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about:blank Cell and Cell Division - Lecture notes 1 Cell and Cell Division Chapter 2 Lecture Outline Cell Cell membrane Nucleus: Nuclear Envelope, Nucleoplasm and Chromatin (DNA + Histones) Cytoplasm: Cytosol and Cell Organelles Cell Division Cell Cycle Mitosis: division of nucleus Cytokinesis: division of cytoplasm Cell Theory Abasic concepts of cell theory are: Cells are the units of structure (building blocks) ofall organisms Cells are the smallest unit of function in all organisms Cells originate only from pre-existing cells by cell division. All cells maintain homeostasis (internal conditions within limits) Cell Membrane Al cells are covered with a thin covering of a double layer of Phospholipids and associated Proteins present here and there. Each phospholipid has a polar (hydrophilic) head and non-polar (hydrophobic) tals. In the double layer the tails face each other forming a hydrophobic barrier which keeps water dissolved contents inside. Proteins may be Intrinsic — embedded in the lipid double layer and Extrinsic associated outside the lipid double layer. Cytoplasm Cytoplasm is the living fluid part between cell membrane and nucleus. It has special structures called Cell Organelles in it. Cytosol is the liquid part of cytoplasm formed of water having dissolved or suspended substances in it. Cell Organelles are organ like each performing specific function/s but formed of molecules and ‘membranes only (sub-cellular). Double Membrane bound Organelles: Mitochondria, Chloroplasts, Endoplasmic Reticulum, Golgi Body, and Nucleus. Single Membrane bound Organelles: Lysosomes, Peroxisomes, Vacuoles Onganelles lacking any membrane: Ribosomes, Centrioles, Nucleolus ‘Nucleus and Ribosomes 1 Genetic Control of the Cell ‘Nucleus: is the most distinct structure inside cell visible with light microscope. It has inside it DNA having all the information needed to form and run the cell. The segments of DNA are called Genes. Nuclear Envelope: is formed of 2 membranes with a gap between them. It has a lange number of Nuclear Pores usually bound by a nuclear complex. The pores are large enough to allow RNA and proteins to pass through. ‘Nucleoplasm: is the liquid part of nucleus and has a different composition than Cytosol. Chromatin fibers: are very long molecules of DNA associated with proteins (Histones and other nuclear proteins). Each chromatin fiber, at the time of cell division, organizes into Chromosomes. ‘Nucleolus: is present in the nucleus when the cell is not dividing, No membrane bounds it. It assembles both units of Ribosomes. 113. 
