Ibn Sina University College of Medicine First Year Biology Lecture Notes PDF

IBN SINA UNIVERSITY COLLEGE OF MEDICINE FIRST YEAR BIOLOGY  is the smallest unit that is capable of performing life functions. Most cells are microscopic. Some cell are not microscopic. ???  Major cell types Prokaryotic Eukaryotic...

IBN SINA UNIVERSITY COLLEGE OF MEDICINE FIRST YEAR BIOLOGY  is the smallest unit that is capable of performing life functions. Most cells are microscopic. Some cell are not microscopic. ???  Major cell types Prokaryotic Eukaryotic cells cells (Archaebacteria) (Plants) (Eubacteria) (Animals) (Fungi) (Protists)  Do not have structures surrounded by membranes (Organelles). They have few internal structures. They are one-celled organisms (Unicellular). The genetic material founds in a region in the cytoplasm called Nucleoid Region. Usually they have a single chromosome composed of a circular DNA.  Contain many organelles surrounded by membranes. Represent most living organisms. The genetic material founds inside a nucleus surrounded by a Nuclear membrane (Nuclear envelope). They have a many chromosomes composed of a linear DNA. Plant Cell Animal Cell  Cell Membrane (Plasma Membrane) Consists of: Phospholipid-bilayer, Proteins, Carbohydrates and cholesterol. Keeps the organelles and the cytoplasm inside the cell. Selectively Permeable, Controls what goes in and out of the cell. Cells obtain nutrients, gain information and rid waste through their plasma membrane.  Cell Wall Surrounds the cells of plants, fungi, algae and most bacteria. Protects and supports cells. Prevents water loss. Composed of cellulose in plants’ cells. Bacteria have cell walls made of peptidoglycan.  Capsule Surrounds the cells of some bacteria. Composed of Glycocalyx. (Layer of polysaccharides lying outside the cell wall). Aids against drying out. Helps bacteria resist a host’s immune system. Helps bacteria attach to almost any surface.  Cytoplasm Gel-like substance includes everything inside the cell except the nucleus. Cytoplasm + Nucleus = Protoplasm. Cytoplasm = Cytosol + Organelles (except nucleus). Cytosol composed of water, salts, dissolved gasses & nutrients.  Cytoskeleton Network of protein fibers extend from nucleus to the plasma membrane. The protein fibers of cytoskeleton are: actin filaments, intermediate filaments, and microtubules. Maintains cell shape (internal support) and allows the cell and its organelles to move.  Nucleus Control center of the cell (The “brain” of the cell). Surrounded by a double membrane (Nuclear envelope). Filled with nucleoplasm.  Contains the genetic material (Chromosomes - Chromatin) and the nucleolus. Found in all cells except the Red Blood Cells (RBCs). Control all cell activities, and control cell division.  Nuclear Envelope It’s a double membrane consists of a Phospholipid- bilayer. Separates the nucleus from the cytoplasm. Has nuclear pores to permit the passage of ribosomal subunits and mRNA out of the nucleus and the passage of proteins into the nucleus.  Chromosomes - Chromatin Chromatin is network of strands, consists of DNA, protein, and some RNA. Chromatin condenses and undergoes coiling into chromosomes during cell division. Genes, composed of DNA, are units of heredity located on the chromosomes.  Nucleolus Nucleolus is not a structure, Just a visible region. Most cells have 2 or more nucleoli. Site of Ribosomal RNA (rRNA) and ribosomal proteins synthesis.  Ribosomes Small dot-like structures. Made up of proteins and RNA. Synthesized in the nucleolus. Found free in the cytoplasm or attached to the Rough Endoplasmic Reticulum (RER). Site of protein synthesis in cells.  The endomembrane system consists of the nuclear envelope, the membranes of the endoplasmic reticulum, the Golgi apparatus, and several types of vesicles. This system compartmentalizes the cell so that particular enzymatic reactions are restricted to specific regions.  The vesicles transport molecules from one part of the system to another. Organelles of the endomembrane system control production, circulation, storage, and delivery of substances produced or taken by the cell.  Endoplasmic Reticulum (ER) Consists of a complicated system of membranous channels and saccules (flattened vesicles). Physically continuous with the nuclear envelope. The ER consists of (Rough ER) and (Smooth ER), which have a different structure and functions.  Rough ER (RER) Continuous with the nuclear envelope. Has bound ribosomes attached to the outside. Synthesizes proteins and glycoproteins and engulfs them in vesicles. The vesicles transport molecules to other parts of the cell, notably the Golgi apparatus.  Smooth ER (SER) Continuous with RER. Has No ribosomes attached to its surface. Its function depends on the organ that it founds in. One function is synthesis of lipids (testosterone in testes). Another function is detoxification of drugs and alcohol in liver. Packages the products in vesicles for transportation.  Golgi Apparatus Consists of a stack of slightly curved, flattened saccules. Modifies lipids and proteins it receives from SER and RER into other products, and packages them in vesicles. Produces different types of packages, such as: Transport vesicles, Secretary vesicles and Lysosomes.  Vesicles Small membrane bounded sacs. Produced either from RER, SER or Golgi apparatus. Contain the products of above mentioned organelles. Can be Transport vesicles, Secretary vesicles or Lysosomes.  Transport vesicles: Deliver the product from its synthesized location to other sites inside the cell. Secretary vesicles: Deliver the product from its synthesized location to the plasma membrane to be excreted outside the cell (Secretion).  Lysosomes Membrane bounded vesicles produced by the Golgi apparatus. Contain powerful hydrolytic-digestive enzymes. Digest material taken into the cell, and they destroy nonfunctional organelles and portions of cytoplasm. The Endomembrane System  Mitochondria Double membrane- bounded organelles. Have their own DNA (mitochondrial DNA, mtDNA). Power-house of the cell: break down macromolecules and process them to obtain energy (ATP) through the process of cellular respiration: (Carbohydrate + oxygen carbon dioxide + water + energy )  Chloroplasts Double membrane- bounded organelles. Have their own DNA. Found in plant cells and some algae. Convert sunlight and CO2 to sugar through the process of Photosynthesis : (Solar energy + carbon dioxide + water Carbohydrate + oxygen)  6. Other Organelles (Centrioles, Peroxisomes, Vacuoles)  Centrioles Short cylinders with nine microtubule triplets. Found in animal cells and most protists. Found as a pair called centrosome. The major microtubule-organizing center for the cell. Produce spindle fibers during cell division.  Peroxisomes Small Single membrane bound vesicles. Containing enzymes that break down fatty acids , amino acids and hydrogen peroxide. Removes harmful oxidants from cells.  Vacuoles vacuoles are membranous sacs “bubbles” that float in the cell. Few animal cells contain vacuoles, but fat cells contain a very large lipid-filled vacuole. Plant Cell has large Central Vacuole for storage of (water, sugars, salts), and give a structural support.  Home Work Compare between prokaryotic, plant and animal cells.