Cell : The Unit of Life

Mitochondria, Plastids, Ribosomes,Cytoskeleton

  • Mitocondria is also called as powerhouse of the cell as they produce 95% of ATP.
  • It is considered as semi - autonomous organelle because it has separate protein syntheeizing machinery (ribosomes & proteins) independent of nuclear control.
  • It was first observed in striated muscles of insects as granules by kolliker (1880), he called them as "sarcosomes".
  • Each mitocondria is a double membrane-bound structure. The inner compartment is called as matrix. The inner membrane forms a number of infoldings called the cristae (singular crista) towards the matrix. (Crista increases the surface area).
  • Oxysomes have ATPase enzyme molecules. so it is responsible for ATP synthesis. These are the functional unit of mitocondria. These elementary particles are also called F0 − F1 particles.
  • Intermediate products of cell respiration are used in the formation of steroids, cytochromes, chlorophyll etc.
  • Mitocondria contain electron transport system. The second step of cellular respiration (energy formation) takes place in mitocondria
  • Plastids are semi-autonomous organelle having DNA, RNA, ribosomes and double membrane envelope. These are largest cell organelles in plant cell.
  • Haeckel (1865) discovered plastid, but the term first used by schimper (1883).
  • Plastids of three types namely Leucoplasts, chromoplasts, and chloroplast.
  • Leucoplasts are colourless plastids.
    Eg:- Amyloplast - synthesize & store starch grain
    Elaioplast (lipidoplast, oleoplast) - store lipids & oils.
    Aleuroplast (proteinoplast) - store proteins.
  • Chromoplast are coloured plastids other than green. They are in red, orange, yellow etc colours are due to the presence of carotenoid they are present in petals & fruits.
  • Chloroplast are double membrane bound organelle and green coloured plastids due to the presence of chlorophyll.
  • They have various shape.
    Cup shaped → Eg :- Chlamydomonas sp.
    Stellate shaped → Eg :- Zygonema.
    Collar (or) gridle → ulothrix.
    Spiral (or) ribbon → Spirogyra
    Reticulate / net → oedogonium
    Discoid → Voucheria
    Spherical → Chlorella
    Biconvex/ovoid → Angiosperm.
  • Chlorophyll a, b, c, d are types of the pigment.
    Chlorophyll a : C55 H72 O5 N4 Mg (with methyl group).
    Chlorophyll b : C55 H70 O6 N4 Mg (with aldehyde group)
    Chlorophyll c : C35 H32 O5 N4 Mg
    Chlorophyll d : C54 H70 O6 N4 Mg
  • Ribosomes are smallest known organelle without membrane. They are known as organelle within organelle. (because it is also present in ER).
  • Types of ribosomes are are 70s and 80s. 70s is present in prokaryotes, mitocondria and plastids of eukaryotes. 80s ribosomes are found in cytoplasm of eukaryotes.
  • Levine and good enough (1874) observed 77s ribosomes in fungal mitocondria, 60s libosome in animal mitocondria and 55s in mammalian mitocondria.
  • Ribosomes are also called as protein factories of the cell enzyme peptidyl transferase occurs in large subunit of ribosome which helps in protein synthesis.
  • Cytoskeleton are framework of fibrous elements became necessary to support the extensive system of membranes. They are of three types namely microtubules, microfilament and intermediate filament.
  • Microfilaments are present in the microvilli, misele fibre (called myofilament) etc. But these are absent in prokaryotes. They are mainly formed of actin (contractile protein).
  • Microfilaments forms a part of cytoskeleton and change the cell shape, motility and division during development.
  • Microtubules are electron microscopic structure found only in the eukaryotic cellular structure like cilia, filagella, centriole basal body, astral fibres, spindle fibres. They are formed of tubulin protein.
  • Microtubules of asters and spindle fibres of the mitotic apparatus helps in movement of chromosomes towards the opposite poles in cell division
  • Intermediate filaments are supportive elements in the cytoplasm of the eukaryotic cells but they are absent in RBC (mammeals) IFs are larger then the microfilaments. (~ 10nm thick)
  • If provide support to myofibrils which is essential for their contraction.

View this video for the topics Mitochondria, Plastids & Ribosomes from 18:18 to 53:23

View this video for the topic Cytoskeleton from 0:13 to 6:45

Disclaimer: Compete.etutor.co may from time to time provide links to third party Internet sites under their respective fair use policy and it may from time to time provide materials from such third parties on this website. These third party sites and any third party materials are provided for viewers convenience and for non-commercial educational purpose only. Compete does not operate or control in any respect any information, products or services available on these third party sites. Compete.etutor.co makes no representations whatsoever concerning the content of these sites and the fact that compete.etutor.co has provided a link to such sites is NOT an endorsement, authorization, sponsorship, or affiliation by compete.etutor.co with respect to such sites, its services, the products displayed, its owners, or its providers.