Botany for Pre-Medicine Students PDF

Botany for Pre- Medicine students. Dr: M. A. Al-Ryani..ales ‫ تنتهي الرتبة بمقﻄﻊ‬Order ‫ كل فصيلة تندرج تحت رتبة‬.opsida ‫ تنتهي بمقﻄﻊ‬Class ‫ كل رتبة تندرج تحت طائفة‬.phyta ‫ التي تنتهي بالمقﻄﻊ‬Division ‫ كل الرتب تنظم تحت أقسامها‬...

Botany for Pre- Medicine students. Dr: M. A. Al-Ryani..ales ‫ تنتهي الرتبة بمقﻄﻊ‬Order ‫ كل فصيلة تندرج تحت رتبة‬.opsida ‫ تنتهي بمقﻄﻊ‬Class ‫ كل رتبة تندرج تحت طائفة‬.phyta ‫ التي تنتهي بالمقﻄﻊ‬Division ‫ كل الرتب تنظم تحت أقسامها‬ Cell Theory: The term cell is derived from the Latin ‘cella’ means storeroom or chamber. The term cell was first used by the English botanist Robert Hooke in 1665, to describe the individual units of the honeycomb-like structure in cork under compound microscope. Cell Theory, which recognizes the cell as the basic unit of life. The Cell Theory further states that all organisms are composed of cells and all cells arise from preexisting cells. This theory is one of the major principles in biology. However the biggest division is between the cell of the prokaryotic Kingdom (Bacteria) and those of the other (Animals, Plants, Fungi, and protista), which are all eukaryotic cells. Procaryotic cells are smaller and simpler than eukaryotic cells, and not have a true nucleus. Summary of the Differences Between Pro and Eu-karyotic cells; Prokaryotic cells Eukaryotic cells Small cells less than( 10μm) Always unicellular. Often multicellar Without nucleus and any membrane-bound Always have and other membrane-bound organelles, such as mitochondria organelles DNA is circular, without protein DNA is linear and associated with proteins to form chromatin. Ribosomes are small(70S) Ribosomes are large(80S) No cytoskeleton Always has cytoskeleton. Motility by rigid rotating flagellum made of By flexible waving cilia or flagellae made flagellin. of tubulin. Cell division by binary fission By mitosis or meiosis. Reproduction is always by asexual. Asexual or sexual. 10 Botany for Pre- Medicine students. Dr: M. A. Al-Ryani. Prokaryotic Cells;  Cytoplasm; contains all enzymes needed for all metabolic reaction, since there are no organelles.  Ribosomes; smaller (70S) type(measured in Svedberg units): their subunits have rates of 30S and 50S.  Nuclear Body: the region of the cytoplasm that contains DNA is not surrounded by a nuclear membrane.  DNA ; always circular and not associated with any proteins to form chromatin.  Plasmid; small loops of DNA used to exchange DNA between bacterial cells. Used in genetic engineering, they often contain gene giving resistance to antibiotics.  Cell membrane; made of phosopholipids and proteins, like eukaryotic membranes.  Mesosomes; A tightly folded region of the cell membrane containing all the membrane-bound proteins required for respiration and photosynthesis. Can also be associated with the nucleoid.  Cell wall; made of murein (not cellulose), which is a glycoprotein (e.i. a protein/carbohydrate complex), also called peptidoglycan. There are two kinds of cell wall, which can be distinguished by grams stain.  Capsule; a thick polysaccharide layer outside the cell wall. Used for sticking cells together, as a food reserve, as protection against desiccation and chemical, and as protection against phagocytosis. 11  Botany for Pre- Medicine students. Dr: M. A. Al-Ryani. Found only in some +ve bacteria if it’s present than flagellate are not.  Flagellum; a rigid rotating helical-shaped tail used for propulsion. The motor is embedded in the cell membrane and is driven by a H+ gradient across the membrane Eucaryotic cells;  Cell wall; thick layer outside the cell membrane of fungi, algae and higher plants. Consist of a network of fibers used to give a cell strength and rigidity.  Cell membrane or plasma membrane; thin, flexible layer round the outside of all cells made of phospholipids and proteins. It separates the contents of the cell from the outside environment, and controls the entry and exit of materials.  Cytoplasm or Cytosol; this is the solution within the cell membrane. It contains enzymes for glycolysis and other metabolic reactions together with sugar, salts, amino acids, nucleotides and everything else needed for the cell to function.  Nucleus; is the largest organelle, surrounded by nuclear envelope, which is a double membrane with nuclear pores, large holes containing proteins 12  Botany for Pre- Medicine students. Dr: M. A. Al-Ryani. that control the exit of substances such as mRNA and ribosomes from the nucleus.  80S Ribosomes; these are smallest and most numerous of the cell organelles, and are the sites of protein synthesis. They are composed of protein and RNA, and are manufactured in the nucleolus of the nucleus. Ribosomes can be free in the cytoplasm, or more commonly are attached to the rough endoplasmic reticulum. They are often found in groups called polysomes.  Endoplasmic reticulum; collection of membrane channels forms an important transport within the cell, allowing molecules to move from one place to another. It is attached to, and formed from, the outer membrane of the nucleus, and play an important part in protein synthesis. It comes in two distinct forms(Rough and Smooth endoplasmic reticulum).  Golgi Body or Apparatus; another series of flattened membrane vesicles, formed from the endoplasmic reticulum. Its job is to transport proteins from Rough endoplasmic reticulum to the cell membrane for export. Parts of the smooth ER containing proteins fuse with one side of the Golgi body membrane, while at the other side small vesicles bud off and move towards the cell membrane, where they fuse, releasing their contents by exocytosis.  Vacuoles these are membrane –bound sacs containing a dilute solution, most cells have small vacuoles but plant cells usually have one very large vacuole, filled with cell sap and are very important in keeping the cell turgid.  Lysosomes; these are small membrane-bound vesicles containing a cocktail of digestive enzymes. They are used to break down unwanted chemical, toxins, organelles or even whole cells, so that the materials may be recycled. They can also fuse with a feeding vacuole to digest its contents. Responsible for cell death autolysis.  Cytoskeleton a network of protein fibers extending throughout all eucaryotic cells, used for support, transport and motility. It’s attached to the cell membrane and gives the cellist shape, as well as holding all the organelles in position. 13