What is the difference between rough and smooth ER?

Question

Accepted Answer

Although the rough and smooth ER form part of the same organelle, there are several differences between the two.

Basis For Comparison
Rough ER
Smooth ER

Appearance
Has a rough membrane surface
Has a smooth membrane surface

Has ribosomes attached to the membrane surface
Yes
No

Structure
Formed mainly of cisternae and few tubules
Formed mainly of tubules and vesicles

Presence of pores
Possesses narrow pores below the ribosomes facilitating the passage of synthesized polypeptides into ER channels.
Pores are absent. Materials synthesized by SER do not pass into its channels.

Location
Often internal. Connected with nuclear envelope.
Often peripheral. May be connected with plasma lemma.

Presence of Ribophorins
Contains Ribophorins that facilitate the attachment to ribosomes.
Ribophorins are absent.

Has enzymes for detoxification
No
Yes

Functions
Protein synthesis, folding and sorting; formation of lysosomes
Synthesis of lipids, glycogen, and steroid hormones; storage and release of calcium ions

Occurrence
Found in abundance in cells involved in protein synthesis e.g. liver cells, plasma cells, pancreatic cells, and goblet cells
Found in abundance in cells involved in lipid metabolism e.g. adipose cells, muscle cells, retinal cells, interstitial cells, leucocytes, and glycogen storing cells of the liver

Basis For Comparison	Rough ER	Smooth ER
Appearance	Has a rough membrane surface	Has a smooth membrane surface
Has ribosomes attached to the membrane surface	Yes	No
Structure	Formed mainly of cisternae and few tubules	Formed mainly of tubules and vesicles
Presence of pores	Possesses narrow pores below the ribosomes facilitating the passage of synthesized polypeptides into ER channels.	Pores are absent. Materials synthesized by SER do not pass into its channels.
Location	Often internal. Connected with nuclear envelope.	Often peripheral. May be connected with plasma lemma.
Presence of Ribophorins	Contains Ribophorins that facilitate the attachment to ribosomes.	Ribophorins are absent.
Has enzymes for detoxification	No	Yes
Functions	Protein synthesis, folding and sorting; formation of lysosomes	Synthesis of lipids, glycogen, and steroid hormones; storage and release of calcium ions
Occurrence	Found in abundance in cells involved in protein synthesis e.g. liver cells, plasma cells, pancreatic cells, and goblet cells	Found in abundance in cells involved in lipid metabolism e.g. adipose cells, muscle cells, retinal cells, interstitial cells, leucocytes, and glycogen storing cells of the liver

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