Anas Zoology

Nucleus: Nucleus is a membrane enclosed organelle that contains the chromosome. It is present inside the cell. The study of nuclei of cells is known as Karyology. Nucleus is present in all cells except mature RBC's and sieve cells of xylem. The shape of nucleus varies. It can be oval, disc shaped, lobular, irregular etc In prokaryotes the nucleus is not covered by well defined membranes. In prokaryotes it is called as prokaryon/genophore/nucleoid. Normally a cell contains one nucleus but their number varies in certain cells e.g. binucleate liver cells and cartilage, polynucleate in osteoblast and skeletal muscles etc. Nucleus is made up of four parts: Nuclear Membrane Nucleoplasm/Karyoplasm Chromatin Network Nucleolus Different parts of Nucleus 1) Nuclear Membrane: It is a perforated double membrane. The pores have pore complex to regulate the size of pore. It seems to separate the contents of nucleus from cytoplasm. The nuclear membrane is made up of phospholipid bilayer. 2) Nucl...

The specialized structures seen inside the living cells are called cell organelles. Different cell organelles present inside a cell are: Nucleus Ribosomes Endoplasmic Reticulum (Smooth and Rough) Cytoskeleton Golgi complex/apparatus Mitochondria Lysosomes Centriole Vacuoles

What are Lipids? A lipid is a class of organic compound which is a fatty acid or its derivative. They are insoluble in water but soluble in organic solvent. Major lipids in cell membrane are: Phospholipids  Cholesterol 1) Phospholipids: The lipid substances containing phosphorous and fatty acids are called phospholipids. There are different types of phospholipids present in cell membrane, they are as follows: Aminophospholipids Phosphatidylinositol Sphingomyelin Phosphatidylserine Phosphatidylcholine Phosphatidylglycerol Phosphatidylethanolamine The phospholipid molecules are arranged in two layers in cell membrane. A phospholipid molecule consist of two parts: head portion and tail portion. The head portion is made up of phosphate group and a glycerol atom and tail portion is made up of two fatty acid chains. Head portion is polar and hydrophilic (Strong affinity for water). The tail portion is non polar and hydrophobic (repelled by water/water fearing). Structure of Phospholipid ...