Anaphy Lec Prelims PDF

Anatomy and Physiology  Branches of Science Anatomy Studies the structure of body parts and relationships to one another Body structures can be seen, felt, and examined closely Physiology Concerns the function of the body How the body pats work...

Anatomy and Physiology  Branches of Science Anatomy Studies the structure of body parts and relationships to one another Body structures can be seen, felt, and examined closely Physiology Concerns the function of the body How the body pats work and carry out their life sustaining activities  Anatomy Greek word “to cut apart” Broad field with many subdivision Provide enough information to be a course in itself Gross or macroscopic Anatomy Study of large body structure visible to the naked eye Heart, lungs, and kidney  Anatomy Approach in different ways: Regional Anatomy All of the structure (muscle, bone, blood vessels) Particular region of the body Abdomen, leg Systemic Anatomy Body structure is studied system by system Cardiovascular system; respiratory system Surface Anatomy Internal structure relationship to the overlying skin surface Microscopic Anatomy Deals with structure too small Tissue, Blood Cytology; Histology Developmental Anatomy Structure change occur throughout the life span  Physiology Operation of specific organ system Renal Physiology Neurophysiology Cardiovascular physiology Focuses on event at the cellular or molecular levels Body’s abilities depend on those of its individual cells, and cells abilities ultimately depend on the chemical reaction that go on within them Rest on principles of physic  Complementarity of Structure and Function Anatomy and Physiology are inseparable Function always reflects structure Key concept is called “The Principle of complementarity of structure and function  Level of Structural organization Chemical Level Atom Molecule Organelles Cellular Level Cells Tissue Level Tissue Organ Level Organ Organ system Level Organ that work together to accomplish a common purpose Organism Level Sum total of all structural level working together to keep us alive Necessary for Life Function  Maintaining Boundaries Every living organism must maintain its boundaries Internal environment (its inside) remains distinct from the external environment (its outside). All body cells are surrounded by a selectively permeable plasma membrane The plasma membrane separates the intracellular fluid inside cells from the extracellular fluid outside. Another important boundary, the integumentary system, or skin, encloses the body as a whole  Movement Activities promoted by the muscular system The skeletal system provides the bony framework that the muscles pull on as they work Movement also occurs when substances such as blood, foodstuffs, and urine  Digestion Breaking down of ingested foodstuffs to simple molecules that can be absorbed into the blood. The nutrient-rich blood is then distributed to all body cells by the cardiovascular system. I  Metabolism Includes all chemical reactions that occur within body cells It includes breaking down substances into simpler building blocks (the process of catabolism), synthesizing more complex substances from simpler building blocks (anabolism),  Excretion Process of removing wastes, or excreta Several organ systems participate in excretion. For example, the digestive system rids the body of indigestible food residues in feces The urinary system disposes of nitrogen-containing metabolic wastes, such as urea, in urine  Reproduction The original cell divides, producing two identical daughter cells that may then be used for body growth or repair. Reproduction of the human organism, or making a whole new person, is the major task of the reproductive system  Growth Increase in size of a body part or the organism as a whole It is usually accomplished by increasing the number of cells. Survival Needs  Ultimate Goal Maintain life Several Factor: Nutrients Taken in via the diet, contain the chemical substances used for energy and cell building. Most plant-derived foods are rich in carbohydrates, vitamins, and minerals, whereas most animal foods are richer in proteins and fats Carbohydrates are the major energy fuel for body cells Oxygen. All the nutrients in the world are useless unless oxygen is also available Because the chemical reactions that release energy from foods are oxidative reactions that require oxygen Water Accounts for 50–60% of our body weight and is the single most abundant chemical substance in the body It provides the watery environment necessary for chemical reactions and the fluid base for body secretions and excretions Normal body temperature Chemical reactions are to continue at life-sustaining rates, normal body temperature must be maintained Appropriate atmospheric pressure Breathing and gas exchange in the lungs depend on appropriate atmospheric pressure.  Homeostasis Ability to maintain relatively stable internal conditions even though outside world change Homeostatic Control Accomplished chiefly by the nervous and endocrine systems Which use neural electrical impulses or blood borne hormones, respectively, as information carriers.  Three component Receptor Sensor that monitors the environment responsible for stimuli Control Center Determine the set point Analyze the input it receive Effector Carries out the control center’s response to the stimulus  Negative feedback mechanism Most homeostatic control mechanisms are negative feedback mechanisms. The output shuts off the original effect of the stimulus or reduces its intensity These mechanisms cause the variable to change in a direction opposite to that of the initial change, returning it to its “ideal” value.  Positive Feedback Mechanism The initial response enhances the original stimulus so that further responses are even greater This feedback mechanism is “positive” because the change that results proceeds in the same direction as the initial change, Causing the variable to deviate further and further from its original value or range.  Homeostatic Imbalance Homeostasis is so important that most disease can be regarded as a result of its disturbance, As we age, our body’s control systems become less efficient, and our internal environment becomes less and less stable. Another important source of homeostatic imbalance occurs when the usual negative feedback mechanisms are overwhelmed and destructive positive feedback mechanisms take over.  Anatomical Position and Directional Terms Anatomical position. Standard body position The body is erect with feet slightly apart “standing at attention,”  Directional terms Explain where one body structure is in relation to another  Regional Terms The two fundamental divisions Axial Makes up the main axis of our body Head, neck, and trunk Appendicular Consists of the appendages, or limbs, which attached to the axis  Body Planes and Sections Anatomical studies The body is often cut, or sectioned, along a flat surface called a plane The most frequently used body planes are sagittal, frontal, and transverse planes  Planes Sagittal plane Vertical plane that divides the body into right and left parts A sagittal plane that lies exactly in the midline is the median plane All other sagittal planes, offset from the midline, are parasagittal planes Frontal planes Divide the body into anterior and posterior A frontal plane is also called a coronal plane A transverse, or horizontal Runs horizontally from right to left, dividing the body into superior and inferior parts Oblique sections Cuts made diagonally between the horizontal and the vertical planes.  Dorsal Body Cavity It protects the fragile nervous system organs Two subdivision Cranial cavity (Skull) Encases the brain Vertebral cavity or spinal cavity (Runs within the bony vertebral column) Encloses the delicate spinal cord The cranial and spinal cavities are continuous with one another. Both the brain and the spinal cord are covered by membranes called meninges  Ventral Body Cavity The more anterior and larger of the closed body cavities Two major subdivision Thoracic cavity Surrounded by the ribs and muscles of the chest. Subdivided: Lateral pleural cavities Enveloping a lung Medial mediastinum (me0de-ah-sti9num). Pericardial cavity Enclose the heart, and surround the remaining thoracic organs (esophagus, trachea)  Ventral Body Cavity Two major subdivision Abdominopelvic cavity Two parts Abdominal cavity Superior part Contains the stomach, intestines, spleen, liver, and other organs Pelvic cavity Inferior part Contains the urinary bladder, some reproductive organs, and the rectum.  Membranes in the Ventral Body Cavity The walls of the ventral body cavity and the outer surfaces of the organs Contains are covered by a thin, double-layered membrane, the SEROSA or SEROUS MEMBRANE It folds in on itself to form the visceral serosa, covering the organs in the cavity. IT is separated not by air but by a thin layer of lubricating fluid, called serous fluid The serous membranes are named for the specific cavity and organs with which they are associated.  Abdominopelvic Regions and Quadrants The abdominopelvic cavity is large and contains several organs It helps to divide it into smaller areas for study  Other Body Cavities Oral and digestive cavities Called the mouth Teeth and tongue Nasal cavity Located within and posterior to the nose Orbital cavities. House the eyes Synovial cavities They are enclosed within fibrous capsules that surround freely movable joints of the body CELL: PARTS AND FUNCTION  CELLS The 100 trillion cells in a human being is a living structure that can survive for months or years, provided its surrounding fluids contain appropriate nutrients. They are the BUILDING BLOCKS OF THE BODY providing structure for the body’s tissues and organs, ingesting nutrients and converting them to energy, and performing specialized functions. They contain the body’s hereditary code that controls the substances synthesized by the cells and permits them to make copies of themselves.  ORGANIZATION OF THE CELL 2 major parts are the nucleus and the cytoplasm. Nucleus is separated from the cytoplasm by a nuclear membrane, Cytoplasm is separated from the surrounding fluids by a cell membrane, also called the plasma membrane. The different substances that make up the cell are collectively called protoplasm. Protoplasm is composed mainly of five basic substances: water, electrolytes, proteins, lipids, and carbohydrates.  PROTOPLASM : Substance that make up the cells WATER IONS The principal fluid medium of the cell Important ions in the cell include potassium, magnesium, phosphate, sulfate, bicarbonate, present in most cells, except for fat cells and smaller quantities of sodium, chloride, and calcium. concentration of 70 to 85 %. Many cellular chemicals are dissolved in the water. The ions provide inorganic chemicals for cellular reactions and also are necessary for Others are suspended in the water as solid operation of some of the cellular control particulates. mechanisms. ions acting at the cell membrane are required Chemical reactions take place among the dissolved chemicals or at the surfaces of the suspended for transmission of electrochemical impulses in particles or membranes. nerve and muscle fibers.  PROTOPLASM (PROTEINS) 2nd most abundant substances in most cells are proteins, normally constitute 10 to 20 % of the cell mass. divided into two types: structural proteins & functional proteins. Structural Proteins Mainly in the form of long filaments that are polymers of many individual protein molecules. Microtubules that provide the “cytoskeletons” of such cellular organelles as cilia, nerve axons, The mitotic spindles of cells undergoing mitosis, and a tangled mass of thin filamentous tubules that hold the parts of the cytoplasm and nucleoplasm together in their respective compartments. Fibrillar proteins are found outside the cell, especially in the collagen and elastin fibers of connective tissue and in blood vessel walls, tendons, ligaments.  PROTOPLASM (PROTEINS) FUNCTIONAL PROTEINS Entirely different type of protein and are usually composed of combinations of a few molecules in tubular-globular form. These proteins are mainly the enzymes of the cell and, in contrast to the fibrillar proteins, are often mobile in the cell fluid. Many of them are adherent to membranous structures inside the cell. The enzymes come into direct contact with other substances in the cell fluid and catalyze specific intracellular chemical reactions. Involved in the chemical reactions that split glucose into its component parts and then combine these with oxygen to form carbon dioxide and water while simultaneously providing energy for cellular function are all catalyzed by a series of protein enzymes.  PROTOPLASM (LIPIDS) Lipids are several types of substances that are grouped together because of their common property of being soluble in fat solvents. Especially important lipids are phospholipids and cholesterol, which together constitute only about 2 percent of the total cell mass. The significance of phospholipids and cholesterol is that they are mainly insoluble in water and therefore are used to form the cell membrane and intracellular membrane barriers that separate the different cell compartments. large quantities of triglycerides, also called neutral fat. In the fat cells, triglycerides often account for as much as 95 % of the cell mass. The fat stored in these cells represents the body’s main storehouse of energy-giving nutrients that can later be used to provide energy wherever in the body it is needed.  PROTOPLASM (CARBOHYDRATES) Structural = glycoprotein molecules – receptors play a major role in nutrition of the cell. Most human cells do not maintain large stores of carbohydrates; the amount usually averages about 1 % of their total mass but increases to as much as 3 % in muscle cells and, occasionally, 6 % in liver cells. However, carbohydrate in the form of dissolved glucose is always present in the surrounding extracellular fluid so that it is readily available to the cell. Also, a small amount of carbohydrate is stored in the cells in the form of glycogen, which is an insoluble polymer of glucose that can be depolymerized and used rapidly to supply the cells’ energy needs. PHYSICAL STRUCTURE OF THE CELL INTRACELLULAR ORGANELLES  MEMBRANE STRUCTURES Most organelles of the cell are covered by membranes composed primarily of lipids and proteins. ✔ cell membrane, ✔ nuclear membrane, ✔ membrane of the endoplasmic reticulum, ✔ membranes of the mitochondria, ✔ lysosomes, and Golgi apparatus.  CELL MEMBRANE Also called the plasma membrane envelops the cell and is a thin, pliable, elastic structure only 7.5 to 10 nanometers thick. It is composed almost entirely of proteins and lipids. The approximate composition is: Proteins – 55% Phospholipids 25 % Cholesterol 13 % Lipids, 4 % Carbohydrates, 3 %  LIPID BILAYER Which is a thin, double-layered film of lipids—each layer only one molecule thick—that is continuous over the entire cell surface. Interspersed in this lipid film are large globular proteins Composed of three main types of lipids: phospholipids, sphingolipids, and cholesterol. Phospholipids are the most abundant of the cell membrane lipids. One end of each phospholipid molecule is soluble in water; that is, it is hydrophilic. The other end is soluble only in fats; that is, it is hydrophobic. The phosphate end of the phospholipid is hydrophilic, and the fatty acid portion is hydrophobic.  LIPID BILAYER The lipid layer in the middle of the membrane is impermeable to the usual water-soluble substances, such as ions, glucose, and urea. Conversely, fat-soluble substances, such as oxygen, carbon dioxide, and alcohol, can penetrate this portion of the membrane with ease. Sphingolipids, derived from the amino alcohol sphingosine, also have hydrophobic and hydrophilic groups and are present in small amounts in the cell membranes, especially nerve cells. Complex sphingolipids in cell membranes are thought to serve several functions, including protection from harmful environmental factors, signal transmission, and as adhesion sites for extracellular proteins. The cholesterol molecules in the membrane are also lipids because their steroid nuclei are highly fat soluble.  MEMBRANE PROTEINS These membrane proteins are mainly glycoproteins. There are two types of cell membrane proteins: integral proteins that protrude all the way through the membrane peripheral proteins that are attached only to one surface of the membrane and do not penetrate all the way through. Many of the integral proteins provide structural channels (or pores) through which water molecules and water- soluble substances, especially ions, can diffuse between the extracellular and intracellular fluids. These protein channels also have selective properties that allow preferential diffusion of some substances over others. Other integral proteins act as carrier proteins for transporting substances that otherwise could not penetrate the lipid bilayer These carrier proteins even transport substances in the direction opposite to their electro- chemical gradients for diffusion, which is called “active transport.” Still others act as enzymes  MEMBRANE PROTEINS Integral membrane proteins can also serve as receptors for water-soluble chemicals, such as peptide hormones, that do not easily penetrate the cell membrane. Interaction of cell membrane receptors with specific ligands that bind to the receptor causes conformational changes in the receptor protein. This process, in turn, enzymatically activates the intracellular part of the protein or induces interactions between the receptor and proteins in the cytoplasm that act as second messengers, relaying the signal from the extracellular part of the receptor to the interior of the cell. In this way, integral proteins spanning the cell membrane provide a means of conveying information about the environment to the cell interior. Peripheral protein molecules are often attached to the integral proteins. These peripheral proteins function almost entirely as enzymes or as controllers of transport of substances through the cell membrane “pores.”  MEMBRANE CARBOHYDRATES “Glycocalyx.” Membrane carbohydrates occur almost invariably in combination with proteins or lipids in the form of glycoproteins or glycolipids. In fact, most of the integral proteins are glycoproteins, and about one tenth of the membrane lipid molecules are glycolipids. The “glyco” portions of these molecules almost invariably protrude to the outside of the cell, dangling outward from the cell surface. Many other carbohydrate compounds, called proteoglycans—which are mainly carbohydrate substances bound to small protein cores—are loosely attached to the outer surface of the cell as well. The entire outside surface of the cell often has a loose carbohydrate coat called the glycocalyx.  MEMBRANE CARBOHYDRATES The carbohydrate moieties attached to the outer surface of the cell have several important functions: 1.They have a negative electrical charge, which gives most cells an overall negative surface charge that repels other negatively charged objects. 2.The glycocalyx attaches one cell to the other 3.act as receptor substances for binding hormones, such as insulin; when bound, this combination activates attached internal proteins that, in turn, activate a cascade of intracellular enzymes. 4.Some carbohydrate moieties enter into immune reactions  CYTOSOL The cytoplasm is filled with both minute and large dispersed particles and organelles. The jelly-like fluid portion of the cytoplasm in which the particles are dispersed is called cytosol and contains mainly dissolved proteins, electrolytes, and glucose. Dispersed in the cytoplasm are neutral fat globules, glycogen granules, ribosomes, secretory vesicles, and five especially important organelles: 1. Endoplasmic reticulum, 2. Golgi apparatus, 3. Mitochondria, 4. Lysosomes, and 5. Peroxisomes.  ENDOPLASMIC RETICULUM Network of tubular and flat vesicular structures in the cytoplasm. Helps process molecules made by the cell and transports them to their specific destinations inside or outside the cell. The tubules and vesicles interconnect, their walls are constructed of lipid bilayer membranes that contain large amounts of proteins, similar to the cell membrane. The total surface area of this structure in some cells—the liver cells, for instance(can be as much as 30 to 40 times the cell membrane area). The space inside the tubules and vesicles is filled with endoplasmic matrix, a watery medium that is different from the fluid in the cytosol outside the endoplasmic reticulum. Electron micrographs show that the space inside the endoplasmic reticulum is connected with the space between the two membrane surfaces of the nuclear membrane.  ENDOPLASMIC RETICULUM (RIBOSOMES) Ribosomes - Attached to the outer surfaces of many parts of the endoplasmic reticulum are large numbers of minute granular particles. Where these particles are present, the reticulum is called the granular endoplasmic reticulum. The ribosomes are composed of a mixture of RNA and proteins, and they function to synthesize new protein molecules in the cell. Agranular Endoplasmic Reticulum -Part of the endoplasmic reticulum has no attached ribosomes. This part is called the agranular or smooth, endoplasmic reticulum. The agranular reticulum functions for the synthesis of lipid substances and for other processes of the cells promoted by intra-reticular enzymes.  GOLGI APPARATUS Closely related to the endoplasmic reticulum. -has membranes similar to those of the agranular endoplasmic reticulum. usually composed of four or more stacked layers of thin, flat, enclosed vesicles lying near one side of the nucleus. This apparatus is prominent in secretory cells, where it is located on the side of the cell from which the secretory substances are extruded. small “transport vesicles” (also called endoplasmic reticulum vesicles, or ER vesicles) continually pinch off from the endoplasmic reticulum and shortly thereafter fuse with the Substances entrapped in the ER vesicles are transported from the endoplasmic reticulum to the Golgi apparatus. The transported substances are then processed in the Golgi apparatus to form lysosomes, secretory vesicles, and other cytoplasmic components  LYSOSOMES Vesicular organelles that form by breaking off from the Golgi apparatus and then dispersing throughout the cytoplasm. Provide an intracellular digestive system that allows the cell to digest: Damaged cellular structures, Food particles that have been ingested by the cell, and Unwanted matter such as bacteria. Different in various cell types, but it is usually 250 to 750 nanometers in diameter. Surrounded by a typical lipid bilayer membrane and is filled with large numbers of small granules 5 to 8 nanometers in diameter, which are protein aggregates of as many as 40 different. hydrolase (digestive) enzymes Hydrolytic enzyme is capable of splitting an organic compound into two or more parts by combining hydrogen from a water molecule with one part of the compound and combining the hydroxyl portion of the water molecule with the other part of the compound.  PEROXISOMES Similar physically to lysosomes, but they are different in two important ways. Formed by self-replication (by budding off from the smooth endoplasmic reticulum) rather than from the Golgi apparatus. They contain oxidases rather than hydrolases. Several of the oxidases are capable of combining oxygen with hydrogen ions derived from different intracellular chemicals to form hydrogen peroxide (H2O2). Hydrogen peroxide is a highly oxidizing sub- stance and is used in association with catalase, another oxidase enzyme present in large quantities in peroxisomes, to oxidize many substances that might otherwise be poisonous to the cell. Half the alcohol a person drinks is detoxified into acetaldehyde by the peroxisomes of the liver cells in this manner. A major function of peroxisomes is to catabolize long chain fatty acids.  Secretory Vesicles Almost all such secretory substances are formed by the endoplasmic reticulum– Golgi apparatus system and are then released from the Golgi apparatus into the cytoplasm in the form of storage vesicles called secretory vesicles or secretory granules. The proenzymes are secreted later through the outer cell membrane into the pancreatic duct and thence into the duodenum, where they become activated and perform digestive functions on the food in the intestinal tract.  MITOCHONDRIA Called the “powerhouses” of the cell - extract enough energy from the nutrients, and essentially all cellular functions present in all areas of each cell’s cytoplasm, but the total number per cell varies from less than a hundred up to several thousand, depending on the amount of energy required by the cell. The cardiac muscle cells (cardiomyocytes), use large amounts of energy and have far more mitochondria than do fat cells (adipocytes), which use less energy. concentrated in those portions of the cell that are responsible for the major share of its energy metabolism. They are also variable in size and shape. (some only a few hundred nanometers in diameter and are globular in shape, whereas others are elongated and are as large as 1 micrometer in diameter and 7 micrometers long)  MITOCHONDRIA Composed mainly of two lipid bilayer– protein membranes: an outer membrane and an inner membrane. Many infoldings of the inner membrane form shelves or tubules called cristae onto which oxidative enzymes are attached. cristae provide a large surface area for chemical reactions to occur. the inner cavity of the mitochondrion is filled with a matrix that contains large quantities of dissolved enzymes that are necessary for extracting energy from nutrients. oxidative enzymes on the cristae to cause oxidation of the nutrients, thereby forming carbon dioxide and water and at the same time releasing energy.  MITOCHONDRIA The liberated energy is used to synthesize a “high-energy” substance called adenosine triphosphate (ATP). ATP is then transported out of the mitochondrion and diffuses throughout the cell to release its own energy wherever it is needed for performing cellular functions. Mitochondria are self-replicative, which means that one mitochondrion can form a second one, a third one, and so on, whenever there is a need in the cell for increased amounts of ATP. Indeed, the mitochondria contain DNA similar to that found in the cell nucleus. The DNA of the mitochondrion plays a similar role, controlling replication of the mitochondrion. Cells that are faced with increased energy demands—which occurs, for example, in skeletal muscles subjected to chronic exercise training—may increase the density of mitochondria to supply the additional energy required.  NUCLEUS The control center of the cell, sends messages to the cell to grow and mature, to replicate, or to die. contains large quantities of DNA, which comprise the genes GENES determine the characteristics of the cell’s proteins, including the structural proteins, as well as the intracellular enzymes that control cytoplasmic and nuclear activities. genes also control and promote reproduction of the cell. The genes first reproduce to create two identical sets of genes; then the cell splits by a special process called mitosis to form two daughter cells, each of which receives one of the two sets of DNA genes.  NUCLEAR MEMBRANE Also called the nuclear envelope actually two separate bilayer membranes, one inside the other. The outer membrane is continuous with the endoplasmic reticulum of the cell cytoplasm, and the space between the two nuclear membranes is also continuous with the space inside the endoplasmic reticulum The nuclear membrane is penetrated by several thousand nuclear pores. Large complexes of protein molecules are attached at the edges of the pores so that the central area of each pore is only about 9 nanometers in diameter. Even this size is large enough to allow molecules up to 44,000 molecular weight to pass through with reasonable ease.  Nucleoli and Formation of Ribosomes The nuclei of most cells contain one or more highly staining structures called nucleoli. The nucleolus does not have a limiting membrane. Instead, it is simply an accumulation of large amounts of RNA and proteins of the types found in ribosomes. Nucleolus becomes considerably enlarged when the cell is actively synthesizing proteins. Formation of the nucleoli (and of the ribosomes in the cytoplasm outside the nucleus) begins in the nucleus. First, specific DNA genes in the chromosomes cause RNA to be synthesized. Some of this synthesized RNA is stored in the nucleoli, but most of it is transported outward through the nuclear pores into the cytoplasm. Here it is used in conjunction with specific proteins to assemble “mature” ribosomes that play an essential role in forming cytoplasmic proteins  End Functional Systems of the Cells  Endocytosis Ingestion by cells Most substance pass through: Diffusion Simple movement through membrane caused by the random motion molecules of the substance Active transport Carrying of substance through membrane by a physical protein structure that penetrate all the way through the membrane  Endocytosis Ingestion by the cells Very large particles enter the cell by a specialized function of the cell membrane  Two Principal form of Endocytosis: Pinocytosis Ingestion of minute particles that form vesicles of extracellular fluid and particulate constituents inside the cell cytoplasm Phagocytosis Ingestion of large particles , such as bacteria , whole cells, or portion of degenerating tissues.  Pinocytosis Occurs rapidly Pinocytosis vesicle are small- usually only 100 to 200 nanometer in diameter Is the only means by which most large macromolecules, such as most protein molecules, can enter cells  STEPS IN PINOCYTOSIS 1. Molecules attach to protein receptors in on the surface of membrane 2. Receptors are generally concentrated in small pits in the outer surface of the cell membrane , called coated pits. 3. Beneath these pits is a lattice work of fibrillar protein called clathrin, as well as other proteins , perhaps contractile filaments of actin and myosin 4. Once the protein molecules have bound with the receptors, surface properties of local membrane changes  STEPS IN PINOCYTOSIS 5. Entire pit invaginates inward and fibrillar protein surrounding the invaginating pits cause the borders to closed over attached proteins 6. Invaginated portion of the membrane breaks away from the surface cell, forming a pinocytic vesicle inside the cytoplasm of the cell 7. This process requires energy from within the cell , which is supplied by ATP 8. This process also requires presence of calcium ions in the extracellular fluid which reacts with contractile protein filaments.  Phagocytosis Similar to pinocytosis, except it involves large particles rather then molecules Certain cells has the capability of phagocytosis: Macrophage, and some WBC Initiated, when particle such as a bacterium, a dead cell, or tissue debris bind with receptors on the surface of the phagocytes  Step in Phagocytosis 1. The cell membrane receptor attached to the surface ligands of the particle 2. The edges of the membrane around the points of attachment evaginate outward to surround the entire particle. Progressively more ligand membrane receptor attach to the particular ligands and form a closed phagocytic vesicle 3. Actin and other contractile fibrils in the cytoplasm surround the phagocytic vesicle and contract around it outer edge, pushing the vesicle to the interior 4. The contractile proteins then pinch the stem of the vesicle so completely that the vesicles separates from the cell membrane, leaving the vesicle in the cell interior in the same way that the pinocytic vesicles are formed  DIGESTIONS BY LYSOSOMES Pinocytic and phagocytic foreign substances are digested inside the cell by lysosomes 1. Once pinocytic or phagocytic vesicles appear, one or more lysosomes become attached to the vesicles and empty their acid hydrolases 2. A digestive vesicle is formed inside the cytoplasm 3. Hydrolases hydrolyzed protein, carbohydrates, lipids and other substances in the vesicle. 4. The products of digestion are small molecules of amino acids, glucose, phosphates and so forth that can diffuse through the membrane of the vesicle into the cytoplasm 5. What is left of the digestive vesicle is called residual body which represents indigestible substances. 6. Residual body is excreted through the cell membrane by a process called exocytosis DIGESTION BY LYSOSOMES  Regression of tissue by Lysosomes Tissue of body often regress to a smaller size Example: Uterus in pregnancy Mammary glands at the end of lactation Muscles during inactivity  AUTOLYSIS OF DAMAGED TISSUES by LYSOSOMES Removal of damaged cells or damaged portions of cells by lysosomes Damage to cells, caused by heat , cold , trauma or any factor induces lysosomes to rupture releasing hydrolase Released hydrolases immediately digest the surrounding organic substances  AUTOLYSIS OF DAMAGED TISSUES by LYSOSOMES If damage is severe, the entire cell is digested, a process called autolysis. Lysozymes contain bactericidal agents that can kill phagocytized bacteria before they can cause cellular damage. 1. Lysozyme –Dissolves bacterial cell membrane 2. Lysoferrin – Binds iron and other substances before they can promote bacterial growth 3. Acid at pH 5.0- Activates hydrolases and inactivates bacterial metabolic systems  AUTOPHAGY by LYSOSOMES Autophagy: is a housekeeping process by which obsolete organelles and large protein aggregates are degraded and recycled. Worn out cells are transferred to lysosomes by auto-phagosomes that are formed in the cytosol. Once inside the lysosomes, organelles are digested and the nutrients are reused by the cell Autophagy contributes to the routine turnover of cytoplasmic components and is a key mechanism for tissue development, and for cell survival when nutrients are scarce.  SYNTHESIS OF CELLULAR STRUCTURES by ENDOPLASMIC RETICULUM Most synthesis of substances begins in the endoplasmic reticulum Products formed in the endoplasmic reticulum are passed on to the Golgi apparatus where they are further processed before released to the cytoplasm Proteins are formed by the Granular Endoplasmic Reticulum Granular reticulum are characterized by large number of ribosomes attached to the outer surface of the endoplasmic reticulum Protein molecules are synthesized within the structures of the ribosomes  SYNTHESIS OF CELLULAR STRUCTURES by ENDOPLASMIC RETICULUM Synthesis of Lipids done by the Smooth Endoplasmic Reticulum The synthesis of lipids, especially phospholipids and cholesterol occur mainly in the endoplasmic reticulum The lipids are incorporated into the lipid bilayer of the endoplasmic reticulum causing the endoplasmic reticulum to grow more extensive. Small vesicles from the endoplasmic reticulum continually breakaway from the smooth reticulum Most of these vesicles migrate to the Golgi apparatus Other functions of endoplasmic reticulum 1. Provides the enzymes that control glycogen breakdown when glycogen is to be used for energy 2. Provides vast number of enzymes that are capable of detoxifying substances , such as drugs that might damage the cell.  SYNTHETIC FUNCTION OF THE GOLGI APPARATUS Major function of the Golgi apparatus is to provide additional processing substances already formed by the endoplasmic reticulum Capability to synthesize some carbohydrates such as large saccharide polymers bound with small amount of protein Ex: chondroitin sulfate and hyaluronic acid PROCESSING OF ENDOPLASMIC SECRETIONS by the GOLGI APPARATUS and FORMATION OF VESICLES  FUNCTION OF THE GOLGI APPARATUS Intracellular vesicles formed by the Golgi Apparatus fuse with the cell membrane or membranes of intracellular structures. This fusion increases the expanse of these membranes and thereby replenishes the membranes as they are used up.  MITOCHONDRIA EXTRACT ENERGY FROM NUTRIENTS The principal substances ( carbohydrates, fats and proteins) from which cell extract energy are foodstuff that react chemically with oxygen Carbohydrates are converted to glucose Proteins are converted to amino acid Fats are converted to fatty acids MITOCHONDRIA EXTRACT ENERGY FROM NUTRIENTS Glucose , fatty acids and amino acids undergo oxidative reactions in the mitochondria and energy is released to form high energy compound ATP ATP is used throughout the cell to energize almost all the subsequent intracellular metabolic reactions.  MITOCHONDRIA EXTRACT ENERGY FROM NUTRIENTS ATP Adenosine Triphosphate Is a nucleotide composed of nitrogenous base adenine, pentose ribose, and 3 phosphate radicals. Contains 12000 calories per mole of ATP When ATP releases its energy , a phosphoric acid radical is split away and adenosine diphosphate is formed. The release of energy is used to energize many of the cell’s other function, such as synthesis of substances  FORMATION OF ATP Glucose is converted into pyruvic acid through the process of glycolysis in the cytoplasm. A small amount of ADP is changed to ATP by energy released during this glycolysis. This amounts to less than 5 % of overall energy metabolism of the cell. 95% of the cell’s ATP formation occurs in the mitochondria The pyruvic acid derived from glucose, fatty acids and amino acids is eventually converted into the compound acetyl-coenzyme A in the matrix of the mitochondria. This substance undergo dissolution in a sequence of chemical reaction called citric acid cycle or Kreb cycle.  FORMATION OF ATP In this citric acid cycle , acetyl CoA is split into component parts, hydrogen atoms and carbon dioxide. Carbon dioxide diffuses out of the mitochondria and out of the cell. The hydrogen atoms combine with oxygen in the mitochondria. The combination releases a tremendous amount of energy which is used by the mitochondria to convert large amount of ADP to ATP The newly formed ATP is transported out of the mitochondria into all parts the cell cytoplasm where energy is used to energized multiple cell functions. FORMATION OF ATP  Uses Of ATP for Cellular function Three major categories of cellular function: Transport of substances through multiple membrane in the cell Synthesis of chemical compound throughout the cell Mechanical work FUNCTIONAL MOVEMENT OF THE CELL Locomotion Amoeboid locomotion Ciliary movement  AMOEBOID MOVEMENT Movement of an entire cell in relation to its surrounding Typically begins with protrusion of pseudopodium from one end of the cell. The pseudopodium projects away from the cell body and partially secures itself in a new tissue area , and then the remainder of the cell is pulled toward the pseudopodium.  AMOEBOID MOVEMENT Results from continual formation of new cell membrane at the leading edge of the pseudopodium and continual absorption of the membrane in the mid and rear portions of the cell Two other effect are essential for forward movement Attachment of pseudopodium to surrounding tissue The attachment is effected by receptor proteins that lines the inside of exocytic vesicles. When vesicles become part of the pseudopodial membrane They open so that their insides evert to the outside, and the receptors now protrude to the outside and attach to ligands in the surrounding tissues  AMOEBOID MOVEMENT Second essential effect –providing energy to pull the cell body in the direction of the pseudopodium In the cytoplasm of all cells is a moderate amount to large amount of the protein actin. Actin polymerize to form a filamentous network and the network contracts when it binds with an actin-binding protein such as myosin. The entire process is energized by the high energy compound ATP  AMOEBOID MOVEMENT Type of cells that exhibit Ameboid Locomotion 1. White blood cells 2. Fibroblast 3. Embryonic cells Control of Ameboid Locomotion Chemotaxis- Most important initiator of ameboid locomotion Results from appearance of certain chemical substance in tissues Characteristic movement or orientation of an organism or cell along a chemical concentration gradient either toward or away from the chemical stimulus Chemotactic substance- Any substance that causes chemotaxis to occur  AMOEBOID MOVEMENT Positive Chemotaxis Locomotion towards the source of a chemotactic substance from an area of lower concentration to an area of higher concentration Negative chemotaxis Locomotion of cells moving away from the chemotactic substance LOCOMOTION OF CELLS: CILIARY MOVEMENTS ▪ Locomotion produced by whip-like movement of cilia on the surfaces of the cells. ▪ Occurs mainly in 2 places in the human body: 1. Surface of respiratory airways 2. Inside surface of the uterine tubes  LOCOMOTION OF CELLS: CILIARY MOVEMENTS surface of respiratory airways ▪ Whip like motions of cilia causes layer of mucus to move at a rate of 1 cm/ min towards the pharynx, causing continues clearing of the passageways of mucus and particles Inside surface of the uterine tubes Cilia causes slow movement of fluid from the ostium of the uterine tube toward the uterus cavity This movement transport the ovum from the ovary to the uterus.  LOCOMOTION OF CELLS: Cilium Sharp-pointed straight or curved hair Projects 2-4 micrometer from the surface of the cell -Covered by outcropping of the cell membrane Supported by 11 microtubules- 9 tubules located around the periphery of the cilium and 2 single tubules Each cilia is an outgrowth of a structure that lies immediately beneath the cell membrane called the basal body of the cilium Moves forward with sudden , rapid whip like stroke 10-20 times per second, bending sharply where it projects from the surface of the cell Moves backward slowly to its position Rapid forward-thrusting whip like movements pushes the fluid adjacent to the cell in the direction the cilium moves The total complex of tubule and cross-linkages is called axoneme LOCOMOTION OF CELLS: CILIARY MOVEMENTS Flagellum of a sperm is similar to a cilium , with same type of structure and same type of contractile mechanism Flagellum however is much longer and moves in quasi-sinusoidal wave instead of whip like movements. END OF LECTURE THANK YOU!!!  Transport of Substance Through the Cell membrane  Differences in concentration are extremely important to the life of the cell  Lipid Barrier and Cell membrane Transport Proteins Cell membrane Lipid bilayer Protein Not miscible with either the extracellular fluid and intracellular fluid Barrier against water molecules and water soluble substance However, Few substance can penetrate, diffusing directly Lipid-soluble substance  Protein molecule in the membrane have entirely different properties for transporting substance Molecular structures interrupt the continuity of the lipid bilayer, constituting an alternative pathway thru the membrane Most if these penetrating proteins, can function as transport proteins Watery spaces all the way through the molecule and allow free movement of water Ion or molecule (channel proteins) Carrier proteins: bind with molecules that are transported  “ Diffusion” vs “Active Transport” Transport through the cell membrane Directly through the lipid bilayer Through the proteins Two basic processes Diffusion Random molecule movement of substance, either through intermolecular spaces or in combination with a carrier protein Energy that cause diffusion is the energy kinetic motion of matter Active transport Substance across the membrane in combination with a carrier protein Carrier protein cause the substance to move against an energy gradient, such as from a low concentration state to a high concentration state Requires additional source of energy beside kinetic energy  Diffusion All molecule and substance are in a constant motion Each particle moving its own separate way Motion of these particles “Heat” The greater the motion, the higher the temperature The motion never ceases under any condition except at absolute zero temperature Diffusion Continual movement of molecules among each another in liquid or in gases  Diffusion Through the cell membrane Two subtype Simple diffusion Kinetic movement of molecule or ions occurs through a membrane opening through intermolecular spaces without any interaction with carrier proteins in the membrane Rate of diffusion is determine by : The amount of substance available. The velocity of kinetic motion. The number and sizes of opening in the membrane through which the molecules or ions can move. Facilitated diffusion Requires interaction of a carrier protein Aids passage of the molecules or ions through the membrane by binding chemically with them and shuttling them through the membrane in this form  Diffusion of Lipid-Soluble Substances Through the Lipid Bilayer Factor in determine the permeability of the substance Lipid solubility Oxygen, nitrogen, carbon dioxide, and alcohol Rate of diffusion through the membrane is directly proportional to its lipid solubility Diffusion of Water and Other Lipid-Insoluble Molecules Through Protein Channels. Water is highly insoluble in the membrane lipids, it readily passes through channels in protein molecules that penetrate all the way through the membrane. As the molecule become larger, their penetration falls off rapidly.  Diffusion Through Protein Pores and Channels— Selective Permeability and “Gating” of Channels Pores Composed of integral cell membrane proteins Forms an open tube through the membrane and are always open The diameter of a pore and its electrical charges provide selectivity that permits only certain molecules to pass through E.x: Aquaporin “water channels”  Protein Channel Two important characteristics Selectively permeable to a certain substance Can be opened or closed by gates that are regulated by electrical signal (voltage-gated channels) or chemicals that bind to the channel proteins (ligand-gated channels)  Selective Permeability of Protein Channels Potassium Channels Permits passage of potassium ions across the cell membrane about 1000 times more readily than they permit passage of sodium ions Sodium Channel Inner surface of this channel are lined with amino acids that are strongly negative charge Negative charged can pull small dehydrated sodium ions into these channels Once in the channels, the sodium ion diffuse either direction according to the usual laws of diffusion  Gating of Protein Channels Provide a means of controlling ion permeability of the channels The gates are actual gate-like extension of transport protein molecule It is controlled in two ways Voltage gating Molecular conformation of the gate or of its chemical bonds responds to the electrical potential across the cell membrane If there is strong negative charge on the inside of the cell membrane, this presumably could cause the outside sodium gates to remain tightly close When the inside of the membrane loses its negative charge, these gates would open suddenly allow tremendous quantities of sodium to pass inward through the sodium pores.  Chemical Ligand Protein channel gate are opened by the binding of chemical substance (Ligand) with the protein Causing a conformational or chemical bonding change in the protein molecule that open or closes the gate Effect of acetylcholine on the acetylcholine channel Important for the transmission of nerve signals from one nerve cell to another  Facilitated Diffusion “Carrier-Mediated Diffusion” Transport molecule using a specific carrier protein to help Carrier facilitates diffusion of the substance to the other side Differs from simple diffusion in the following important way: Rate of diffusion approaches a maximum, called Vmax as the concentration of the diffusing substance increases  Limit rate of Facilitated Diffusion.  Limit rate of Facilitated Diffusion The rate at which molecules can be transported by this mechanism can never be greater than the rate at which the carrier protein molecule can undergo change back and forth between its two states. Important substance that cross cell membrane by facilitated diffusion Glucose Amino acid  Factors that Affect Net Rate of Diffusion Net Diffusion Rate Is Proportional to the Concentration Difference Across a Membrane The rate at which the substance diffuses inward is proportional to the concentration of molecules on the outside  Effect of Membrane Electrical Potential on Diffusion of Ions—The “Nernst Potential.” Applying electrical charge will create an electrical gradient across the membrane  Effect of a Pressure Difference Across the Membrane. When the pressure is higher on one side of a membrane than on the other The result is that increased amounts of energy are available to cause net movement of molecules from the high-pressure side toward the low pressure side.  Osmosis Across Selectively Permeable Membranes—“Net Diffusion” of Water Osmosis Net movement of water caused by concentration difference of water Concentration difference for water can develop across a membrane When this happen, net movement of water does occur across the cell membrane Causing the cell either to swell or shrink, depending on the direction of the water movement  Osmotic Pressure Applying exact amount of pressure required to stop the osmosis  Importance of Number of Osmotic Particles (Molar Concentration) in Determining Osmotic Pressure. Osmotic Pressure - determined by the number of particles per unit volume of fluid NOT by the mass of the particles Osmole- concentration of a solution in terms of number of particles OsmolaLity = osmole / solvent (osmole per kilogram of water) OsmolaRity = osmole / solution (osmole per kilogram of particles) Importance of Number of Osmotic Particles (Molar Concentration) in Determining Osmotic Pressure  “Active Transport” of Substances Through Membranes When a cell membrane moves molecules or ions “uphill” against a concentration gradient (or “uphill” against an electrical or pressure gradient) Different substances that are actively transported through at least some cell membranes include: Sodium, potassium, calcium, iron, hydrogen, chloride, iodide, and urate ions, several different sugars, and most of the amino acids. Two type of Active transport according to the source of the energy used: Primary Active Transport The energy is derive from breakdown of adenosine triphosphate (ATP) or some other high-energy phosphate compound Secondary active transport Energy is derived secondarily from energy that has been stored in the form of ionic concentration differences of secondary molecular or ionic substance between the two sides of a cell membrane, created originally by primary active transport  Primary Active Transport Sodium Potassium Pump (Na+ - K+) Transport process that pumps sodium ions out-ward through the cell membrane of all cells and at the same time pump potassium ions from the outside to the inside Maintain the Na and K concentration differences across the cell membrane, as well as for establishing a negative electrical voltage inside Basis of nerve function, transmitting nerve signals throughout the nervous system  Primary Active Transport Sodium-Potassium Pump Carrier Protein a subunit (smaller) Function is still unknown B subunit (larger) Has three specific features that are important for the functioning of the pump It has three receptor sites for binding sodium ion on the portion of the protein that protrudes to the insides of the cell Two receptor sites for potassium ions on the outside The inside portion of this protein near the sodium site has ATPase activity  When two potassium ions bind on the outside of the carrier protein and three sodium ions bind on the inside The ATPase function of the protein becomes activated This liberated energy is then believed to cause a chemical and conformational change in the protein carrier molecule, extruding the three sodium ions to the outside and the two potassium ions to the inside  The Na+ - K+ ATPase pump can run in reverse If the electrochemical gradients for Na+ and K+ are experimentally increased enough so that the energy stored in their gradients is greater than the chemical energy of ATP hydrolysis These ions will move down their concentration gradients and the Na+ - K+ pump will synthesize ATP from ADP and phosphate.  The Na+ - K+ Pump is Important For Controlling Cell Volume Without function of this pump, most cells of the body would swell until they burst The mechanism for controlling the volume is as follows: Inside the cell are large numbers of proteins and other organic molecules that cannot escape from the cell Most of these are negatively charged and therefore attract large numbers of potassium, sodium, and other positive ions as well All these molecules and ions then cause osmosis of water to the interior of the cell.  Three Na+ ions to the outside of the cell for every two K+ ions pumped to the interior. The membrane is far less permeable to sodium ions than to potassium ions Once the sodium ions are on the outside, they have a strong tendency to stay there. Thus, this represents a net loss of ions out of the cell, which initiates osmosis of water out of the cell as well. If a cell begins to swell for any reason, this automatically activates the Na+ -K+ pump, moving still more ions to the exterior and carrying water with them. Therefore, the Na+ -K+ pump performs a continual surveillance role in maintaining normal cell volume  Primary Active Transport of Calcium Ions Another important primary active transport mechanism is the calcium pump Calcium ions are normally maintained at extremely low concentration in the intracellular This is achieved mainly by two primary active transport calcium pumps One is in the cell membrane and pumps calcium to the outside of the cell The other pumps calcium ions into one or more of the intracellular vesicular organelles of the cell Sarcoplasmic reticulum of muscle cells and the mitochondria in all cells  Primary Active Transport of Hydrogen Ions Two important places in the body: In the gastric glands of the stomach Deep-lying parietal cells Basis for secreting hydrochloric acid in the stomach Late distal tubules and cortical collecting ducts of the kidney Intercalated cells in the distal tubules and cortical collecting ducts  ENERGY REQUIREMENT IN ACTIVE TRANSPORT Determined by how much the substance is concentrated during transport 1 osmole of a substance 10-fold is about 1400 calories, whereas to concentrate it 100-fold, 2800 calories are required Secondary Active Transport—Co-Transport and Counter-Transport Two type: Co- transport When sodium ions are transported out of cells by primary active transport, a large concentration gradient of sodium ions across the cell membrane usually develops—high concentration outside the cell and low concentration inside The excess sodium outside the cell membrane is always attempting to diffuse to the interior. Under appropriate conditions, this diffusion energy of sodium can pull other substances along with the sodium through the cell membrane For sodium to pull another substance along with it, a coupling mechanism is required. This is achieved by means of still another carrier protein in the cell membrane. The carrier in this instance serves as an attachment point for both the sodium ion and the substance to be co-transported.  Counter-Transport The substance to be transported is on the inside of the cell and must be transported to the outside At the same time sodium binding to the carrier protein. Where it projects to the exterior surface of the membrane. The substance to be counter-transported binds to the interior projection of the carrier protein Once both have bound, a conformational change occurs, and energy released by the sodium ion moving to the interior causes the other substance to move to the exterior.  Active Transport Through Cellular Sheets Transport of this type occurs through ✔ Intestinal epithelium ✔ Renal tubules epithelium ✔ Epithelium of ALL exocrine glands ✔ Epithelium of the gallbladder ✔ Membrane of the choroid plexus of the brain  The basic mechanism for transport of a substance through a cellular sheet is: Active transport through the cell membrane on one side of the transporting cells in the sheet, either simple diffusion or facilitated diffusion through the membrane on the opposite side of the cells THANK YOU!!! Cell Cycle Cell cycle consist of interphase and a mitotic phase Series of changes a cell goes through from the time it is formed until it reproduces Two major period Interphase Cells grows and carriers on its usual activities Cell division/Mitotic Phase Cell divided in two Interphase Period from cell formation to cell division During interphase a cell is carrying out all its routine activities and is “resting” only from dividing. “metabolic phase or growth phase” Prepare cell for next division Interphase into(subphases): G1 S G2 “G- gaps and Synthetic” In all subphases the cell grows by producing protein but, chromatin is reproduced only during the S subphase.  G1 (gap 1 Subphase) Cell is metabolically active synthesizing proteins rapidly and growing vigorously This is the most variable phase in terms of length. lasts several minutes to hours, but it may last for days or even years. G0 : Cells that permanently stop dividing Most G1, virtually no activities directly related to cell division occur G1 ends, the centrioles start to replicate in preparation for cell division  S phase DNA is replicated Ensuring that the two future cells being created will receive identical copies of the genetic material New histones are made and assembled into chromatin. Without a proper S phase, there can be no correct mitotic phase.  G2 (gap subphase) Final phase of interphase Enzymes and other proteins needed for division are synthesized and moved to their proper sites By the end of G2: Centriole replication (begun in G1) is complete. At the end of this phase: The G2/M checkpoint when the cell ensures that all DNA is replicated and damaged DNA has been repaired.  DNA Replication Before a cell can divide DNA must be replicated exactly That identical copies of the cell’s genes can be passed to each of the two resulting daughter cells During the S phase: Replication begins simultaneously on several chromatin threads and continues until all the DNA has been replicated  Sequence of Replication Uncoiling Enzymes unwind the DNA molecule Forming a replication bubble Separation: The two DNA strands separate as the hydrogen bonds between base are broken The point at which the strand unzip “replication fork” Assembly: With old (parental) strands acting as template Enzyme DNA polymerase position complementary free nucleotides along the template strands, forming two strands Replication proceeds in a 5’ to 3’ direction. One strand, the leading strand, is synthesized as one continuous strand utilizing the 3’ to 5’ template. The other strand, the lagging strand, is synthesized in small segments called Okazaki fragments from the 5’ to 3’ template. Since each new molecule consists of one old and one new nucleotide strand, this mechanism is known as semiconservative replication. Restoration Ligase enzymes Splice short segments of DNA together, restoring the double helix structure  The progression from DNA replication to cell division proceeds smoothly when the newly formed DNA is undamaged. If damage occurs, the cycle stops at the G2/M checkpoint until the DNA repair mechanism has fixed the problem. Histones (Made in the cytoplasm and imported into the nucleus) Provide structural support for chromosomes Button-like chromatin strands uniting chromatin strands which held together until the cell enters the anaphase stage of mitotic cells  Cell Division Essential for body growth and tissue repair Cells that continually wear away Cells of the skin and intestinal lining Reproduce themselves almost continuously Others divide more slowly to maintain the size of the organ they compose but retain the ability to reproduce quickly if the organ is damaged Liver Most cells of nervous tissue, skeletal muscle, and heart muscle lose their ability to divide when they are fully mature Repairs are made with scar tissue (a fibrous type of connective tissue).  Cell division (Mitotic) Phase Two distinct events Mitosis: Division of nucleus Series of events that parcels out the replicated DNA of the parent cell to two daughter cells Cytokinesis: Division of cytoplasm Begins during late anaphase and is completed after mitosis ends  Mitosis Four phases Prophase Metaphase Anaphase Telophase Meiosis Produces sex cells (ova and sperm) with only half the number of genes found in other body cells.  Cytokinesis A contractile ring made of actin filaments Draws the plasma membrane inward to form a cleavage furrow over the center of the cell. The furrow deepens until it pinches the cytoplasmic mass into two parts, yielding two daughter cells  Control of Cell Division Regulated by both internal Factor and external Factor: The ratio of cell surface area to cell volume Cells grows, its volume increases more rapidly than its surface area Bigger cells require more nutrients Chemical signals such as growth factors and hormones released by other cells. The availability of space Normal cells stop proliferating when they begin touching, a phenomenon known as contact inhibition.  Restriction point G1 checkpoint Key point at which a stop signal halt further growth Cyclins and Cyclin dependent kinases (Cdks) Two groups of proteins Crucial to a cell’s ability to finish the S phase and enter mitosis Cdks Activated and deactivated by cyclin Function in a regulatory role Initiates enzymatic cascades needed for cell division At the end of mitosis, enzymes destroy the cyclins and the process begins again. MITOSIS  Interphase Interphase is the period of a cell’s life when it carries out its normal metabolic activities and grows Interphase is not part of mitosis DNA-containing material is in the form of chromatin The nuclear envelope and one or more nucleoli are intact and visible There are three distinct periods of interphase: G1, S, and G2.  Prophase First phase of mitosis Early prophase The chromatin coils and condenses, forming barlike chromosomes. Each duplicated chromosome consists of two identical threads Called sister chromatids, held together at the centromere As the chromosomes appear The nucleoli disappear, and the two centrosomes separate from one another The centrosomes act as focal points for growth of a microtubule assembly Mitotic spindle As the microtubules lengthen they propel the centrosomes toward opposite ends (poles) of the cell. Microtubule arrays called asters (“stars”) extend from the centrosome matrix  Prophase Late prophase The nuclear envelope breaks up Allowing the spindle to interact with the chromosomes. Some of the growing spindle microtubules attach to kinetochores Kinetochore microtubules The remaining (unattached) spindle microtubules are called nonkinetochore microtubules The microtubules slide past each other, forcing the poles apart. The kinetochore microtubules pull on each chromosome from both poles in a tug-of-war Ultimately draws the chromosomes to the center, or equator, of the cell.  Metaphase Second phase of mitosis The two centrosomes are at opposite poles of the cell. The chromosomes cluster at the midline of the cell Their centromeres precisely aligned at the spindle equator. This imaginary plane midway between the poles is called the metaphase plate At the end of metaphase Enzymes that will act to separate the chromatids from each other are triggered  Anaphase Third phase of mitosis The shortest phase of mitosis Begins abruptly as the centromeres of the chromosomes split simultaneously Each chromatid now becomes a chromosome in its own right The nonkinetochore microtubules slide past each other lengthen, and push the two poles of the cell apart. The moving chromosomes look V shaped. The centromeres lead the way The chromosomal “arms” dangle behind them Diffuse threads of chromatin would trail, tangle, and break, resulting in imprecise “parceling out” to the daughter cells.  Telophase Final phase of mitosis – like phrophase in reverse Begins as soon as chromosomal movement stops The identical sets of chromosomes at the opposite poles of the cell begin Uncoil and resume their threadlike chromatin form. A new nuclear envelope forms around each chromatin mass Nucleoli reappear within the nuclei Spindle breaks down and disappears. Mitosis is now ended For just a brief period, is binucleate (has two nuclei)  Cytokinesis Division of cytoplasm Begins during late anaphase and continues through and beyond telophase Contractile ring of actin microfilaments forms the cleavage furrow and pinches the cell apart RNA  Role of RNA in Protein Synthesis Decoding and Messenger function RNA Single stranded It has the sugar ribose instead of deoxyribose The base uracil (U) instead of thymine (T) Three form: Messenger RNA (mRNA) Long nucleotide strands resembling “half-DNA” molecules Carries the coded information to the cytoplasm, where protein synthesis occurs Ribosomal RNA (rRNA) Along with proteins, forms the ribosomes, which consist of two subunits (large and small) Two subunit will combine to form functional ribosomes (site for protein synthesis) Transfer RNA (tRNA) Small, roughly L-shaped molecules that ferry amino acids to the ribosomes There they decode mRNA’s message for amino acid sequence in the polypeptide to be built  All types of RNA are formed on the DNA in the nucleus The DNA helix separates and one of its strands serves as a template for synthesizing a complementary RNA strand Once formed, the RNA molecule migrates into the cytoplasm  Two major steps for Polypeptide synthesis Transcription Which DNA’s Information is encoded in mRNA Translation Which the information carried by mRNA is decoded and used to assemble polypeptide  Transcription Information is converted from one form or format to another. Transfers information from a DNA base sequence to the complementary base sequence of an mRNA molecule Different form, but same information is being conveyed Transcription cannot begin until gene-activating chemicals called TRANSCRIPTION FACTORS Stimulate histones at the gene transcription site to loosen. Bind to promoter Special DNA that contains the start point Specifies which DNA strand is going to serve as the template strand  RNA polymerase Enzymes that initiate transcription once preparation are made Three basic phases: Initiation Elongation Termination  Translation Step of protein synthesis The language of nucleic acids (base sequence) is translated into the language of proteins (amino acid sequence). Genetic code The base sequence of a gene is translated into an amino acid sequence Codon Correspond to three-base sequence on mRNA Stop Codon Out of 64 codons three stop codon “stop sign” It call for termination of polypeptide synthesis  Role transfer RNA (tRNA) Shape like a handheld drill Dual function Binding amino acid and an mRNA codon Amino acid is from the cytoplasmic pool Anticodon other end  Translation occurs in the cytosol Each phase of translation require energy in the form of ATP and a specific set of protein factors and enzymes. Sequence of Event: Initiation Elongation Termination Initiation A small ribosomal subunit binds to a special methionine-carrying initiator tRNA, and then to the “new” mRNA to be decoded With the initiator tRNA still in tow, the small ribosomal subunit scans along the mRNA until it encounters the start codon The first AUG (Start codon) triplet it meets When the initiator tRNA’s UAC anticodon “recognizes” and binds to the start codon Large ribosomal subunit unites with the small one, forming a functional ribosome. As this phase ends The mRNA is firmly positioned in the groove between the ribosomal subunits The initiator tRNA is sitting in the P site, and the A site is vacant Ready for the next aminoacyl tRNA to deliver its cargo. Elongation Three step cycle: Codon recognition The incoming aminoacyl-tRNA binds to a complementary codon in the A site of a ribosome. Peptide bond formation An enzymatic component in the large ribosomal subunit catalyzes peptide bond formation between the amino acid of the tRNA Translocation The ribosome translocates, or moves, shifting its position one codon along the mRNA This shift moves the tRNA in the A site to the P site. The unloaded (vacant) tRNA is transferred to the E site During the three-step cycle the ribosome moves along the mRNA Termination The mRNA strand is read sequentially until its last codon Stop codon UGA, UAA, or UAG The stop codon is the “period” at the end of the mRNA sentence It tells the ribosome that translation of that mRNA is finished. As a result, water instead of an amino acid is added to the polypeptide chain This hydrolyzes (breaks) the bond between the polypeptide and the tRNA in the P site.  End Tissue  Tissue (Tissu = woven) Groups of cells that are similar in structure and perform a common or related function. Four primary tissue types interweave form the “fabric” of the body Epithelial Cover Connective Support Muscle Moves Nervous control EPITHELIAL TISSUE  Epithelial Tissue Epithelium or epithelial Sheet of cells Cover a body surface or lines a body cavity Two forms: Covering and lining epithelium Forms the outer layer of the skin; Dips into and lines the open cavities of the urogenital, digestive, and respiratory systems Covers the walls and organs of the closed ventral body cavity Glandular epithelium Fashions the glands of the body  Function of epithelium: Protection Filtration Excretion Secretion Sensory reception  Special Characteristic of Epithelium Polarity Epithelial tissue have two surface that differ in structure and functions and exhibit apical-basal polarity Apical surface Not attached to surrounding tissue and is exposed to either the outside of the body or cavity of an internal organ Basal Surface attached to the underlying connective tissue  Apical Surface Some are smooth and slick, most have microvilli Microvilli tremendously increase the exposed surface area (Those lining the intestine or kidney tubules, for instance) They are often so dense that the cell apices have a fuzzy appearance called a brush border. Some epithelia, such as that lining the trachea (windpipe), have motile cilia That propel substances along their free surface Basal surface Thin supporting sheet called the basal lamina Acts as a selective filter that determines which molecules diffusing from the underlying connective tissue are allowed to enter the epithelium. acts as scaffolding along which epithelial cells can migrate to repair a wound.  Specialized Contacts Epithelial cells fit closely together to form continuous sheets except for glandular epithelia The sides of adjacent cells are tied together by tight junctions and desmosomes That tight junctions prevent substances from leaking through spaces between cells Desmosomes keep cells from pulling apart  Supported by Connective tissue All epithelial sheets rest upon and are supported by connective tissue. Basement membrane Between the epithelial and connective tissues Reinforces the epithelial sheet, helps it resist stretching and tearing, and defines the epithelial boundary. Two layer: Basal lamina Reticular Lamina Deep to the basal lamina Consists of a layer of extracellular material containing a fine net work of collagen protein fibers  Avascular but innervated Avascular (no blood vessels) Innervated (supplied by nerve fibers) Nourished by substances diffusing from blood vessels in the underlying connective tissue Regeneration High regenerative capacity As long as epithelial cells receive adequate nutrition, they can replace lost cells by cell division  Classification of Epithelial Tissue Name of each epithelium has two parts First name Indicates number of cell layers Simple Consist of a single cell layer Typically found where absorption, secretion, and filtration occur and a thin epithelial barrier is desirable Stratified Composed of two or more cell layers stacked on top of each other Common in high-abrasion areas where protection is important skin surface and the lining of the mouth.  Name of each epithelium has two parts Second name Shape of its cells Three common shapes Squamous cells Flattened and scale-like Nucleus flattened disc Cuboidal cells Boxlike, approximately as tall as they are wide. Spherical Columnar cells Tall and column shaped. Elongated from top to bottom  Simple epithelial Most concerned with absorption, secretion, and filtration. They consist of a single cell layer and are usually very thin, protection is not one of their specialties.  Simple Squamous Epithelium Flattened laterally, and their cytoplasm is sparse Thin and often permeable Found where filtration or the exchange of substances by rapid diffusion is a priority Kidneys - Forms part of the filtration membrane that filters blood to make urine Lungs - Forms the walls of the air sacs across which gas exchange occurs Two simple squamous epithelia in the body have special names that reflect their location. Endothelium Provides a slick, friction-reducing lining in lymphatic vessels and in all hollow organs of the cardiovascular system Capillaries: Thinness encourages the efficient exchange of nutrients and wastes between the bloodstream and surrounding tissue cells. Mesothelium Found in serous membranes membranes lining the ventral body cavity and covering its organs.  Simple cuboidal epithelium A single layer of cells as tall as they are wide Important functions are for secretion and absorption This epithelium forms the walls of the smallest ducts of glands and of many kidney tubules.  Simple Columnar Epithelium Single layer of tall, closely packed cells, aligned like soldiers in a row It lines the digestive tract from the stomach through the rectum Mostly associated with absorption and secretion, and the digestive tract lining Two distinct modifications that make it ideal for that dual function: Dense microvilli on the apical surface of absorptive cells Tubular glands made primarily of cells that secrete mucus containing intestinal juice Simple columnar epithelia display cilia on their free surfaces Help move substances or cells through an internal passageway.  Pseudostratified Columnar Epithelium Vary in height All of its cells rest on the basement membrane But only the tallest reach the free surface of the epithelium. Pseudo: The cell nuclei lie at different levels above the basement membrane Gives the false impression that several cell layers are present This epithelium secretes or absorbs substances A ciliated version containing mucus-secreting goblet cells lines most of the respiratory tract. The motile cilia propel sheets of dust-trapping mucus away from the lungs.  Stratified Epithelia Contain two or more cell layers. They regenerate from below The basal cells divide and push apically to replace the older surface cells. Considerably more durable than simple epithelia, and protection is their major role  Stratified Squamous Epithelium The most widespread of the stratified epithelia Composed of several layers, it is thick and well suited for its protective role in the body Its free surface cells are squamous, and cells of the deeper layers are cuboidal or columnar. Found in areas subjected to wear and tear Two type: Keratinized Surface contains keratin, a tough protective protein Non-Keratinized  Stratified Cuboidal Rare in the body Mostly found in the ducts of some of the larger glands Sweat glands, mammary glands Stratified columnar epithelium Found in the pharynx, the male urethra, and lining some glandular ducts Occurs at transition areas or junctions between two other types of epithelia.  Transitional Epithelium Forms the lining of hollow urinary organs Stretch as they fill with urine Cells of its basal layer are cuboidal or columnar The apical cells vary in appearance, depending on the degree of distension (stretching) of the organ. Distended with urine Appears to thin from about six cell layers to as few as three, and its dome like apical cells flatten and become squamous-like The ability to change their shape allows a greater volume of urine to flow through a tubelike organ  Glandular Epithelia Consists of one or more cells that make and secrete a particular product “Secretion” An aqueous (water-based) fluid that usually contains proteins However, some glands release a lipid- or steroid-rich secretion. Glands are classified according to two sets of traits: Where they release their product Endocrine – internally secreting Exocrine – Externally secreting Number of cells Unicellular Scattered within epithelial sheets Multicellular Invagination (inward growth) of an epithelial sheet into the underlying connective tissue  Endocrine Glands Ductless glands Lose their ducts during development Produce hormones Most are compact multicellular organs But some individual hormone-producing cells are scattered in the digestive tract lining (mucosa) and in the brain Giving rise to their collective description as the diffuse endocrine system  Exocrine Glands Secrete their products onto body surfaces (skin) or into body cavities Exocrine glands are diverse They include the liver (which secretes bile); the pancreas (which synthesizes digestive enzymes); mucous, sweat, oil, and salivary glands; and many others. Unicellular Exocrine Glands The only important examples are mucous cells and goblet cells. In goblet cells, accumulating mucin distends the top of the cell, making the cells look like a glass with a stem  Exocrine Gland Multicellular Exocrine Glands Structurally more complex They have two basic parts: Derived duct and a secretory unit (acinus) Classified by structure and by mode of secretion Structural classification Simple glands have an unbranched Compound glands have a branched duct. Further categorization: Tubular - secretory cells form tubes Alveolar - secretory cells form small, flask-like sacs Tubuloalveolar - they have both types of secretory units  Exocrine glands cont. Modes of secretion Merocrine, holocrine, or apocrine glands Merocrine glands: The secretory cells are not altered in any way pancreas, most sweat glands, and salivary glands belong to this class Holocrine glands Secretory cells accumulate their products within them until they rupture. Holocrine gland secretions include the synthesized product plus dead cell fragments Their cells “die for their cause.” Sebaceous (oil) glands of the skin are the only true example of holocrine glands Apocrine glands Accumulate their products, but in this case only just beneath the free surface. The apex of the cell pinches off, releasing the secretory granules and a small amount of cytoplasm. The closest to an example of this process in humans is the release of lipid droplets by lactating mammary glands Connective Tissue  Connective Tissue Most abundant and widely distributed tissue in the body Four Main classes Connective tissue proper: Fat and fibrous tissue of ligaments Cartilage Bone Blood Major functions Binding and supporting Protecting Insulating Storing reserve fuel Transporting substance  Connective tissue Two characteristics Extracellular matrix It can bear weight, withstand great tension, and endure abuses, such as physical trauma and abrasion, that no other tissue can tolerate. Common origin Arise for mesenchyme (an embryonic tissue). Three component: Ground substance Extracellular Fibers matrix cells  Ground substance Unstructured material that fills the space between the cells and contains the fibers. Three components: Interstitial fluid Functions as a molecular sieve through which nutrients and other dissolved substances can diffuse between the blood capillaries and the cells. Cell adhesion proteins Serve mainly as a connective tissue glue that allows connective tissue cells to attach to the extracellular matrix. Proteoglycans Consist of a protein core to which large polysaccharides called glycosaminoglycans Tend to form huge aggregates which intertwine and trap water, forming a substance that varies from a fluid to a viscous gel  Fibers Collagen fiber Constructed primarily of the fibrous protein collagen Collagen fibers are extremely tough and provide high tensile strength (the ability to resist being pulled apart) to the matrix. Elastic Fiber These fibers contain a rubberlike protein, elastin Allows them to stretch and recoil like rubber bands. For example, in the skin, lungs, and blood vessel walls Reticular Fiber Made of a different type of collagen than the more common, thicker collagen fibers. They connect to the coarser collagen fibers, but they branch extensively, forming delicate networks Surround small blood vessels and support the soft tissue of organs. They are particularly abundant where connective tissue is next to other tissue types Basement membrane of epithelial tissues, and around capillaries  Connective tissue cells Each major class of connective tissue has a resident cell type Blast – immature, mitotically active Secrete ground substance and the fibers characteristic of their particular matrix. Cyte – Mature, less active Maintain the health of the matrix. Fibroblasts: in connective tissue proper become fibrocytes. Chondroblasts: in cartilage become chondrocytes. Osteoblasts: in bone become osteocytes. Blood Is an exception to the generalization Its immature blood cell–forming type (once called a hemocytoblast) is called a hematopoietic stem cell It is not located in “its” tissue (blood) and does not make the fluid matrix (plasma) of that tissue.  Connective tissue cont. Home to an assortment of other cell types, such as: Adipocytes: called adipose or fat cells, which store energy as fat. White blood cells: Concerned with tissue response to injury Mast cells: These oval cells detect foreign microorganisms and initiate local inflammatory responses against them Macrophages: Devour a broad variety of foreign materials, ranging from foreign molecules to entire bacteria to dust particles  Types of Connective Tissue Their major differences reflect cell type, and the types and relative amounts of fibers Mesenchyme has a fluid ground substance containing fine sparse fibers and star-shaped mesenchymal cells. It arises during the early weeks of embryonic development and eventually differentiates (specializes) into all other connective tissue cells. Some mesenchymal cells remain and provide a source of new cells in mature connective tissues  Loose Connective Tissue Areolar Connective tissue Most widely distributed connective tissue in the body Serves as a universal packing material between other tissues. It binds body parts together while allowing them to move freely over one another Functions: Supporting and binding other tissues (the job of the fibers) Holding body fluids (the ground substance’s role) Defending against infection (via the activity of white blood cells and macrophages) Storing nutrients as fat in adipocytes (fat cells)  Areolar Connective tissue Most obvious structural feature of this tissue is the loose arrangement of its fibers. Because of its loose nature, it provides a reservoir of water and salts for surrounding body tissues Fibroblasts Flat branching cells that appear spindle shaped (tapered at both ends) in profile, are the predominant cell type The ground substance of areolar connective tissue is viscous like molasses Because of its high concentration of hyaluronic acid  Adipose Tissue Similar to areolar tissue in structure and function But its nutrient-storing ability is much greater The matrix is scanty and the cells are packed closely together, giving a chicken-wire appearance to the tissue A glistening oil droplet (almost pure triglyceride) occupies most of an adipocyte’s volume and displaces the nucleus to one side Adipose tissue is richly vascularized High metabolic activity Adipose tissue is certainly abundant: It constitutes 18% of an average person’s body weight.  Adipose tissue May develop almost anywhere, but it usually accumulates in subcutaneous tissue Acts as a shock absorber, as insulation, and as an energy storage site The abundant fat beneath the skin serves the general nutrient needs of the entire body White fat Stores nutrients (mainly for other cells) Brown fat Contains abundant mitochondria that use the lipid fuels to generate heat (instead of generating ATP molecules).  Reticular Connective tissue Resembles areolar connective tissue, but the only fibers in its matrix are reticular fibers Which form a delicate network along which fibroblasts called reticular cells It forms a labyrinth-like stroma (“bed” or “mattress”), or internal framework Support many free blood cells (mostly lymphocytes) in lymph nodes, the spleen, and bone marrow.  Dense Connective tissue