and helps them in the correct positioning of their organelles.Apart from this it provides a path for the transportation of vesicles and helps the cell in their movement.

Endoplasmic reticulum (ER) on the other hand is a separate organelle of a cell,that is made up of two subunits;rough ER and smooth ER.It is network of membranes called cisternae,which is held together by the cytoskeleton.