Cell structure and function class 8 notes
Answers
Answer:
Cell Organelle Occurrence/ Characteristic & Structure Function
Cell Membrane/ Plasma Membrane • Present in both plant cell and animal cell.
• Selectively Permeable: Allows the materials in and out of the cell according to the requirement of the cell.
• Made up of lipid layer and protein (Fluid Mosaic Model)
• Encloses the contents of the cell.
• Provides shape: animal cell.
• Allows transport: by Diffusion and Osmosis.
Cell Wall • Present only in a plant cell.
• Hard and rigid.
• Fully permeable.
• Made up of Cellulose in plant and peptidoglycan in bacteria. • Protection
• Gives shape and turgidity.
Cytoplasm • Contains 80-90% water and many organic and inorganic compounds.
• Colloidal, Viscous, Jelly like fluid inside the cell. • Contains enzymes responsible for all the metabolic activity taking place inside the cell.
Nucleus
(Director/ Brain of the Cell)
• Covered by a double membranous nuclear membrane in a Eukaryotic Cell.
• Contains DNA, RNA, Protein, nucleolus, and Chromatin network.
• Controls the activity of the cell.
• Starts cell division.
• It has the chromosomes or DNA which controls the hereditary characters
Mitochondria (The Power House of The Cell / Storage Batteries) • Double membranous structure.
• Autonomous body as contains its own DNA.
• Self-duplicates
• The main seat of respiration.
• Stores energy in the form of ATP molecules.
Golgi Bodies
(Shipping Department of Cell) • Discovered by Camillo Golgi in 1898.
• Originates from RER.
• Contains Sac like Cisternae and Vesicles.
• Has two faces – cis face or receiving face and trans face or supplying face.
• Modification, Packaging, and transport of materials
• Synthesis of lysosomes, plasma membrane
Endoplasmic Reticulum
(Framework of Cell) • A network of membranes.
• RER bears ribosomes and appears rough
• SER does not have ribosomes • Forms the skeletal framework of the cell.
• Transport of materials from one cell to other.
• Provides a surface for the synthesis of material – Proteins in RER and Lipids in SER.
• Formation of lysosomes, Golgi bodies and vacuoles
• Membrane Biogenesis
• Detoxification of harmful substances in the liver.
Vacuole • Arise from ER and GB
• Surrounded by tonoplast and filled with cell sap
• Store cell sap which may be liquid or solid food, toxic byproduct.
• Provide rigidity and turgidity to plant cell
Lysosomes (Suicidal bags of Cell, natural scavenger, cellular housekeeper) • Membrane-bound organelles
• Present in all animal cells and few plant cells
• Tiny circular single membrane-bound structures filled with digestive enzymes • Intracellular digestion of food in unicellular organisms.
Ribosomes (Protein Factories) • Without a membrane
• Consist of two subunits – 60S and 40S in eukaryote both made up of RNA
• Synthesis of Proteins
Plastids • Double membrane-bound
Types-
1. Leucoplast –Colourless plastid;
2. Chromoplast –Coloured Plastid – blue, red, yellow
3. Chloroplast – Green plastid
• Autonomous self-duplicating body • Chloroplast – Perform Photosynthesis – Helps in the release of oxygen
• Chromoplast – impart colour to flowers which help in pollination
• Leucoplast – Storage
• Amyloplast –Store starch
• Aleuroplast – Store Protein
• Elaioplast – Store fat
Chloroplast are present in green parts of the plant like leaves, the stem of cactus, raw mango fruit etc
• Chromoplast are present in colourful parts of the plant like flowers, fruits etc
• Leucoplast is present in parts not exposed to sunlight like roots, potato etc.
a. Transporting channels of the cell—— Endoplasmic Reticulum
b. Powerhouse of the cell—— Mitochondria
c. Packaging and dispatching unit of the cell—— Golgi Body
d. Digestive bag of the cell—— Lysosomes
e. Storage sacs of the cell—— Vacuole
f. Kitchen of the cell—— Chloroplast
g. Control room of the cell—— Nucleus
Explanation: