Cytology Part 2 PDF

## CYTOLOGY - Part 2 ### **Mohammed Walid Elçanai** ### **Seek your dream and you will reach it** **Online Biology for Pre-Medical Students** **More information call us:** 0919072560 **@Biology_2003** ### **CYTOLOGY - Part 2** #### **Nucleus** - Large sized spherical in shape - Surrounded by...

## CYTOLOGY - Part 2 ### **Mohammed Walid Elçanai** ### **Seek your dream and you will reach it** **Online Biology for Pre-Medical Students** **More information call us:** 0919072560 **@Biology_2003** ### **CYTOLOGY - Part 2** #### **Nucleus** - Large sized spherical in shape - Surrounded by a nuclear envelope - Nuclear envelope composed of two layers of membrane separated by a distance of 20-40 nm - The merges of the two layers in many places to form nuclear pores. - The genetic material DNA exists in the form of filaments #### **Functions of nucleus** - Contains the genetic material inherited from one cell to another by division. - Regulate the activity of the cell. #### **Cytoplasm** - It is jelly-like cell material located between the cell membrane, and the nucleus. - Consists of: - 80% water - 15% proteins - 5% fats, sugars, and mineral salts - It is composed of two parts: - Cytosol is the liquid part. - Organelles: the rigid part. - Cytosol is the part of the cytoplasm that does not contain organelles. #### **Functions of Cytoplasm** - Most of the important activities of the cell occur in the cytoplasm because it contains enzymes which are responsible for breaking down waste and metabolic activity. - Cytoplasm is responsible for giving a cell its shape because it helps to fill out the cell and keeps organelles in their place. #### **Mitochondria** - Considered among the largest cell organelles in the size. - Its rod organelle or spherical - Surrounded by double membranes, the inner membrane bends inwards forming folds called cristae - The cavity of the mitochondria fill by thick liquid called matrix. - The matrix contains enzymes that are involved in: - Chemical processes like **cellular respiration** (Krebs cycle & electron transport chain) - The greater the need for the cell to power: have the greater the number & thesize of mitochondria. #### **Functions of mitochondria** - Is the place where the energy (ATP) is made up - Contains mitochondrial DNA which is capable of self-cleavage #### **Endoplasmic reticulum (ER)** - Multifold membranous structure within Animal & plant cells. - There are 2 types: - Rough (RER) & Smooth (SER) - The two types separate entities & not joined together. - ER play a role in Synthesis of complex molecules required by the cell. - Cells producing proteins have more RER & ribosomes. - Cells producing fat & steroids have more (SER). - RER have many ribosomes giving it (rough) appearance. #### **Functions of SER and RER** - The smooth ER synthesis lipids such as phospholipids and cholesterol. - The rough ER synthesis and modification of the proteins. #### **Ribosomes** - Non membranous organelles - Consist of 2 units: one large & one small - The two units don't unit only when synthesis of protein - Translation of mRNA into amino acids - Synthesis of peptides & proteins - It is the ONLY place where the amino acids is created. #### **Peroxisomes** - Vesicles contain enzymes crash toxic organic compounds, such as hydrogen peroxide and then decomposition of this toxic compound to water and oxygen. #### **Golgi apparatus** - Composed of flat sacs known as **Cisternae** - Small hollow spheres of membrane called vesicles. #### **Functions** 1. Synthesis of vesicles such as lysosome. 2. Responsible for manufacturing, warehousing & shipping cellular products produced by the endoplasmic reticulum (ER) - May few or may hundreds depending on the type of the cell. - Cells that specialize in secreting various substances typically have a high number of golgi. #### **Lysosomes** - Small vesicles are formed in the Golgi apparatus - Contain enzymes analyst of carbohydrates, proteins & lipids - Lysosomes are formed by inclusion of digestive enzymes such as proteases & lipases - Found in cell which are phagocytics, carry out process of phagocytosis - The enzymes contained within lysosomes are isolated from the rest of the cell by the lysosomes membrane, because their release would result in self digestion of the cell. - Self digestion of the cell for instances disease called (Rheumatoid arthritis) where the cartilage of the joint is attacked by lysosomes enzymes. #### **Phagocytosis** - Food particle, Food vacuole, Exocytic vesicle containing undigested material. #### **Cytoskeleton** - The cytoskeleton has three different types of protein elements. - From narrowest to widest they are: - Microfilaments (actin filament) - Intermediate filaments (keratin filament) - Microtubules (tubulin) #### **Centrioles** - Small hollow cylindrical non membranous organelle present in pairs. - Each one is made up of nine triple of microtubules (9 + 0). - During cell division the centriole replicate themselves to the opposite poles of the cell. - Have a role in formation of spindle fibers - Have shown that centrioles is the site of formation of the whole cytoskeleton network, not just spindle, so it is renamed (microtubule organizing center). #### **Cilia and Flagella** - Organelles, they are thin cytoplasmic threads projecting from the surface of the cell, also containing microtubules - Have similar structure (9 + 2) arrangement. - Flagella longer 100 mm & fewer in number moves the whole cell or organism - Flagella sites: in prokaryotes. - Flagella sites: in the sperm cells single flagellum. - Cilia shorter 5-10 mm - Cilia higher in number - Cilia beat backwards&forward in one direction. - Cilia sites: trachea - Cilia & flagella both contain a characteristics arrangement of nine outer pairs & two central ones, this is called (9 + 2) arrangement #### **Microvili** - Finger like projections present in outer surface of the cell. - Sites in the small intestine, function: increase surface area of cells, increased absorption of materials, faster uptake of the products of digestion #### **The endomembrane system** - Is a group of membranes organelles in eukaryotic cells that works together. - Function: modify, package & transport lipids & proteins - It include nuclear envelope, lysosome, vesicles, ensoplasmic reticulum, golgi, cell membrane - The endomembrane system does not include the membranes of either mitochondria or chloroplasts #### **Plasma (Cell) membrane** - All membranes have similar structures. - Some organelles have single membrane (golgi), but the others have double membrane (nucleus, mitochondria) - The phospholipids molecules naturally consist of bilayer. - Membranes are composed of phospholipids with proteins scattered amongst them. - The plasma membrane is selectively permeable this means that the membrane allows some materials to freely enter or leave the cell, while others materials cannot move freely. - Phospholipids are molecules wich are made up Phosphate (head), fatty acid (tail). - Phosphate is attracted to water & described as HYDROPHILIC(waterloving) - Fatty acid repelled by water & are called HYDROPHOBIC (water heating). - The main purpose of hydrophobic center of the membrane is to prevent the free diffusion of water & polar molecules through the membrane. - Its act as barrier for free movement. - If the membrane is disrupted by molecules passing through it, its easy springs back into the original position with phosphate on the outside & fatty acids on the inside. #### **Proteins on cell membrane** - There are proteins floating in the cell membrane between phospholipids. - **The main functions of the proteins:** - Is to provide support & stability in the fluid structural. - Transport of the molecules across membrane. #### **Types of the proteins in cell membrane** 1. Transport proteins 2. Channel proteins 3. Receptors 4. Carrier proteins 5. Enzymatic 6. Recognition proteins #### **Glycoproteins and glycolipids** - It is polysaccharide - Always on outside of the cell surface membrane. - Lipid + polysaccharide = glycolipid - Protein + polysaccharide = glycoprotein - Function of glycoprotein and glycolipids: - Both form hydrogen bonds with water molecules outside the cell helping to stabilize the membrane. - Some glycoprotein and glycolipid act as receptor sites. - Both involved in cells to cell recognition - The varying CHO chains emerging from cell surface membrane of the red blood cell are responsible for producing the different type blood group A, B, AB and O.