What structural and functional attributes must a cell have to be called a living cell?
Both prokaryotic and eukaryotic organisms are made up of the cell. Cell is the structural and fundamental unit of all living organisms. The main structural attributes of a cell are:-
(i) Cell membrane – Every living cell is . covered by a thin, elastic, transparent, semi-permeable and regenerative membrane called cell membrane or plasma membrane. It is made up of lipids, proteins and carbohydrates. It separates the interna] environment of the cell from external environment and helps in regulating the entry and exit of molecules into and out of the cell.
(ii)Genome – In prokaryotes the genetic material is not bounded by a definite nuclear membrane. It is called nucleoid or genophore. It consists of single membrane circular strand of DNA duplex embedded freely in the cytoplasm, with evolution, eukaryotes developed.
In eukaryotes, nucleus is bounded with well defined nuclear envelope. Nucleus contains nuclear envelope, nucleoplasm, nucleolus and chromatin. It contains all the genetic information for controlling all essential processes related to metabolism and transmission.
In prokaryotes, there are no well defined organelles but with evolution, in eukaryotes well defined membrane bound organelles developed e.g., mitochondria, plastids, ER.
Functional attributes of the cell are growth, cell division, response to stimuli. These functional attributes are found in every cell.
Give the biochemical composition of plasma membrane. How are lipid molecules arranged in the membrane?
The genomic content of the nucleus is constant for a given species where as the extra chromosomal DNA is found to be variable among the members of a population. Explain.
Are the different types of plastids interchangable? If yes, give examples where they are getting converted from one type to another.
Structure and function are correctable in living organisms. Can you justify this by taking plasma membrane as an example?
Are the different types of plastids interchangable? If yes, give examples where they are getting converted from one type to another.
Is there a species specific or region specific type of plastids? Flow does one distinguish one from the other?
Discuss briefly the role of nucleolus in the cells actively involved in protein synthesis.
Write the functions of the following
(a) Centromere (b) Cell wall
(c) Smooth ER (d) Golgi apparatus
(e) Centrioles
Is extra genomic DNA present in prokaryotes and eukaryotes? If yes, indicate their location in both the types of organisms.
Eukaryotic cells have organelles which may
(a) not be bound by a membrane
(b) bound by a single membrane
(c) bound by a double membrane
Group the various sub-cellular organelles into these three categories.
Briefly give the contributions of the following scientists in formulating the cell theory.
(a) Rudolf Virchow
(b) Schleiden and Schwann
Differentiate between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER).