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Class 9, Science, Chapter-5, Lecture-5, Cytoplasm (Notes)

CYTOPLASM:

The fluid content (protoplasmic mass) inside the plasma membrane including cell organelles but excluding nucleus of a cell is termed as cytoplasm.

Two parts:

  1. Cytosol - water + ions + enzymes + vitamins + amino acids + carbohydrates + lipids + proteins
  2. Cell organelles:
    Sub-microscopic structures present in the cytoplasm of a cell which perform specific cellular functions are called cell organelles.
    (a) Endoplasmic Reticulum (ER) -
    Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER)
    (b) Golgi apparatus
    (c) lysosome
    (d) Mitochondria (=)
    (e) Plastid (=)
    (f) Vacuole

ENDOPLASMIC RETICULUM (ER):

A complex network consisting of membrane-bound tubes (tubules) , sheets (cisternae) and vesicles present in the cytoplasm of an eukaryotic cell is termed as Endoplasmic Reticulum.

Two types:

  1. Rough endoplasmic Reticulum (RER)
  2. Smooth endoplasmic Reticulum (SER)

Role of ER:

  1. Helps in transport of materials.
  2. Provides surface for biochemical activities.
  3. SER helps in synthesis of lipids.
  4. SER helps in detoxification of the cell from poisons and drugs.
  5. RER helps in the transport of protein synthesised by the ribosomes.

Differences Between:

Feature

RER

SER

Structure

Ribosomes are present on the surface

Ribosomes are not present on the surface.

Function

Helps in the transport of protein synthesised by the ribosomes

(i) helps in synthesis of lipids (fats)
(ii) helps in detoxification of the cell from poisons and drugs.

GOLGI APPARATUS:

A cell organelle consisting of membrane-bound cisternae arranged parallel to each other and associated vesicles which stores, modifies, packages and dispatches various chemicals in the cell is called Golgi apparatus or Golgi complex.

Two Parts:

  1. Cis (proximal): the formative convex face of cisterna which is closer to the nucleus.
  2. Trans (distal): the mature concave face of cisterna which is away from the nucleus.

Role of Golgi Apparatus:

  1. Storage of various chemicals.
  2. Modification and packaging of chemicals for their secretion (dispatch).
  3. Formation of complex sugar from simple sugar.
  4. Formation of lysosomes (Packing of digestive enzymes in lysosomes).
  • Golgi apparatus is NOT found in bacteria, blue-green algae, sperms, RBC
  • Golgi apparatus is called DICTYOSOME in plant cells

LYSOSOMES:

Small spherical membrane-bound sacs present in the cytoplasm which contain digestive enzymes are called lysosomes.

Role of Lysosomes:

  1. Protects from foreign particles by destroying them.
  2. Helps in the intra-cellular digestion of food particles (AUTOLYSIS).
  3. Removes dead organelles from the cell.
  4. Destroys the cell in which it is present, when the cell does not function properly.
  • Lysosomes are NOT found in RBC and Plant cells.

Lysosomes are called ‘digestive bags’:
Reason: Lysosomes contain powerful digestive enzymes capable of breaking down all organic compounds.
Lysosomes fuse with the food particles and break them into simpler compounds and thus digest the food.

Lysosomes are called ‘suicide bags:
Reason: Lysosomes contain powerful digestive enzymes capable of breaking down all organic compounds.
Lysosomes burst and release the enzymes to digest the organelles when the cell does not function properly and thus kill the cell. 

Lysosomes are called ‘demolition squad:
Reason: Lysosomes contain powerful digestive enzymes capable of breaking down all organic compounds.
Lysosomes fuse with the dead and worn out cell organelles and break them into simpler compounds and thus clean the cell.

Lysosomes are called ‘cellular scavengers:
Reason: Lysosomes contain powerful digestive enzymes capable of breaking down all organic compounds.
Lysosomes fuse with the dead and worn out cell organelles and break them into simpler compounds and thus clean the cell.