Structure and function are correctable in living organisms. Can you justify this by taking plasma membrane as an example?
In living organisms, the structure and function of the cell organelle are correlated. E.g., every living cell is covered by a thin, elastic, transparent, semi-permeable and regenerative membrane called plasma membrane. It is made up of lipids, proteins and carbohydrates. The cell membrane is composed of lipid which forms a bilayer with protein molecules embedded in it at places and carbohydrates. The lipid molecules are amphipathic in nature and have polar hydrophilic head and nonpolar hydrophobic tail. Depending upon the ease of extraction, the ratio of protein and lipid varies considerably in different cell types.
According to fluid mosaic model, the lipid bilayer and integral proteins appear like a mosaic arrangement and the quasi-fluid ‘nature of lipid enables the lateral movement of the proteins within the overall bilayer.
This ability of proteins to move within the membrane indicate the fluidity of the lipid part. The fluid nature of the membrane is important for interactions of molecules within the membrane as well as other functions like formation of intercellular junctions, cell growth, secretion, endocytosis, cell division, etc. It is a selectively permeable or semi- permeable membrane, allows only selected substances to pass inwardly. Membranes have carrier proteins for active transport. Cell membrane contain enzymes which perform certain reaction on their surface, e.g., ATPase, phosphatase, etc.
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).