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Class 9, Science, Chapter-5, Lecture-6, Mitochondria (Notes)

MITOCHONDRIA: 

A rod shaped cell organelle consisting of bi-layered membrane found in aerobic eukaryotes which releases ATP by the process of oxidation is termed as mitochondria. 

Two parts:

  1. Limiting Membrane: 
    A bi-layered membrane which consist of
    (a) Outer membrane - smooth and porous
    (b) Inner membrane - folded to form cristae (mitochondrial crests) with partially embedded oxysomes.
  2. Matrix: 
    A dense gel which contains 
    (a) DNA 
    (b) Ribosomes
    (c) Enzymes

Role of Mitochondria: 

  1. Performs Krebs Cycle (Aerobic Respiration)
  2. Releases ATP molecules which store energy.

PLASTIDS:

A cell organelle found only in plant cells which synthesis or store organic substances is termed as plastid.

Three types:

  1. Leucoplast- colourless plastids without pigments 
    (i) Amyloplast stores starch 
    (ii) Aleuroplast stores protein 
    (iii) Elaioplast stores oil
  2. Chromoplast - coloured plastid containing carotenoid
  3. Chloroplast- coloured plastid containing chlorophyll

Structure of Chloroplast:

  1. Bilayered membrane
  2. Stroma:
    (i) Granum (stack of THYLAKOIDS containing chlorophyll and xanthophyll) 
    (ii) Stroma Lamellae- connects the adjacent grana.

Role of Plastids: 

  1.  Leucoplasts stores food. 
  2. Chromoplasts provide colour to fruits and flowers which help in pollination. 
  3.  Chloroplasts synthesise food by photosynthesis. 
     
  • Plastids are absent in animal cells

VACUOLES:

Single-membrane-bound spaces filled with non-living solid or liquid contents are called vacuoles.

Three types:

  1. Sap Vacuoles
  2. Food Vacuoles
  3. Contractile Vacuoles

Role of Vacuoles:

  1. Store salts, sugar, amino acids, proteins and organic acids.
  2. Stores metabolic wastes for disposal
  3. Maintain water balance (Osmoregulation)
  4. Maintain turgidity and rigidity