Lec 2 Cell Components PDF

Biology Lecture 2 : Cell Components & Transport Cells Prokaryotic Cell Prokaryotes are all single celled organisms, like : Bacteria Eukaryotic Cell Ex : Can be Unicellular organisms, like : Amoeba & Protozoa And Cells of all Multicellular organisms Organism : Prokaryotes :  Is single-celled organis...

Biology Lecture 2 : Cell Components & Transport Cells Prokaryotic Cell Prokaryotes are all single celled organisms, like : Bacteria Eukaryotic Cell Ex : Can be Unicellular organisms, like : Amoeba & Protozoa And Cells of all Multicellular organisms Organism : Prokaryotes :  Is single-celled organisms of the domains Bacteria and Archaea.  Animal cells, plant cells, fungi, and protists are eukaryotes. Organism : Eukaryotes :  Can be Single-celled or multicellular.  Its cells have a membranebound nucleus and other membrane-bound compartments or sacs, called organelles.  Eukaryotic cells have diameters ranging from 10‒100 μm Organelles : Plasma Membrane :  Eukaryotic cells have a plasma membrane.  Made up of a phospholipid bilayer with embedded proteins that separates the internal contents of the cell from its surrounding environment. Organelles : Plasma Membrane :  Membrane regulates the passage of some substances, such as organic molecules, ions, and water, preventing the passage of some to maintain internal conditions, while actively bringing in or removing others.  Other compounds move passively across the membrane. Outside of the cell Plasma Membrane Inside of the cell (Cytoplasm) Organelles : Plasma Membrane :  The plasma membranes of cells that specialize in absorption are folded into fingerlike projections called microvilli (singular = microvillus).  This folding increases the surface area of the plasma membrane.  Such cells are typically found lining the small intestine to absorbs nutrients from digested food (function will be matched with structure ) Organelles : Plasma Membrane : Organelles : Cytoplasm :  Cytoplasm comprises the contents of a cell between the plasma membrane and the nuclear envelope  Made up of organelles suspended in the gellike cytosol, the cytoskeleton, and various chemicals. Plasma membrane Inside of the cell (Cytoplasm) Nuclear membrane Organelles : Cytoplasm :  Consists of 70 to 80 percent water with semisolid consistency, which comes from the proteins within it.  Also there is glucose and other simple sugars, polysaccharides, amino acids, nucleic acids, fatty acids, and derivatives of glycerol, Ions of sodium, potassium, calcium, and many other elements  Many metabolic reactions, including protein synthesis, take place in the cytoplasm. Organelles : Endomembrane system :  The endomembrane system (endo = within) is a group of membranes and organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins.  Include : Nuclear envelope, Lysosomes, Vesicles, Endoplasmic reticulum Golgi apparatus. Organelles : Nucleus :  The nucleus (plural = nuclei)  Houses the cell's DNA in the form of chromatin  Directs the synthesis of ribosomes and proteins. Organelles : Nucleus :  The nuclear envelope is ( phospholipid bilayers).  The nuclear envelope is punctuated with pores that control the passage of ions, molecules, and RNA between the nucleoplasm and the cytoplasm but not the DNA (large ) Organelles : Nucleus :  Chromosomes are structures within the nucleus that are made up of DNA (the hereditary material) and proteins.  Chromatin is the combination of DNA & proteins  In eukaryotes, chromosomes are linear structures.  Every species has a specific number of chromosomes in the nucleus of its body cells, in humans the number is 46 Organelles : Nucleus : Organelles : Nucleus : Organelles : Endoplasmic Reticulum :  A series of interconnected membranous tubules that collectively modify proteins and synthesize lipids.  These two functions are performed in separate areas of : the rough endoplasmic reticulum and the smooth endoplasmic reticulum, respectively. Organelles : Endoplasmic Reticulum :  The ribosomes synthesize proteins while attached to the ER, resulting in transfer of their newly synthesized proteins into the lumen of the RER where they undergo modifications such as folding or addition of sugars. Organelles : Endoplasmic Reticulum :  The RER is engaged in modifying proteins that will be secreted from the cell, it is abundant in cells that secrete proteins, such as the liver.  The SER is continuous with the RER but has few or no ribosomes on its cytoplasmic surface.  The SER's functions include synthesis of carbohydrates, lipids (including phospholipids), and steroid hormones; detoxification of medications and poisons; alcohol metabolism; and storage of calcium ions. Organelles : Golgi Apparatus :  The sorting, tagging, packaging, and distribution of lipids and proteins occur.  Has a receiving face near the ER and a releasing face toward the cell membrane.  The transport vesicles that form from the ER travel to the receiving face, fuse with it, and empty their contents into the lumen of the Golgi apparatus.  As the proteins and lipids travel through the Golgi, they undergo further modifications !! Organelles : Golgi Apparatus : Organelles : Golgi Apparatus :  The most frequent modification is the addition of short chains of sugar molecules.  Finally, the modified and tagged proteins are packaged into vesicles that bud from the opposite face of the Golgi.  Transport vesicles, deposit their contents into other parts of the cell where they will be used,  Secretory vesicles, fuse with the plasma membrane and release their contents outside the cell. Organelles : Golgi Apparatus : Organelles : Golgi Apparatus :  The amount of Golgi in different cell types follows function within cells.  High amount found in cells that have a great deal of secretory activity (such as cells of the salivary glands that secrete digestive enzymes or cells of the immune system that secrete antibodies) Organelles : Lysosomes :  Digestive enzymes within the lysosomes aid the breakdown of proteins, polysaccharides, lipids, nucleic acids, worn-out organelles ,disease causing pathogens  These enzymes active at a much lower pH (more acidic) than those located in the cytoplasm.  Many reactions that take place in the cytoplasm could not occur at a low pH. Organelles : Lysosomes :  Macrophages ( subtype of WBC), in process of phagocytosis, a section of the plasma membrane of it (folds in) and engulfs a pathogen.  The invaginated section, with the pathogen inside, then pinches itself from the plasma membrane and becomes a vesicle.  The vesicle fuses with a lysosome.  The lysosome's hydrolytic enzymes then destroy the pathogen. Organelles : Lysosomes : Organelles : Vesicles :  Vesicles are membranebound sacs that function in storage and transport.  Vesicles can fuse with other membranes within the cell system. Organelles : Ribosomes :  The cellular structures (enzyme complexes) responsible for protein synthesis.  May be attached to either the cytoplasmic side of the plasma membrane or the cytoplasmic side of ER.  Because protein synthesis is essential for all cells, ribosomes are found in practically every cell.  Particularly abundant in immature red blood cells. Organelles : Ribosomes : Organelles : Mitochondria :  Mitochondria (singular = mitochondrion)  The powerhouses or energy factories of a cell (responsible for making adenosine triphosphate (ATP)  ATP formation from the breakdown of glucose (cellular respiration).  Mitochondria are oval-shaped, double-membrane organelles that have their own ribosomes and DNA. Organelles : Mitochondria :  Each membrane is a phospholipid bilayer embedded with proteins.  The inner layer has folds called cristae, which increase the surface area of the inner membrane.  The area surrounded by the folds is called the mitochondrial matrix.  Muscle cells have a very high concentration of mitochondria because muscle cells need a lot of energy to contract. Organelles : Mitochondria : Transport Mechanisms Passive Transport Mechanisms :  Plasma membranes are selectively permeable allow certain substances to enter and leave a cell, while preventing harmful material from entering and essential material from leaving.  The most direct forms of membrane transport are passive (does not require the energy )  In passive transport, substances move from an area of higher concentration to an area of lower concentration in a process called diffusion. Passive Transport Mechanisms : Passive Transport Mechanisms : Selective Permeability :  Lipid-soluble material can easily slip through the hydrophobic lipid core of the membrane.  Substances such as the fat soluble vitamins A, D, E, and K readily pass through the plasma membranes in the digestive tract and other tissues.  Molecules of oxygen and carbon dioxide (relative small )pass through by simple diffusion. Selective Permeability :  Some polar molecules cannot readily pass through the lipid core of the plasma membrane.  The charge of small ions prevents them from passing.  Ions such as sodium, potassium, calcium, and chloride must have a special means of penetrating plasma membranes.  Simple sugars and amino acids need help with transport across plasma membranes Diffusion :  Passive process of transport (expend no energy).  A single substance move from an area of high concentration to an area of low concentration until the concentration is equal across the space.  Several factors affect the rate of diffusion: 1. Extent of the concentration gradient , 2. Mass of the molecules , 3. Temperature Diffusion : Facilitated transport :  Material moves across the plasma membrane with the assistance of trans-membrane proteins down concentration gradient (from high to low concentration) without the expenditure of cellular energy.  The material being transported is first attached to protein or glycoprotein receptors on the exterior surface of the plasma membrane.  The integral protein involved in facilitated transport transports proteins, function as either channels for the material or carriers. Osmosis :  The diffusion of water through a semipermeable membrane according to the concentration gradient of water across the membrane.  Osmosis transports only water across a membrane and the membrane limits the diffusion of solutes in the water. Osmosis : Tonicity :  The amount of solute in a solution.  Three terms hypotonic, isotonic, and hypertonic A. In a hypotonic solution :  The extracellular fluid has a lower concentration of solutes than the fluid inside the cell, and water enters the cell.  The extracellular fluid has a higher concentration of water than does the cell.  In this situation, water will follow its concentration gradient and enter the cell.  This may cause an animal cell to burst, or lyse. Tonicity : B. In a hypertonic solution :  The extracellular fluid contains less water than the cell does, such as seawater.  Because the cell has a lower concentration of solutes, the water will leave the cell. the solute is drawing the water out of the cell.  This may cause an animal cell to shrivel (Shrink). Tonicity : C. In an isotonic solution :  The extracellular fluid has the same osmolarity as the cell.  If the concentration of solutes of the cell matches that of the extracellular fluid, there will be no net movement of water into or out of the cell. Tonicity : Active Transport Mechanism :  Require the use of cell energy mostly as ATP  Substance must move into the cell against its concentration gradient ( concentration of the substance inside the cell must be greater than its concentration in the extracellular fluid  Some active transport mechanisms move small-molecular weight material, some move large molecules such as ions, through the membrane. Active Transport Mechanism :  There are several types of active transport.  Primary active transport, which uses a combination of ATP energy and a transport protein to move substances across the membrane against the concentration gradient.  ATP is hydrolyzed, via an enzyme-catalyzed reaction, to ADP and the lost phosphate group attaches to the protein ,leading to conformational change in the shape of the transport protein and the particular substance is moved across the membrane against the concentration gradient.  An example of primary active transport is the sodium-potassium pump. Active Transport Mechanism : The sodium-potassium pump Endocytosis :  Endocytosis is a type of active transport that moves particles, such as large molecules, parts of cells, and even whole cells, into a cell.  The plasma membrane of the cell invaginates, forming a pocket around the target particle.  The pocket pinches off, resulting in the particle being contained in a newly created vacuole that is formed from the plasma membrane. Endocytosis : Exocytosis :  Is the opposite of the endocytosis in that its purpose is to expel material from the cell into the extracellular fluid.  A particle enveloped in membrane fuses with the interior of the plasma membrane.  This fusion opens the membranous envelope to the exterior of the cell, and the particle is expelled into the Extracellular space. Exocytosis :