Chloroplasts, Biology

CHLOROPLASTS

  • Schimper (1883) coined the term chloroplastid for green plastids.
  • Mayer called them Autoplast. Chloroplast name proposed by Erera.
  • Green plastids with chlorophylls and other photosynthetic pigments.
  • Shape of chloroplasts vary in different plants.

Discoidal or oval    -           Higher plants

Girdle shaped        -           Ulothrix

Cup shaped           -           Chlamydomonas

Reticulate              -           Oedogonium

Spiral    -                             Spirogyra

Stellate                  -           Zygnema

  • Largest cell organelle in plants and second largest structure in plant.
  • Double unit membranous cell organelles.
  • Each chloroplast has two parts -

(i) Grana - Made up of Granum lamellae arranged in the form of stacks of coins. Each granum lamella is surrounded by well-defined membrane called Thylakoid (Thylakoid discovered by Menke). Each granum lamella, granular structures called Quantasomes are present. Quantasomes are photosynthetic units. (Quantasomes discovered by Park, Pon and Biggins) Each qunatasome has 230 chlorophyll molecules. Each chlorophyll molecule has two parts - head and tail. Head part is responsible for green colour which is controlled by Mg++. Due to presence of chlorophyll in granum lamellae, the light reaction of photosynthesis takes place in the granum. Lamellae which connects grana are called stroma thylakoids or fret channels (Weier 1966).

1863_chloroplast.png

(ii) Stroma - The non pigmented enzymatic part of chloroplast is called stroma. It is present in form of matrix. Due to presence of enzymes in stroma, dark reactions of photosynthesis take place here. Stroma contains osmophilic droplets called Plastoglobuli. These store lipids. Stoma of chloroplast contains proteins, phospholipids, nucleic acids, ribosome and fewer amounts of enzymes. Ris and Plaut, Ruthe sager discovered DNA in chloroplast, which is called ctDNA or plastidial DNA. Genetic system of chloroplast is called Plastidome. Due to presence of DNA, RNA and ribosomes chloroplast is called semiautonomous unit like mitochondria having a complete protein synthesis apparatus in stroma.

Posted Date: 10/5/2012 7:31:35 AM | Location : United States







Related Discussions:- Chloroplasts, Assignment Help, Ask Question on Chloroplasts, Get Answer, Expert's Help, Chloroplasts Discussions

Write discussion on Chloroplasts
Your posts are moderated
Related Questions

Define Sex as a determinants of nutrient requirements? There are some differences in requirements between the two sexes. However, except for iron, these are apparent rather tha

Explain Pro-Oxidants Transition metals, particularly those possessing two or more valency states and a suitable oxidation - reduction potential between them (e.g., cobalt, cop

Autogamy - Patterns of Sexual Reproduction It is known to take place in many ciliate protozoans including Paramecium. Autogamy involves same nuclear behavior like in conjugati

Explain the Biochemical Approach in Taxonomy Comparative biochemistry is being used increasingly in the systematic of animals, both for identification of organisms as well as f

Define Equilibrium Conditions in Multicomponent Systems? This chapter applies equilibrium theory to a variety of chemical systems of more than one component. Two different appr

What are the similarities between chlorplasts and prokaryotic cells?

What is A biologic Failure A biologic Failure can be defined as the inadequacy of the host to establish or to maintain osseointegration. The inability to establish osseoint

How plants use the pattern of changes in day/night length to solve the paradox that day length is equal twice a year. Plants possess the ability to balance the daily changes in

Menstrual cycle in human beings: 1) The cycle of changes in the female reproductive system that leads to formation of Ovum is called 'menstrual cycle'. It occurs once in 28 to