the cytoplasm and cell organelles

12TH PHYSICS

the cytoplasm and the cell orgsnelles

the cytoplasm contains many cell organelles of which we should learn that

  1. those that trap and release the energy e.g. mitochondria and chloroplasts
  2. those that are secretory or involved in synthesis and transport e.g. golgi , ribosomes and endoplasmic reticulum
  3. the organelles for the motilty e.g. cilia and flagella
  4. the suicidal bags i.e. lysosomes
  5. the nucleus which controls all activities of the cell and carries the hereditary material
  6. mitochondria and chloroplast – the energy transformers
  7. mitochondria found in plant and animals cells are the enrgy releasers and the chloroplasts found in green plantsd are the energy trappers .
  8. mitochondria = singular mitochondrion
  9. appear as tiny like structurs under the microscope .approximately 0.5 – 1.00 micrometer
  10. number usually a few hundreds to a few  thousand per cell smallest number is just one in an alga micromonas .
  11. structure –

the general plan of the internal structure of a mitpochondrion observed by means of electron microscope figure .

  • well made up of double membrane
  • the inner membrane is folded to form projections called cristae hich project into the inner compartment called the matrix
  • function :
  • oxidises pyruvic acid breakdown product of glucose to release energy which gets stored in the form of ATP for ready use .this proces is also called cellular respiration .that is why mitochondria are called the powerhouse of the cell .
  • a highly simplified flow chart of the fate of the glucose to release energy is shown below ..
  • incytoplasm glucose enters cells containing 6 atoms of carbon —–> broken into two pyruvic acid molecules containing 3 atoms of carbon —–> in mitochondria Acetyl Co-A is oxidised into CO2 , H2O AND ATP .
  • PLASTIDS :
  • plastids are found only in a plant cell these may be colourless or coloured .based on this fact there are three types of plastids
  • leucoplast – white or colourless
  • chromoplast – blue , red, yellow etc .
  • chloroplast – green

CHLOROPLAST :

FOUND IN all green plant cells in the cytoplasm .

number 1 to 1008 how so definite .

shape : usually disc shaped or laminate in the mist plants around you in some ribbon shaped as in an alga spirogyra or cup shaped as in  another alga chlamydomonas .

structure :

figure

note the following parts

  • wall made uo of double membrane i.e. outer membrane and inner membrane numerous stack like piles , goups or grana singular granum are interconnected by lamellae .
  • sac like structures called thylkoids placed one above the other constitute a granum .
  • inside the chloroplast is filled with a fluid medium called stroma .
  • function: chloroplasts are the site of photosynthesis production of sugar , from carbon dioxide and water in the presence of sunlight .

CHLOROPLASTS VS MITOCHONDRIA

one trapp the solar energy looking it in complex molecule by photosynthesis .and the other release the energy by breaking the complex molecule by respiration .

similarities .

both contin their own DNA the gentic material as well as their own RNA for protein synthesis thus they can self rduplicate to produce more of their own kind without the help of nucleus .

thought the chloroplasts and mitochondria contain their own DNA the hereditary molecule and also their own ribosomes they are termed as semiautonomous only because they are incapable of independent existance outside the cytoplasm for a long time .since most of their proteins are synthesised with the help of the nuclear RNA .

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