31FACTS
HGH
YIELD
Class XI
Analysis of various PMTs from 2012-201620122013201420152016AIPMT/NEET63448AIIMS12AMU4243Kerala323K-CET131J & K14Cell : The Unit of Life - II
• We have already discussed the general organisation of prokaryotic and eukaryotic cells
along with the endomembrane system in previous issue. In continuation to that remaining
cell organelles are discussed here.
• Cytoplasm contains a variety of organelles. Mitochondria, plastids and peroxisomes
are not considered as a part of endomembrane system because their function is not
coordinated with the organelles of endomembrane system.
MITOCHONDRIA
• They were first observed by Kolliker in 1880 while the name “mitochondrium”, was
given by Benda (1897).
• Mitochondria are organelle of aerobic eukaryotes and are absent in prokaryotes and
mature RBCs.
• They are called power house of cell because they help in cellular respiration and
energy generation.
Structure
• Mitochondria are cylindrical, double membranous structure having length of about 1.0
- 4.1 μm and a diameter of 0.2 - 1.0 μm.
• The outer membrane is smooth and permeable to many metabolites due to presence
of protein channels called porins.
• The inner membrane is folded into finger like projections called cristae.
• Inner membrane and cristae possess mushroom-like projections called elementary
particles or oxysomes (F 0 - F 1 particles).
• These particles are related to ATP synthesis during oxidative phosphorylation.
• Mitochondrial matrix contains ribosomes (55S to 70S type), double stranded circular
DNA (mDNA or mt DNA), RNA and enzymes of Krebs cycle.
• Mitochondria are semi-autonomous in nature as they have their own DNA
which can replicate independently and produce its own mRNA, tRNA and rRNA to
syntheise some of their proteins. New mitochondria are produced by pre-existing
mitochondria.