11. Nucleus
Most cells have a nucleus. Some have more than one. The nucleus is called the “brain” of the cell, as it contains genetic code that drives all reactions and process in the body. It is also the starting point of protein syntheses. Within the nucleus are the cells hereditary units called Genes. Genes are arranged along Chromosomes (equines have 64, 32 from each parent) Each chromosome is a long molecule of DNA coiled with proteins and some RNA called a Chromatin (beads-on-a-string structure) Each bead is a Nucleosome consisting of double-stranded DNA wrapped twice around a core of 8 proteins called Histones. String between the bead is called the Linker DNA holding adjacent nucleosomes together. Coiling of nucleosomes in larger diameter loops is Chromatin Fiber. Total genetic information is called the Genome
Nucleus Structure : i) Nuclear envelope : phospholipid bilayer surrounding the nucleus ii) Nuclear pores : in the nuclear envelope surrounded by proteins. That allow substances to pass through iii) Nucleolus : cluster of DNA, RNA, and proteins within the nucleus iv) Chromatin : complex bundle of strands of DNA and RNA wrapped around a protein (in the nucleus) v) Chromatid : strand of DNA that has been concentrated in order to prepare for cell division.
TRANSPORT
For the cells to perform their functions, they must be able to receive materials from the blood stream and the interstitial fluid, as well as to get rid of waste products and deliver materials to these other fluid compartments. Depending on the material being transported, different methods are used. They are categorized broadly as those that do not require energy (passive transport) and those that need energy (active transport) and those needing to be transported within another structure (vesicle transport).
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