Table

Structure and Function of Cell Organelles

OrganelleStructureFunction
Cell WallFound in plant cells only; mainly made up of cellulose and hemicellulose, chitin (fungus), protein (bacteria).
  • It provides shape, strength and rigidity to the cells.
  • Cell protectio.
  • Transport of various substances.
  • Helps in cell expansion.
NucleusContains DNA and protein; limited by a nuclear membrane in eukaryotic cells, nuclear membrane not found in prokaryotic cells, contains nucleolus; nucleoplasm contains chromatin material.
  • Division of the cell.
  • Inheritance of characters.
  • Controls various metabolic activities of the cell.
MitochondriaDouble membraneous, outer and inner membrane folded inside forming cristae; the inner surface of the inner membrane has a number of F1or elementary particles.
  • Site of celluar respiration (Krebs cycle and electron transport chain); associated with the release of energy by the oxidation of food (oxidative phosphorylation).
PlastidsDouble membraneous structure, inner membrane in the form of thylakoids forming stroma and grana. They are of three types:

  1. Chloroplasts contain chlorophyll.
  2. Chromoplasts contain pigments other than chlorophyll.
  3. Leucoplasts do not contain any pigment.
  • Site of photosynthesis in green plants i.e., kitchen of a plant cell.
  • Release of energy in the process of photosynthesis (photo-phosphorylation).
  • Provide different colours to flowers and fruits.
  • Store the food of the plant body.
Endoplasmic

  • reticulum
Membrane folds forming cisternae, vesicles and tubules; of two types SER (without ribosomes) and RER (with ribosomes).
  • Providers surface for various chemical reactions and the transport of substances within the cell.
Golgi ComplexStacks of membranes in the form of cisternae, vacuoles and vesicles; in plant cells known as dictyosomes.
  • Secretion, hence excretion. Absorption and transport of various susbtances within the cell.
LysosomesSingle membrane sacs containing hydrolytic enzymes; classified as primary lysosomes, secondary lysosomes, autophagic vacuoles and residual bodies depending upon the physiological state of their action.
  • Digestion of own cell organelles during starvation or of ageing cell hence called ‘suicidal bags of a cell’.
Microbodies

  • Peroxisomes
  • Spherosomes
  • Glyoxysomes
Small-sized organelles containing enzymes like catalyses and oxidases. Small spherical bodies having high deposits of fats and lipids; enzymes like acid phosphates are found. Small bodies found in the seeds of groundnut and castor (that contain fatty acids).
  • Photorespiration in plant cells and lipid metabolism in animal cells. Exact function not known. Show some lytic activity.
  • During germination converts fatty acids to soluble carbohydrates-glyoxylate cycle.
RibosomesSmall bodies containing RNA and proteins; a group of ribosomes attached to a mRNA strand forms polyribosomes.
  • Site of protein synthesis, protein factories of a cell.
CentrioleTwo dot-like bodies present near the nucleus; shows 9+0 pattern of arrangement of milcrotubules.
  • Forms spindle-fibres at the timw of cell division.
  • Involved in the formation of cilia and flagella of the cell. Involved in the formation of cilia and flagella of the cell.
  • Helps in the formation of sperms from spermatids.
Cilia and FlagellaSurrounded by a membraneous covering; shows 9+2 pattern of arrangement of microtubules.
  • Locomotion in unicellular organisms.
Microtubules and MicrofilamentsLong, unbranched cylindrical tubes made up of proteins like tubulin and actin; forms net-work in the cytoplasm of the cell.Transport of substances in higher organisms.

  • Maintenance of cell and chromosome movements.
  • Contraction and relaxation of muscles.
VacuolesUnit membraneous bags filled with cell-fluids; membrane is known as tonoplast.
  • Contain various materials.
  • Osmo-regulatory in function.
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