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:
- 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. - Matrix:
A dense gel which contains
(a) DNA
(b) Ribosomes
(c) Enzymes
Role of Mitochondria:
- Performs Krebs Cycle (Aerobic Respiration)
- 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:
- Leucoplast- colourless plastids without pigments
(i) Amyloplast stores starch
(ii) Aleuroplast stores protein
(iii) Elaioplast stores oil - Chromoplast - coloured plastid containing carotenoid
- Chloroplast- coloured plastid containing chlorophyll
Structure of Chloroplast:
- Bilayered membrane
- Stroma:
(i) Granum (stack of THYLAKOIDS containing chlorophyll and xanthophyll)
(ii) Stroma Lamellae- connects the adjacent grana.
Role of Plastids:
- Leucoplasts stores food.
- Chromoplasts provide colour to fruits and flowers which help in pollination.
- 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:
- Sap Vacuoles
- Food Vacuoles
- Contractile Vacuoles
Role of Vacuoles:
- Store salts, sugar, amino acids, proteins and organic acids.
- Stores metabolic wastes for disposal
- Maintain water balance (Osmoregulation)
- Maintain turgidity and rigidity