Endoplasmic Reticulum

Question 1

What is an Endomembrane System?

Answer 1

The interior of a Eukaryotic cell is made up of many membrane bound organelles that function in a coordinated manner and make up an Endomembrane System.

Question 2

What are the constituents of an Endomembrane system? Why are Mitochondria, Choloroplasts and Peroxisomes not involved in the above system?

Answer 2

• It consists of Endoplasmic Reticulum, Golgi Complex, Lysosomes and Vacuoles.
• Mitochondria, Chloroplasts and Peroxisomes are not coordinated with the above mentioned organelles and thus are not apart of the system.

Question 3

What is Endoplasmic Reticulum?
Where are they found?

Answer 3

When studied using an electron microscope, eukaryotic cells show a network of tiny, tubular structures found scattered in the cytoplasm.

Question 4

What is the Endoplasmic Reticulum composed of?

Answer 4

It is composed of 3 kinds of structures-
(a) Cisternae
(b) Tubules
(c) Vesicles

Question 5

What are Cisternae in the E.R? What is their structure and function?

Answer 5

• They are long, flattened, parallel, sac like interconnected structures.
• These are found in cells which have synthetic roles. (eg.: cells of pancreas and brain)
• They are usually associated with large subunit (60S) of ribosomes.

Question 6

What are Tubules in the E.R? What is their structure and function?

Answer 6

• They are either branched or unbranched structures forming the reticular system along with cisternae and vesicles.
• They are free of ribosomes and are common in cells involved in lipid and sterol synthesis.

Question 7

What are Vesicles in the E.R? What is their structure and function?

Answer 7

• They are oval, membrane bound and vacuolar structures.
• They are free of ribosomes.
• They are abundant in pancreatic cells and the only ER structures found in spermatocytes.

Question 8

The ER divides the intracellular space into two distinct compartments.

Answer 8

1. Luminal Compartment: the internal space enclosed by ER membrane.
2. Extra Luminal Compartment: the external space, outside the ER, in the cytoplasm.

Question 9

There are 2 types of ER on the basis of presence of ribosomes on the surface of ER.

Answer 9

1. Smooth Endoplasmic Reticulum (SER)
2. Rough Endoplasmic Reticulum (RER)

Question 10

What is SER? What is Sarcoplasmic Reticulum?

Answer 10

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