14 Nov 2020 9:04 am
Chapter 5: Cell Structure and Organization.
B: Endoplasmic Reticulum
C: Golgi complex
Functions of Mitochondria:
i. Shape of the mitochondria may be oval or spherical or like a spiral strip.
ii. It is a double membrane-bound organelle.
iii. Outer membrane is permeable to various metabolites due to the presence of a protein-Porin or Parson’s particles.
iv. The inner membrane is selectively permeable to a few substances only.
v. Both membranes are separated by intermembrane space.
vi. The inner membrane shows several finger-like or plate-like folds called as cristae which bears numerous particle oxysomes and cytochromes/electron carriers.
vii. Inner membrane encloses a cavity called the inner chamber, containing a fluid-matrix.
viii. Matrix contains few coils of circular DNA, RNA, 70S types of ribosomes, lipids, and various enzymes of Krebs’ cycle and other pathways.
Functions of Endoplasmic Reticulum:
i. Smooth endoplasmic reticulum (SER):
a. Depending on cell type, it helps in synthesis of lipids for e.g. Steroid secreting cells of cortical region of adrenal gland, testes and ovaries.
b. Smooth endoplasmic reticulum plays a role in detoxification in the liver and storage of calcium ions (muscle cells).
ii. Rough Endoplasmic Reticulum (RER):
a. Rough ER is primarily involved in protein synthesis. For e.g. Pancreatic cells synthesize the protein insulin in the ER.
b. These proteins are secreted by ribosomes attached to rough ER and are called secretory proteins. These proteins get wrapped in a membrane that buds off from the transitional region of ER. Such membrane-bound proteins depart from ER as transport vesicles.
c. Rough ER is also involved in the formation of membrane for the cell. The ER membrane grows in place by the addition of membrane proteins and phospholipids to its own membrane. Portions of this expanded membrane are transferred to other components of the endomembrane system.