PHYSIOLOGY_LC2_THE CELL.pdf

- Microtubules - Provide the cytoskeletons of cellular COURSE OUTLINE...

- Microtubules - Provide the cytoskeletons of cellular COURSE OUTLINE organelles - Fibrillar Proteins - Found I. THE CELL outside the cell, especially in II. PROTOPLASM the collagen and elastin fibers III. CELL STRUCTURE of connective tissue, and A. Cell Membrane elsewhere, such as in blood B. Cytoplasm and its Organelles vessel walls, tendons, and IV. FUNCTIONAL SYSTEMS OF THE CELL ligaments. V. LOCOMOTION OF CELL I. THE CELL The building blocks of the body Contains the body’s hereditary code 2 Major Parts: ○ Nucleus ○ Cytoplasm Figure 2. Structure of cell cytoskeleton b. Functional Proteins - Composed of combinations of a few molecules in tubular-globular form. - These are mainly the enzymes Figure 1. Structure of the cell as seen with light microscope of the cell - Are often mobile in the cell fluid - Many of them are adherent to II. PROTOPLASM membranous structures inside the cell and catalyze specific Composed mainly of five basic substance: intracellular chemical reactions. 1. WATER 4. LIPIDS 70% to 85% Several types of substances that are Many cellular chemicals are dissolved in grouped together because of their the water. common property of being soluble in fat Others are suspended in the water as solvents. solid particulates. Phospholipids and Cholesterol Chemical reactions take place among ○ 2% of the total cell mass the dissolved chemicals or at the ○ Mainly insoluble in water surfaces of the suspended particles or ○ Are used to form the cell membrane membranes. and intracellular membrane barriers 2. ELECTROLYTES that separate the different cell Important ions: compartments. ○ Potassium Triglycerides ○ Magnesium ○ Also called “neutral fats” ○ Phosphate ○ 95% of the cell mass in ○ Sulfate ADIPOCYTES ○ Bicarbonate ○ Body’s main storehouse of Smaller quantities: energy-giving nutrients that can ○ Sodium later be used to provide energy wherever it is needed in the body. 3. PROTEINS 10% to 20% of the cell mass 5. CARBOHYDRATES 2 TYPES: Play a major role in cell nutrition. a. Structural Proteins Have structural functions as parts of - Present in the cell mainly in the glycoprotein molecules: form of long filaments that are ○ 1% of the total mass of the cells polymers of many individual ○ 3% in muscle cells protein molecules. ○ 6% in liver cells BATCH 2028 1B 1 ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 Dissolved glucose is always present in A. CELL MEMBRANE the surrounding extracellular fluid so that it is readily available to the cell. aka PLASMA MEMBRANE Glycogen Envelops the cell and is a thin, pliable, ○ A small amount of carbohydrate elastic structure only 7.5 to 10 nanometers is stored in cells. thick. ○ An insoluble polymer of glucose Composed almost entirely of proteins and that can be depolymerized and lipids. used rapidly to supply the cell’s The approximate composition is energy needs. ○ 55% proteins ○ 25% phospholipids ○ 13% cholesterol III. CELL STRUCTURE ○ 4% other lipids The cell contains highly organized physical ○ 3% carbohydrates structures called Intracellular Organelles Figure 4. Membrane structure Figure 3. Cell with its organelles surrounded by the cytoplasm and its nucleus. Its basic structure is a LIPID BILAYER - is a thin double-layered film of lipids MEMBRANOUS STRUCTURES OF THE CELL each layer only one molecule thick Most organelles of the cell are covered by 3 main types of lipids membranes composed primarily of lipids and ○ Phospholipids proteins. ○ Sphingolipids These membranes include: ○ Cholesterol ○ Cell membrane ○ Nuclear membrane LIPID BILAYER ○ Membrane of the endoplasmic reticulum ○ Membranes of the mitochondria, lysosomes, and Golgi apparatus The lipids in membranes provide a barrier that impedes movement of water and water-soluble substances from one cell compartment to another because water is not soluble in lipids Protein molecules often penetrate all the way through membranes, thus providing specialized pathways, often organized into actual pores, for passage of specific substances through membranes Many other membrane proteins are enzymes, which catalyze a multitude of different Figure 5. Lipid bilayer and its composition chemical reactions Middle of the Membrane ○ Impermeable to the usual water-soluble substances, such as ions, glucose, and urea. ○ Fat-soluble substances, such as oxygen, carbon dioxide, and alcohol, can penetrate this portion of the membrane with ease. BATCH 2028 1B 2 ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 ○ 2 Types Of Glycoprotein 1. Integral Proteins Sphingolipids - Protrude all the way through ○ Derived from the amino alcohol the membrane. sphingosine - Many of the integral proteins ○ Also have hydrophobic and hydrophilic provide structural channels groups (or pores) through which ○ Present in small amounts in the cell water molecules and membranes, especially nerve cells water-soluble substances, ○ FUNCTIONS: especially ions, can diffuse - Protection from harmful between extracellular and environmental factors intracellular fluids. - Signal transmission - These protein channels also - Adhesion sites for extracellular have selective properties that proteins allow preferential diffusion of Cholesterol some substances over ○ Membranes are also lipids because their others. steroid nuclei are highly fat-soluble. - Other integral proteins act as ○ These molecules are dissolved in the carrier proteins for bilayer of the membrane. transporting substances that ○ They mainly help determine the degree otherwise could not of permeability (or impermeability) of the penetrate the lipid bilayer. bilayer to water-soluble constituents of - Sometimes, these carrier body fluids. proteins even transport ○ Cholesterol controls much of the fluidity substances in the direction of the membrane as well. opposite to their electrochemical gradients for diffusion, which is called active transport. Still others act as enzymes. - Integral protein 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 Figure 6. Components of lipid bilayer process, in turn, enzymatically activates the Glycoproteins intracellular part of the ○ Globular masses floating in the lipid protein or induces bilayer. 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 2. Peripheral Proteins - Attached only to one surface of the membrane and do not penetrate all the way through. - Often attached to integral proteins - They function almost entirely as enzymes or as controllers of transport of substances through cell membrane pores Figure 7. Membrane Structure Membrane Carbohydrates ○ Membrane carbohydrates + Proteins= Glycoproteins: most of the integral proteins are glycoproteins BATCH 2028 1B 3 ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 ○ Membrane carbohydrates + Lipids= 1. ENDOPLASMIC RETICULUM Glycolipids: one-tenth of the membrane lipid molecules. ○ Proteoglycans: which are mainly carbohydrates bound to small protein cores—are loosely attached to the outer surface of the cell ○ Glycocalyx : loose carbohydrate coat covering the entire surface of the cell Functions Of The Carbohydrate Moieties Attached To The Outer Surface Of The Cell ○ Many of them have a negative electrical charge, which gives most cells an overall negative surface charge that repels other negatively charged objects. ○ The glycocalyx of some cells Figure 9. Structure of endoplasmic reticulum attached to the nucleus attaches to the glycocalyx of other cells, thus attaching cells to one another. A network of tubular structures called ○ Many of the carbohydrates act as cisternae and flat vesicular structures in receptors for binding hormones, such the cytoplasm as insulin. When bound, this Helps process molecules made by the cell combination activates attached and transports them to their specific internal proteins that in turn activate destinations inside or outside the cell a cascade of intracellular enzymes. The tubules and vesicles interconnect ○ Some carbohydrate moieties enter Their walls are constructed of lipid bilayer into immune reactions membranes that contain large amounts of proteins, similar to the cell membrane. The space inside the tubules and vesicles is filled with ENDOPLASMIC MATRIX, a B. CYTOPLASM AND ITS ORGANELLES watery medium that is different from fluid in the cytosol outside the endoplasmic \ The vast surface area of this reticulum and the multiple enzyme systems attached to its membranes provide the mechanisms for a major share of the cell’s metabolic functions reticulum Figure 8. Structure of cell and its cytoplasm CYTOPLASM Figure 10. Structure of endoplasmic reticulum Filled with minute and large dispersed particles and organelles a. RIBOSOMES and the R.E.R. The jelly-like fluid portion of the cytoplasm - Granular particles that are attached to the in which the particles are dispersed is called outer surfaces of many parts of the CYTOSOL and contains mainly dissolved endoplasmic reticulum proteins, electrolytes, and glucose. - Are composed of a mixture of RNA and Dispersed in the cytoplasm are neutral fat proteins; they function to synthesize new globules, glycogen granules, ribosomes, protein molecules in the cell. secretory vesicles, and 5 especially a. SMOOTH (AGRANULAR) important ORGANELLES: ENDOPLASMIC RETICULUM ○ Endoplasmic reticulum - part of the endoplasmic reticulum has no ○ Golgi apparatus attached ribosomes. ○ Mitochondria - functions for the synthesis of lipid ○ Lysosomes substances and for other processes of the ○ Peroxisomes cells promoted by intra-reticular enzymes. BATCH 2028 1B 4  ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 2. GOLGI APPARATUS Membranes are similar to those of the smooth endoplasmic reticulum. Usually composed of four or more stacked layers of thin, flat, enclosed vesicles lying near one side of the nucleus Prominent in secretory cells, where it is located on the side of the cell from which secretory substances are extruded. ER vesicles 🡪 GA 🡪 lysosomes, secretory vesicles, and other cytoplasmic components Figure 13. Endocytosis and exocytosis process in cell 4. PEROXISOMES Major function: Catabolize long-chain fatty acids. Physically similar to lysosomes but they differ in two ways: ○ Formed by self-replication (or perhaps by budding off from the smooth endoplasmic reticulum) rather than from the Golgi Figure 11. Golgi apparatus and SER similarity apparatus. ○ Contain oxidases rather than hydrolases. LYSOSOME PEROXISOME Form by breaking off Self-replication from the Golgi (perhaps by budding apparatus off from the smooth endoplasmic reticulum) Hydrolase Oxidase Table 1. Lysosome vs Peroxisome Several of the oxidases are capable of combining oxygen with hydrogen ions derived from different intracellular Figure 12. Structure of golgi apparatus chemicals to form hydrogen peroxide (H2O2 ). 3. LYSOSOMES ○ Hydrogen Peroxide is a highly Vesicular organelles that form by breaking off oxidizing substance and is used in from the Golgi apparatus; they then disperse association with catalase, another throughout the cytoplasm. oxidase enzyme present in large Provide an intracellular digestive quantities in peroxisomes, to oxidize system. It digest the ff: many substances that might ○ Damaged cellular structures. ○ Food particles that have been otherwise be poisonous to the cell. ingested by the cell. ○ Unwanted matter such as bacteria. 5. SECRETORY VESICLES or “SECRETORY It has 40 different hydrolase (digestive) GRANULES” enzymes. Secretory substances are formed by the Protein → Amino Acid ER–Golgi apparatus system and are Glycogen → Glucose then released from the Golgi apparatus Lipids → Fatty acids & Glycerol into the cytoplasm in the form of storage vesicles. BATCH 2028 1B 5  ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 Figure 14. Exocytosis. Figure 17. Overview of ATP production. Secretory vesicles inside pancreatic acinar cells 7. CELL CYTOSKELETON store protein proenzymes. a. Microfilaments Secreted later through the outer cell membrane Frequently occur in the outer zone of into the pancreatic duct and then into the the cytoplasm, called the duodenum 🡪 activated and perform digestive ECTOPLASM, to form an elastic functions on the food in the intestinal tract. support for the cell membrane. Figure 15. Secretory vesicles inside pancreatic acinar cells. 6. MITOCHONDRIA Powerhouses of the cell. Figure 18. Microfilament. Concentrated in those portions of the cell responsible for the major share of its b. Intermediate Filaments energy metabolism. Strong ropelike filaments that often The liberated energy is used to synthesize work together with microtubules, a high-energy substance called adenosine providing strength and support for triphosphate (ATP). the fragile tubulin structures. Self-replicative whenever the cell needs Specific intermediate filaments found increased amounts of ATP. in various cells: Contain DNA similar to that found in the ○ Desmin filaments in muscle cells cell nucleus. ○ Neurofilaments in neurons ○ Keratins in epithelial cells Figure 16. Mitochondria. Figure 19. Intermediate Filament. BATCH 2028 1B 6  ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 c. Microtubules Nucleolus Special type of stiff filament composed ○ An accumulation of large amounts of of polymerized tubulin molecules. RNA and proteins of the types found in ribosomes. Functions: ○ It enlarges considerably when the cell ○ Provide rigid physical structures for is actively synthesizing proteins. certain parts of cells. ○ Participates in cell division, allows cells to move, and IV. FUNCTIONAL SYSTEMS OF THE provides a tracklike system that CELL directs the movement of organelles in the cells. 1. ○ Serve as the conveyor belts for 2. DIFFUSION the intracellular transport of Substances move through cell membrane vesicles, granules, and organelles pores or, in the case of lipid-soluble substances, through the lipid matrix of the such as mitochondria. membrane. Examples: ○ Tubular skeletal structure in the 3. ACTIVE TRANSPORT center of each cilium that radiates Involves actually carrying a substance upward from the cell cytoplasm to through the membrane by a physical the tip of the cilium. protein structure that penetrates all the way through the membrane. ○ The centrioles and mitotic spindles of cells undergoing mitosis are 4. ENDOCYTOSIS composed of stiff microtubules. a. Pinocytosis - Means the ingestion of minute particles that form vesicles of extracellular fluid and particulate constituents inside the cell cytoplasm Figure 20. Microtubule. 8. NUCLEUS Control center of the cell and sends Figure 22: Pinocytosis Mechanism messages to the cell to grow and mature, replicate, or die b. Phagocytosis - Means the ingestion of large particles, such as bacteria, whole cells, or portions of degenerating tissue - Occurs in much the same way as pinocytosis - Involves large particles rather than molecules - Only certain cells have the capability of phagocytosis - TISSUE MACROPHAGES and some WHITE BLOOD CELLS. Figure 21: Nuclear structure Contains large quantities of DNA, which comprise the genes Nuclear Membrane ○ “Nuclear Envelope” ○ Actually two separate bilayer membranes, one inside the other. BATCH 2028 1B 7  ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 5. PROTEINS SYNTHESIS BY THE ROUGH ENDOPLASMIC RETICULUM Figure 23: Digestion of substances in pinocytotic or phagocytic Large numbers of ribosomes attached to vessels by enzymes derived from lysosomes the outer surfaces of the endoplasmic reticulum membrane LYSOSOMES DIGEST PINOCYTOTIC AND Protein molecules are synthesized within PHAGOCYTIC FOREIGN SUBSTANCES INSIDE the structures of the ribosomes THE CELL LYSOSOMES Contain BACTERICIDAL AGENTS that can kill phagocytized bacteria before they cause cellular damage: ○ LYSOZYME - dissolves the bacterial cell wall. ○ LYSOFERRIN - binds iron and other substances before they can promote bacterial growth ○ Acid at a pH of about 5.0 - activates the hydrolases and inactivates bacterial metabolic systems. Causes tissues of the body to regress to a smaller size ○ Uterus after pregnancy ○ Muscles during long periods of Figure 25: Formation of proteins, lipids, and cellular vesicles by inactivity the endoplasmic reticulum and golgi apparatus ○ Mammary glands at the end of lactation Removes of damaged cells or damaged 6. LIPID SYNTHESIS BY THE SMOOTH portions of cells from tissues ENDOPLASMIC RETICULUM ○ Heat Synthesis of lipids, especially ○ Cold phospholipids and cholesterol ○ Trauma Small vesicles called ER vesicles or ○ Chemicals transport vesicles continually break away ○ Any other factor from the smooth reticulum AUTOPHAGY Most of these vesicles then migrate rapidly ○ “to eat oneself.” to the Golgi apparatus. ○ Lysosomes play a key role in the Other Functions of the Endoplasmic process Reticulum ○ a housekeeping process whereby ○ It provides the enzymes that control ○ obsolete organelles and large protein glycogen breakdown when glycogen aggregates are degraded and recycled is to be used for energy. ○ It provides a vast number of enzymes that are capable of detoxifying substances, such as drugs, that might damage the cell. ○ It achieves detoxification by processes such as coagulation, oxidation, hydrolysis, and conjugation with glycuronic acid. 7. GOLGI APPARATUS FUNCTIONS Provide additional processing of substances already formed in the endoplasmic reticulum. Can also synthesize certain carbohydrates that cannot be formed in the endoplasmic reticulum Large saccharide polymers bound with small amounts of protein a. Hyaluronic acid b. Chondroitin sulfate FUNCTIONS OF HYALURONIC ACID AND CHONDROITIN SULFATE: ○ They are the major components of proteoglycans secreted in mucus and other glandular secretions. ○ They are the major components of the Figure 24: Recycling of cell organelles Autophagy ground substance, or non fibrous components of the extracellular matrix, outside the cells in the BATCH 2028 1B 8 ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 interstitial spaces, which act as fillers between collagen fibers and cells. ○ They are principal components of the organic matrix in both cartilage and bone. ○ They are important in many cell activities, including migration and proliferation. TYPES OF VESICLES FORMED BY THE GOLGI APPARATUS a. Secretory Vesicles b. Lysosomes *Exocytosis, in most cases, is stimulated by entry of calcium ions into the cell. Figure 28. Three phosphate radicals 8. THE MITOCHONDRIA EXTRACT ENERGY The last two phosphate radicals are connected with FROM NUTRIENTS the remainder of the molecule by high-energy The principal substances from which cells phosphate bonds, which are represented in the extract energy are foods that react formula shown by the symbol. chemically with oxygen: ○ Carbohydrate - Glucose ○ Fats - Fatty Acids ○ Proteins - Amino Acids FUNCTIONAL CHARACTERISTICS OF ADENOSINE TRIPHOSPHATE ○ ATP is a nucleotide composed of the following: a. The nitrogenous base adenine Figure 29. The last two phosphate radicals Chemical Processes in the Formation of ATP ○ About 95% of the cell’s ATP formation occurs in the mitochondria ○ This overall process for formation of ATP is called the chemiosmotic mechanism of Figure 26. The nitrogenous base adenine ATP formation. b. The pentose sugar ribose Figure 30. The chemiosmotic mechanism of ATP formation Figure 27. The nitrogenous base ribose The chemical and physical details of this mechanism are c. Three phosphate radicals presented in Chapter 68, and many of the detailed metabolic functions of ATP in the body are discussed in Chapters 68 through 72. BATCH 2028 1B 9 ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 Uses of ATP for Cellular Function ○ Transport of substances through multiple V. LOCOMOTION OF CELL cell membranes ○ Synthesis of chemical compounds The most obvious type of movement in the throughout the cell body is that which occurs in skeletal, cardiac, ○ Mechanical work and smooth muscle cells, which constitute ○ To supply energy for the transport of almost 50% of the entire body mass. sodium through the cell membrane 2 OTHER TYPES OF MOVEMENT ○ To promote protein synthesis by the 1. AMEBOID LOCOMOTION ribosomes Crawling-like movement of an entire ○ To supply the energy needed during cell in relation to its surroundings, muscle contraction such as movement of white blood cells through tissues Figure 32. The ameboid locomotion Ameboid locomotion begins with the protrusion of a pseudopodium from one Figure 31. Simplified pattern of ATP formation end of the cell Partially secures itself in a new tissue area The remainder of the cell is pulled toward Energy from ATP is also required for the the pseudopodium membrane transport of: Types Of Cells That Exhibit Ameboid ○ Potassium Locomotion ○ Calcium a. The WBCs when they move out of ○ Magnesium the blood into the tissues to form ○ Phosphate tissue macrophages ○ Chloride b. Fibroblasts move into a damaged ○ Urate area to help repair the damage ○ Hydrogen ions c. Germinal cells of the skin ○ Many other ions d. Embryonic Cells ○ Various organic substances e. Some types of Cancer Cells (e.g. sarcomas) which arise from connective tissue cells Chemotaxis - initiator of ameboid locomotion ○ CHEMOTACTIC SUBSTANCE - any chemical substance that causes chemotaxis to occur ○ POSITIVE CHEMOTAXIS - move toward the source of a chemotactic substance -- from an area of lower concentration toward an area of higher concentration ○ NEGATIVE CHEMOTAXIS – movement of cells away from the source BATCH 2028 1B 10 ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 2. CILIA AND CILIARY MOVEMENTS Figure 34. The parts of a sperm cell b. NONMOTILE or PRIMARY CILIA ○ Nonmotile and generally occur only as a single cilium on each cell ○ They function as cellular ‘’SENSORY ANTENNAE” which coordinate cellular signaling pathways involved in chemical and mechanical sensation, signal transduction, and cell growth. ○ In the kidneys, primary cilia are found in most epithelial cells of the tubules, projecting into the tubule lumen and acting as a flow Figure 33. The parts of a cilium and ciliary movements sensor. ○ Defects in signaling by A sharp-pointed straight or curved hair primary cilia in renal that projects 2 to 4 micrometers from tubular epithelial cells are the surface of the cell thought to contribute to Many motile cilia project from a single various disorders, cell including the development Is covered by an outcropping of the of large fluid-filled cysts, a cell membrane, and it is supported by condition called 11 microtubules—nine double tubules POLYCYSTIC KIDNEY located around the periphery of the DISEASE. cilium and two single tubules down the center REFERENCES: Each cilium is an outgrowth of a structure that lies immediately 1. Dr. K. Figuerres (August 12,2024) The Cell beneath the cell membrane, called the lecture and powerpoint presentation basal body of the cilium. 2. John E. Hall, P. (2016). Guyton and Hall 2 TYPES OF CILIA: Textbook of Medical Physiology 13th edition. a. MOTILE CILIA Philadelphia: Elsevier Saunders. ○ Can undergo a whiplike movement on the surfaces of cells - Surfaces of the respiratory airway - On the inside surfaces of the uterine tubes (fallopian tubes) of the reproductive tract ○ FLAGELLUM OF A SPERM - Similar to a motile cilium - Has much the same type of structure and same type of contractile mechanism - Much longer and moves in quasi sinusoidal waves instead of whiplike movements BATCH 2028 1B 11 ANATOMY LC 2: THE CELL Dr. FIGUERRES, K. 08/12/2024 BATCH 2028 1B 12